Oxnard City Council
June 16, 2026

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Agreement No. 32600488
days after concluding the Project, Consultant and each of its subcontractors shall submit to City a verified statement of the journeyman and apprentice hours performed under this Agreement.

7. Consultant may not be debarred or suspended throughout the Agreement Term pursuant to Labor Code Section 1777.1 or 1777.7. If he, she or it becomes debarred or suspended in the Agreement Term, Consultant must immediately notify City.

8. Consultant is not qualified to bid on, be listed in a Bid proposal, or engage in the performance of any contract for public work, as defined in Labor Code Sections 1720 through 1861, unless currently registered and qualified to perform public work pursuant to Labor Code Section 1725.5. Consultant shall continue without interruption to stay registered and qualified to perform public work pursuant to Section 1725.5 for the duration of the term of this Agreement. This provision does not apply to construction, alteration, demolition, installation or repair work of $25,000 or less or to maintenance work of $15,000 or less.

9. Consultant acknowledges that 8 hours labor constitutes a legal day’s work.

Consultant shall comply with and be bound by Labor Code Section 1810.

10. Consultant shall comply with and be bound by Labor Code Section 1813 concerning penalties for workers who work excess hours. Consultant shall, as a penalty to City, forfeit $25 for each worker employed in the performance of this Agreement by Consultant or by any subcontractor for each calendar day during which such worker is required or permitted to work more than 8 hours in any calendar day and 40 hours in any one calendar week in violation of the provisions of Division 2, Part 7, Chapter 1, Article 3 of the Labor Code. Pursuant to Labor Code Section 1815, work performed by Consultant’s employees in excess of 8 hours per day and 40 hours per week shall be permitted upon public work upon compensation for all hours worked in excess of 8 hours per day at not less than 1 ½ times the basic rate of pay.

11. The Project listed in the Agreement is subject to compliance monitoring and enforcement by the DIR.

12. Consultant shall be responsible for each and every one of its subcontractors’ compliance with Chapter 1, the DIR’s rules and regulations, and Labor Code Sections 1860 and 3700. Consultant shall include in the written contract between it and each subcontractor a copy of, and a requirement that each subcontractor shall comply with, those statutory provisions. Consultant shall be required to take all actions necessary to enforce such contractual provisions and ensure subcontractors’ compliance, including without limitation, conducting a periodic review of the certified payroll records of each subcontractor, and upon becoming aware of the failure of the subcontractor to pay its workers the specified prevailing rate of wages, Consultant shall diligently take corrective action to halt or rectify any failure.

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Agreement No. 32600488

13. To the maximum extent, Consultant shall hold harmless, defend (with counsel approved by the City Attorney) and indemnify City, its legislative bodies, and its officials, officers, employees and agents from any demand or claim for damages, compensation, fines, penalties or other amounts arising out of or incidental to any acts or omissions listed above by any person or entity (including Consultant, its subcontractors, and each of their officials, officers, employees and agents) in connection with any work undertaken or in connection with the Agreement, including without limitation the payment of all attorneys’ fees and other related costs. All duties of Consultant under this Section shall survive Agreement termination.

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CITY COUNCIL AGENDA REPORT

INFORMATION/CONSENT AGENDA
AGENDA ITEM NO. L.15
DATE: June 16, 2026
TO: City Council
FROM: Michael Wolfe, Public Works Director, (805) 385-8055, [email protected] SUBJECT: Fourth Amendment to Agreement 32400156 Roesling Nakamura Terada Architects, Inc. for Architecture and Engineering Services for the Wastewater Division New Maintenance Building Project.

RECOMMENDATION
That the City Council approve and authorize the Mayor to execute a Fourth Amendment to an Agreement with Roesling Nakamura Terada Architects, Inc. in the amount of $200,000 for a new not to exceed value of $1,300,000, and to extend the term through December 5, 2029, for additional planning, design and architecture work required for the New Wastewater Maintenance Building Project Number C2236.
(This item did not originate in Committee as this is a capital improvement project specifically listed in the City's Capital Improvement Program budget, which was previously approved by the City Council.)

BACKGROUND
On December 5, 2023, the City Council approved Agreement No. 32400156 with Roesling Nakamura Terada Architects, Inc. (RNT) for $1,000,000 to provide architectural and engineering services for the Wastewater Division’s New Maintenance Building Project. The existing 9,032-square-foot Maintenance Building, constructed in 1978, does not meet current staffing levels, no longer meets operational needs, does not meet current seismic standards and is at the end of its useful life.

The original scope of work included:
• Project Management
• Data Gathering, Site Visit, and Preliminary Investigations • Schematic Design Phase
• Design Development Phase
• Construction Document Phase
• Bid Phase Services
• Construction Administration Phase
• Scope and program Verification, and Building Commission On September 17, 2024, the Purchasing Department approved the First Amendment to Agreement No. 32400156 to extend the agreement term through December 5, 2025, and revise the Schedule of Compensation to reflect updated project service and compensation requirements associated with the continued progression of the New Wastewater Maintenance Building Project.

On March 4, 2025, the City Council approved the Second Amendment to Agreement 32400156 for an additional $100,000 to accommodate additional design requirements which were not known at the start of the project but were discovered during the design and permitting phase. The additional scope of work included:
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• Additional paving, parking, and driveway access
• New storm drain facilities
• Relocating and adding new outdoor lighting
• Relocation of existing utilities
On October 15, 2025, the Purchasing Department approved the Third Amendment to Agreement No. 32400156, extending the agreement through December 5, 2026.

Capital Improvement Program (CIP) Reference:

Project No. C2236 - Wastewater: Maintenance Building Expansion - CIP 2025-2029 - Adopted June 4, 2024 - Page 152.

DISCUSSION
The design of the new Maintenance Building is approximately 90% complete. To improve construction efficiency (i.e. mitigate construction costs) and minimize operational disruptions, a portion of the existing WRRF property south of the existing fenceline is now recommended for construction access and a contractor laydown area. Because the use of this area was not originally contemplated in the project planning phase, use of this area will now require a biological resources survey and environmental assessment, potential coordination with outside agencies, and compliance with fire access requirements. The proposed access road will be approximately 30 feet wide and 700 feet long and connect to Perkins Road via a new construction access gate. The area will also include a turnaround and laydown area.

Specific Additional Tasks Include
• Biological and environmental survey and assessment
• Access road alignment, grading, and curb cut at Perkins Road • Additional survey
• Final grading, drainage, and sewer plans
• Incorporation of required fire access road
• Consultant coordination
• Project Management
RNT submitted a proposal for $50,521 to complete the environmental survey and the access road design. In addition, staff is requesting an additional $149,479 to cover design updates, analysis, and/or permitting documents anticipated with the ongoing plan check process and related final design activities, for a total contract increase of $200,000.

STRATEGIC PRIORITIES
This agenda item supports the Infrastructure and Natural Resources strategy. The purpose of the Infrastructure and Natural Resources strategy is to preserve and improve our roads, utilities, parks, trees, water supply and natural resources through effective planning, prioritization, and an equitable and efficient use of available funding.

FINANCIAL IMPACT
This amendment with RNT for additional planning, design and architecture work required for the New Wastewater Maintenance Building will increase the contract amount by $200,000 to $1,300,000 through December 5, 2029. There are sufficient budgeted funds available in the Wastewater: Maintenance Building Expansion Project (C2236) funded from the Wastewater Fund (613), to cover this project cost.

COMMITTEE OUTCOME
This item did not originate in Committee as this is a capital improvement project specifically listed in the City's Capital Improvement Program budget, which was previously approved by the City Council.

Prepared by: Jan Hauser, Wastewater Division Manager
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ATTACHMENTS

1. Fourth Amendment

2. Original Amendment - Third Amendment
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FOURTH AMENDMENT TO CONSULTANT/PROFESSIONAL AGREEMENT (V-01-17-19)) Agreement No. 32400156

FOURTH AMENDMENT TO CONSULTANT/PROFESSIONAL SERVICE

AGREEMENT
This Fourth Amendment (“Fourth Amendment”) to the Consultant/Professional Service Agreement (“Agreement”) is made and entered into in the County of Ventura, State of California, this ______ day of __________, 20___, by and between the City of Oxnard, a municipal corporation (“City”), and Roesling Nakamura Terada Architects, Inc.(“Consultant”).

This Fourth Amendment amends the Agreement entered into on December 6, 2023 by City and Consultant. The Agreement previously has been amended on September 17, 2024, by a First Amendment, on March 4, 2025, by a Second Amendment, and on November 6, 2025, by a Third Amendment.

RECITALS
WHEREAS, the City of Oxnard and Roesling Nakamura Terada Architects, Inc. (“Consultant”) entered into Agreement No. 32400156 effective December 6, 2023, for architectural and engineering services associated with the Wastewater Division New Maintenance Building Project PW 22-36; and
WHEREAS, the existing Wastewater Maintenance Building was constructed in 1978 and no longer meets the operational, staffing, seismic, and functional needs of the Wastewater Division, necessitating the design and construction of a new maintenance facility; and WHEREAS, the term of Agreement No. 32400156 was limited to four years, with no further options to extend; and
WHEREAS, it is necessary to modify of Agreement No. 32400156 to complete the services as set forth in the Agreement, because during the course of design development and coordination with multiple City departments and regulatory agencies, the Project encountered additional scope requirements, extended review durations, and unforeseen project complexities that were not fully known at the time the original Agreement was executed; and WHEREAS, additional architectural, engineering, environmental, permitting, coordination, and project management services are required to support final design completion, construction bidding, construction administration, temporary construction access improvements, environmental review, regulatory compliance, consultant coordination, and project closeout activities; and
WHEREAS, the parties desire to modify the term of the agreement as stated in Section 3 and increase the funding amount of the contract to cover the costs of unforeseen work required to complete the project, among other terms.

City and Consultant agree as follows:

1. The recitals are true and correct and incorporated by this reference as though fully set forth herein.
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2 2. Pursuant to Section 12, the City is modifying the Agreement as follows: The Agreement shall be extended for an additional three (3) years and the end term in Section 3 shall be amended to December 5, 2029.

3. The not to exceed amount in Section 4 of the Agreement is hereby amended to “$1,300,000.00.”

4. The reference to the Schedule of Compensation Exhibit B-1 everywhere it is listed in the Agreement is hereby amended to include the Schedule of Compensation Exhibit B-2. The Schedule of Compensation Exhibit B-2 is attached hereto and incorporated herein by this reference. The effective date of the Schedule of Compensation Exhibit B-2, is June, 16, 2026.

5. As so amended, the Agreement remains in full force and effect. [Signatures on next page]
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Agreement No. 32400156
FOURTH AMENDMENT TO CONSULTANT/PROFESSIONAL AGREEMENT (V-01-17-19) IN WITNESS WHEREOF, the parties hereto have executed the Amendment on the date first written above.

CITY OF OXNARD ROESLING NAKAMURA TERADA
ARCHITECTS, INC.

☐Luis A. Mc Arthur, Mayor1 Date Chikako Terada, CEO Date ☒Libertad Macias, Purchasing Agent 2

Christopher Bradbury, CFO 3 Date
ATTEST:

Lourdes A. López, City Clerk Date
(only if Mayor signs)
APPROVED AS TO FORM:

Stephen M. Fischer, Date
City Attorney (always required)
1 The City Council must authorize and the Mayor must execute any agreement over $220,000. 2 The Purchasing Agent may execute any authorized agreement up to $220,000. 3 The City requires the following for any contract:
● For a corporation, the signatures of the Board President, CEO or Vice President and of the Board Secretary, Assistant Secretary, CFO or Assistant Treasurer;
● For an LLC, the signatures of at least two managers of the LLC (company directors, not lower-level managers); or ● For a partnership, the signature of a partner. If the partnership is a limited partnership, the signer must be a general partner.

If the company has a different structure, or if the above-listed persons are not the appropriate signers, please submit to the City Attorney legally-binding documentation stating who can sign and bind your company. 722
Agreement No. 32400156
FOURTH AMENDMENT TO CONSULTANT/PROFESSIONAL AGREEMENT (V-01-17-19) EXHIBIT B-2

SCHEDULE OF COMPENSATION

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Agreement No. 32400156
FOURTH AMENDMENT TO CONSULTANT/PROFESSIONAL AGREEMENT (V-01-17-19) 3 724
Agreement No. 32400156
FOURTH AMENDMENT TO CONSULTANT/PROFESSIONAL AGREEMENT (V-01-17-19) 4 725
Agreement No. 32400156

FIRST AMENDMENT TO CONSULTANT/PROFESSIONAL SERVICES AGREEMENT This First Amendment ("First Amendment") to the Consultant/Professional Services Agreement ("Agreement") is made and entered into in the County of Ventura, State of California, this (1 day of ;Sp~ 2024, by and between the City of Oxnard, a municipal corporation ("City"), and Roesling Nakamura Terada Architects, Inc. ("Consultant"). This First Amendment amends the Agreement entered into on December 6, 2023, by City and Consultant.

City and Consultant agree as follows:

1. Pursuant to Section 3.3, the City is exercising its first one year option term. The Agreement will be extended for one additional year beginning on December 6, 2024, through December 5, 2025. The City has two option terms remaining pursuant to Section 3.3.

2. The reference to the Schedule of Compensation Exhibit B everywhere it is listed in the Agreement is hereby amended to the Schedule of Compensation Exhibit B-1 Effective December 6, 2024. The Schedule of Compensation Exhibit B is hereby disincorporated; instead, the Schedule of Compensation Exhibit B-1 Effective December 6, 2024, is attached hereto and incorporated herein by this reference.

3. As so amended, the Agreement remains in full force and effect. [Signatures on next page]
FIRST AMENDMENT TO CONSULTANT/PROFESSIONAL SERVICES AGREEMENT (V-01-17-19)) 726
Agreement No. 32400156
IN WITNESS WHEREOF, the parties hereto have executed the Amendment on the date first written above.

CITY OF OXNARD
q/1'1f
D ohn C. Zaragoza, a or1 Date
0J ennifer Yates, Purchasing Agent 2
ATTEST:

Rose Chaparro, City Clerk Date
(only if Mayor signs)
APPROVED AS TO FORM:

ROESLING NAKAMURA
TERADA ARCHITECTS, INC.

Chikako Terada, CEO Date
CJvu.o- &uJ.48- - Sept 6th, 2024
Christopher Bradbury, CFO 3 Date
I The City Council must authorize and the Mayor must execute any agreement over $200,000. 2 The Purchasing Agent may execute any authorized agreement up to $200,000. 3 The City requires the following for any contract:
• For a corporation, the signatures of the Board President, CEO or Vice President and of the Board Secretary, Assistant Secretary, CFO or Assistant Treasurer;
• For an LLC, the signatures of at least two managers of the LLC (company directors, not lower-level managers); or • For a partnership, the signature of a partner. If the partnership is a limited partnership, the signer must be a general partner.

If the company has a different structure, or if the above-listed persons are not the appropriate signers, please submit to the City Attorney legally-binding documentation stating who can sign and bind your company.

FIRST AMENDMENT TO CONSULTANT/PROFESSIONAL SERVICES AGREEMENT (V-01-17-19) 727
SCHEDULE OF COMPENSATION EXHIBIT B-1 EFFECTIVE DECEMBER 6, 2024 Position Hourly
Roesling Nakamura
Principal $ 296.40
Project Manager $ 254.80
Project Architect $ 218.40
Principal Designer $ 218.40
Drafter $ 166.40
Administrative 114.40
ECG Civil
Principal $ 218.40
Senior II $ 197.60
Senior I $ 182.00
Associate $ 166.40
Assistant $ 140.40
2-Man Survey Crew $ 291.20
Administrative $ 83.20
BMA
Principal Engineer (Mechanical) $ 265.20
Project Manager $ 174.72
Project Engineer (Plumbing) $ 145.60
Designer $ 124.80
Energy Analyst $ 145.60
Environmental
Principal $ 301.60
Project Manager $ 202.80
Technical Associate $ 202.80
Senior Planner $ 156.00
Assistant Planner and Support $ 130.00
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CITY COUNCIL AGENDA REPORT

PUBLIC HEARINGS
AGENDA ITEM NO. M.1
DATE: June 16, 2026
TO: City Council
FROM: Michael Wolfe, Public Works Director, (805) 385-8055, [email protected] SUBJECT: 2025 Urban Water Management Plan and Water Shortage Contingency Plan.

RECOMMENDATION
That the City Council:

1. Receive a presentation and receive public comment regarding the City of Oxnard’s 2025 Urban Water Management Plan and Water Shortage Contingency Plan;

2. Hold a Public Hearing on the 2025 Urban Water Management Plan and Water Shortage Contingency Plan; and

3. Adopt a resolution to approve the 2025 Urban Water Management Plan and Water Shortage Contingency Plan and authorize City staff to file the plans with the State of California. (Public Works and Transportation Committee approved 3-0 on May 26, 2026.) (Presentation will be live upon consultant's request.)

BACKGROUND
The City is subject to the provisions of the California Urban Water Management Planning Act, which requires urban water purveyors providing water to more than 3,000 customers or supplying more than 3,000 Acre Feet of water annually to prepare and adopt an Urban Water Management Plan (UWMP) at least once every five years. The purpose of the UWMP is to ensure that urban water suppliers give careful consideration to water demands, water supplies, water conservation, alternative water supplies, reliability of water supplies, water quality, and have a water shortage contingency plan in place. UWMPs must describe how projected (i.e., estimated) demands will be met through time, in various types of hydrologic conditions. Additionally, the California Department of Water Resources (CDWR) requires water suppliers to adopt and submit UWMPs in order to be eligible for certain grants, loans, and assistance that it administers.

Please note that the 2020 UWMP assumed a 2025 water demand for the City of Oxnard of 28,819 AF. Actual water demand for Oxnard in 2025 was 23,206 AF. This information is pointed out to show that while UWMPs are good (and State required) planning tools, there are still assumptions, estimates, and projections. Additionally, it should be noted that there has been a reduction in water demand by Oxnard customers, from a high in 2021 of 27,248 AF to a total demand of 23,206 (which includes water transferred to Port Hueneme Water Agency) in 2025. These types of downward trends, despite the addition of new housing and commercial development in Oxnard since 2021, mean there is more time and flexibility to address alternative sources of water and strategies for future water resilience and sustainability.

DISCUSSION
The 2025 Urban Water Management Plan (UWMP) and Water Shortage Contingency Plan (WSCP) were prepared in compliance with the California Water Code (§§10610–10657 and §10632) with the assistance of the City’s consultant, Water Systems Consulting, Inc. The UWMP evaluates estimated water demands and assumed water supplies through the 733
year 2050 and identifies resource management strategies to manage long-term water supply reliability for the City of Oxnard under normal, single-dry, and multiple-dry year conditions.

As an urban water supplier that receives imported water from the Sacramento-San Joaquin Delta, the City is required to demonstrate consistency with Delta Plan Policy WR P1 related to reducing reliance on the Delta. This analysis is included in Appendix B of the UWMP.

The WSCP has been prepared as a standalone document in accordance with current statutory requirements and is included as Appendix A. The WSCP serves as the City’s operational framework for managing water shortages and includes procedures for conducting the Annual Water Supply and Demand Assessment, which has been implemented since 2022. The WSCP outlines staged response actions to address varying levels of water shortage and is designed to support proactive and adaptive management of the City’s water system.

Since the adoption of the 2020 UWMP, the regulatory framework governing urban water management has evolved. Senate Bill 606 and Assembly Bill 1668 established long-term water use efficiency standards commonly referred to as “Making Conservation a California Way of Life”. These requirements establish water-use objectives based on indoor residential use, outdoor irrigation, commercial and institutional irrigation, and system water loss. The City has incorporated these standards into its demand estimates and water conservation programs and will continue to refine its water use objectives as State guidance is updated.

The City maintains a diversified water supply portfolio consisting of local groundwater, groundwater purchases from United Water Conservation District, imported surface water purchased from Calleguas Municipal Water District, and recycled water supplies. Since the 2020 UWMP, the City has continued to invest in water supply reliability through the implementation of advanced water purification and groundwater recharge initiatives, including the Fox Canyon Ground Water Management Agency’s (FCGMA) resolution 2023-02 (attached for reference) and resolution 03-04 (attached for reference), and resolution 03-05 (attached for reference) for the Aquifer Storage and Recovery (ASR) pilot project (attached for reference). These efforts are intended to expand local water supplies, improve drought resilience, and reduce dependence on imported water.

Groundwater remains a critical component of the City’s water supply, but its availability is subject to increasing regulatory constraints and legal challenges. Groundwater resources within the Oxnard Basin are managed by FCGMA, which has adopted groundwater allocation ordinances, Groundwater Sustainability Plans (GSPs), and a GSP Update in accordance with the Sustainable Groundwater Management Act (SGMA). These plans, included in Appendix F, establish a framework for achieving long-term groundwater sustainability and may result in reduced groundwater pumping over time. As a result, the City must continue to diversify its water supply portfolio to maintain long-term reliability.

The City, like all groundwater pumpers in the Oxnard Sub-basin (and the Pleasant Valley Basin), is subject to a current legal action, called a groundwater basin adjudication (“Adjudication”). As such, there is uncertainty regarding the access and availability of groundwater in the basins going forward. Meaning, while the UWMP contemplates many at-risk scenarios (e.g., multiple dry years), rulings from the Adjudication may impact some of the assumptions and/or water reliability and resiliency strategies going forward.

The UWMP also evaluates water supply reliability under a range of hydrologic conditions and incorporates a drought risk assessment to assess the City’s ability to meet demands over a five-year planning horizon. These analyses consider potential reductions in imported supplies, groundwater limitations, and climate variability. The UWMP demonstrates that, with implementation of planned supply and demand management strategies, the City can meet projected water demands under normal and dry-year conditions as shown in the graph below:
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The City has implemented and continues to expand water conservation and demand management programs, including public outreach, rebate programs, and water use efficiency measures. The City has implemented technologies such as advanced metering infrastructure to improve water use monitoring and customer engagement.

Preparation of the UWMP included coordination with regional water agencies, including Calleguas Municipal Water District, United Water Conservation District, the Fox Canyon Groundwater Management Agency, and neighboring jurisdictions. Documentation of agency coordination, outreach, and required notifications is included in Appendix D, and public hearing notices are included in Appendix E.

In conclusion, the 2025 UWMP demonstrates that the City of Oxnard is well-positioned to meet current and future water demands through a combination of diversified supplies, continued conservation, and strategic investments in local water resources. The UWMP reflects measurable progress in reducing water use even as the community grows, while also acknowledging the increasing constraints on groundwater supplies due to regulatory requirements and long-term sustainability goals. By advancing projects such as advanced water purification, groundwater recharge, and Aquifer Storage and Recovery, the City is strengthening its resilience to drought, climate variability, and supply uncertainty. Through proactive planning, regional coordination, and compliance with evolving State efficiency standards, the City remains committed to ensuring a reliable, sustainable, and locally resilient water supply for the Oxnard community through 2050 and beyond.

STRATEGIC PRIORITIES
This agenda item supports the Infrastructure and Natural Resources strategy. The purpose of the Infrastructure and Natural Resources strategy is to preserve and improve our roads, utilities, parks, trees, water supply and natural resources through effective planning, prioritization, and an equitable and efficient use of available funding.

FINANCIAL IMPACT
No direct fiscal impacts to the City's operating budget are expected as a result of this recommended adoption.

COMMITTEE OUTCOME
The Public Works and Transportation Committee approved 3-0 on May 26, 2026 to approve the staff recommendation and to forward the item for Council approval.

Please click here to view the May 26, 2026 Public Works and Transportation Committee Meeting recording. 735
Prepared by: Chris Peyton, Water Division Manager

ATTACHMENTS

1. Resolution

2. FCGMA Resolution 03-04

3. FCGMA Resolution 03-05

4. FCGMA Resolution 2023-02

5. Oxnard Subbasin Groundwater Sustainability Plan

6. 2025 Urban Water Management Plan - Public Draft

7. Presentation
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RESOLUTION NO. ____________

RESOLUTION OF THE CITY COUNCIL OF THE CITY OF OXNARD,
CALIFORNIA, ADOPTING THE CITY'S 2025 URBAN WATER MANAGEMENT

PLAN AND WATER SHORTAGE CONTINGENCY PLAN
WHEREAS, the California Urban Water Management Planning Act, Water Code section 10610 et seq. (the Act), which the Legislature passed to actively pursue the efficient use of water by requiring urban water suppliers to develop urban water management plans (UWMPs) every five years, defines an "urban water supplier" as a supplier, either publicly or privately owned, providing water for municipal purposes either directly or indirectly to more than 3,000 customers or supplying more than 3,000 acre feet of water annually; and WHEREAS, City of Oxnard (City) is an urban water supplier for purposes of the Act and an urban retail water supplier for the purposes of SBX7-7; and WHEREAS, the City previously adopted its 2015 and 2020 UWMPs in compliance with State law; and
WHEREAS, the Act requires the City to update and submit its 2025 UWMP to the California Department of Water Resources (DWR); and
WHEREAS, SBX7-7 established water use reduction targets and Senate 606 and Assembly Bill 1668 established long-term water use efficiency standards; and WHEREAS, the City has incorporated applicable water use efficiency standards into the 2025 UWMP; and
WHEREAS, the City is located within the Oxnard Subbasin, which is subject to the Sustainable Groundwater Management Act (SMGA), and the Basin’s Groundwater Sustainability Plan establishes a sustainability goal of 2040; and
WHEREAS, the City’s 2025 UWMP has been prepared to be consistent with the Groundwater Sustainability Plan and supports achieving sustainability by 2040; and WHEREAS, the City evaluated water supply reliability under normal, single dry year, and multiple dry year scenarios; and
WHEREAS, the City prepared the UWMP in accordance with DWR guidance, including applicable UWMP Guidebooks and methodologies; and
WHEREAS, in accordance with Water Code Sections 10608.26 and 10642 and Government Code Section 6066, the City made the draft UWMP available for public review, published two notices of public hearing at least seven days apart on May 28, 2026; and June 4, 2026 and
WHEREAS, the City held a duly noticed public hearing on June 16, 2026, and considered all oral and written comments received; and
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Resolution No.

WHEREAS, the City Council has reviewed the 2025 UWMP and determined that it complies with the requirements of the Act; and

NOW, THEREFORE, BE IT RESOLVED, DETERMINED AND ORDERED
BY THE CITY COUNCIL OF THE CITY OF OXNARD AS FOLLOWS:

1. The City Council hereby adopts the City’s 2025 Urban Water Management Plan and Water Shortage Contingency Plan pursuant to Water Code 10632 and 10632.1.

2. The Public Works Director is authorized to make non-substantive edits and finalize the UWMP.

3. The Public Works Director shall file the UWMP with the California Department of Water Resources, the California State Library, and all cities and counties within which the City provides water within 30 days of adoption.

4. The UWMP shall be made available for public inspection within 30 days of filing with DWR.

5. The Public Works Director shall provide the Water Shortage Contingency Plan to all applicable agencies within 60 days of filing.

6. The Public Works Director is authorized to implement the UWMP, Water Shortage Contingency Plan, and conservation programs.

7. The Public Works Director may recommend additional actions necessary to ensure compliance with the Act, SBX7-7, SB 606, AB 1668, and SGMA.

PASSED and ADOPTED THIS ___ day of _____, 2026, by the following vote:

AYES:

NOES:

ABSENT:

ABSTAIN:
______________________________
Luis A. Mc Arthur, Mayor
ATTEST:
________________________________
Lourdes A. López, City Clerk
APPROVED AS TO FORM:
___________________________________
Stephen M. Fischer, City Attorney
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1 Resolution 2023 –02
Of the
Fox Canyon Groundwater Management Agency

RESOLUTION OF THE BOARD OF DIRECTORS OF FOX CANYON GROUNDWATER

MANAGEMENT AGENCY REGARDING THE ACCRUAL, EXTRACTION, AND TRANSFER

OF RECYCLED WATER PUMPING ALLOCATION
WHEREAS, the Fox Canyon Groundwater Management Agency ("Agency") is a special district created by the California Legislature with the enactment of the Fox Canyon Groundwater Management Agency Act [Stats. 1982, c. 1023] ("Act") to preserve the groundwater resources within the territory of the Agency for agricultural, municipal, and industrial uses; and WHEREAS, under the Sustainable Groundwater Management Act [Water Code, § 10720 et seq.] ("SGMA"), the Agency is the exclusive groundwater sustainability agency ("GSA") within its statutory boundaries responsible for the sustainable groundwater management of, among other basins, (i) the Pleasant Valley Basin (Basin No. 4-006) and (ii) the Oxnard Subbasin (Subbasin No. 4-004.02) (collectively, the "Basins"); and WHEREAS, the California Department of Water Resources ("DWR") designated the Basins as high-priority basins, subject to critical conditions of overdraft, requiring the preparation of groundwater sustainability plans ("GSP") by January 31, 2020; and WHEREAS, the Agency has prepared, and DWR has approved, GSPs to meet the sustainability goals established by the Agency for the Basins; and WHEREAS, the Agency manages the Basins, consistent with the Act and SGMA, by implementing and enforcing its ordinances, resolutions, GSPs, and other plans that, among other things, establish allocations for the extraction of groundwater from the Basins and provide for the transfer of such allocations; and
WHEREAS, the City of Oxnard (the "City ") extracts groundwater from the Oxnard Subbasin for the municipal use of its residential customers and for the agricultural and industrial uses of other customers; and
WHEREAS, in September 2024, the City approved the Groundwater Recovery Enhancement and Treatment Program ("GREAT Program"), which is a collection of wastewater recycling, groundwater injection, and groundwater desalination projects and programs designed to provide local and regional water supply and quality benefits; and WHEREAS, Phase 1 of the GREAT Program consists of several elements, including a conjunctive use program whereby the City produces and delivers approximately 2,800 AFY of recycled water from new tertiary/advanced treatment facilities to agricultural customers in the Oxnard Pumping Depression Management Area and the Saline Intrusion Management Area of the Basin in exchange for the transfer of unused allocations to be exercised by the City or UWCD for extracting groundwater from their Water Yard facilities and O-H facilities, respectively, outside of the Oxnard Pumping Depression Management Area and the Saline Intrusion Management Area 745
2 to reduce the regional effects of overdraft conditions (e.g., seawater intrusion) in the Basins (collectively, "In-Lieu Program"); and
WHEREAS, in September 2004, the City certified a final Program Environmental Impact Report ("PEIR") [on file with the City of Oxnard] that analyzed the potential environmental impacts of Phase 1 of the GREAT Program, including the In-Lieu Program; and WHEREAS, using a 2000 UWCD model update to a 1993 United State Geological Survey groundwater flow model of the Santa Clara-Calleguas Basin, the PEIR concluded the impacts of the In-Lieu Program would be less than significant, and did not require any mitigation, because, even though extraction of transferred allocations by the City and UWCD would reduce groundwater elevations by 10 feet in both the Upper Aquifer System ("UAS") and the "Lower Aquifer System ("LAS") across the northern Oxnard Plain and Oxnard Forebay areas, the In-Lieu Program would increase groundwater elevations (2.5 feet and 10 feet in the UAS and LAS, respectively) in the southern Oxnard Plain and Pleasant Valley area and reduce overdraft conditions along the Oxnard Plain coastline (increase groundwater elevation in the UAS by 5.8 feet reduce overdraft reduction in the LAS by 4-6%); short- and long-term climatic cycles play a larger role in dictating groundwater elevations across the Oxnard Plain and Pleasant Valley areas than the In-Lieu Element; and the transfer and extraction of unused allocations by the City and UWCD would be performed pursuant with Agency ordinances and requirements designed to protect the beneficial uses of the regional groundwater resources and the safe yield of the Basins; and
WHEREAS, on June 26, 2013, the Agency approved Resolution No. 2013-02 [Attachment A], which approved the In-Lieu Program subject to conditions on the accrual and extraction of unused allocations transferred to the City, known under Resolution No. 2013-02 as Recycled Water Pumping Allocation ("RWPA"); and
WHEREAS, under Resolution No. 2013-02, the City would accrue up to 5,200 AFY of RWPA for the delivery of each acre-foot of recycled water that resulted in an acre-foot reduction of groundwater extraction from areas of the Basins more impacted by seawater intrusion; and WHEREAS, among other conditions, Resolution No. 2013-02 limited the City's extraction of "RWPA from the [Oxnard] Forebay when evacuated groundwater from storage in the [Oxnard] Forebay reaches 80,000 acre-feet (as regularly determined by UWCD), or groundwater levels in the [Oxnard] Forebay reach 19 feet above mean sea level" unless otherwise authorized by meetings of the Agency, the City, UWCD, and Pleasant Valley County Water District; and WHEREAS, the Resolution No. 2013-02 conditions were based on a Recycled Water Impact Analysis ("RWIA") Plan [Attachment A to Resolution No. 2013-02], prepared by UWCD, which expressed concern about the potential for RWPA extraction to result in local and regional effects along the Oxnard Plain coastline, including local and regional lowered groundwater elevations which it determined had the potential to increase seawater intrusion; and thus the RWIA Plan recommended careful monitoring and reduced pumping of RWPA, "if groundwater elevations in the [Oxnard] Forebay reach critical depletion levels (80,000 AFY of available storage or 19 feet above sea level)…and create a landward gradient that pulls seawater further into the aquifers"; and
WHEREAS, since the adoption of Resolution No. 2013-02, the City has accrued approximately 6,600 of RWPA but had been unable to extract any of it until 2023 because conditions in the Oxnard Forebay had remained below the critical depletion levels included in 746
3 Resolution No. 2013-02 and the RWIA Plan (i.e., 80,000 AF of evacuated storage or 19 feet above mean sea level); and
WHEREAS, the City has proposed modifying the In-Lieu Program to include updated estimates for its recycled water production, additional locations and water year types for RWPA extraction, and the transfer of RWPA to additional parties (other than UWCD) for their extraction of groundwater in excess of existing allocations and for them to reduce extractions that exceed allocations in prior water years; and accordingly, the City has proposed modifying Resolution No. 2013-02 to revise the provisions governing the accrual, extraction, and transfer of RWPA; and WHEREAS, at the request of the Agency, the City requested UWCD prepare the Recycled Water Pumping Allocation Impact Analysis ("RWPA Impact Analysis") [Attachment B], which uses UWCD's peer-reviewed numerical groundwater model ("UWCD Coastal Plain Model") to evaluate the effects of seawater intrusion in the Oxnard Subbasin, to update and replace the RWIA Plan; and
WHEREAS, the RWPA Impact Analysis evaluates the potential benefits and impacts of the City's proposed modifications to the In-Lieu Program, specifically scenarios involving delivery of 1,000 AFY and 2,000 AFY of recycled water to agricultural customers in the SIMA and PDMA and the extraction of 3,000 AF to 6,000 AF of RWPA at the City's Water Yard and/or Rice Avenue facilities and/or UWCD's O-H facilities; and
WHEREAS, the RWPA Impact Analysis concludes that the City's proposed modification to the In-Lieu Program is likely to provide a net reduction in seawater intrusion along the coast of the Oxnard Subbasin, but all modeled scenarios (i.e., updated annual recycled water production estimates, extraction at additional locations, extraction in additional water year types) resulted in increased seawater intrusion in the UAS in the coastal segment at Port Hueneme, where seawater intrusion has been documented; and
WHEREAS, the RWPA Impact Analysis found that seawater intrusion along the Port Hueneme coastal segment may be potentially significant when RWPA extractions exceed 3,000 AFY; however, the RWPA Impact Analysis found that RWPA extractions between 3,000 – 6,000 AFY would be less than significant so long as such extractions occurred at the City's Rice Avenue Facilities and/or UWCD's O-H facilities and the immediately preceding three water years types are not consecutively "below normal," "dry," and/or "critical," and WHEREAS, the Oxnard Subbasin GSP provides that nitrate concentrations in the Oxnard Forebay Management Area, which exceed water quality objectives and basin management objectives for the Oxnard Subbasin, are highly dependent on the amount of surface water diverted from the Santa Clara River, increasing during periods of dry conditions and drought; and WHEREAS, the RWPA Impact Analysis demonstrates that the potential benefits and impacts of the City's proposed modifications to the In-Lieu Program are consistent with the findings and conclusions of the PEIR's evaluation of the 2003 In-Lieu Program's impacts and the RWIA Plan's evaluation of the 2013 In-Lieu Program's impacts; and WHEREAS, this Resolution is intended to supersede and replace Resolution No. 2013-02 by approving the modified In-Lieu Program and providing the greatest flexibility for the extraction and transfer of RWPA consistent with the Agency's statutory obligations and responsibilities to protect, preserve, and ensure the sustainable management of the Basins. 747
4 NOW, THEREFORE, the Board of Directors of Fox Canyon Groundwater Management Agency hereby resolves, approves, and directs as follows:

1. The above recitals are true and correct and made a part of this Resolution.

2. This Resolution supersedes and restates Resolution No. 2013-02 in its entirety.

3. All RWPA accrued by the City, including RWPA accrued under Resolution No. 2013-02, shall be extracted and transferred according to this Resolution.

4. Accrual of RWPA
A. The City shall accrue one (1) AF of RWPA in any Water Year (October 1 to September 30) that it delivers recycled water that results in a corresponding AF reduction in annual groundwater extracted from wells located in the Saline Intrusion Management Area, the Oxnard Pumping Depression Management Area, and/or the Pleasant Valley Pumping Depression Management Area, as those management areas are defined by the Agency.

B. As a condition precedent to accruing RWPA, the City and the owners and operators (including UWCD) to which recycled water is delivered shall comply with the reporting and documentation requirements of Section 6.

C. No RWPA shall accrue for the delivery of recycled water to users that are not in compliance with all ordinances, resolutions, rules, and requirements of the Agency.

D. No RWPA shall accrue for the delivery of recycled water that results in the reduction of groundwater extraction that would have been subject to surcharges under an Agency ordinance.

E. No RWPA shall accrue for the delivery of recycled water that displaces UWCD surface water deliveries to those same users, when and if UWCD determines, in its discretion, that it is concurrently physically not capable of diverting that volume of surface water to UWCD recharge basins because the recharge basins and the Forebay are full.

F. No carryover allocation or any type of allocation credit shall accrue or otherwise be realized under any Agency ordinance or resolution for any extraction allocation that results in the accrual of RWPA.

5. Extraction and Transfer of RWPA
A. Up to 3,000 AFY of RWPA may be extracted and/or transferred from the Oxnard Subbasin, regardless of Water Year type (e.g., "below normal" or "dry," as those water year types are defined in the GSP for the Oxnard Subbasin and reported GSP Annual Reports published by the Agency), subject to the following conditions:
i. The City may extract and/or transfer RWPA. Only the City may transfer RWPA.
748
5 ii. RWPA may be transferred to owners and operators (including UWCD) for extraction in the current Water Year, or to reduce extractions that exceed allocations in the current Water Year or the immediately preceding Water Year.
iii. The City shall extract RWPA only from its Water Yard facilities and its Rice Avenue facilities, and UWCD shall extract RWPA only from its O-H facilities.
iv. RWPA transferred to owners and operators for extraction, and/or use to reduce extractions that exceed allocations, from wells in the Saline Intrusion Management Area and the Oxnard Pumping Depression Management Area of the Oxnard Subbasin will be reduced by a factor of 0.75 such that each AF of RWPA will only offset 0.75 AF of extractions in these management areas. v. RWPA may be transferred only after a completed "Application for RWPA Transfer," on a form to be prepared by the Agency, completed and signed by the City and the transferee under penalty of perjury, is submitted to the Agency indicating whether the transfer is for use of RWPA in the current or immediately preceding water year and if the transferee's well(s) are in the Saline Intrusion Management Area and the Oxnard Pumping Depression Management Area of the Oxnard Subbasin. A separate "Application for RWPA Transfer" shall be completed and submitted to the Agency for each proposed transfer of RWPA (i.e., each transfer of RWPA between the City and an owner or operator).

B. Up to an additional 3,000 AFY of RWPA (3,001-6,000 AF) may be extracted from the Oxnard Subbasin subject to the following conditions:
i. RWPA subject to this Section 5.B may be extracted only by the City at its Rice Avenue facilities and/or UWCD from its O-H facilities. ii. RWPA subject to this Section 5.B shall not be transferred. iii. Except as authorized under Section 5.A, no RWPA shall be extracted in the current Water Year if the Agency determines that the immediately preceding three Water Years have been "below normal," "dry," and/or "critical," as those terms are defined in the GSP for the Oxnard Subbasin and reported GSP Annual Reports published by the Agency.

C. No RWPA shall be extracted by or transferred to owners or operators (including the City and UWCD) that are not in compliance with all applicable well registration and reporting ordinances and requirements of the Agency or have not paid all fees, charges, penalties, and interest due and payable to the Agency.

6. Monitoring, Reporting, and Documentation Requirements A. Each year, by December 1, the City will report to the Agency the quantity of recycled water delivered to each owner and operator in the Saline Intrusion Management Area, the Oxnard Pumping Depression Management Area, and/or the 749
6 Pleasant Valley Pumping Depression Management Area of the Basins in the previous Water Year.

B. Each year, by December 1, each owner and operator in the Saline Intrusion Management Area, the Oxnard Pumping Depression Management Area, and/or the Pleasant Valley Pumping Depression Management Area of the Basins to which the City delivers recycled water will report to the Agency the quantity of recycled water delivered by the City to each of them in the previous Water Year.

C. The City's delivery of recycled water, and operators' reduction in groundwater extraction, shall be documented and reported on forms prepared by the Agency. All forms shall be signed by an authorized representative of the City and each operator under penalty of perjury.

D. The City shall report its extraction and/or transfer of RWPA to the Agency on semi-annual extraction reports as otherwise required under applicable Agency ordinances. The City’s extraction of RWPA during any given Water Year shall not be counted against its Extraction Allocation for that Water Year.

E. Each owner and operator that extracted transferred RWPA shall report its extraction and use of RWPA to the Agency on semi-annual extraction reports as otherwise required under applicable Agency ordinances. An owner and operator’s extraction of RWPA during any given Water Year shall not be counted against its Extraction Allocation for that Water Year.

F. Each year, UWCD will prepare and submit to the Agency a draft annual monitoring report of Oxnard Forebay conditions for the preceding Water Year by February 1, and a final annual monitoring report of Oxnard Forebay conditions for the preceding Water Year by April 1. The monitoring report shall include groundwater elevations, water quality monitoring, especially nitrate concentrations, and any other data that the Agency's executive officer requests that UWCD regularly monitors.

G. This Resolution and the accrual, extraction, and transfer of RWPA shall be reviewed and updated as appropriate every five (5) years in coordination with and on the same schedule as the Agency's regular GSP evaluation and update. Changes, if any, to the accrual, extraction and transfer of RWPA will be prospective. Extraction and transfer of RWPA accrued prior to the effective date of any update to this Resolution will not be altered. Any update to this Resolution shall be based on an updated technical report, using UWCD's then-current numerical groundwater flow model for the Oxnard Subbasin and Pleasant Valley Basin, that, at a minimum, examines and identifies potential impacts of continued RWPA extraction and transfer against then-current conditions and forecasts of groundwater conditions and seawater intrusion in the UAS and LAS of the Basins.

7. California Environmental Quality Act.

A. Later Activities of GREAT Program.
i. CEQA Guidelines provide that if an agency finds, pursuant to CEQA Guidelines section 15162, that no subsequent EIR would be required, then the agency can approve the activity as being within the scope of the project covered 750
7 by a program EIR, and no new environmental document would be required. (CEQA Guidelines, § 15168(c)(2).)
ii. The Agency's Board of Directors finds that the City's modified InLieu Program does not require preparation of a subsequent environmental impact report under CEQA Guidelines section 15162, and therefore the Agency may approve the modified In-Lieu Program as an activity with the scope of the original In-Lieu Program covered by the GREAT Program EIR, for the following reasons:

1. The City's proposed modifications to the In-Lieu Program do not require major revisions to the 2003 GREAT Program PEIR (which analyzed the original In-Lieu Program) or the 2013 RWIA Plan (which analyzed the City's first modification to the In-Lieu Program) that involve new significant environmental effects or a substantial increase in the severity of previously identified significant effects. (CEQA Guidelines, § 15168(a)(1).)

2. The geographic and climatic conditions under which the City's proposed modifications to the In-Lieu Program would be undertaken do not require major revisions of 2003 GREAT Program PEIR to account for new significant environmental effects or a substantial increase in the severity of previously identified significant effects. (CEQA Guidelines, § 15168(a)(2).)

3. The RWPA Impact Analysis shows that the City's proposed modification to the In-Lieu Program (i) will not result in one or more significant effects not discussed in the 2003 GREAT Program PEIR; (ii) will not substantially increase the severity of any significant effect shown in the 2003 GREAT Program PEIR; and (iii) does not include a feasible mitigation measure or alternative that the City have declined to accept or adopt. (CEQA Guidelines, § 15168(a)(3)(A)-(D).)
B. Exemption for Natural Resources Maintenance, Restoration, and Enhancement.
i. CEQA Guidelines categorically exempt projects and actions taken by regulatory agencies as authorized by state law or local ordinance to assure the maintenance, restoration, or enhancement of a natural resource where the regulatory process involves procedures for protection of the environment. (CEQA Guidelines, § 15307.)
ii. Under authority granted to it by the Act and SGMA, the Agency adopts this Resolution for the maintenance, restoration, and enhancement of the Basins, including specifically to implement a conjunctive use program that uses recycled water to offset and protect the Basins' groundwater resources and reduce the local and regional impacts of seawater intrusion.
iii. This Resolution includes provisions that will protect the groundwater supplies and groundwater quality of the Basins, including provisions requiring verification of in-lieu use prior to RWPA extraction; conditions on the 751
8 amount of RWPA that may be extracted, the location of RWPA extraction and transfers, and the water year types RWPA can be extracted and transferred. iv. Based on the foregoing, the Agency's Board of Directors finds that the approval of this Resolution is categorically exempt from CEQA as a regulatory action to assure the maintenance, restoration, or enhancement of the Basins, where the Agency's regulatory authority hereunder includes procedures for protection of the Basins. (CEQA Guidelines, § 15307.) The Agency's executive officer shall prepare and file a notice of exemption for the adoption of this Resolution.

8. Miscellaneous.

A. The Agency retains the authority to rescind this Resolution if any lawsuit or administrative action is filed that challenges the adoption of this Resolution or any of its provisions.

B. All decisions by the Agency's executive officer under this Resolution may be reviewed by the Agency's Board of Directors if an appeal is filed with the Agency within 30 days of the date of the decision by the Agency's executive officer. [CONTINUED ON NEXT PAGE]
752
753
Groundwater Sustainability Plan
for the Oxnard Subbasin
Fox Canyon Groundwater Management Agency
800 South Victoria Avenue
Ventura, California 93009-1610
December 2019
754
755
9837
December 2019
December 13, 2019 9837
Board of Directors
Fox Canyon Groundwater Management Agency
800 South Victoria Avenue
Ventura, CA 93009
Subject: Groundwater Sustainability Plan for the Oxnard Subbasin Dear Board of Directors:

Dudek is pleased to submit this Groundwater Sustainability Plan (GSP) for the Oxnard Subbasin to the Fox Canyon Groundwater Management Agency. This GSP was prepared this in accordance with California Code of Regulations, Title 23. Water, Division 2. Department of Water Resources, Chapter 1.5. Groundwater Management, Subchapter

2. Groundwater Sustainability Plans.

Respectfully Submitted,
_____________________________________
Ronald Schnabel, PG #7836, CHG #867
Senior Hydrogeologist
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Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 TOC-i

TABLE OF CONTENTS
Section Page No.

EXECUTIVE SUMMARY .................................................................................................... ES-1 ES.1 Introduction....................................................................................................... ES-2 ES.2 Summary of Basin Setting and Conditions....................................................... ES-3 ES.3 Overview of Sustainability Criteria .................................................................. ES-5 ES.4 Overview of the Subbasin Monitoring Network............................................... ES-7 ES.5 Projects and Management Actions.................................................................... ES-8 1 ADMINISTRATIVE INFORMATION....................................................................... 1-1

1.1 Purpose of the Groundwater Sustainability Plan .................................................1-1

1.2 Agency Information.............................................................................................1-2

1.2.1 Agency Name...........................................................................................1-2

1.2.2 Agency Address.......................................................................................1-2

1.2.3 Organization and Management Structure ................................................1-3

1.2.4 Plan Manager ...........................................................................................1-4

1.2.5 Legal Authority........................................................................................1-4

1.2.6 Groundwater Sustainability Plan Implementation and Cost Estimate ...........................................................................................1-5

1.3 Description of Plan Area....................................................................................1-11

1.3.1 Description.............................................................................................1-11

1.3.2 Geography..............................................................................................1-13

1.4 Existing Monitoring and Management Plans.....................................................1-20

1.4.1 Monitoring Programs.............................................................................1-21

1.4.2 Management Programs ..........................................................................1-21

1.4.3 Operational Flexibility Limitations........................................................1-22

1.5 Existing Conjunctive-Use Programs..................................................................1-23

1.6 Land Use Elements or Topic Categories of Applicable General Plans.............1-26

1.6.1 General Plans.........................................................................................1-27

1.6.2 Urban Water Management Plans...........................................................1-31

1.6.3 Additional Plan Summaries ...................................................................1-39

1.7 Well Permitting Policies and Procedures...........................................................1-43

1.7.1 FCGMA .................................................................................................1-44

1.7.2 Ventura County......................................................................................1-45

1.7.3 City of Oxnard .......................................................................................1-46

1.7.4 Additional Well Permitting Policies and Procedures.............................1-46

1.8 Notification and Communication.......................................................................1-46

1.8.1 Notification and Communication Summary ..........................................1-46

1.8.2 Summary of Beneficial Uses and Users.................................................1-47 758

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1.8.3 Public Meetings Summary.....................................................................1-50

1.8.4 Summary of Comments and Responses.................................................1-50

1.8.5 Summary of Initial Information on Relationships between State and Federal Regulatory Agencies.................................................1-51

1.8.6 Communication......................................................................................1-51

1.9 References Cited ................................................................................................1-52 2 BASIN SETTING .......................................................................................................... 2-1

2.1 Introduction to Basin Setting ...............................................................................2-1

2.2 Hydrogeologic Conceptual Model.......................................................................2-2

2.2.1 Geology....................................................................................................2-3

2.2.2 Basin Bottom ...........................................................................................2-5

2.2.3 Principal Aquifers and Aquitards.............................................................2-6

2.2.4 Data Gaps and Uncertainty in the Hydrogeologic
Conceptual Model..................................................................................2-12

2.3 Groundwater Conditions....................................................................................2-12

2.3.1 Groundwater Elevation Data..................................................................2-12

2.3.2 Estimated Change in Storage .................................................................2-25

2.3.3 Seawater Intrusion .................................................................................2-27

2.3.4 Groundwater Quality .............................................................................2-33

2.3.5 Subsidence .............................................................................................2-41

2.3.6 Groundwater–Surface Water Connections ............................................2-42

2.3.7 Groundwater-Dependent Ecosystems....................................................2-43

2.3.8 Potential Recharge Areas.......................................................................2-46

2.4 Water Budget .....................................................................................................2-46

2.4.1 Sources of Water....................................................................................2-47

2.4.2 Sources of Water Discharge...................................................................2-54

2.4.3 Current and Historical Water Budget Analysis .....................................2-56

2.4.4 General Uncertainties in the Water Budget ...........................................2-60

2.4.5 Projected Future Water Budget and Sustainable Yield..........................2-61

2.5 Management Areas ............................................................................................2-75

2.6 References Cited ................................................................................................2-77 3 SUSTAINABLE MANAGEMENT CRITERIA......................................................... 3-1

3.1 Introduction to Sustainable Management Criteria ...............................................3-1

3.2 Sustainability Goal...............................................................................................3-2

3.3 Undesirable Results .............................................................................................3-3

3.3.1 Chronic Lowering of Groundwater Levels..............................................3-3

3.3.2 Reduction of Groundwater Storage .........................................................3-5

3.3.3 Seawater Intrusion ...................................................................................3-6 759

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3.3.4 Degraded Water Quality ..........................................................................3-8

3.3.5 Land Subsidence ......................................................................................3-9

3.3.6 Depletions of Interconnected Surface Water.........................................3-10

3.3.7 Defining Subbasin-Wide Undesirable Results.......................................3-11

3.4 Minimum Thresholds.........................................................................................3-13

3.4.1 Chronic Lowering of Groundwater Levels............................................3-14

3.4.2 Reduction of Groundwater Storage .......................................................3-15

3.4.3 Seawater Intrusion .................................................................................3-16

3.4.4 Degraded Water Quality ........................................................................3-17

3.4.5 Land Subsidence ....................................................................................3-18

3.4.6 Depletions of Interconnected Surface Water.........................................3-19

3.5 Measurable Objectives.......................................................................................3-20

3.5.1 Chronic Lowering of Groundwater Levels............................................3-21

3.5.2 Reduction of Groundwater in Storage ...................................................3-23

3.5.3 Seawater Intrusion .................................................................................3-24

3.5.4 Degraded Water Quality ........................................................................3-24

3.5.5 Land Subsidence ....................................................................................3-25

3.5.6 Depletions of Interconnected Surface Water.........................................3-26

3.6 References Cited ................................................................................................3-27 4 MONITORING NETWORKS ..................................................................................... 4-1

4.1 Monitoring Network Objectives..........................................................................4-1

4.2 Description of Existing Monitoring Network......................................................4-1

4.2.1 Groundwater Monitoring .........................................................................4-2

4.2.2 Surface Conditions Monitoring................................................................4-3

4.3 Monitoring Network Relationship to Sustainability Indicators...........................4-5

4.3.1 Chronic Lowering of Groundwater Levels..............................................4-5

4.3.2 Reduction of Groundwater Storage .........................................................4-7

4.3.3 Seawater Intrusion ...................................................................................4-7

4.3.4 Degraded Water Quality ..........................................................................4-9

4.3.5 Land Subsidence ....................................................................................4-10

4.3.6 Depletions of Interconnected Surface Water.........................................4-10

4.4 Monitoring Network Implementation................................................................4-10

4.4.1 Groundwater Elevation Monitoring Schedule .......................................4-10

4.4.2 Groundwater Storage Monitoring Schedule ..........................................4-11

4.4.3 Seawater Intrusion Monitoring Schedule...............................................4-11

4.4.4 Water Quality Monitoring Schedule......................................................4-11

4.4.5 Groundwater Extraction Monitoring Schedule......................................4-12

4.5 Protocols for Data Collection and Monitoring...................................................4-12

4.6 Potential Monitoring Network Improvements...................................................4-13 760

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4.6.1 Water Level Measurements: Spatial Data Gaps ....................................4-13

4.6.2 Water Level Measurements: Temporal Data Gap .................................4-14

4.6.3 Groundwater Quality Monitoring ..........................................................4-15

4.6.4 Subsidence Monitoring ..........................................................................4-15

4.6.5 Shallow Groundwater Monitoring near Surface Water Bodies and GDEs...............................................................................................4-15

4.6.6 Surface Water: Flows in Agricultural Drains in the Oxnard Plain .......4-16

4.7 References Cited ................................................................................................4-16 5 PROJECTS AND MANAGEMENT ACTIONS......................................................... 5-1

5.1 Introduction to Projects and Management Actions.............................................5-1

5.2 Project No. 1 – GREAT Program Advanced Water Purification Facility ...........5-2

5.3 Project No. 2 – GREAT Program Advanced Water Purification Facility Expansion Project ................................................................................................5-5

5.4 Project No. 3 – RiverPark–Saticoy GRRP Recycled Water Project....................5-8

5.5 Project No. 4 – Freeman Expansion Project ......................................................5-10

5.6 Project No. 5 – Temporary Agricultural Land Fallowing Project .....................5-12

5.7 Management Action No. 1 – Reduction in Groundwater Production................5-14

5.8 Management Action No. 2 – Water Market Pilot Program ..............................5-17

5.9 References Cited ................................................................................................5-18

APPENDICES
A GSA Formation Documentation
B Public Outreach
C UWCD Model Report
D Water Elevation Hydrographs
E UWCD Model Peer Review
F Coastal Seawater Intrusion WL vs. CL Plots
G Water Quality Hydrographs
H FCGMA Water Quality Statistics
I Oxnard 303(d) List Reaches
J GeoTracker Open Sites
K TNC GDE Tech Memo
L UWCD GSP Model Documentation
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Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 TOC-v

FIGURES
1-1 Vicinity Map for the Oxnard Subbasin.......................................................................... 1-75 1-2 Administrative Boundaries for the Oxnard Subbasin .................................................... 1-77 1-3 Weather Station and Stream Gauge Locations .............................................................. 1-79 1-4 Average Daily Flows (ADF) and Monthly Minimum ADF in Oxnard Surface Waters............................................................................................................... 1-81 1-5 Oxnard Plain Annual Precipitation ................................................................................ 1-83 1-6 Long-Term Precipitation Trends in the Oxnard Plain ................................................... 1-85 1-7 Land and Water Use....................................................................................................... 1-87 1-8 Ventura County Water Purveyors.................................................................................. 1-89 2-1 Oxnard Subbasin Vicinity Map ................................................................................... 2-109 2-2 Geology of the Oxnard Subbasin................................................................................. 2-111 2-3 Cross Section A–A′...................................................................................................... 2-113 2-4 Cross Section B–B′ ...................................................................................................... 2-115 2-5 Upper Aquifer System 2015 Extraction (acre-feet) in Oxnard and Pleasant Valley ... 2-117 2-6 Lower Aquifer System 2015 Extraction (acre-feet) in Oxnard and Pleasant Valley... 2-119 2-7 Groundwater Elevation Contours in the Oxnard Aquifer, March 2–29, 2015............. 2-121 2-8 Groundwater Elevation Contours in the Oxnard Aquifer, October 2–29, 2015 .......... 2-123 2-9a Groundwater Well Hydrographs in the Oxnard Aquifer – Oxnard Plain .................... 2-125 2-9b Groundwater Well Hydrographs in the Oxnard Aquifer – Forebay Area ................... 2-127 2-10 Groundwater Elevation Contours in the Mugu Aquifer, March 2–29, 2015............... 2-129 2-11 Groundwater Elevation Contours in the Mugu Aquifer, October 2–29, 2015............. 2-131 2-12 Groundwater Well Hydrographs in the Mugu Aquifer................................................ 2-133 2-13 Groundwater Elevation Contours in the Hueneme Aquifer, March 2–29, 2015 ......... 2-135 2-14 Groundwater Elevation Contours in the Hueneme Aquifer, October 2–29, 2015....... 2-137 2-15 Groundwater Well Hydrographs in the Hueneme Aquifer.......................................... 2-139 2-16 Groundwater Elevation Contours in the Fox Canyon Aquifer, March 2–29, 2015..... 2-141 2-17 Groundwater Elevation Contours in the Fox Canyon Aquifer, October 2–29, 2015...................................................................................................... 2-143 2-18 Groundwater Well Hydrographs in the Fox Canyon Aquifer...................................... 2-145 2-19 Groundwater Elevation Contours in the Grimes Canyon Aquifer, March 2–29, 2015 ........................................................................................................ 2-147 2-20 Groundwater Elevation Contours in the Grimes Canyon Aquifer, October 2–29, 2015...................................................................................................... 2-149 2-21 Groundwater Well Hydrographs in the Grimes Canyon Aquifer................................ 2-151 2-22 Oxnard Subbasin Annual Change in Storage............................................................... 2-153 2-23 Oxnard Subbasin Cumulative Change in Storage........................................................ 2-155 2-24 Oxnard Subbasin Annual Change in Storage Without Coastal Flux ........................... 2-157 762

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Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 TOC-vi
2-25 Oxnard Subbasin Cumulative Change in Storage Without Coastal Flux .................... 2-159 2-26 Approximate 2015 North–South Saline Water Intrusion Extent ................................. 2-161 2-27 Semi-Perched Aquifer Coastal Chloride Concentrations, Fall 2015 ........................... 2-163 2-28 Oxnard Aquifer Coastal Chloride Concentrations, Fall 2015...................................... 2-165 2-29 Mugu Aquifer Coastal Chloride Concentrations, Fall 2015 ........................................ 2-167 2-30 Hueneme Aquifer Coastal Chloride Concentrations, Fall 2015 .................................. 2-169 2-31 Fox Canyon Aquifer Coastal Chloride Concentrations, Fall 2015.............................. 2-171 2-32 Grimes Canyon Aquifer Coastal Chloride Concentrations, Fall 2015 ........................ 2-173 2-33 Groundwater Flux along the Coast in the Upper Aquifer System............................... 2-175 2-34 Groundwater Flux along the Coast in the Lower Aquifer System............................... 2-177 2-35 Selected Historical Records of Water Elevation and Chloride Concentration ............ 2-179 2-36 Locations of Selected Coastal Wells with Historical Measurements of Chloride Concentration and Water Elevation.............................................................. 2-181 2-37a Upper Aquifer System – Most Recent Total Dissolved Solids (mg/L) Measured 2011–2015................................................................................................... 2-183 2-37b Upper Aquifer System, Forebay Area – Most Recent Total Dissolved Solids (mg/L) Measured 2011–2015 ........................................................................... 2-185 2-38 Lower Aquifer System – Most Recent Total Dissolved Solids (mg/L) Measured 2011–2015................................................................................................... 2-187 2-39a Upper Aquifer System – Most Recent Chloride (mg/L) Measured 2011–2015.......... 2-189 2-39b Upper Aquifer System, Forebay Area – Most Recent Chloride (mg/L) Measured 2011–2015................................................................................................... 2-191 2-40 Lower Aquifer System – Most Recent Chloride (mg/L) Measured 2011–2015 ......... 2-193 2-41a Upper Aquifer System – Most Recent Nitrate (mg/L as Nitrate) Measured 2011–2015................................................................................................... 2-195 2-41b Upper Aquifer System, Forebay Area – Most Recent Nitrate (mg/L as Nitrate) Measured 2011–2015................................................................................................... 2-197 2-42 Lower Aquifer System – Most Recent Nitrate (mg/L as Nitrate) Measured 2011–2015.................................................................................................................... 2-199 2-43a Upper Aquifer System – Most Recent Sulfate (mg/L) Measured 2011–2015............. 2-201 2-43b Upper Aquifer System, Forebay Area – Most Recent Sulfate (mg/L) Measured 2011–2015................................................................................................... 2-203 2-44 Lower Aquifer System – Most Recent Sulfate (mg/L) Measured 2011–2015 ............ 2-205 2-45a Upper Aquifer System – Most Recent Boron (mg/L) Measured 2011–2015.............. 2-207 2-45b Upper Aquifer System, Forebay Area – Most Recent Boron (mg/L) Measured 2011–2015................................................................................................... 2-209 2-46 Lower Aquifer System – Most Recent Boron (mg/L) Measured 2011–2015 ............. 2-211 2-47 Oil Fields in the Vicinity of FCGMA Groundwater Basins........................................ 2-213 2-48 Impaired Surface Waters in the Vicinity of FCGMA Groundwater Basins................ 2-215 763

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Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 TOC-vii
2-49 Constituents of Concern at Open GeoTracker Cases with Impacted Groundwater within FCGMA Groundwater Basin Boundaries................................... 2-217 2-50 Groundwater Elevation Contours in the Semi-Perched Aquifer, March 2–29, 2015 ........................................................................................................ 2-219 2-51 Groundwater Elevation Contours in the Semi-Perched Aquifer, October 2–29, 2015...................................................................................................... 2-221 2-52 Groundwater-Dependent Ecosystems for the Oxnard Subbasin.................................. 2-223 2-53 Lower Santa Clara River Groundwater-Dependent Ecosystems................................. 2-225 2-54 McGrath Lake Groundwater Dependent Ecosystems.................................................. 2-227 2-55 Ormond Beach Groundwater-Dependent Ecosystems................................................. 2-229 2-56 Mugu Lagoon Groundwater Dependent Ecosystems .................................................. 2-231 2-57 Oxnard Potential Recharge Areas................................................................................ 2-233 2-58 Oxnard Subbasin Stream Gauges and Water Infrastructure ........................................ 2-235 2-59 Freeman Diversion and Uses in the Oxnard Subbasin................................................. 2-237 2-60 UWCD Groundwater Recharge ................................................................................... 2-239 2-61 Water Deliveries to the PVCWD and UWCD............................................................. 2-241 2-62 Groundwater Pumping................................................................................................. 2-243 2-63 Coastal Flux from the UWCD Model Scenarios ......................................................... 2-245 2-64a UWCD Model Particle Tracks, Oxnard Aquifer, Future Baseline .............................. 2-247 2-64b UWCD Model Particle Tracks, Mugu Aquifer, Future Baseline................................. 2-249 2-64c UWCD Model Particle Tracks, Hueneme Aquifer, Future Baseline........................... 2-251 2-64d UWCD Model Particle Tracks, Upper Fox Canyon Aquifer, Future Baseline ........... 2-253 2-64e UWCD Model Particle Tracks, Basal Fox Canyon Aquifer, Future Baseline............. 2-255 2-65 UWCD Model Zones................................................................................................... 2-257 2-66a UWCD Model Particle Tracks, Oxnard Aquifer, Future Baseline With Projects .............................................................................................................. 2-259 2-66b UWCD Model Particle Tracks, Mugu Aquifer, Future Baseline With Projects .............................................................................................................. 2-261 2-66c UWCD Model Particle Tracks, Hueneme Aquifer, Future Baseline With Projects .............................................................................................................. 2-263 2-66d UWCD Model Particle Tracks, Upper Fox Canyon Aquifer, Future Baseline With Projects................................................................................................. 2-265 2-66e UWCD Model Particle Tracks, Basal Fox Canyon Aquifer, Future Baseline With Projects................................................................................................. 2-267 2-67a UWCD Model Particle Tracks, Oxnard Aquifer, Reduction With Projects Simulation – 26,500 AFY Groundwater Production in the UAS ................................ 2-269 2-67b UWCD Model Particle Tracks, Mugu Aquifer, Reduction With Projects Simulation – 26,500 AFY Groundwater Production in the UAS ................................ 2-271 764

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2-67c UWCD Model Particle Tracks, Hueneme Aquifer, Reduction With Projects Simulation – 12,800 AFY Groundwater Production in the LAS................................. 2-273 2-67d UWCD Model Particle Tracks, Upper Fox Canyon Aquifer, Reduction With Projects Simulation – 12,800 AFY Groundwater Production in the LAS.......... 2-275 2-67e UWCD Model Particle Tracks, Basal Fox Canyon Aquifer, Reduction With Projects Simulation – 12,800 AFY Groundwater Production in the LAS.......... 2-277 2-68a UWCD Model Particle Tracks, Oxnard Aquifer, Reduction Without Projects Simulation 1 – 27,200 AFY Groundwater Production in the UAS ............................. 2-279 2-68b UWCD Model Particle Tracks, Mugu Aquifer, Reduction Without Projects Simulation 1 – 27,200 AFY Groundwater Production in the UAS ............................. 2-281 2-68c UWCD Model Particle Tracks, Hueneme Aquifer, Reduction Without Projects Simulation 1 – 11,600 AFY Groundwater Production in the LAS................ 2-283 2-68d UWCD Model Particle Tracks, Upper Fox Canyon Aquifer, Reduction Without Projects Simulation 1 – 11,600 AFY Groundwater Production in the LAS................ 2-285 2-68e UWCD Model Particle Tracks, Basal Fox Canyon Aquifer, Reduction Without Projects Simulation 1 – 11,600 AFY Groundwater Production in the LAS................ 2-287 2-69 Oxnard Subbasin Management Areas.......................................................................... 2-289 3-1 Minimum Thresholds and Groundwater Elevation Contours in the Oxnard Aquifer, October 2–29, 2015 ......................................................................................... 3-33 3-2 Minimum Thresholds and Groundwater Elevation Contours in the Mugu Aquifer, October 2–29, 2015 ......................................................................................... 3-35 3-3 Minimum Thresholds and Groundwater Elevation Contours in the Hueneme Aquifer, October 2–29, 2015 ......................................................................................... 3-37 3-4 Minimum Thresholds and Groundwater Elevation Contours in the Fox Canyon Aquifer, October 2–29, 2015............................................................................ 3-39 3-5 Minimum Thresholds and Groundwater Elevation Contours in the Grimes Canyon Aquifer, October 2–29, 2015............................................................................ 3-41 3-6a Key Well Hydrographs for Wells Screened in the Oxnard Aquifer.............................. 3-43 3-6b Key Well Hydrographs for Wells Screened in the Oxnard Aquifer.............................. 3-45 3-7a Key Well Hydrographs for Wells Screened in the Mugu Aquifer................................. 3-47 3-7b Key Well Hydrographs for Wells Screened in the Mugu Aquifer................................. 3-49 3-8a Key Well Hydrographs for Wells Screened in the Hueneme Aquifer........................... 3-51 3-8b Key Well Hydrographs for Wells Screened in the Hueneme Aquifer........................... 3-53 3-9a Key Well Hydrographs for Wells Screened in the Fox Canyon Aquifer ...................... 3-55 3-9b Key Well Hydrographs for Wells Screened in the Fox Canyon Aquifer ...................... 3-57 3-10 Key Well Hydrographs for Wells Screened in the Grimes Canyon Aquifer................. 3-59 3-11 Key Well Hydrographs for Wells Screened in Multiple Aquifers................................. 3-61 3-12 Interim Milestones for Dry and Average Conditions – Linear Interpolation ................ 3-63 765

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3-13 Distribution of 5-Year Average Climate Conditions in the Historical Record of Precipitation on the Oxnard Plain.............................................................................. 3-65 4-1 Monitoring Wells Screened in the Semi-Perched Aquifer in the Oxnard Subbasin...... 4-35 4-2 Monitoring Wells Screened in the Oxnard Aquifer in the Oxnard Subbasin ................ 4-37 4-3 Monitoring Wells Screened in the Mugu Aquifer in the Oxnard Subbasin................... 4-39 4-4 Monitoring Wells Screened in the Hueneme Aquifer in the Oxnard Subbasin............. 4-41 4-5 Monitoring Wells Screened in the Fox Canyon Aquifer in the Oxnard Subbasin......... 4-43 4-6 Monitoring Wells Screened in the Grimes Canyon Aquifer in the Oxnard Subbasin............................................................................................................ 4-45 4-7 Active Surface Water Monitoring Network for the Oxnard Subbasin .......................... 4-47 4-8 Active Precipitation Monitoring Network for the Oxnard Subbasin............................. 4-49 4-9 Existing and Potential New Wells for Monitoring Groundwater Conditions in the Semi-Perched Aquifer.......................................................................................... 4-51 4-10 Existing and Potential New Wells for Monitoring Groundwater Conditions in the Oxnard Aquifer.................................................................................................... 4-53 4-11 Existing and Potential New Wells for Monitoring Groundwater Conditions in the Mugu Aquifer....................................................................................................... 4-55 4-12 Existing and Potential New Wells for Monitoring Groundwater Conditions in the Hueneme Aquifer..................................................................................................... 4-57 4-13 Existing and Potential New Wells for Monitoring Groundwater Conditions in the Fox Canyon Aquifer ............................................................................................ 4-59 4-14 Existing and Potential New Wells for Monitoring Groundwater Conditions in the Grimes Canyon Aquifer....................................................................................... 4-61 TABLES
1-1 Estimate of Project Cost and Water Supply for First 5 Years ....................................... 1-57 1-2 Groundwater Sustainability Plan Estimated Implementation Cost through 2040 ......... 1-57 1-3 Groundwater Sustainability Agencies in the Oxnard Subbasin..................................... 1-58 1-4 Summary of Land Ownership in the Oxnard Subbasin ................................................. 1-58 1-5 Oxnard Plain Stream Gauge Information ...................................................................... 1-59 1-6 Oxnard Plain Precipitation Station Information ............................................................ 1-60 1-7 Drought Periods in the Oxnard Plain............................................................................. 1-62 1-8 Past and Present Land Uses within the Oxnard Plain, 1990–2015................................ 1-62 1-9 Past, Current, and Projected Population for Ventura County, the Cities of Oxnard and Port Hueneme, and the Oxnard Plain......................................................... 1-63 1-10 Oxnard Subbasin Existing Water Resources Monitoring Programs.............................. 1-65 1-11 Oxnard Subbasin Existing Water Resources Management Projects, Programs, and Strategies................................................................................................................. 1-66 1-12 FCGMA Public Meetings on Oxnard Subbasin GSP .................................................... 1-71 766

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2-1 Oxnard Subbasin Stratigraphic and Hydrostratigraphic Nomenclature......................... 2-84 2-2 Vertical Gradient............................................................................................................ 2-85 2-3 Seawater/Saline Water Historical Reports and Studies................................................. 2-87 2-4 Basin Plan and FCGMA Water Quality Thresholds for Groundwater in the Oxnard Subbasin.................................................................................................. 2-87 2-5 Modeled Surface Water Percolation from Streams in the Oxnard Subbasin................. 2-88 2-6 Ecological Assets........................................................................................................... 2-89 2-7a Groundwater Recharge and Discharge in the Semi-Perched Aquifer ........................... 2-91 2-7b Groundwater Recharge and Discharge in the Upper Aquifer System........................... 2-92 2-7c Groundwater Recharge and Discharge in the Lower Aquifer System........................... 2-94 2-8 UWCD Diversions and Usage of Santa Clara River Water (AF).................................. 2-95 2-9 United Water Conservation District Water (AF)........................................................... 2-96 2-10 Summary of Water Deliveries ....................................................................................... 2-97 2-11 Recharge by Type (AF) ................................................................................................. 2-99 2-12 Stream Flows in Arroyo Las Posas and Conejo Creek, and Conejo Creek Diversion and Deliveries to the Pleasant Valley County Water District (AF) ............ 2-101 2-13 Sales and Usage of Imported Water Supplied by the Calleguas Municipal Water District (AF)...................................................................................................... 2-103 2-14 Oxnard Subbasin Groundwater Used........................................................................... 2-105 2-15 Modeled 2040–2069 Groundwater Extraction Rates and Surface Water Deliveries for the Oxnard Subbasin............................................................................ 2-107 3-1 Minimum Threshold Groundwater Elevations by Well, Management Area, and Aquifer for Key Wells in the Oxnard Subbasin...................................................... 3-29 3-2 Measurable Objectives and Interim Milestones............................................................. 3-31 4-1 Network of Stations Monitoring Surface Flows in the Vicinity of the Oxnard Subbasin............................................................................................................ 4-19 4-2 Network of Stations Monitoring Precipitation in the Vicinity of the Oxnard Subbasin............................................................................................................ 4-19 4-3 VCWPD Monitoring Schedule of Wells in the Oxnard Subbasin................................. 4-20 4-4 UWCD Monitoring Schedule of Wells in the Oxnard Subbasin ................................... 4-24 767
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 ACR-i
Acronym/Abbreviation Definition
AEA Annual Efficiency Allocation
AFY acre-feet per year
AMI advanced metering infrastructure
ASR Aquifer Storage and Recovery
AWMP Agricultural Water Management Plan
AWPF Advanced Water Purification Facility
bgs below ground surface
BM benchmark
BMO Basin Management Objective
BMP best management practice
BTEX benzene, toluene, ethyl benzene, and xylenes
cfs cubic feet per second
CIMIS California Irrigation Management Information System CMWD Calleguas Municipal Water District
COCs constituents of concern
DAC Disadvantaged Community
DBS&A Daniel B. Stephens & Associates Inc.

DPWM Distributed Parameter Watershed Model
DWR California Department of Water Resources
EOPMA East Oxnard Plain Management Area
Evap evaporation
FCA Fox Canyon Aquifer
FCGMA Fox Canyon Groundwater Management Agency
GDE groundwater-dependent ecosystem
gpm gallons per minute
GREAT Groundwater Recovery Enhancement and Treatment
GRRP Recycled Water/Groundwater Replenishment Reuse Project GSA Groundwater Sustainability Agency
GSP Groundwater Sustainability Plan
IE irrigation efficiency
IRWM Integrated Regional Water Management
LAS Lower Aquifer System
M&I municipal and industrial
MCL maximum contaminant level
mgd million gallons per day
mg/L milligrams per liter
msl above mean sea level
MTBE methyl tertiary butyl ether
MWD Metropolitan Water District of Southern California
OHWS Oxnard–Hueneme Water System
OPV Oxnard Subbasin–Pleasant Valley Basin

ACRONYMS AND ABBREVIATIONS
768

ACRONYMS AND ABBREVIATIONS
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 ACR-ii
Acronym/Abbreviation Definition
PCB polychlorinated biphenyl
PHWA Port Hueneme Water Agency
RMSE root-mean-squared error
SCAG Southern California Association of Governments
SGMA Sustainable Groundwater Management Act
SMP Salinity Management Pipeline
SNMP Salt and Nutrient Management Plan
SWP State Water Project
SWRCB State Water Resources Control Board
TAG Technical Advisory Group
TBA tert-butyl alcohol
TDS total dissolved solids
UAS Upper Aquifer System
USGS U.S. Geological Survey
UWCD United Water Conservation District
UWMP urban water management plan
UWMPA Urban Water Management Planning Act
VCGP Ventura County General Plan
VCWPD Ventura County Watershed Protection District
VOC volatile organic compound
VWD City of Ventura Water Department
VWRF Ventura Water Reclamation Facility
WOPMA West Oxnard Plain Management Area
WQO Water Quality Objective
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Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 ES-1

EXECUTIVE SUMMARY
The Fox Canyon Groundwater Management Agency (FCGMA, or the Agency) has developed this Groundwater Sustainability Plan (GSP) for the Oxnard Subbasin (Subbasin; DWR Basin 4-004.02) of the Santa Clara River Valley Groundwater Basin (DWR Basin 4-004), in compliance with the 2014 Sustainable Groundwater Management Act (SGMA; California Water Code, Section 10720 et seq.). The purpose of this GSP is to define the conditions under which the groundwater resources of the entire Oxnard Subbasin, which support agricultural, municipal and industrial, and environmental uses, will be managed sustainably in the future.

Historical groundwater production has resulted in seawater intrusion in the five primary aquifers of the Subbasin. These aquifers have been divided into an Upper Aquifer System, which comprises the Oxnard and Mugu Aquifers, and a Lower Aquifer System, which comprises the Hueneme, Fox Canyon, and Grimes Canyon Aquifers. The average rate of groundwater production from the Upper Aquifer System between 2015 and 2017 was approximately 40,000 acre-feet per year (AFY). The average production from the Lower Aquifer System between 2015 and 2017 was approximately 29,000 AFY. Numerical groundwater simulations indicate that if these production rates were carried into the future, seawater intrusion would continue in the Subbasin and the area currently impacted by concentrations of chloride greater than 500 milligrams per liter would grow. The landward extent of this area is referred to as the saline water impact front. 1 Combinations of projects and management actions were explored to estimate the rate of groundwater production that would prevent future expansion of the area of the Subbasin currently impacted by concentrations of chloride greater than 500 milligrams per liter. This rate of groundwater production is referred to as the sustainable yield. With the currently available projects and management actions, the sustainable yield of the Upper Aquifer System, was calculated to be approximately 32,000 AFY, with an uncertainty of ± 4,100 to 6,000 AFY.

The sustainable yield of the Lower Aquifer System was calculated to be approximately 7,000 AFY, with an uncertainty of ± 2,300 to 3,600 AFY.

Adoption of this GSP represents the first step in achieving groundwater sustainability within the Oxnard Subbasin by 2040, as required by SGMA. Evaluation of this GSP is required at a minimum of every 5 years following submittal to the California Department of Water Resources (DWR). As part of the 5-year evaluation process, the sustainable yield for each aquifer system will be refined and adjusted. These refinements will be based on new data, additional studies undertaken to fill data gaps, and groundwater modeling. Refinements and adjustments will also be made to the minimum threshold water levels developed to avoid

1 Sources of water high in chloride in the Oxnard Subbasin include modern-day seawater as well as non-marine brines and connate water in fine-grained sediments. Therefore, the area of the Subbasin impacted by concentrations of chloride greater than 500 milligrams per liter is referred to as the saline water impact area, rather than the seawater intrusion impact area, to reflect all the potential sources of chloride to the aquifers in this area. 770
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undesirable results, the measurable objective water levels that account for the need to continue groundwater production during drought cycles and the associated interim milestones to help gauge progress toward sustainability over the next 20 years.

In order to minimize the pumping reductions required to achieve sustainable management of the Subbasin, investment in large-scale projects to increase water supply, provide the infrastructure to redistribute pumping, and/or directly control seawater intrusion should be investigated. Basin optimization studies, groundwater modeling, and project feasibility studies will be conducted over the next 5 years to explore practicable processes and approaches to increasing the sustainable yield of the Oxnard Subbasin.

ES.1 INTRODUCTION
The Oxnard Subbasin is a coastal alluvial groundwater subbasin, located in Ventura County, California, that is in hydrologic communication, to varying degrees, with adjoining groundwater basins to the north and east, and with the Pacific Ocean to the west and southwest. The climate is typical of coastal Southern California, with average daily temperatures ranging generally from 50°F to 78°F in summer and from 40°F to 75°Fin winter. Land use on the Oxnard Plain is roughly equally divided between agricultural and urban uses. DWR has designated the 90-square-mile Subbasin as high priority and subject to critical conditions of overdraft.

Historical groundwater production in the Subbasin was first found to have induced seawater intrusion into the aquifers of the Oxnard Subbasin in the 1930s. In 1982, the California Legislature formed the FCGMA, an independent special district, to manage and protect the aquifers within its jurisdiction for the common benefit of the public and all groundwater users. Extractors within FCGMA jurisdiction are subject to the Agency’s GSPs, ordinances, and policies created for the sustainable management of groundwater management actions.

Three groundwater sustainability agencies (GSAs) have jurisdiction over portions of the Subbasin.

FCGMA is the GSA for the area of the Subbasin that falls within its jurisdiction. The Camrosa Water District–Oxnard Subbasin GSA has jurisdictional control over the portion of the Camrosa Water District service area in the Subbasin that is south and east of the Bailey Fault, and the Oxnard Outlying Areas GSA has jurisdictional control over portions of the Subbasin not within FCGMA or Camrosa Water District–Oxnard Subbasin GSA jurisdiction. This FCGMA GSP is the sole GSP prepared for the Subbasin, and covers the entire Subbasin, including all areas of the Subbasin outside of FCGMA’s jurisdiction.

Public participation and stakeholder feedback have played a critical role in the development of this GSP. The FCGMA maintains a list of stakeholders interested in the GSP process, known as the List of Interested Parties. A monthly newsletter, meeting notices, and notices of GSP documents available for review were sent electronically to the List of Interested Parties. Public workshops 771
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were held to inform stakeholders and the general public on the contents of the GSPs and to solicit feedback on that content. To further facilitate stakeholder understanding, the FCGMA Board of Directors (Board) approved release of a preliminary draft GSP for public comment in November 2017. Additionally, the FCGMA Board formed a Technical Advisory Group, which held monthly public meetings throughout the GSP development process beginning in July 2015. Updates on the development of the GSP were given at meetings of the FCGMA Board beginning in April 2015.

All FCGMA Board meetings, Technical Advisory Group meetings, Board-appointed committee meetings, and Board special workshops were noticed in accordance with the Brown Act, and opportunities for public comment were provided at all FCGMA Board meetings, Technical Advisory Group meetings, Board-appointed committee meetings, and workshops.

ES.2 SUMMARY OF BASIN SETTING AND CONDITIONS
There are five commonly recognized aquifers in the Subbasin: the Oxnard, Mugu, Hueneme, Fox Canyon, and Grimes Canyon Aquifers. These aquifers are grouped into the Upper Aquifer System and the Lower Aquifer System, with the Oxnard and Mugu Aquifers composing the Upper Aquifer System and the Hueneme, Fox Canyon, and Grimes Canyon Aquifers composing the Lower Aquifer System. The majority of recharge that replenishes the Subbasin comes from surface water diversions of the Santa Clara River, which are directed to spreading basins in the Oxnard Forebay operated by the United Water Conservation District (UWCD). In the Forebay, the Upper Aquifer System rests directly on the folded and eroded upper surface of the Hueneme Aquifer and the Fox Canyon Aquifer. Elsewhere in the Subbasin, the aquifers of the Lower Aquifer System are separated from those of the Upper Aquifer System by low-permeability clay beds. A lowpermeability clay cap also overlies the aquifers of the Upper Aquifer System throughout the Subbasin, except in the Forebay. Water that recharges in the Forebay is able to migrate throughout the Subbasin.

Groundwater elevations and flow directions have varied historically in the Subbasin. During periods of above average precipitation, when UWCD has been able to operate its recharge basins from the diversion of Santa Clara River water, groundwater elevations have been higher than sea level, generating a seaward-directed gradient that prevents seawater intrusion. At other times in the past, and since the onset of the drought period beginning in 2011, groundwater elevations have been below sea level, creating a landward gradient that allows for inland migration of seawater.

Absolute changes in groundwater levels over cycles of drought and recovery vary both geographically and vertically within the aquifers of the Subbasin, although the general patterns of decline and recovery are similar throughout the Subbasin.

Seawater intrusion tends to occur preferentially in the vicinity of Port Hueneme and Point Mugu, where submarine canyons are close to the coast, and the onshore freshwater aquifer units are exposed in the canyon walls. The current extent of seawater intrusion varies by aquifer, but in 772
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Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 ES-4
general the impacted area of the Subbasin lies to the south of Hueneme Road and west of Highway 1. Groundwater quality not related to seawater intrusion is also a concern in the Forebay of the Subbasin, where nitrate concentrations exceeding the water quality objectives for the Subbasin are present in the groundwater. These concentrations are likely a legacy of historical septic discharges and historical agricultural fertilizer application practices, and may also be influenced by current agricultural return flows.

The water budget for the Subbasin provides an accounting and assessment of the average annual volume of groundwater and surface water entering (i.e., inflow) and leaving (i.e., outflow) the Subbasin and enables an accounting of the cumulative change in groundwater in storage over time.

UWCD developed the Ventura Regional Groundwater Flow Model, a MODFLOW numerical groundwater flow model, for the Oxnard Subbasin, the Mound Basin, the western part of the Las Posas Valley Basin, and the Pleasant Valley Basin. A peer review study of the UWCD model was conducted for this GSP. The historical groundwater budget for the Subbasin is based on the UWCD model, which had a historical base period from 1985 to 2015. During average conditions (1988, 1991, 1992, 1994, 1996, 1997, 2000, 2001, 2003, 2006, 2008, 2010, and 2011), which are defined as water years in which the precipitation in the Oxnard Subbasin was between 75% and 150% of the average annual precipitation, the net change in groundwater storage for the Upper Aquifer System without seawater intrusion was an increase in 1,856 AFY and the net change in storage without seawater intrusion in the Lower Aquifer System was a decrease of 4,196 AFY. The net seawater intrusion during these years was 4,189 AFY in the Upper Aquifer System, and 5,225 AFY in the Lower Aquifer System. Groundwater pumping during these average condition years averaged 47,080 AFY in the Upper Aquifer System and 28,893 AFY in the Lower Aquifer System.

Several model scenarios were developed to assess the future sustainable yield of the Subbasin.

Each future scenario covered a 50-year timeframe, from 2020 to 2069. In two scenarios, the 2015– 2017 average groundwater extraction rate was continued throughout the 50-year modeled period.

The results of each of these scenarios indicated that continuing the 2015–2017 extraction rate would contribute to net seawater intrusion in both the Upper Aquifer System and Lower Aquifer System. In three additional scenarios, the groundwater production rate was decreased gradually over the first 20 years. These model scenarios indicated that reduced groundwater production from the Subbasin can eliminate net seawater intrusion in the Subbasin over periods of drought and recovery. Based on the suite of model scenarios, the sustainable yield of the Upper Aquifer System was calculated to be approximately 32,000 AFY, with an uncertainty of ± 4,100 to 6,000 AFY.

The sustainable yield of the Lower Aquifer System was calculated to be approximately 7,000 AFY, with an uncertainty of ± 2,300 to 3,600 AFY.

It is anticipated that the analysis for the 5-year update to the GSP will focus on developing new water supply projects, as well as examining the potential impacts of differential extractions on the coast and inland, particularly in the Lower Aquifer System. Additional modeling is recommended for the 773
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5-year update process to understand how changes in pumping patterns and the addition of new water supply projects can increase the overall sustainable yield of the Subbasin. As this understanding improves, projects to support increases in the overall sustainable yield can be developed.

To reflect the current understanding of the hydrogeologic characteristics of the Subbasin, and in anticipation of future management strategies the Subbasin has been divided into five management areas. These areas are the Forebay Management Area, the West Oxnard Plain Management Area, the Oxnard Pumping Depression Management Area, the Saline Intrusion Management Area, and the East Oxnard Plain Management Area. These areas are separated by hydrogeologic and water quality characteristics.

ES.3 OVERVIEW OF SUSTAINABILITY CRITERIA
The sustainability goal in the Subbasin is to increase groundwater elevations inland of the Pacific coast in the aquifers that compose the Upper Aquifer System and the Lower Aquifer System to elevations that will prevent the long-term, or climatic cycle net (net), landward migration of the area currently impacted by seawater intrusion; prevent net seawater intrusion in the Upper Aquifer System; and prevent net seawater intrusion in the Lower Aquifer System.

Under SGMA, undesirable results occur when the effects caused by groundwater conditions occurring throughout the Subbasin cause significant and unreasonable impacts to any of the six sustainability indicators:
 Chronic lowering of groundwater levels
 Reduction of groundwater storage
 Seawater intrusion
 Degraded water quality
 Land subsidence
 Depletions of interconnected surface water
All six sustainability indicators are applicable to the Subbasin. Minimum thresholds and measurable objectives, which are quantitative metrics of groundwater conditions in the Subbasin, were established for the sustainability indicators determined to be a current and/or potential future undesirable result. Groundwater elevations that achieve the sustainability goal for seawater intrusion were used as a proxy for other sustainability indicators in establishing the minimum thresholds and measurable objectives. This is because if the minimum thresholds and measurable objectives for seawater intrusion are achieved, then undesirable results for the other sustainability indicators are avoided.
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The measurable objective water levels for the Subbasin are the groundwater levels throughout the Subbasin, at which there is neither seawater flow into nor freshwater flow out of the Upper Aquifer System or Lower Aquifer System. If groundwater levels in the Subbasin remained at the measurable objective in perpetuity, no groundwater would flow from the aquifer systems into the Pacific Ocean, and no ocean water would flow into the aquifer systems. To allow for operational flexibility during drought periods, water levels in the Subbasin are allowed to fall below the measurable objective. In order to prevent net seawater intrusion over periods of drought and recovery, the periods during which groundwater elevations are below the measurable objective must be offset by periods when the groundwater elevations are higher than the measurable objective.

The minimum thresholds for all six sustainability indicators are groundwater levels that were selected to limit seawater intrusion and allow declines in groundwater elevations during periods of future drought to be offset by recoveries during future periods of above-average rainfall. These thresholds were tested with future groundwater model simulations. The model simulations suggest that if groundwater levels fall below the minimum threshold elevations, the Subbasin is likely to experience net landward migration of the 2015 saline water impact front after 2040. These minimum thresholds are anticipated to improve the beneficial uses of the Subbasin by limiting seawater intrusion. This allows for long-term use of groundwater supplies in the Subbasin.

Although exceedance of a minimum threshold at any given well in the Subbasin may indicate an undesirable result is occurring in the Subbasin, a single exceedance is not necessarily sufficient to indicate that Subbasin-wide conditions are causing undesirable results. Additionally, conditions in the Upper Aquifer System may differ from those in the Lower Aquifer System. Therefore, to define the conditions under which undesirable results will occur in the Subbasin, criteria were developed for each aquifer system. The Upper Aquifer System would be determined to be experiencing an undesirable result if:
 In any single monitoring event, groundwater levels in 6 of 15 identified key wells are below their respective minimum thresholds.
 The groundwater elevation at any individual key well is below the historical low water level for that well.
 The groundwater level in any individual key well is below the minimum threshold for either three consecutive monitoring events or three of five consecutive monitoring events, which occur in the spring and fall of each year.

The Lower Aquifer System would be determined to be experiencing an undesirable result if:
 In any single monitoring event, groundwater levels in 8 of 19 identified key wells are below their respective minimum thresholds.
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 The groundwater elevation at any individual key well is below the historical low water level for that well.
 The groundwater level in any individual key well is below the minimum threshold for either three consecutive monitoring events or three of five consecutive monitoring events, which occur in the spring and fall of each year.

ES.4 OVERVIEW OF THE SUBBASIN MONITORING NETWORK
The overall objective of the monitoring network in the Subbasin is to track and monitor parameters that demonstrate progress toward meeting the sustainability goals. In order to accomplish this objective, the monitoring network in the Subbasin must be capable of the following:
 Monitoring changes in groundwater conditions (in six sustainability indicator categories)  Monitoring progress toward minimum thresholds and measurable objectives  Quantifying annual changes in water budget components The existing network of groundwater wells includes both monitoring wells and production wells.

This network is capable of delineating the groundwater conditions in the Subbasin and has been used for this purpose in the past. The current groundwater well network will be used to monitor groundwater conditions moving forward, in order to continue to assess long-term trends in groundwater elevation and groundwater quality in the Subbasin.

Although the current monitoring network is adequate to monitor groundwater conditions in the Subbasin, it can be improved as funding becomes available An additional well, or wells, in the Oxnard Pumping Depression Management Area would provide aquifer-specific groundwater elevations in an area that does not have local wells screened solely in the Mugu Aquifer or the Hueneme Aquifer, and does not have a dedicated monitoring well screened in any of the primary aquifers.

Additionally, the monitoring network in the West Oxnard Plain Management Area could be improved by adding a monitoring well to the area north of Highway 101 and south of the Oxnard Forebay, and adding a monitoring well to the area north of 6th Street and west of Ventura Road.

A monitoring well north of Highway 101 and south of the Oxnard Forebay would provide for aquifer-specific water levels adjacent to the West Las Posas Management Area boundary. These groundwater levels could be used to constrain the gradient between the West Las Posas Management Area and the Subbasin. A monitoring well north of 6th Street and west of Ventura Road would help constrain groundwater gradients in the northwestern Subbasin.

There are currently no monitoring wells in the East Oxnard Plain Management Area, which has minimal known groundwater production. Addition of a monitoring well in the vicinity of Calleguas 776
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Creek in this management area would help constrain the relationship between groundwater elevations in the East Oxnard Plain Management Area and groundwater conditions in the adjacent Oxnard Pumping Depression and Saline Intrusion Management Areas.

In addition to supplementing the existing monitoring network with new wells, monitoring can also be improved in the future by coordination of monitoring schedules to ensure that groundwater monitoring activities occur over a 2-week window during the key reporting periods and mid-March and mid-October. As funding becomes available, pressure transducers should be added to wells in the groundwater monitoring network. Pressure transducer records provide the high-temporalresolution data that allows for a better understanding of water level dynamics in the wells related to groundwater production, groundwater management activities, and climatic influence.

In the future, to the extent possible, additional dedicated monitoring wells will be incorporated into the existing monitoring network. These wells will provide information on groundwater conditions in geographic locations where data gaps have been identified, or where a dedicated monitoring well would better represent conditions in the aquifers than a production well currently used for monitoring.

ES.5 PROJECTS AND MANAGEMENT ACTIONS
Projects and management actions have been identified to address potential impacts to beneficial uses and users of groundwater in the Subbasin resulting from groundwater production in excess of the current sustainable yield. The five projects included in this GSP were suggested by stakeholders and were reviewed by the Operations Committee of the FCGMA Board. The inclusion of these projects does not constitute a commitment by the FCGMA Board to construct or fund the projects, but rather signals that these projects were sufficiently detailed to be included in groundwater modeling efforts that examined the quantitative impacts of the projects on groundwater elevations and the sustainable yield of the Subbasin. Projects included in the GSP or any amendment thereof that increase the available supply of groundwater are necessary to meet the sustainability goal for the Subbasin in a manner that avoids adverse impacts to beneficial uses and users of groundwater within the Subbasin.

Project No. 1 – GREAT Program Advanced Water Purification Facility Under this project, the City of Oxnard’s Groundwater Recovery Enhancement and Treatment (GREAT) Program’s Advanced Water Purification Facility (AWPF) could provide the Subbasin with a source of reclaimed water that can be used for landscape irrigation, agricultural, industrial process water, and groundwater recharge. The AWPF product water that will be put to use in the Subbasin is secondary wastewater effluent that is currently discharged to the Pacific Ocean.

Therefore, this project provides a new source of water for use in the Subbasin. 777
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Project No. 2 – GREAT Program Advanced Water Purification Facility Expansion Project The purpose of the GREAT Program AWPF Expansion Project is to increase the production of high-quality recycled water within the City of Oxnard, the Subbasin, and the Pleasant Valley Basin. This project will provide additional reclaimed water for Subbasin recharge, in-lieu groundwater production, or indirect potable reuse. The AWPF Expansion Project product water that will be put to use in the Subbasin is secondary wastewater effluent that is currently discharged to the Pacific Ocean. Therefore, this project provides a new source of water for use in the Subbasin.

Project No. 3 – RiverPark–Saticoy GRRP Recycled Water Project The RiverPark–Saticoy Groundwater Replenishment and Reuse Project (GRRP) Recycled Water Project will convey water produced by the GREAT Program AWPF Expansion Project to the Saticoy Groundwater Recharge Facility and El Rio Groundwater Recharge Facility operated by UWCD. The RiverPark–Saticoy Pipeline and the GRRP will help ensure that excess flows from the AWPF will be used for groundwater recharge and implementation of this project is expected to improve groundwater quality in the Forebay.

Project No. 4 – Freeman Expansion Project
The Freeman Expansion Project will expand the recharge facilities operated by UWCD adjacent to the Santa Clara River, to be able to accommodate diversions from the river at higher flow rates.

The benefits of this project are multifold. It will provide additional recharge, improve water quality in the Forebay, and reduce pump lift, and therefore energy consumption, for municipal and agricultural pumpers.

Project No. 5 – Temporary Agricultural Land Fallowing
The Temporary Agricultural Land Fallowing Project will decrease groundwater production in the portions of the Subbasin that are susceptible to seawater intrusion. This project will benefit the Subbasin by mitigating seawater intrusion in the Subbasin and would complement a water market that is currently being developed for the Subbasin by providing an alternative method for landowners to monetize pumping allocations.

Management Action No. 1 – Reduction in Groundwater Production The primary management action proposed under this GSP is a reduction in groundwater production from the Subbasin. FCGMA has had the authority to monitor and regulate groundwater production in the Subbasin since 1983. The primary benefit related to reduction in groundwater production is recovery of groundwater elevations that have historically allowed for seawater intrusion in the Subbasin. Reduction in groundwater production can be used to close any differential between 778
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groundwater elevations that can be obtained through implementation of projects and the groundwater elevations necessary to prevent future net seawater intrusion in the Upper Aquifer System and the Lower Aquifer System.

FCGMA approved an ordinance to establish an allocation system for the Oxnard Subbasin and the Pleasant Valley Basin on October 23, 2019. The purpose of this ordinance is to facilitate adoption and implementation of the GSP and to ensure that the Oxnard Subbasin and the Pleasant Valley Basin are operated within their sustainable yields. It is not the purpose of the ordinance to determine or alter water right entitlements, including those that may be asserted pursuant to California Water Code Sections 1005.1, 1005.2, or 1005.4.

Management Action No. 2 – Water Market Pilot Program
A water market pilot program is currently being conducted by FCGMA as a means of increasing operational management of groundwater in the Subbasin. Analysis of the water market pilot program will be conducted and its suitability for incorporation as a management action for the Subbasin will be determined after the pilot program is completed in July 2019. 779
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CHAPTER 1

ADMINISTRATIVE INFORMATION

1.1 PURPOSE OF THE GROUNDWATER SUSTAINABILITY PLAN
The Fox Canyon Groundwater Management Agency (FCGMA), acting as the Groundwater Sustainability Agency (GSA) for the Oxnard Subbasin of the Santa Clara River Valley Groundwater Basin (4-004; Oxnard Subbasin [Subbasin]), has developed this Groundwater Sustainability Plan (GSP) in compliance with the 2014 Sustainable Groundwater Management Act (SGMA) (California Water Code, Section 10720 et seq.). This GSP has been developed to apply to the entirety of the Oxnard Subbasin, including those portions of the Subbasin that lie outside FCGMA’s jurisdictional boundary, primarily consisting of fringe areas of the Subbasin. The County of Ventura (County) and the Camrosa Water District (CWD) have each elected to act as the GSA for portions of the Subbasin not within FCGMA’s jurisdiction. The County and CWD will rely on this GSP and coordinate with FCGMA as necessary to ensure that the Subbasin is sustainably managed in its entirety, in accordance with SGMA.

SGMA defines sustainable groundwater management as the management and use of groundwater in a manner that can be maintained over a 50-year planning and implementation horizon without causing undesirable results. Undesirable results are defined in SGMA and are summarized here as any of the following effects caused by groundwater conditions occurring throughout the Subbasin:1  Chronic lowering of groundwater levels indicating a significant and unreasonable depletion of supply
 Significant and unreasonable reduction of groundwater storage  Significant and unreasonable seawater intrusion
 Significant and unreasonable degraded water quality
 Significant and unreasonable land subsidence
 Depletions of interconnected surface water that have significant and unreasonable adverse impacts on beneficial uses of the surface water
As described in Chapter 2, Basin Setting, of this GSP, undesirable results within the Oxnard Subbasin are occurring with respect to significant and unreasonable reduction of groundwater storage and seawater intrusion. Portions of the Subbasin are experiencing, or under threat of experiencing, degraded water quality. Chronic lowering of groundwater levels has not occurred because declines in groundwater elevation are offset by seawater intrusion. Land subsidence has occurred historically in the Subbasin and has the potential to occur in the future if groundwater

1 As defined in SGMA, “basin” means a groundwater basin or subbasin identified and defined in Bulletin 118 or as modified pursuant to California Water Code, Section 10720 et seq. (Basin Boundaries). 780
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conditions are not managed sustainably. Depletions of interconnected surface water have not occurred historically in the Subbasin, because the Groundwater-Dependent Ecosystems (GDEs) in the Subbasin are supported by shallow groundwater flows that are generally separated and disconnected from the primary groundwater aquifers (see Section 1.3.2, Geography; Section 2.2.1, Geology; and Section 2.3.7, Groundwater-Dependent Ecosystems).

The purpose of this GSP is to define the conditions under which the groundwater resources of the entire Oxnard Subbasin, which support agricultural, municipal and industrial (M&I), and environmental uses, will be managed sustainably in the future. The adoption of this GSP represents the first step in achieving groundwater sustainability within the Oxnard Subbasin by 2040, as required by SGMA. Over the next 20 years, data will continue to be gathered and used to refine the estimated sustainable yield and potential paths for achieving sustainability set forth in the following chapters. As the understanding of the Subbasin improves, this GSP will be updated to reflect the new understanding of the Subbasin. This GSP outlines a plan for annual reporting and periodic (5-year) evaluations (Chapter 1); characterizes groundwater conditions, trends, and the cumulative impacts of groundwater pumping for each of the SGMA-defined sustainability indicators (Chapter 2); establishes minimum thresholds, measurable objectives and interim milestones by which sustainability can be measured and tracked (Chapter 3, Sustainable Management Criteria); outlines the monitoring network used to support and document progress toward sustainability (Chapter 4, Monitoring Networks); and identifies projects and management actions to be implemented by the GSA and/or stakeholders to minimize undesirable results (Chapter 5, Projects and Management Actions).2 This GSP documents a viable path, determined by the GSA in collaboration with stakeholders and informed by the best available information, to achieving the sustainability goal within the Oxnard Subbasin.

1.2 AGENCY INFORMATION

1.2.1 Agency Name
Fox Canyon Groundwater Management Agency (FCGMA or Agency)

1.2.2 Agency Address
Mailing Address:

Fox Canyon Groundwater Management Agency
800 South Victoria Avenue
Ventura, California 93009-1610

2 All references in this GSP to minimizing, limiting, or mitigating undesirable results means doing so in a manner that culminates in the absence of (i.e., avoidance of) undesirable results by 2040 and thereafter during the planning and implementation horizon. 781
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Office Location:

Ventura County Government Center
Hall of Administration
800 South Victoria Avenue
Ventura, California 93009

1.2.3 Organization and Management Structure
FCGMA is governed by five Board of Directors (Board) members who represent (1) the County, (2) the United Water Conservation District (UWCD), (3) the seven mutual water companies and small water districts within the Agency (Alta Mutual Water Company, Pleasant Valley County Water District (PVCWD), Berylwood Mutual Water Company, Calleguas Municipal Water District (CMWD), CWD, Zone Mutual Water Company, and Del Norte Mutual Water Company), (4) the five incorporated cities within FCGMA (Ventura, Oxnard, Camarillo, Port Hueneme, and Moorpark), and (5) the farmers (FCGMA 2019a). Four of these Board members, representing the County, UWCD, the mutual water companies and small water districts, and the incorporated cities, are appointed by their respective organizations or groups. The representative for the farmers is appointed by the other four seated Board members from a list of candidates jointly supplied by the Ventura County Farm Bureau and the Ventura County Agricultural Association. An alternate Board member is selected by each appointing agency or group in the same manner as the regular member and acts in place of the regular member in case of absence or inability to act.

All members and alternates serve for a 2-year term of office, or until the member or alternate is no longer an eligible official of the member agency. All Board members and alternates serve on a volunteer basis and no compensation is provided for attendance at FCGMA meetings or events.

Information regarding current FCGMA Board representatives can be found on the Agency’s website (FCGMA 2019b).

Extractors within Oxnard Subbasin will be subject to FCGMA’s GSP and any management actions created for this GSP. These actions are administered by the Agency Executive Officer, who is appointed by the FCGMA Board. The Agency Executive Officer and other FCGMA staff are provided by the County of Ventura Public Works Agency pursuant to a contract with the County of Ventura. FCGMA does not construct, operate, or maintain capital facilities but does have the authority to adopt ordinances requiring registration of groundwater wells, requiring reporting of groundwater use, regulating groundwater extractions, and requiring fees. FCGMA contracts with the County to provide staff to support FCGMA (FCGMA 2019a). 782
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1.2.4 Plan Manager
Executive Officer of FCGMA, Jeff Pratt, PE
Mailing Address:

Fox Canyon Groundwater Management Agency
800 South Victoria Avenue
Ventura, California 93009-1610
Phone: 805.654.2073
Email: [email protected]

1.2.5 Legal Authority
FCGMA is an independent special district formed by the California Legislature in 1982 to manage and protect the aquifers within its jurisdiction for the common benefit of the public and all agricultural, domestic, and M&I users (FCGMA et al. 2007). FCGMA’s jurisdiction was established as the area overlying the FCA and includes portions of the Oxnard Subbasin and the Las Posas Valley Basin (LPVB), the Pleasant Valley Basin (PVB), and the Arroyo Santa Rosa Valley Basin. FCGMA may adopt ordinances for the purpose of regulating, conserving, managing, and controlling the use and extraction of groundwater within its territory (FCGMA Act, Section 403).

The FCGMA Act prohibits the Agency from engaging in water supply activities normally and historically undertaken by its member agencies. Nonetheless, FCGMA may exercise the water supply powers and authorities authorized under SGMA provided the Board makes a finding that FCGMA is otherwise unable to sustainably manage the basin.

The full text of the FCGMA Act, Assembly Bill 2995, as well as amendments and additional legislation, can be accessed on the Agency’s website (FCGMA 2019c). FCGMA is identified in SGMA as an agency created by statute to manage groundwater that is the exclusive GSA within its territory with powers to comply with SGMA (SGMA, Section 10723[c][1][D]). FCGMA notified the California Department of Water Resources (DWR) of its intent to undertake sustainable groundwater management under SGMA on January 26, 2015, and was granted exclusive GSA status under SGMA, Section 10723(c) (Appendix A, GSA Formation Documentation, to this GSP).
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1.2.6 Groundwater Sustainability Plan Implementation and Cost Estimate
This GSP will be implemented by FCGMA, with cooperation from the Camrosa Water District– Oxnard Subbasin GSA and County for the small portion of the Subbasin outside FCGMA jurisdiction (see Section 1-3, Description of Plan Area). The following sections provide a discussion of the standards for and costs associated with GSP implementation, including annual reporting, periodic updates, monitoring protocols, and projects and management actions. Potential funding sources and mechanisms are presented along with a tentative schedule for implementing the GSP’s primary components. In addition, annual reporting and 5-year evaluation procedures for the Oxnard Subbasin are described.

1.2.6.1 Standards for Plan Implementation
Annual Reporting
The GSA shall submit an annual report to DWR by April 1 of each year following the adoption of the GSP. The annual report shall include the following components for the preceding water year (23 CCR, Section 356.2):
 General information, including an executive summary and a location map depicting the basin covered by the report
 A detailed description and graphical representation of o Groundwater elevation data from wells identified in the monitoring network o Groundwater extraction for the preceding water year
o Change in groundwater in storage
o Surface water supply used or available for use
o Total water use
 A description of progress toward implementing the Plan, including achieving interim milestones, and implementation of projects or management actions since the previous annual report
The description and graphical representation of groundwater elevations will include groundwater elevation contour maps for each principal aquifer in the Subbasin illustrating, at a minimum, the seasonal high and seasonal low groundwater conditions. Additionally, hydrographs of groundwater elevations and water year type using historical data to the greatest extent available, including from January 1, 2015, to current reporting year, will be included in the annual report. As described in Section 1.2.6.2, Data Collection, Validation, and Analysis, relevant data collected by 784
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entities within the PVB are regularly provided to FCGMA and will be used to prepare the annual reports submitted to DWR.

The description and graphical representation of change in groundwater storage will include a graph depicting water year type, groundwater use, the annual change in groundwater in storage, and the cumulative change in groundwater in storage for the basin based on historical data to the greatest extent available, including from January 1, 2015, to the current reporting year.

Five-Year Evaluation
FCGMA will evaluate the GSP at least every 5 years. This 5-year evaluation will be provided as a written assessment to DWR. The assessment shall describe whether the Plan implementation, including implementation of projects and management actions, are meeting the sustainability goal in the basin. The evaluation will include the following:
 A description of current groundwater conditions for each applicable sustainability indicator relative to measurable objectives, interim milestones, and minimum thresholds  A description of the implementation of any projects or management actions, and the effect on groundwater conditions resulting from those projects or management actions  Revisions, if any, to the basin setting, management areas, or the identification of undesirable results and the setting of minimum thresholds and measurable objectives  An evaluation of the basin setting in light of significant new information or changes in water use, and an explanation of any significant changes  A description of the monitoring network within the basin, including whether data gaps exist, or any areas within the basin are represented by data that does not satisfy the requirements of the GSP Regulations (23 CCR, Sections 352.4 and 354.34[c])  A description of significant new information that has been made available since GSP adoption, amendment, or the last 5-year assessment
 A description of relevant actions taken by the Agency, including a summary of regulations or ordinances related to the GSP
 Information describing any enforcement or legal actions taken by the Agency in furtherance of the sustainability goal for the basin
 A description of completed or proposed GSP amendments  A summary of coordination that occurred between FCGMA and other agencies, if appropriate, in the Subbasin, as well as between FCGMA and other agencies in hydrologically connected basins
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1.2.6.2 GSP Implementation Budget
The primary costs associated with implementing the GSP are anticipated to be connected with the following:
 Data collection, validation, and analysis
 Ongoing data gap analysis and assessments of priorities for filling data gaps o Filling of data gaps
o Operations and maintenance
 Annual report preparation and preparation of the 5-year GSP evaluation  Regional studies for basin optimization, groundwater modeling  Management, administration, and other costs
Data Collection, Validation, and Analysis
FCGMA has historically obtained data from the Ventura County Watershed Protection District (VCWPD) to monitor streamflow, precipitation, groundwater elevation, and groundwater quality throughout the Oxnard Subbasin. Besides VCWPD, entities that monitor groundwater level and groundwater quality in the Oxnard Subbasin include the United Water Conservation District (UWCD), the Cities of Oxnard and Camarillo, PVCWD, and small mutual water companies.

Relevant data collected by these entities is regularly provided to VCWPD, and the data are shared with FCGMA for use in the FCGMA annual groundwater reports. This process will continue, but analysis will now include comparison of collected data against sustainable management criteria established by this GSP.

The majority of water level and water quality data in the Oxnard Subbasin are generated by VCWPD and UWCD. To date, this data sharing has not required expenditures from FCGMA because FCGMA did not control the location or timing of data and sample collection. The existing monitoring schedules and locations are discussed in Chapter 4, Monitoring Networks. It is anticipated that as long as the existing schedules are maintained, VCWPD will continue to host the data for the Oxnard Subbasin and FCGMA will be able to use the data for annual monitoring reports and the 5-year GSP evaluations.

However, to the degree that monitoring schedules and locations will change, a cost-sharing agreement will be developed between VCWPD and FCGMA.

Data Gap Analysis and Priorities
During the initial 5-year period after the GSP is adopted, FCGMA will explore options for filling data gaps identified in this GSP. The primary data gaps identified in the historical data are spatial and temporal gaps in groundwater elevation and groundwater quality measurements. 786
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In order to assess the priorities for filling these gaps, FCGMA plans to review options and potential costs associated with those options to direct funding toward the solutions that are needed most. One option that will be investigated would include adding pressure transducers to existing agricultural wells in the monitoring network. These transducers would record water levels at regular intervals (e.g., hourly) to determine static, or recovered, water levels. The cost for purchasing and installing transducers in agricultural wells must be assessed and incorporated into the cost of GSP implementation. As instrumentation is added to the monitoring network, the annual cost of operations and maintenance will also be factored in to the budget for GSP implementation.

In addition to assessing the need for new instrumentation, the analysis of data gaps and priorities will review the potential cost and need to substitute existing agricultural wells in the monitoring network with dedicated monitoring wells, or install monitoring wells in key areas where there are no appropriate wells to monitor. While monitoring wells are often preferred to agricultural wells, for the time being, the agricultural well data provide a link to historical data. This link is critical in assessing progress toward sustainability. Therefore, the data gap analysis and priorities assessment will review which agricultural wells may need to be substituted and which wells should be retained for ongoing historical comparison.

Annual Report Preparation and Preparation of the 5-Year Evaluation Details of the information that will be included in the annual reports are presented in Section

1.2.6.1, Standards for Plan Implementation. It is currently anticipated that the annual reports will be produced by FCGMA staff and the costs associated with these reports will be incorporated in the annual operating budget of FCGMA.

Every fifth year of GSP implementation and whenever the GSP is amended, the GSA is required to prepare and submit an Agency Evaluation and Assessment Report to the DWR together with the annual report for that year. The tasks associated with preparing this report include updating the water budget, updating the groundwater model, and reassessing the sustainable yield, minimum thresholds, and measurable objectives (see Section 1.2.6.1). Additionally, the evaluation will provide an assessment of the pumping and groundwater conditions. It is currently anticipated that the 5-year evaluation reports will be produced by FCGMA staff with the assistance of consultants and that the costs associated with these reports will be incorporated in the annual operating budget of FCGMA.

Basin Optimization Studies, Groundwater Modeling, and Project Feasibility During the initial 5-year period after the GSP is adopted, FCGMA will explore opportunities to optimize basin management. The work required to assess these opportunities includes implementing and supporting regional studies and groundwater modeling efforts that assess how 787
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to maximize the sustainable yield of the Oxnard Subbasin and adjoining basins. These studies are anticipated to include more detailed feasibility studies of projects that were proposed and modeled for this GSP, as well as an investigation of how the projects will be implemented, the costs associated with project implementation, and potential cost-sharing agreements for these projects.

It should be noted that Chapter 5 of this GSP includes projects that were far enough along in development and/or implementation that meaningful information could be included about their potential to improve sustainable management of the Subbasin. Additional projects may be implemented within the next 20 years to, for example, minimize the need for pumping reductions.

This GSP does not preclude future projects or existing projects that are too early in the stage of development to be included in Chapter 5 from being investigated or undergoing feasibility analysis in the coming years. Relevant information about new projects and/or updates to existing projects described in Chapter 5 will be provided in annual reports and 5-year evaluations.

Current anticipated costs for implementing projects in the Oxnard Subbasin that were analyzed as part of this GSP are presented in Table 1-1.

In addition, it is anticipated that basin optimization studies will be undertaken in the initial 5-year period after the GSP is implemented adopted to assess projects that were not included in this GSP.

This assessment is expected to include an investigation of how adjustments to the location of groundwater production will minimize seawater intrusion in the Oxnard Subbasin, while maximizing the sustainable yield of the combined aquifer systems of the Oxnard Subbasin, the PVB, and the West Las Posas Management Area. Basin optimization investigations are inherently tied to groundwater modeling, which would be conducted to provide the estimated sustainable yield for all scenarios analyzed.

Lastly, as part of the project feasibility analyses, FCGMA anticipates evaluating potential revenue streams for implementing the projects required to optimize basin management. This analysis will include a review of the potential for implementing basin replenishment fees and the costs associated with proposing and passing such fees.

Cost Estimate
The estimated total GSP implementation costs are presented in Table 1-2. The starting cost for monitoring systems, coordination of data collection, obtaining data form other GSAs in the basin is estimated to be $1 million for 2020. Costs were increased annually, using a 2.8% inflation rate, from 2020 to 2040 (Table 1-2). The annual reviews to DWR are anticipated to be included as part of the operations and monitoring costs for FCGMA. The management, administration, and other costs for 2020 are based on the 2019–2020 fiscal year budget, in which these costs are estimated to be $1,455,000.
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The 5-year evaluation costs are anticipated to cover the professional specialty services to evaluate and assess the GSP and perform the additional work necessary to fill data gaps and analyze projects and management actions for the Oxnard Subbasin, as well as for the PVB and LPVB. FCGMA has prepared the GSPs for the entire area of the Oxnard Subbasin, Las Posas Valley Basin, and Pleasant Valley Basin. FCGMA will be responsible for evaluating these GSPs, for each basin, every 5 years.

Cost sharing for these evaluations may be investigated with the other GSAs in each basin in the future. Initial costs for the 5-year evaluation were estimated to be $100,000 per basin, with 2.8% inflation between 2020 and 2024. Costs for 2025 through 2029 were estimated to be $100,000 if the work were performed in 2020, but the costs in the budget account for 2.8% annual inflation between 2020 and 2025. Costs between 2030 and 2033 were calculated from the 2.8% annual inflation on $50,000. Subsequent years were calculated either based on 2.8% inflation on $100,000, or 2.8% inflation on $50,000, depending on whether the year included preparation of a physical report for DWR.

Finally, the estimated implementation costs include a 10% contingency on the total operating and monitoring costs, management administration and other costs, and the 5-year evaluation.

1.2.6.3 Funding Sources
In general, FCGMA plans to fund its basic operations costs using groundwater extraction charges. Surcharges for extractions in excess of an allocation may also be used in carrying out FCGMA’s groundwater management functions. FCGMA collects a groundwater extraction base rate fee of $6 per acre-foot and imposes a surcharge of up to $1,961 for excess extractions.

Together, these pump fees have generated more than $1 million in operating revenues each fiscal year (ending in June) between 2013 and 2016. FCGMA anticipates using this existing revenue structure, along with eventual implementation of a replenishment fee, to fund the GSP implementation and direct costs.

Under SGMA, FCGMA gained additional authority to impose regulatory fees and currently collects a sustainability of fee of $11 per acre-foot in addition to its groundwater extraction fee.

The sustainability fee is projected to generate additional annual revenue of $1,375,000. The sustainability fee will increase to $14 per acre-foot in 2020 and generate an additional $375,000 in annual revenue. Upon adoption of this GSP, FCGMA will have authority to impose replenishment fees and to fund projects and management actions that can influence groundwater supply. Projects to achieve sustainability are anticipated to require funding beyond that generated by the existing extraction and sustainability fees. FCGMA anticipates working with other agencies and stakeholders to understand how individual projects will impact stakeholders and identify the most appropriate funding sources for these projects.
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1.3 DESCRIPTION OF PLAN AREA

1.3.1 Description
The Oxnard Subbasin (the Subbasin; DWR Groundwater Basin 4-004.02) is a coastal alluvial subbasin of the Santa Clara River Valley Groundwater Basin (4-004). It is bounded to the east by the LPVB (4-008), the Camarillo Hills, and the PVB (4-006); to the southeast by the Santa Monica Mountains; to the west and southwest by the Pacific Ocean; and to the north by the Mound (4-004.03) and Santa Paula (4-004.04) Subbasins of the Santa Clara River Valley Groundwater Basin (Figure 1-1, Vicinity Map for the Oxnard Subbasin).

The Oxnard Subbasin is in hydrologic communication, to varying degrees, with the LPVB and PVB to the east, the Mound and Santa Paula Subbasins to the north, and the Pacific Ocean to the west and southwest.

The Oak Ridge and McGrath Faults form the boundary between the Oxnard Subbasin and the Mound and Santa Paula Subbasins to the north (DWR 2016a). The boundary between the Oxnard Subbasin and the LPVB is a jurisdictional boundary that corresponds to property lines and associated water sources. It is parallel and proximal to the surface expression of the Wright Road Fault. The boundary between the Oxnard Subbasin and the PVB is defined by a facies change between the predominantly coarse-grained sand and gravel deposits that compose the Upper Aquifer System (UAS) in the Oxnard Subbasin and finer-grained clay- and silt-rich deposits in the PVB. The southeastern boundary of the Oxnard Subbasin is the contact between permeable alluvium and semi-permeable rocks of the Santa Monica Mountains (SWRCB 1956; DWR 2016a).

The Oxnard Subbasin has historically been divided into two subareas by local practitioners (UWCD 2014). Across most of the Oxnard Plain, the main water-producing aquifers are confined beneath a low-permeability, clay-rich layer that separates the UAS from the topmost unconfined semi-perched aquifer groundwater unit. This clay layer and the semi-perched aquifer are absent in the northeastern area known as the Oxnard Forebay, and as a result, unconfined aquifer conditions exist in the UAS in this area (Figure 1-1).

In this report, to distinguish between features on the land surface and in the subsurface, the term “Oxnard Plain” will be used to refer to the geographic area overlying the Oxnard Subbasin. 790
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Administrative Boundaries
Multiple boundaries have been used to define or manage the Subbasin (Figure 1-2, Administrative Boundaries for the Oxnard Subbasin), including the following:

1. The boundary of the Subbasin defined by DWR in its 2016 Basin Boundary Modification

2. The jurisdictional boundary of FCGMA

3. The boundaries of the Oxnard Forebay historically used by FCGMA

4. The boundary of the Oxnard Subbasin historically used by FCGMA The boundary of the Oxnard Subbasin defined by DWR in its 2016 Basin Boundary Modification extends beyond FCGMA jurisdiction to the southeast, northwest, and northeast (Figure 1-2). The jurisdictional boundary of FCGMA was established based on a vertical projection of the interpreted extent of the FCA, as provided by the Fox Canyon Groundwater Management Agency Act (FCGMA Act) in 1982. The FCA is absent in the areas of the DWR Bulletin 118 boundaries for the Oxnard Subbasin that lie outside of FCGMA jurisdiction (Figure 1-2). The majority of the area that is outside FCGMA jurisdiction but inside the 2016 Subbasin boundary lies within the jurisdiction of the County of Ventura. The County has filed to be the GSA for the Oxnard Basin Outlying Areas (see Appendix A; Figure 1-2). The remaining area outside of FCGMA jurisdiction but within the boundary of the Subbasin currently used by DWR will be managed by CWD, which has filed to be the GSA for the Camrosa Water District–Oxnard Subbasin, which covers the portion of CWD’s service area that lies within the Oxnard Subbasin (Appendix A; Figure 1-2). Table 1-3 presents a breakdown of all GSAs that intersect the boundary of the Oxnard Subbasin defined by DWR in its 2016 Basin Boundary Modification. The 2016 Basin Boundary Modification was used instead of the 2018 Basin Boundary Modification to be consistent with the groundwater model used in this GSP. The County (by Resolution 17-088) and CWD (by Resolution 17-11) have each elected to act as the GSA for portions of the Subbasin not within FCGMA’s jurisdiction (Appendix A). The County and CWD will rely on this GSP and coordinate with the FCGMA, as necessary, to ensure that the Subbasin is sustainably managed in its entirety, in accordance with SGMA.

The external boundary of the Oxnard (4-004.02), Mound (4-004.03), and Santa Paula (4-004.04) Subbasins were adjusted in DWR’s 2018 Basin Boundary Modification process (DWR 2019). The adjustment was made by request of the Mound Basin GSA, who notified FCGMA of the proposed change, which was ultimately approved by DWR in 2019. The purpose of the boundary change was to better align the boundaries of the Mound Subbasin, FCGMA, and the Santa Paula basin adjudication. Compared with the 2016 boundary for the Oxnard Subbasin, the 2018 Basin Boundary Modification aligned the north-northwestern border of the Subbasin with FCGMA’s jurisdictional boundary, resulting in subtraction of 75.2 acres from the Subbasin near the Pacific Coastline south of the Santa Clara River, and the addition of 614.7 acres to the Subbasin in a narrow zone north of the Santa Clara River (DWR 2016a, 2019). 791
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From a technical and sustainable management perspective, the effect of the change in area for the Oxnard Subbasin between 2016 and 2018 is negligible, because the area does not newly include or exclude representative monitoring sites or production wells and does not affect the model domain, boundary conditions, and/or other parameters used in the Ventura Regional Groundwater Flow Model. Therefore, the effect on water budget for the Subbasin would be limited to the inclusion and/or exclusion of model grid cells for inflow and outflow calculations along the northern boundary of the Subbasin. The dimension of the model grid cells (2,000 feet) is greater than the maximum change in distance between the 2016 and 2018 boundaries for the Oxnard Subbasin (1,300 feet or less), which suggests that any difference could be within the margin of error associated with the model grid resolution. Because this change represents just 0.9% of the Subbasin’s total area and is an administrative rather than a scientific/technical boundary modification, and because this GSP was largely completed prior to adoption of the change in 2019, Subbasin condition information presented in this GSP reflects DWR’s 2016 Basin Boundary Modification.

Land Ownership and Jurisdiction
Land within the Oxnard Subbasin is under a variety of municipal, County, state, and federal jurisdictions. The City of Oxnard and Port Hueneme are entirely encompassed by the Oxnard Subbasin. The Cities of Ventura and Camarillo lie primarily outside the Subbasin; however, the cities’ outer edges are crossed by the Subbasin boundary. Land under County jurisdiction outside the incorporated cities composes the majority (55.5%) of the Subbasin’s land area. State agencies that own and/or manage land within the Oxnard Subbasin include the California Department of Parks and Recreation, California State University, and California Department of Corrections and Rehabilitation. Federal land within the Subbasin consists of the Naval Base Ventura County (Naval Construction Battalion Center Port Hueneme and Point Mugu Naval Air Station), which occupies about 10% of the Subbasin’s land area. Finally, The Nature Conservancy owns and manages land along the lower reach of the Santa Clara River and Ormond Beach for conservation purposes. A summary of land ownership and jurisdiction is provided in Table 1-4.

1.3.2 Geography

1.3.2.1 Surface Water and Drainage Features
The dominant surface water bodies in the Oxnard Plain are the Santa Clara River, Revolon Slough, and Calleguas Creek, all three of which drain watersheds that extend beyond the boundaries of the Subbasin. In addition, the relatively flat areas within the Cities of Oxnard and Port Hueneme are drained by several lined drains that discharge directly into the Pacific Ocean (Figure 1-3, Weather Station and Stream Gauge Locations).

The Santa Clara River is close to and generally parallels the northern boundary of the Oxnard Subbasin and discharges to the Pacific Ocean through the Santa Clara River Estuary north of the 792
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Oxnard Subbasin. Flow in the channel infiltrates into sediments overlying the Oxnard Forebay and is a source of recharge to the aquifers in the Subbasin. In addition, UWCD, under permit, diverts surface water from the Santa Clara River at the Freeman Diversion. The diversion, which was constructed in 1991, replaced an earthen diversion that had been in place since 1928. The diversion is located upstream of the Subbasin boundary and discharges Santa Clara River water to infiltration basins overlying the Oxnard Forebay (Figure 1-3). West of the Oxnard Forebay, the Santa Clara River channel overlies a confining clay layer and does not communicate directly with the confined aquifers of the UAS and the Lower Aquifer System (LAS). In this portion of the channel (including the estuary) the semi-perched aquifer, which is located above the uppermost confining clay layer, supplies water to the Lower Santa Clara River (Section 2.1, Introduction to Basin Setting).

Revolon Slough drains the eastern portion of the Oxnard Plain and the western portions of the LPVB and PVB (which are east of the Oxnard Plain) (Figure 1-3). The drainage area of Revolon Slough includes western Camarillo. Flow in the slough is generally southward, parallel to the eastern Oxnard Subbasin boundary, until it joins with Calleguas Creek. Calleguas Creek drains the approximately 250-square-mile Calleguas Creek Watershed to the northeast of the Oxnard Subbasin and crosses the Oxnard Subbasin boundary with the PVB at the base of the Santa Monica Mountains (Figure 1-3). Within the Oxnard Subbasin, Calleguas Creek flows generally southward along the southeastern boundary of the Subbasin and discharges into the Pacific Ocean through Mugu Lagoon near Point Mugu (Figure 1-3). Recharge from surface waters into the Oxnard Subbasin is discussed in Section 2.3.6, Groundwater–Surface Water Connections.

Characterization of Flow
Streamflow records for four active and five inactive streamflow gauging stations (Figure 1-3; Table 1-5) were used to characterize flow in the Santa Clara River (Stations 708, 708A, 723, and 724), in the Revolon Slough Watershed (Stations 776, 776A, 780, and 782), and in Calleguas Creek (Station 805).

Some reaches of the Santa Clara River are typically dry in dry weather (for example, at Stations 708 and 708A; Figure 1-3). Sources of dry-weather flow to Revolon Slough include discharge from private tile drains in the Oxnard Plain. Although dry-weather flow is observed in some portions of Calleguas Creek (i.e., at Station 805), in other reaches, Calleguas Creek is dry in dry weather (VCWPD 2009). The primary sources of dry-weather flow to Calleguas Creek are two wastewater treatment plants: the Hill Canyon Wastewater Treatment Plant, operated by the City of Thousand Oaks, which discharges to Arroyo Conejo, a tributary to Arroyo Santa Rosa; and the Camarillo Sanitary District Wastewater Treatment Plant, operated by the City of Camarillo, which discharges to Conejo Creek. Both Arroyo Santa Rosa and Conejo Creek are tributaries of Calleguas Creek. Irrigation water from agriculture and/or landscaping may also serve as a source of flow in all three channels during some parts of the year.
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In the Santa Clara River, the available stream flow record within the Subbasin extends from 1927 to 2014, with a gap from 1932 to 1950 (Figure 1-4, Average Daily Flows [ADF] and Monthly Minimum ADF in Oxnard Surface Waters [A]). Peak flow typically occurs between November and April of any given water year and baseflow generally falls to 0 cubic feet per second (cfs) between July and September, except in reaches above and below the Oxnard Forebay. There are some exceptions, particularly in 1980, 1983, 1993, 1998, and 2005, when flow continued through the summer months.

The highest gauged flow was 92,300 cfs in March 1969 (Figure 1-4[A]).

In the Revolon Slough, the available streamflow record within the Subbasin extends from 1979 to 2014. Peak flow typically occurs between December and March of any given water year, and baseflow tends to drop to between 2 and 25 cfs between July and September. The highest gauged flow was 2,870 cfs in January 2005 (Figure 1-4[B]).

In Calleguas Creek, the available streamflow record within the Subbasin extends from 1968 to 2014. Peak flow typically occurs between December and March of any given water year, and baseflow tends to drop to between 5 and 13 cfs between July and September. The highest gauged flow was 9,686 cfs in March 1983 (Figure 1-4[C]).

To quantitatively assess changes in baseflow, all streamflow gauges were assigned a minimum average daily flow for each month of the record, and this monthly minimum was plotted in Figures 1-4(D) through 1-4(F). In Calleguas Creek, flows from 2005 to 2015 were lower than those in the 1980s and 1990s. The low flows correspond with a period of below-average rainfall associated with the recent drought. Because surface water in Calleguas Creek and its tributaries is diverted by property owners and by CWD and delivered as a water supply in lieu of groundwater pumping, decreased flow in Calleguas Creek will affect groundwater management in the Subbasin. On the Santa Clara River, decreased flows in the past 5 years have impacted artificial recharge operations and other management decisions made by UWCD.

1.3.2.2 Current, Historical, and Projected Climate
Current Climate
The climate of the Oxnard Plain is typical of coastal Southern California, with average daily temperatures ranging generally from 50°F to 78°F in summer and from 40°F to 75°F in winter, as measured at the California Irrigation Management Information System (CIMIS) weather station in Oxnard, which was active from October 2001 through April 2017 (CIMIS 2018). Typically, approximately 85% of precipitation in the Ventura County region falls between November and April (Hanson et al. 2003).
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Records of rainfall were collected from VCWPD weather stations located within the boundary of the Oxnard Plain (12 active and 11 inactive; Figure 1-3, Figure 1-5 (Oxnard Plain Annual Precipitation), and Table 1-6). Annual precipitation varies from gauge to gauge (Figure 1-5 and Table 1-6).

Evaporation as pan evaporation rate is measured at one VCWPD weather station within the Oxnard Plain (Station 239, El Rio–UWCD Spreading Grounds). The Station 239 evaporation record begins in 1972 and ends in 2016. Monthly average evaporation ranges from 3.7 inches in January to 7.2 inches in July, with an average total annual evaporation of 63.0 inches.

Evapotranspiration is measured at CIMIS Station 156, located on the River Ridge Golf Course, approximately 800 feet south of the Santa Clara River and 725 feet west of North Ventura Road.

The monthly average evapotranspiration calculated for data collected between 2001 and 2017 using the Penman–Monteith equation at Station 156 ranges from 2.01 inches in December to 5.12 inches in July. The average total annual evapotranspiration is 44.93 inches.

Historical Climate Trends
In order to characterize rainfall variability in the Oxnard Plain over the past century, two stations whose combined records cover the entire period were selected: Stations 032 and 168 (Figure 1-3). Station 032 (Oxnard–Water Department) is located approximately 1.5 miles east of Station 168 (Oxnard Airport).

Precipitation records can vary based on several factors, including geographic location, the type of gauge used to measure precipitation, and the physical characteristics of the area surrounding a measurement site. Therefore, in order to examine how rainfall recorded at these two stations compared to the other stations, correlation coefficients (R) were calculated for the period of time in which the station records overlap. The correlation coefficients between all pairs of station records, excepting pairs that included Stations 223, 273, 412, and 503, exceeded 0.9. Stations 273, 412, and 503 have less than 8 years of overlapping data, which may explain the poorer correlation between these sites and Stations 032 and 168. The low correlation between Station 223, which is located near the southwest corner of the Oxnard Plain near Point Mugu, and Stations 032 and 168 is due in part to anomalously low values recorded at Station 223 in some years in the 1950s, 1960s, and 1970s. Because the record from Station 223 does not correlate with the records from any other station in the area, this station cannot be used to typify trends in the Oxnard Plain.

The variability in the records of precipitation measured at Stations 032 and 168 is similar to that measured at the other precipitation stations, and can be used to characterize the precipitation trends in Oxnard Plain over the 113-year period from 1903 to 2015 (Figure 1-5).

The long-term trend record was based on the record from Station 032 for the period from 1902 to 2003. After 2003, no data are available for Station 032. Therefore, from 2003 to 2016, the annual precipitation value recorded at Station 168 was used to predict a value for the location of Station 795
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032, based on a linear regression of the annual precipitation values in the 46 years of overlap (1957–2002) in the records for Stations 032 and 168 (see formula below).

Station 032 (inches) = 1.0127 * Station 168 (inches) + 0.0011 (R2 = 0.9766) The root-mean-squared error (RMSE) between the observed annual precipitation at Station 032 and the predicted precipitation using Station 168 was 1.3 inches per year. The bias was −0.00058 inches. Thus, some uncertainty is introduced by extending the Station 032 record using Station 168. However, this slight uncertainty does not outweigh the benefit of being able to use the resulting 113-year record to characterize long-term climate trends.

Based on this long-term record, the calculated mean annual precipitation in the central Oxnard Plain is 14.4 inches (Figure 1-6, Long-Term Precipitation Trends in the Oxnard Plain). For each water year in the record, the total annual precipitation was compared to the long-term mean annual precipitation in order to calculate the cumulative departure from mean precipitation (Figure 1-6).

Historical drought periods were defined as a falling limb on the cumulative departure from the mean curve (Figure 1-6). Based on the historical record, a drought in the Oxnard Plain can be defined as a period of years in which the area experiences no more than one consecutive year of above-average precipitation and at least 24 inches of cumulative precipitation deficit (see Table 1-7 and Figure 1-6).

The century-long precipitation record demonstrates that drought cycles have frequently impacted the Oxnard Plain. The average drought duration in the past century was 8.2 years, and the average cumulative rainfall deficit during the droughts was −30.25 inches. The duration of periods of average or above-average rainfall was rarely more than 10 years. In this historical context, the approximately 20-year period in the 1990s and 2000s constitutes an unusually long wet period (Figure 1-6). Consequently, planning for drought cycles in the coming decades will be an integral component of water resources management.

The FCGMA contracted and received evapotranspiration data collected at private weather stations located in the Oxnard Subbasin during the period 1992 to 2013. The number of weather stations in the Subbasin fluctuated over the years. The data collected from the private weather stations were used for determining the annual irrigation efficiency allocation during the period 1992 to 2013.

These data are available from FCGMA Board Meeting Agenda packets and were reported to FCGMA on a monthly basis.
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Projected Climate
The literature review conducted in support of the U.S. Bureau of Reclamation’s Los Angeles Basin Stormwater Conservation Study Task 3.1 Report found that the following changes are anticipated in Southern California due to global climate change (Bureau of Reclamation 2013):
 Increased temperature (1°C to 3°C)
 Increased evaporation rate
 Decrease in annual precipitation (2% to 5%)
 Increase in extreme precipitation events
Future climate conditions were modeled for the Oxnard Subbasin using climate change factors provided by DWR. The impacts to the future water budget are discussed in more detail in Chapter 2, Basin Setting.

1.3.2.3 Historical, Current, and Projected Land Use
Historical land uses on the Oxnard Plain were determined based on review of data from the Southern California Association of Governments (SCAG), which has mapped more than 105 land use categories to a minimum 2-acre resolution for the years 1990, 1993, 2001, and 2005 (SCAG 2005). Current land uses within the Oxnard Plain were determined based on review of the General Plan land use map for Ventura County (VCPD 2015), and are shown on Figure 1-7, Land and Water Use. Existing land use patterns and trends are expected to continue, and are described based on information contained in General Plan documents.

The majority of the Oxnard Plain consists of unincorporated areas of Ventura County, though it also encompasses nearly all of the Cities of Oxnard and Port Hueneme. Land use on the Oxnard Plain consists of 47% agriculture, 47% urban uses, and 6% vacant/open space (Table 1-8). About 83% of the agricultural uses consist of orchards, cropland, and improved pasture land with the remaining 17% consisting of nurseries, horse ranches, and other uses (Table 1-8). The primary crops grown in the Oxnard Plain are strawberries, raspberries, celery, peppers, kale, cut flowers, and nursery stock (VCFB 2016). Urban and residential land uses are concentrated in Oxnard and Port Hueneme. Federal lands consist of two Naval Base Ventura County operations within the Oxnard Subbasin, Point Mugu and Port Hueneme, and the Channel Islands Air National Guard Station. The Naval Base Ventura County was formed in 2000 through the merger of Naval Air Station Point Mugu (located in the southern portion of the Oxnard Subbasin in unincorporated Ventura County) and Naval Construction Battalion Center Port Hueneme (located in the westcentral part of the Oxnard Subbasin within the City of Port Hueneme along the coast). Currently, there are about 19,000 military, civilian, and contract personnel working or stationed at Naval Base Ventura County (City of Oxnard 2011).
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Recreational land uses on the Oxnard Plain consist of state and local beaches, golf courses, and community parks in Oxnard and Port Hueneme. Open space (i.e., not consisting of agricultural, military, or urban uses) is limited to the Santa Clara River corridor, beaches, and lagoons. Table 1-8 shows the County General Plan land uses within the Oxnard Plain, tabulated by area in acres and by percentage of total area.

With the exception of several high-rise buildings in north Oxnard, the City of Oxnard is characterized by one- or two-story residential and commercial buildings and several industrial areas (City of Oxnard 2011). Most of Oxnard’s higher-intensity development lies adjacent to primary thoroughfares, such as Highway 101, Gonzales Road, Rose Avenue, Rice Avenue, Oxnard Boulevard, Hueneme Road, Ventura Road, Victoria Avenue, and Saviers Road, and in the central business district (City of Oxnard 2011). Growth is directed into one of Oxnard’s 14 Specific Plans, which are in various stages of planning or buildout. City of Oxnard projects currently in the planning, permitting, or construction stages consist of 19 residential projects (greater than 50 units), 18 commercial projects, and 6 industrial projects (City of Oxnard 2016a). The largest planned development consists of the Teal Club Specific Plan (located west of Ventura Road between Doris Avenue and Teal Club Road), where up to 990 residential units are envisioned (City of Oxnard 2016a).

In the future, agricultural preservation and open space land use policies are expected to limit the rate and reach of “greenfield” development and direct growth through infill development and zoning policies that allow higher-density and mixed-use development (VCPD 2015).

Furthermore, large-scale development is highly restricted in the California Coastal Zone, so development is likely to be concentrated on the urban fringes of Oxnard and Port Hueneme that are outside the coastal zone. For unincorporated areas within the Oxnard Plain, the Ventura County General Plan Environmental Impact Report identifies the widening of roads as a potential growth-inducing effect of the General Plan land uses and policies, as well as policies that allow for the creation of substandard-sized parcels for farmworker housing complexes and an increase in allowable building coverage for farmworker housing complexes in Agricultural and Open Space designations (VCPD 2005). Demographics and population growth within the Oxnard Plain are addressed in Section 1.3.2.4.

1.3.2.4 Historical, Current, and Projected Demographics There are several sources of population data for the Oxnard Plain, most of which are derived from decennial census counts, which last occurred in 2010. Sources of population information are as follows:
 U.S. Census Bureau: The U.S. Census Bureau conducts a census count every 10 years.

Census data are gathered by tracts, blocks, and census-designated places. Census tracts were intersected with the Oxnard Plain boundary to determine the population overlying the 798
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Oxnard Subbasin for 2010. Census tracts that intersected the boundaries of the Oxnard Plain were area-weighted to determine the population that falls within the Oxnard Plain.  City and County General Plans: The Cities of Oxnard and Port Hueneme and the County of Ventura gather data on development, growth, and land use patterns, and make population estimates in conjunction with census data. The cities’ and county’s general plans and websites were reviewed for historical and current population data.  Southern California Association of Governments: SCAG is the nation’s largest metropolitan planning organization, representing 6 counties, 191 cities, and more than 18 million residents. SCAG produces demographics data and growth forecasts for the entire Southern California region.

At a countywide level, population growth is skewed toward incorporated cities. The population distribution within Ventura County is the result of a 1969 County–City agreement, called the Guidelines for Orderly Development, which directs urban-level development to incorporated cities in Ventura County (VCPD 2015). That agreement limits urban-level development and services within unincorporated areas. The total increase in population within unincorporated areas in Ventura County was only 1.9% from 2000 to 2010, whereas population in the cities increased by

10.4% over the same period.

Table 1-9 shows the past, current, and projected population for Ventura County, the Cities of Oxnard and Port Hueneme, and the Oxnard Plain. The population of the Oxnard Plain is estimated to have been 237,871 in 2010, based on census data. The population of the City of Oxnard is over 200,000 residents, as of 2015, with an average household size of 3.99 (City of Oxnard 2011; SCAG 2016). The City of Port Hueneme has about 22,000 residents and an average household size of

2.99 (City of Port Hueneme 2016a). The population of unincorporated areas within the Oxnard Plain is less than 10% of the total population of the Oxnard Plain.

The aforementioned population information is limited to the population that resides within the Oxnard Subbasin boundary. It should be noted that the City of Ventura overlies a portion of the Oxnard Subbasin, but this portion consists of commercial, recreational, and industrial land uses, with a negligible permanent population. The City of Ventura relies on groundwater from the Oxnard Plain for part of its groundwater supply. The population for the City of Ventura’s water service area, as reported in its 2015 UWMP, is 112,412 (City of Ventura 2016).

1.4 EXISTING MONITORING AND MANAGEMENT PLANS
Over the past few decades, multiple agencies have implemented programs to monitor and manage water within the Oxnard Subbasin. Local and state agencies have worked together and with stakeholders to develop management strategies and monitoring programs. Table 1-10 and Table 799
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1-11 summarize the monitoring and management programs, projects, and strategies that are currently in effect.

1.4.1 Monitoring Programs
Table 1-10 provides a summary of existing monitoring programs. It is subdivided into monitoring programs that are primarily for surface water and those primarily for groundwater. These monitoring programs are anticipated to continue, independent of the development of this GSP; however, the data from these programs will continue to be used to help assess groundwater conditions in the Oxnard Subbasin. Specifically, groundwater elevation data collected by VCWPD at key wells throughout the Subbasin will be compared to the minimum thresholds and measurable objective established in Chapter 3, Sustainable Management Criteria, of this GSP. VCWPD will continue to host the data for the Oxnard Subbasin and FCGMA will use the data for annual monitoring reports and the 5-year GSP evaluations (Section 1.2.6, Groundwater Sustainability Plan Implementation and Cost Estimate).

1.4.2 Management Programs
Table 1-11 provides a summary of management programs, projects, and strategies. Similar to Table 1-10, it is subdivided into projects that address primarily surface water and those that address primarily groundwater. It also contains a third category, “other,” for projects that address both surface water and groundwater or an additional parameter.

Table 1-11 indicates whether each project or program is associated with conjunctive use. As used herein, “conjunctive use” applies to programs, projects, and strategies that meet the 2003 Bulletin 118 definition of the term: “Conjunctive management in its broadest definition is the coordinated and combined use of surface water and groundwater to increase the overall water supply of a region and improve the reliability of that supply” (DWR 2016a). For example, CWD provides reclaimed wastewater from the Hill Canyon WWTP diverted from Conejo Creek to its non-potable customers in the Arroyo Santa Rosa Valley Basin and the PVB and to PVCWD for delivery to agricultural users in the Oxnard Subbasin and PVB, thereby reducing the amount of groundwater pumped from these basins (FCGMA 2014a). For a description of some of the most important projects and programs, see Section 1.5, Existing Conjunctive-Use Programs.

Due to the overlapping jurisdictions of the agencies that manage groundwater resources, there are many programs that occur within the Subbasin or benefit multiple basins. Therefore, Tables 1-10 and 1-11 include a column (“Multi-Basin Program”) that lists the basins in which the programs are conducted or those that benefit from each program.
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1.4.3 Operational Flexibility Limitations
Operational flexibility is a key consideration in integrated water resource management because it helps water purveyors adapt to known legal, operational, and environmental constraints, and plan for an uncertain future, especially as it relates to drought resiliency and the effects of climate change. Operational flexibility can be measured over a given time horizon and/or geographic scale (e.g., water district service area) as the difference between available water supply and service area demand. Operational flexibility is maximized when a water purveyor has a large variety of sources in a water supply portfolio, when it has local control over such sources, and when such sources are connected to each other (i.e., conjunctively managed). On a general statewide scale, water purveyors are increasingly looking to minimize reliance on imported water supplies by promoting stormwater recharge, maximizing wastewater recycling, and sustainably developing local sources of water.

For the Oxnard Subbasin, water purveyors collectively draw from a combination of sources— including local surface water, groundwater, imports from the State Water Project (SWP), and increasingly, recycled water—which differ in terms of the volume available, area served, timing of peak availability, and reliability. Climate and regulatory constraints (e.g., water quality standards, water rights, and minimum environmental flows) have historically had a greater impact on the availability of surface water supplies. Groundwater sources with adequate water quality were historically limited only by the capacity of production wells accessing the aquifer until 1991, when FCGMA initiated a groundwater allocation reduction system. With the passage of SGMA and the sustainable management criteria established in this GSP (Chapter 3), once adopted, groundwater extraction will be further limited by minimum thresholds established for each sustainability indicator. FCGMA has exercised its authority to limit groundwater production since 1983, and thus has managed the basin in an effort to avoid critical overdraft. Because in 2015 the State Department of Water Resources listed the Oxnard Subbasin as being in a state of Critical Overdraft, the sustainable management criteria adopted in this GSP may limit operational flexibility by further reducing allowable groundwater production.

The GSP complements and enhances existing projects and programs currently in place to maximize beneficial use of water resources and increase operational flexibility within the Oxnard Plain and within FCGMA jurisdiction as a whole. Existing water monitoring and management activities are described in Tables 1-10 and 1-11. Because the basins are all interconnected either physically or through water sources, the opportunity for operational flexibility exists and has been used by FCGMA and local water agencies. Examples of projects that have increased operational flexibility within the Oxnard Plain include the City of Oxnard’s Groundwater Recovery Enhancement and Treatment (GREAT) Program and the Oxnard–Hueneme (OH) Pipeline and the Freeman Diversion Project, both operated by UWCD (Table 1-11). 801
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Despite the coordination of projects and programs within the Oxnard Subbasin, limits to operational flexibility remain. These limits include constraints imposed by interaction with other regulatory programs, including the federal Endangered Species Act and the Recycled Water Policy (2009, amended 2013) that was adopted by the State Water Resources Control Board. The Recycled Water Policy intends to encourage the safe use of recycled water by recognizing its benefits, establishing statewide recycled water goals and targets, clarifying regulatory agency roles and permitting approaches for various types of recycled water projects, and establishing an approach to avoid or minimize potential adverse consequences (e.g., excessive salts, nutrients, and/or constituents of emerging concern). For example, the policy requires that local water and wastewater entities prepare Salt and Nutrient Management Plans (SNMPs) for the groundwater basin in which they operate. The SNMP for the Lower Santa Clara River, which includes the Oxnard Forebay, has been accepted by the Los Angeles Regional Water Quality Control Board (LARWQCB), and the SNMP for the Oxnard Plain and Pleasant Valley Basins has been submitted to the LARWQCB (VCWPD 2015; City of Oxnard 2016b).

UWCD has prepared a Multiple Species Habitat Conservation Plan as part of its application for incidental take permits under Section 10(a)(1)(B) of the federal Endangered Species Act (UWCD 2018). The Multiple Species Habitat Conservation Plan specifies conditions under which flow diversions from the Santa Clara River would be allowed. The diverted flow at the Freeman Diversion, one of the oldest and most important sources of supply to the Oxnard Subbasin, is used to recharge groundwater and provided for in-lieu use in both the Oxnard Subbasin and the PVB.

The operational flexibility provided by this project is constrained by habitat requirements for the federally endangered Southern California steelhead (Oncorhynchus mykiss) in the Santa Clara River. Climate fluctuations and future climate may also impact the quantity of water diverted from the Santa Clara River. Currently, the project permit limits access to flows. Water diversion is primarily during the recession of a large storm event and during conditions allowed per National Marine Fisheries Service diversion constraints.

In addition to local projects, parts of the Oxnard Plain depend on imported water from the SWP.

Such supplies have been, and may continue to be, limited by climate, infrastructure, and increased commitment for environmental and supply purposes (see Section 1.6.2, Urban Water Management Plans, under Calleguas Municipal Water District UWMP).

1.5 EXISTING CONJUNCTIVE-USE PROGRAMS
In the California Water Plan, DWR (2013) describes conjunctive use as follows: “Conjunctive management or conjunctive use refers to the coordinated and planned use and management of both surface water and groundwater resources to maximize the availability and reliability of water supplies in a region to meet various management objectives. Surface water and groundwater resources typically differ significantly in their availability, quality, management needs, and 802
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development and use costs. Managing both resources together, rather than in isolation, allows water managers to use the advantages of both resources for maximum benefit. Conjunctive management thus involves the efficient use of both resources through the planned and managed operation of a groundwater basin and a surface water storage system combined through a coordinated conveyance infrastructure.”
Due to the history of interagency collaboration on groundwater management within FCGMA jurisdiction on the Oxnard Plain, multiple conjunctive-use programs are currently operational.

These are identified and described in Table 1-11, as introduced in Section 1.4, Existing Monitoring and Management Plans. Some of the most important of these projects and programs are described in this section. The GSP will occur in conjunction with and build upon existing and planned conjunctive use programs in the Subbasin.

UWCD Freeman Diversion Project. The UWCD Freeman Diversion Project is a critical component of water supply within the Oxnard Subbasin. Its predecessor was constructed in 1927 as a series of earthen levies that diverted water from the Santa Clara River, which were washed out and replaced after large flows. The current project, constructed in 1991, diverts on average more than 62,000 acre-feet per year (AFY). About 75% of the water diverted has been sent to spreading basins within the Oxnard Forebay for groundwater recharge. Water from the project is also delivered to the Oxnard Subbasin and PVB through the Pumping Trough Pipeline and Pleasant Valley Pipeline, which supply water for non-potable applications (see Table 2-10, Summary of Water Deliveries). The water provided by the Freeman Diversion Project offsets groundwater production in coastal areas of the Subbasin, thereby helping to alleviate seawater intrusion. One of the projects and management actions identified in this GSP (Chapter 5) would build upon the existing facilities by increasing the Freeman Diversion Project’s capability to divert surface flows (by capturing higher flow rates with higher sediment loads) and by developing additional recharge capabilities (using two former gravel mines).

City of Oxnard Advanced Water Purification Facility. The City of Oxnard’s Advanced Water Purification Facility (AWPF) is part of the City of Oxnard’s GREAT Program, which focuses on using existing water resources more efficiently. As the key project of the GREAT Program, the AWPF provides the City with Title 22 recycled water source that can be used for landscape irrigation, agriculture, industrial process water, and groundwater recharge. The AWPF is designed to initially treat approximately 8 to 9 million gallons per day (mgd) of secondary effluent and produce 6.25 mgd (7,000 AFY) of product water for reclaimed water uses with infrastructure in place to ultimately produce 25 mgd (28,000 AFY) of product water for reuse. The main treatment processes consist of microfiltration, reverse osmosis, and ultraviolet disinfection using advanced oxidation. Several of the projects and management actions identified in this GSP (Chapter 5) could build upon the GREAT Program by expanding the AWPF’s capacity, increasing utilization of the recycled water in lieu of groundwater for irrigation.
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CMWD SWP Deliveries. SWP deliveries are an important source of water within the Oxnard Subbasin. Supplied by CMWD, the vast majority of SWP water is delivered to and used by the City of Oxnard, with minor amounts used by the Port Hueneme Water Agency (PHWA). CMWD treats SWP water to potable standards and delivers it to M&I customers within its service area (see Section 2.4, Water Budget, for a discussion of this in the context of the water budget, including Table 2-10). In addition, up to 5,000 AFY of the Ventura County SWP allocation may be delivered to Lake Piru and later released for percolation or diversion at the Freeman Project. Note that CMWD is a member agency of the Metropolitan Water District of Southern California (MWD), which supplies water from a number of sources, including the Colorado River. One of the management actions to be implemented by FCGMA will be to reduce groundwater extraction allocations over time to a rate that will prevent net seawater intrusion after 2040. Reduced groundwater allocations may put increased pressure on water purveyors to use the maximum SWP allocations available, which are already highly limited by climate and competing demands.

However, other projects and management actions in the GSP—including temporary agricultural land fallowing, expansion of recycled water sources and reach, and better utilization of existing and new stormwater recharge facilities—are expected to minimize this potential effect.

Fox Canyon Groundwater Management Agency Programs. FCGMA has been charged with groundwater management for decades and implements several programs that encourage efficient use of groundwater, new water sources, and brackish groundwater. Most programs apply to the entire FCGMA jurisdiction, but some management programs apply to specific areas. In addition to programs and ordinances that require reporting and fees for groundwater use, FCGMA implements a groundwater storage credit program that provides groundwater credits for surface water or imported water delivered equal to the amount of water that was used in lieu of pumping groundwater and that could have been used for groundwater recharge (spreading or injection).

By Resolution 2014-01, FCGMA approved the Conejo Creek Water Pumping Program involving CWD and PVCWD using the Conejo Creek Diversion (Conejo Creek Project). The Conejo Creek Project provides for the use of recycled water produced by the Hill Canyon Wastewater Treatment Plant in Thousand Oaks within the PVCWD service area through CWD. CWD diverts recycled water discharged to Conejo Creek and delivers it to the PVCWD service area for use in lieu of pumping. The FCGMA resolution allows the PVCWD to transfer credits generated by using recycled water in lieu of groundwater pumping within its service area to CWD. If monitoring data indicate that the Subbasin will support it, the resolution provides for extraction of up to 4,500 acrefeet (AF) from CWD-owned wells in an amount equal to the volume of recycled water delivered by PVCWD in lieu of pumping. However, flows from the Hill Canyon WWTP have decreased in response to conservation programs and are expected to decrease further in the future, thus reducing the potential yield of the project. Diversions of surface water on Conejo Creek prior to 2002 were estimated to average 2,450 AFY from 1985 to 2002 (see Chapter 2 of this GSP). 804
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FCGMA approved an ordinance to establish an allocation system for the Oxnard Subbasin and PVB on October 23, 2019. The purpose of this ordinance is to facilitate adoption and implementation of the GSP and to ensure that the Oxnard Subbasin and PVB are operated within their sustainable yields. It is not the purpose of the ordinance to determine or alter water right entitlements, including those that may be asserted pursuant to California Water Code Sections 1005.1, 1005.2, or 1005.4. A copy of this ordinance is included in Appendix A.

1.6 LAND USE ELEMENTS OR TOPIC CATEGORIES OF

APPLICABLE GENERAL PLANS
SGMA requires that the GSP include a description of the consideration given to the applicable county and city general plans and the various adopted water-resources-related plans and programs and an assessment of how the GSP may affect those plans (California Water Code, Section 10727.2[g]). In addition to these elements, the GSP may include processes to review land use plans and efforts to coordinate with land use planning agencies to assess activities that potentially create risks to groundwater quality or quantity (California Water Code, Section 10727.2[g]). Several kinds of land use plans contain provisions that affect water use and sustainability within the Oxnard Subbasin.

Sustainable management of the FCGMA basins and the SGMA legislation require that the provisions of these plans be considered and coordinated in the development of DWR requires that the GSP include a summary of these plans and a description of how these plans may change water demands or affect FCGMA’s ability to achieve sustainability and how the GSP addresses these potential effects, and how the GSP may affect the water supply assumptions made in these plans (DWR 2016b, Sections 354.8[f] and 354.8[g]). The California Water Code requires that the GSP include processes to review land use plans and coordinate with planning agencies related to groundwater issues (California Water Code, Section 10727.2). Plan types relevant to FCGMA jurisdiction and individual basins within it include county and city General Plans and associated area-specific and community plans and urban water management plans (UWMPs). There are no agricultural water management plans applicable to the Oxnard Subbasin because none of the water purveyors serve more than 25,000 irrigated acres within the Subbasin (excluding recycled water deliveries). The CWD has a 2015 Agricultural Water Management Plan, and although the southern end of CWD’s service area extends into the Oxnard Subbasin near California State University Channel Islands, its agricultural service area occurs outside the Subbasin (CWD 2017).

California state law requires that cities and counties prepare and adopt a “comprehensive longterm general plan for the physical development of the county or city” and that “elements and parts [of the plan] comprise an integrated, internally consistent and compatible statement of policies for the adopting agency” (California Government Code, Sections 65300 and 65300.5). Among the required elements of the plan is the conservation, development, and utilization of water developed in coordination with groundwater agencies such as FCGMA (California Government Code, Section 65302[d][1]).
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The Urban Water Management Planning Act of 1983 requires urban water suppliers to report on water sources, deliveries, demand, and efficiency, as well as performing water shortage contingency planning. Such plans are to be updated every 5 years (in years ending in 0 and 5) and submitted to DWR. The Urban Water Management Planning Act applies both to urban retail suppliers that provide potable municipal water to more than 3,000 end users or 3,000 AFY and to urban wholesale water suppliers that provide more than 3,000 AFY at wholesale (DWR 2016c).

The applicable codes have been modified multiple times to include various provisions for waterrelated reporting.

For more than three decades, FCGMA has participated in the management of water within its jurisdiction. Such management includes oversight of many aspects of groundwater production and use, as well as coordination with all other entities responsible for water supply and land use issues.

Because of these long-term relationships, many of the plans described in this section are consistent with the goal of sustainable groundwater management over the planning and implementation horizon. Due to the high level of coordination among agencies within the Oxnard Plain and FCGMA jurisdiction, it is anticipated that water demand among land uses managed by City and County jurisdiction, as well as water customers served by water purveyors, will be monitored and managed in a manner consistent with the provisions of SGMA and this GSP.

The following sections contain a description of the land use and water management plans that are applicable to water planning within the Oxnard Plain, a discussion of the consideration given to the land use plans, and an assessment of how the GSP may affect those plans. The plans included were selected as the plans with the most salient information relating to sustainable management. However, this is not intended to be a comprehensive list; other plans that include information pertinent to water management in the Oxnard Subbasin include the City of Port Hueneme UWMP, PHWA UWMP, MWD UWMP, the City of Oxnard General Plan, and the Naval Base Ventura County Joint Land Use Study (City of Port Hueneme 2016b; PHWA 2016; MWD 2016; City of Oxnard 2011; NBVC 2015). These plans are discussed in brief in Section 1.6.3, Additional Plan Summaries.

1.6.1 General Plans
General plans are considered applicable to the GSP to the extent that they may change water demands within the Oxnard Subbasin or affect the ability of the GSA to achieve sustainable groundwater management over the planning and implementation horizon. General Plans applicable to the Oxnard Subbasin are (1) the Ventura County General Plan, (2) the City of Oxnard 2030 General Plan, and (3) the 2015 General Plan and Local Coastal Program for the City of Port Hueneme. Small parts of the City of Ventura and City of Camarillo partially overlap the Subbasin, but implementation of their general plans are expected to have a negligible effect on 806
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implementation of the GSP within the Oxnard Subbasin. The areas of Ventura and Camarillo that extend into the Subbasin are already built out or zoned as agriculture and open space.

FCGMA staff has participated on the Ventura County General Plan Update Water Element Focus Group and continues to work with Ventura County planning staff to ensure that the GSP and the General Plan Update are mutually consistent. Furthermore, the FCGMA Board includes a representative for both the County and all the incorporated cities within FCGMA’s jurisdiction, ensuring representation and coordination between the GSA, the County, and the incorporated cities.

Based on the timing of the adoption of the General Plan Update and the GSP, the GSA will be subject to the following California Government Code sections pertaining specifically to the coordination of planning and SGMA-related documents:
 California Government Code, Section 65350.5 – requires that the planning agency review and consider GSPs prior to General Plan adoption.
 California Government Code, Section 65352 – requires that prior to adoption of a General Plan Update, the legislative body must refer the plan to the GSA for review.  California Government Code, Section 65352.5 – requires that the GSA provide the current version of the GSP to planning agencies preparing to update or adopt the General Plan.

All existing general plans and future updates undergo an analysis of environmental impacts under the California Environmental Quality Act (CEQA). In addition, all discretionary projects proposed within the Oxnard Subbasin under municipal, County, and/or state jurisdiction are required to comply with CEQA. In 2019, the Governor’s Office of Planning and Research released an update to the CEQA Guidelines that included a new requirement to analyze projects for their compliance with adopted GSPs. Specifically, the applicable significance criteria include the following:
 Would the program or project substantially decrease groundwater supplies or interfere substantially with groundwater recharge such that the project may impede sustainable groundwater management of the basin?
 Would the program or project conflict with or obstruct implementation of a water quality control plan or sustainable groundwater management plan? Therefore, to the extent general plans allow growth that could have an impact on groundwater supply, such projects would be evaluated for their consistency with adopted GSPs and for whether they adversely impact the sustainable management of the Subbasin. Under CEQA, potentially significant impacts identified must be avoided or substantially minimized unless significant impacts are unavoidable, in which case the lead agency must adopt a statement of overriding considerations. 807
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Ventura County General Plan
Plan Description
The Ventura County General Plan (VCPD 2015) applies to the County as a whole and includes areaspecific plans for distinct unincorporated areas. For example, the El Rio/Del Norte Area Plan includes policies to (1) protect the Oxnard Forebay Basin and its recharge area within the El Rio/Del Norte area in order to protect groundwater resources and (2) ensure that sewage treatment facilities provide maximum feasible protection and/or enhancement of groundwater resources. The County General Plan was last amended in October 2015. However, the County Planning Department is now undertaking a comprehensive update of the plan, thereby providing an immediate opportunity for coordination between FCGMA (as the GSA) and the County Planning Department, as required by SGMA.

The comprehensive update of the County General Plan is due to be completed by mid-2020 and will have a planning horizon of 20 years.

How the Plan May Affect Sustainable Water Management
Because General Plans and the associated elements define long-term policy related to community growth, development, and land use, General Plans are integral to the implementation of sustainable water management. The County General Plan is in the process of undergoing a comprehensive update, which provides the opportunity for consistency in regard to the relevant areas of the County General Plan and the GSP. Areas where FCGMA will coordinate with the County include the following:
 The compatibility of County land use with the goals and requirements of SGMA and groundwater sustainability. This includes County programs and policies for the protection or redesignation of urban, agriculture, and open space for the purpose of reducing or adjusting groundwater use, recharge, or groundwater quality.  The consistency of discretionary development as it pertains to the FCGMA basins’ water resources.
 The development of thresholds by the County for development within available water supply limits as determined by the GSPs for the FCGMA basins.  Coordinated water-related monitoring programs within the FCGMA basins.  The inclusion of land subsidence, drought, and point-source pollution as “hazards,” as identified in the County General Plan.
 The coordination of goals, policies, and programs of the Water Resources section of the General Plan.
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 The coordination of goals, policies, and programs of the Water Resources section of the General Plan, which pertain to groundwater overdraft, environmental uses of surface water, groundwater and surface water quality, and demand management and reuse. The programs of the Water Resources section specifically address the coordination of water agencies and County support of FCGMA plans.
 The coordination of capital projects or programs proposed as part of the GSP to achieve sustainability within the FCGMA basins.
 The regulatory authority of the GSA as it relates to that of the County.

How the GSP May Impact the Water Supply Assumptions of the General Plan Sections 1.3.1 through 1.3.3 of the General Plan (VCPD 2015) describe the goals, policies, and programs that apply to water resources. The goals outlined in Section 1.3.1 of the General Plan include monitoring water supply and quality, maintaining or restoring water quality and supply, balancing supply and demand, protection of aquifer recharge areas and protecting and restoring wetlands. The GSP includes specific provisions for each of these: the monitoring of water resources (Chapter 4), the definition and maintenance of groundwater-dependent ecosystems (wetlands), definition of sustainability as it pertains to water resources (Chapter 3), and projects and management actions by which these goals will be obtained (Chapter 5, Projects and Management Actions). The General Plan also has a resource appendix that describes in general terms the groundwater resources within Ventura County. The next time the general plan is updated, the information in the GSP will be used to provide information relevant to the groundwater resources appendix.

The General Plan policies listed in Section 1.3.2 (VCPD 2015) include provisions and requirements for discretionary development. Some of the projects of the GSP will likely constitute discretionary development and therefore require consistency with General Plan or demonstration of “overriding considerations.” The GSAs within the Subbasin will encourage municipalities to consider the GSP in the implementation of each of their general plans, and incorporate groundwater management criteria, where applicable and relevant, from the GSP into future general plan updates. General Plan Section 1.3.3 lists specific programs that County divisions will support in the application of the General Plan. Programs (management actions) implemented by FCGMA as part of the GSP may be added to those supported by the General Plan.

The 1998 Save Open Space and Agricultural Resources ordinance generally requires an approval by the electorate for any General Plan Amendment that changes land use designations for agricultural, rural, or open-space-designated lands. This and similar ordinances are in effect for much of the FCGMA area, including the Cities of Camarillo, Oxnard, and Ventura and unincorporated County areas, through at least 2050 (VCPD 2015). Should implementation of the 809
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GSP result in the conversion of agricultural, rural, or open space lands to other uses, either to accommodate GSP projects or as a result of management actions that reduce water demand, a vote of the electorate would be required.

It is not the role of a general plan to make water supply assumptions, but to take into consideration existing and anticipated water supply conditions in planning for growth. This includes FCGMA’s water supply allocations, as incorporated into the 5-year UWMPs. General plan policies for all jurisdictions include provisions to maximize water conservation for both indoor use and outdoor irrigation/landscaping. Furthermore, the areas zoned for development are generally already built out, so growth, where it occurs, is likely to consist of redevelopment projects or small areas of new development. As all new development is subject to supply mitigation, which includes installing dual plumbing and the use of nonpotable water where feasible, any offset of or increase in the volume of water used on the land being developed or redeveloped is mitigated; land conversion and changes in land use planning are not anticipated to adversely affect implementation of the GSP. Furthermore, city and County officials make up part of the FCGMA Board, and like the SGMA process, both UWMPs and general plans are living documents subject to periodic updates and reviews.

1.6.2 Urban Water Management Plans
UWMPs are prepared by urban water suppliers every 5 years. These plans support the suppliers’ long-term resource planning to ensure that adequate water supplies are available to meet existing and future water needs (California Water Code, Sections 10610–10656 and 10608). Every urban water supplier that either provides over 3,000 AF of water annually or serves more than 3,000 urban connections is required to submit a UWMP. Within UWMPs, urban water suppliers must:
 Assess the reliability of water sources over a 20-year planning time frame.  Describe demand management measures and water shortage contingency plans.  Report progress toward meeting a targeted 20% reduction in per-capita (per-person) urban water consumption by the year 2020.
 Discuss the use and planned use of recycled water.

The information collected from the submitted UWMPs is useful for local, regional, and statewide water planning. Besides annual review of the GSP, the 5-year evaluation interval required for GSPs under SGMA works well with the equivalent review interval for UWMPs, ensuring that information on water supply, and groundwater in particular, is updated appropriately. Water suppliers that operate groundwater wells within the jurisdiction of FCGMA and the other GSAs (County and CWD) in the Subbasin will update their water supply projections in accordance with the allocation of groundwater production available. Groundwater supply assumptions made by urban water suppliers in their 2015 UWMPs will be superseded by the groundwater allocation reduction management actions discussed in Chapter 5 of this GSP. 810
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Calleguas Municipal Water District UWMP
Description/Summary of Agency and Plan
CMWD is an independent special district and a wholesale water provider, the service area of which includes significant parts of each of the basins and the Oxnard Subbasin within the FCGMA area (Figure 1-8, Ventura County Water Purveyors; FCGMA et al. 2007). Within the Oxnard Plain, CMWD supplies the Cities of Oxnard and Port Hueneme (Figure 1-8). It has been a member agency of MWD since 1960, and provides wholesale water to 19 retail water purveyors. CMWD supplies water mainly for M&I uses. Most of the water supplied by CMWD is water from the SWP purchased from MWD. Storage facilities available to CMWD include a surface water reservoir in Thousand Oaks and underground storage in the LPVB via the Las Posas Aquifer Storage and Recovery Project (see Table 1-11).

CMWD does not operate any wastewater treatment facilities but supports the use of recycled water through the ownership and operation of recycled water pipelines and pumping facilities. The Salinity Management Pipeline transfers salty water away from surface waters in the southwestern Ventura County region to other beneficial uses or the Pacific Ocean (Table 1-11). CMWD actively conducts water conservation programs. Such programs include rebate/incentive programs, school programs, social media campaigns, and workshops.

The UWMP, adopted June 15, 2016, has a planning horizon of 25 years. The production of the UWMP was coordinated with, and obtained information from, numerous water suppliers and management agencies, including CWD, City of Camarillo, City of Oxnard, City of Port Hueneme, City of Moorpark, Ventura County Waterworks District 1, Ventura County Waterworks District 19, FCGMA, MWD, and UWCD. CMWD notified the appropriate agencies and the public of the production of the UWMP, conducted a public hearing, and incorporated public comments prior to adopting the plan.

Coordination with SGMA and Other Agencies
The UWMP contains a section describing FCGMA and the programs that it implements (CMWD 2016, Section 6-2). The SGMA legislation and GSP requirements are also described in this section, including FCGMA’s role as the GSA and its role in preparing the GSPs.

In January of 2016, the CMWD Board of Directors adopted a strategic plan, one of the provisions of which is to, “Work with FCGMA, United Water Conservation District, agricultural pumpers, purveyors, and other groundwater interests to encourage, support, and facilitate the development and implementation of groundwater sustainability plans within the service area that increase certainty in groundwater management and promote conjunctive use operations” (CMWD 2016, p. 7-13).
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How the Plan May Change Water Demands within the Subbasin Due to the extensive collaboration between FCGMA as the historical management agency and GSA and the CMWD as a major wholesale water supplier within the FCGMA basins, the UWMP incorporates and reflects water demand and sustainability issues that must be addressed under SGMA.

Implementation of this GSP will require continued coordination between the many agencies and stakeholders within the Oxnard Subbasin and periodic adjustment of assumptions regarding climate, population, land use, environmental requirements, and other factors impacting water demand. The CMWD UWMP recognizes those factors and provides for adaptation where necessary.

Such adaptation includes support of Senate Bill (SB) X7-7 goals for conservation, an extensive demand management program, and participation in capital projects that provide for conjunctive use on a regional scale.

How the Plan May Affect Sustainable Groundwater Management within the Subbasin For the reasons noted previously, the CMWD UWMP largely fosters the goals of sustainable management within the Oxnard Subbasin. Both CMWD and MWD have recognized and are pursuing remedies to improve the reliability of water supplies within their respective service areas.

UWMP strategies to remediate reliability issues of water supplies include pursuing demand management programs and local water supply projects such as increased use of recycled and brackish groundwater. In regard to SWP supply reliability, MWD and CMWD support DWR in projects and strategies to increase reliability from the Sacramento/San Joaquin Delta. These programs include California WaterFix and California EcoRestore (CMWD 2016, p. 7-2).

How the GSP May Impact the Assumptions of the UWMP
The UWMP presents strategies for preparing for SWP reliability challenges, climate variability, and emergency shortages. For planning purposes, the UWMP considers demand to be the total demand within the service area after accounting for local supplies. The GSP anticipates groundwater extraction reductions for M&I and agricultural uses even if planned projects discussed in the 2015 UWMP are developed. The UWMP assumes an increase in imported normal year demand of 5% between 2020 and 2040. Therefore, the UWMP may underestimate the demand upon which supply calculations are made. The UWMP assumes future water projects and demand management measures in water demand and reliability calculations. Those assumptions may be modified by those projects and management actions included in the GSP.
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United Water Conservation District UWMP (Oxnard–Hueneme Water System) Description/Summary of Agency and Plan
UWCD is a wholesale water supplier that was established as a public agency in 1950; its predecessor agency, the Santa Clara Water Conservation District, had been in existence since 1927. UWCD is also a water conservation district established under the California Water Code. UWCD is tasked with managing, protecting, and supplying water within the Santa Clara River Valley and the Oxnard Plain.

It provides potable water to several retail systems within the Oxnard Subbasin, including the City of Oxnard, PHWA, and several mutual water companies (Figure 1-8). Its service area encompasses the entire extent of the Oxnard Plain, as well as portions of the Las Posas Valley and Pleasant Valley, and part of the Santa Clara River Watershed (Figure 1-8). The UWCD UWMP applies only to the Oxnard–Hueneme Water System (OHWS) within the Oxnard Plain.

UWCD facilities include the OHWS, the Freeman Diversion, Lake Piru Reservoir, the Pumping Trough Pipeline, the Pleasant Valley Pipeline, and multiple recharge basins located in the Oxnard Forebay (see Table 1-11). Components of the OHWS include 12 extraction wells proximal to the recharge basins of the Oxnard Forebay, the El Rio Treatment Plant, and approximately 12 miles of transmission pipelines (UWCD 2016, p. 7). The OHWS supplies water mainly for residential, commercial, and industrial uses. The Pumping Trough Pipeline and Pleasant Valley Pipeline provide non-potable surface water or blended surface water and groundwater to agriculture in the central and southern portions of the Subbasin, thus offsetting groundwater pumping in the area in order to reduce the risk of seawater intrusion.

As a party to the SWP contract between Ventura County Flood Control District and DWR, UWCD purchased 1,260 AF of SWP water from Casitas Mutual Water District in 2012 and 1,890 AF of SWP water from the City of San Buenaventura in 2013. This water was released from Lake Piru into the Santa Clara River, from which it could be diverted at the Freeman Diversion, and served as a potential supply source for the OHWS (UWCD 2016, p. 17). The UWCD also routinely purchases Table A SWP water when available.

Potential UWCD projects to be implemented in the future could include the Full Advanced Treatment Program, which would entail a collaborative agreement between the City of Oxnard or another source and several agricultural entities to deliver recycled water through UWCD’s Pumping Trough Pipeline and the Pleasant Valley Pipeline for agricultural users in the Oxnard Plain. A study completed by UWCD indicated that desalination opportunities may be feasible.

However, such a system would not supply water to the OHWS (UWCD 2016).

As a wholesale supplier, UWCD complies with demand management requirements through metering, public education, and stakeholder outreach. All components of the OHWS are fully metered, including the 12 supply wells at the El Rio Spreading Grounds. The UWCD conducts 813
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tours, lectures, workshops, and other outreach as part of their water conservation program. In addition, UWCD is subject to demand management and other programs instituted by FCGMA.

The UWCD UWMP was adopted June 8, 2016, and included coordination with Ventura County and the Cities of Oxnard and Port Hueneme, among other entities.

Coordination with SGMA and Other Agencies
As a wholesale water provider located within the Oxnard Plain, UWCD is within the jurisdiction of, and therefore subject to the allocations and requirements of, FCGMA. A UWCD representative sits on the FCGMA Board of Directors.

UWCD conducts monitoring programs for groundwater levels, surface flow, and water quality and produces an annual report summarizing these data (Table 1-10). This information is vital for the implementation of monitoring and management programs within the Oxnard Plain. The UWCD Resolution 2014-01, adopted March 12, 2014, addresses cooperation among all of the water users within FCGMA jurisdiction and the Santa Clara River basins to undertake conservation measures, support the FCGMA emergency ordinance, and pursue alternative water supplies (UWCD 2016, Appendix E).

How the Plan May Change Water Demands within the Subbasin Due to the high level of coordination among agencies within the Oxnard Plain and FCGMA jurisdiction, it is anticipated that water demand among users of the OHWS will be monitored and managed consistent with the provisions of SGMA and this GSP. In addition, UWCD conducts demand management programs and activities in conjunction with the other water agencies in the Oxnard Plain.

How the Plan May Affect Sustainable Groundwater Management within the Subbasin Because UWCD takes an active role in FCGMA, the implementation of SGMA, and monitoring programs within the Oxnard Plain, this and future versions of the UWMP will continue to support sustainable groundwater management. The UWMP states that aquifer protection is mainly the responsibility of FCGMA and that, “As the designated Groundwater Sustainability Agency, FCGMA has the primary responsibility for aquifer protection … FCGMA has the legal authority to implement the GSP when adopted” (UWCD 2016, p. 34). Historically, the OHWS has had little reliance on imported water supplies and therefore is minimally subject to issues related to declining reliability of that source.

Water quality concerns within the Oxnard Subbasin include seawater intrusion, release of connate brines, nitrate concentrations, and salt accumulation. To the extent that UWCD operations allow for diversion of generally higher-quality surface water than that usually found in groundwater and 814
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offset pumping in coastal areas, the plan fosters sustainable management with respect to water quality. Nitrate concentrations in water extracted from UWCD shallow supply wells have been found to increase during periods of drought, when artificial recharge of diverted Santa Clara River water decreases. The UWMP recommends the deepening of existing wells in the vicinity of the El Rio Spreading Grounds in order to draw water from areas with lower nitrate concentrations.

How the GSP May Impact the Assumptions of the UWMP
The UWCD UWMP assumes a 75% reduction in groundwater extractionsfrom historical levels. Those provisions are superseded by the yields determined in this GSP (see Chapter 2). In addition, the GSP proposes minimum thresholds for water levels in coastal wells that are significantly higher than those of the recent past in order to reduce the impacts of seawater intrusion (see Section 3.4.3, Seawater Intrusion). These provisions of the GSP will impact UWCD operations within the Subbasin, including groundwater extractions from UWCD wells, and deliveries through the OHWS.

The UWMP assumes future water projects and demand management measures in water demand and reliability calculations. Those assumptions may be modified by those projects and management actions included in the GSP.

City of Oxnard UWMP
Description/Summary of Agency and Plan
The City of Oxnard was incorporated in 1903. The City of Oxnard serves as a retail water purveyor, providing potable and recycled water for commercial, industrial, residential, and agricultural use.

The City of Oxnard’s water service area includes the City of Oxnard and limited unincorporated areas of Ventura County. Oxnard’s water supplies include imported water from CMWD, groundwater from UWCD, and groundwater produced from local wells. These sources may be blended to meet water quality requirements and to optimize for cost and supply. The City of Oxnard also operates wastewater treatment facilities for its own service area and surrounding areas. The City of Oxnard conducts a water conservation program with public information, water efficiency rebates, and water waste patrols. It is also compliant with SB X7-7, requiring a 20% reduction in per-capita urban water use by the year 2020.

As part of its water supply infrastructure, the City of Oxnard owns and operates 10 groundwater wells and 6 blending stations within the Oxnard Subbasin boundary. In 2009, as part of its GREAT Program, the City constructed the AWPF, which produces recycled water. The GREAT Program also includes brackish water desalters, one of which currently operates at a production rate of 7,500 AFY, and is planned to expand to 15,000 AFY. The AWPF now has a capacity of 7,000 AFY and its use is expected to increase as consumers are identified and pipelines are constructed. The facility recycles effluent from, and is located near, the wastewater treatment plant in the southern 815
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part of the City of Oxnard. Consumers of this recycled water include PVCWD and some other agricultural operators. Potential consumers could include PHWA and UWCD (City of Oxnard 2015). In addition to recycling water for landscape and agricultural irrigation, the City of Oxnard plans to construct and operate an aquifer storage and recovery well program through which recycled water may be stored or extracted.

The City of Oxnard is considering future water projects, including expansion of the AWPF by 7,000 AFY for groundwater recharge and expansion of aquifer storage and recovery facilities to inject and store treated water in the LAS. A dozen or more wells may be constructed by the early 2030s as part of this program (City of Oxnard 2015). This program has the capacity to provide predictable quantities of reclaimed water to the region for a variety of conjunctive uses, without borrowing from existing sources of water. The project reclaims and reuses treated effluent that would otherwise be conveyed to the ocean.

Coordination with SGMA and Other Agencies
The UWMP was adopted June 20, 2016, and has a planning horizon of 25 years. The production of the UWMP was coordinated with, and obtained information from, numerous water suppliers and management agencies, including the CMWD, UWCD, MWD, PHWA, FCGMA, and the Ventura County Local Agency Formation Commission (LAFCo). The City of Oxnard notified the appropriate agencies and the public of the production of the UWMP, conducted a public hearing, and incorporated public comment prior to adopting the plan.

How the Plan May Change Water Demands within the Subbasin The City of Oxnard is entirely within FCGMA jurisdiction. As such, it is subject to the FCGMA ordinances and groundwater management activities described in Table 1-11. Many of the City of Oxnard’s plans for water project expansion have been developed with, and require approval by, FCGMA. Implementation of this GSP will require continued coordination between the agencies and stakeholders within the Oxnard Subbasin and periodic adjustment of assumptions regarding climate, population, land use, environmental requirements, and other factors impacting water demand. Currently, the City has a net-zero policy on new development, which requires a proposed development to provide their groundwater allocation to the City (subject to FCGMA approval) or contribute to City programs designed to offset potable water use. Because of the existing level of coordination with FCGMA, the Oxnard UWMP is not expected to affect the water demand within the Oxnard Subbasin.

How the Plan May Affect Sustainable Groundwater Management within the Subbasin Due to the jurisdictional overlap of FCGMA and the City of Oxnard, the Oxnard UWMP largely fosters the goals of sustainable management within the Oxnard Subbasin. Because the City of 816
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Oxnard at times relies on imported water from MWD via CMWD, the declining reliability of that supply may affect future management decisions. MWD is strategically addressing issues related to source reliability (CMWD 2016). Assumptions within the UWMP that may impact sustainable management of the basin include the continuation of current pumping allocations and the future availability of potable reuse supplies.

How the GSP May Impact the Assumptions of the UWMP
The UWMP indicates consistency with FCGMA management actions, including extraction reductions in accordance with Ordinance 8, Ordinance E, and the 100,000 acre-foot (AF) basin maximum extraction target of the 2007 FCGMA Basin Management Plan. However, the GSP contemplates reductions in groundwater extractions as compared to the historical averages and maintaining increased groundwater elevations near the coast for the management of seawater intrusion (see Chapters 2 and 3). Because the City of Oxnard is a coastal city partially dependent on groundwater extractions and UWCD supplies, its UWMP will be impacted by these GSP components. The UWMP assumes future water projects and demand management measures in water demand and reliability calculations. Those assumptions may be modified by those projects and management actions included in the GSP.

City of Ventura UWMP
Description/Summary of Agency and Plan
The City of Ventura, which was originally incorporated in 1866, is located on the Pacific Coast to the north of the Oxnard Subbasin, with a small portion of the city extending into the Subbasin. The City of Ventura Water Department (VWD), a retail water provider, supplies water to the city and several unincorporated areas of Ventura County. Parts of the city’s water system are within both Casitas Municipal Water District and UWCD jurisdictions. VWD provides potable water for commercial, industrial, residential, and irrigation customers. VWD also provides recycled water for the irrigation of parks and golf courses (City of Ventura 2016).

VWD’s supplies are from Lake Casitas, the Ventura River, groundwater, and reclamation facilities. Although the City of Ventura has a 10,000 AFY allocation of SWP water, there are currently no facilities by which SWP water can be delivered to the city. VWD extracts groundwater from the Oxnard Subbasin for use within the City’s service area. The City’s full Historical Allocation (HA) was 5,472 AFY (in 1990) and has since been adjusted by FCGMA ordinances to 4,104 AFY (a 25% reduction of HA in 2013) and 3,862 AFY (20% reduced Temporary Extraction Allocation since 2016). The City of Ventura has complied with SB X7-7, requiring 20% reduction in per-capita water use, and implements demand management programs, including a prohibition on water waste, conservation pricing, and public education. 817
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Wells used by the City of Ventura for its municipal water supply that are located within the Oxnard Subbasin consist of three wells at the Buenaventura Golf Course (City of Ventura Well Nos. 5, 6, and 7) (City of Ventura 2016).

Coordination with SGMA and Other Agencies
The City of Ventura UWMP was adopted in June 2016, and has a planning horizon of 25 years.

The production of the UWMP was coordinated with, and obtained information from, numerous water suppliers and management agencies, including FCGMA, CMWD, UWCD, City of Oxnard, and Ventura County LAFCo. The City of Ventura notified the appropriate agencies and the public of the production of the UWMP, conducted a public hearing, and incorporated public comments prior to adopting the plan.

How the Plan May Change Water Demands within the Subbasin The City of Ventura UWMP will not likely change the water demand within the Oxnard Subbasin.

How the Plan May Affect Sustainable Groundwater Management within the Subbasin Although the City of Ventura is located primarily outside the Oxnard Subbasin and the FCGMA area, the City extracts approximately 3,860 AFY of groundwater from the Subbasin that FCGMA has approved to be exported for use within the City’s service area. To the extent that the UWMP assumes continuation of this exportation of groundwater, these continued extractions will need to be addressed as part of FCGMA’s ongoing efforts to sustainably manage groundwater in the Oxnard Subbasin. However, the extraction has historically been subject to FCGMA management ordinances and will be subject to future FCGMA policies.

How the GSP May Impact the Assumptions of the UWMP
The UWMP assumes continued extractions from the Oxnard Subbasin. This assumption may be impacted by GSP management actions that reduce annual extractions within the Subbasin. These management actions would be undertaken to maintain coastal groundwater levels at higher than historic averages (see Chapters 2 and 3).

1.6.3 Additional Plan Summaries
Port Hueneme Water Agency UWMP
PHWA is a wholesale urban water supplier that delivers approximately 4,000 AFY of SWP water and groundwater to Naval Base Ventura County, the City of Port Hueneme, and the Channel Islands Beach Community Services District (PHWA 2016). Approximately 20% of the PHWA water supply is purchased SWP water from CMWD. The remaining 80% of the water supply is 818
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groundwater, provided to PHWA by UWCD as part of a 40-year supply agreement negotiated in 1996 (PHWA 2016). PHWA does not directly pump groundwater from the Oxnard Subbasin, but relies on the groundwater produced by UWCD.

City of Port Hueneme UWMP
The City of Port Hueneme is a retail water agency that supplies approximately 1,903 AFY of SWP water and groundwater purchased from PHWA (City of Port Hueneme 2016b). The City of Port Hueneme does not directly pump groundwater in the Oxnard Subbasin (City of Port Hueneme 2016b).

Metropolitan Water District UWMP
MWD is a public agency that delivers water from the Colorado River and the SWP to its member agencies (MWD 2016). The member agencies of MWD include 14 cities, 11 municipal water districts, and 1 county water agency (MWD 2016). Relevant to water supplies in the Oxnard Basin, PHWA purchases water from CMWD, which is a member agency of MWD. MWD supplies imported water to CMWD. MWD does not directly or indirectly pump groundwater in the Oxnard Subbasin.

City of Oxnard General Plan
The City of Oxnard owns and operates a municipal water supply system, providing both imported water and local groundwater in its service area. The General Plan addresses groundwater resources in both the Infrastructure and Community Services Goals section and the Environmental Resources Goals section of the General Plan. These goals include supporting the FCGMA policies that protect, enhance, and replenish the aquifers of the Oxnard Subbasin and adhering to recommendations regarding groundwater extractions and quality from the Ventura County Regional Water Quality Planning Program (City of Oxnard 2011, Goals ICS-11.5 and ICS-11.9). Additionally, Goal ER-5 states: “well managed water supply and wastewater treatment programs that together meet expected demand, prevent groundwater overdraft, and ensure water quality” (City of Oxnard 2011). Under this goal, reducing dependence on groundwater through development of the GREAT Program is specified as supporting the policies of FCGMA (City of Oxnard 2011). Specifically, Policy ER-5.3 states “The City shall maintain a minimal dependence on Basin 4A groundwater consistent with the Groundwater Resource Encroachment and Treatment (GREAT) Program and support the policies of the Fox Canyon Groundwater Management Agency to protect, enhance, and replenish the aquifers underlying the Oxnard Plain” (City of Oxnard 2011).

The City of Oxnard General Plan includes several policies that address a range of water supply and groundwater resource issues. These include the following (City of Oxnard 2011):
 Policies ICS-1.1 (Maintain Existing Service Levels), ICS-1.2 (Development Impacts to Existing Infrastructure), and ICS-1.3 (Funding for Public Facilities) require the City 819
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to plan and ensure that a variety of funding methods (including developer fees, grants, and public facility fees) are used to expand the range of public services and utilities (including water supply infrastructure) consistent with community needs.  Policy ICS-11.4 (GREAT Program Implementation) requires the City to continue supporting and implementing this program as a key way to meet the City’s long-term water supply needs.
 Policies ICS-11.2 and ICS-11.7 encourage the City to continue its promotion of a variety of water conservation measures (including landscaping and low-flow fixtures) as part of all future development.
 Policy ICS-11.6 (Sustainability of Groundwater) calls for the continued support of the various policies of the local groundwater management agency and Policy ICS-11.9 (Groundwater Extractions) calls for continued adherence to the Ventura County Regional Water Quality Planning Program’s recommendations regarding groundwater quality and extractions.
 Policy ICS-11.12 (Water for Irrigation) encourages the use of non-potable water supplies for landscape irrigation.
 Policy ICS-11.10 (Water Supply Assessment for All Projects) requires the preparation of water supply studies prior to the approval of future development projects.  Implementation Measure No. 59 requires the City to maintain and periodically update water, wastewater, and drainage infrastructure master plans to ensure that sufficient levels of infrastructure are planned for and financed in the City.

The General Plan does not contain water supply assumptions that would conflict with the sustainable management criteria or the projects and management actions proposed in this GSP.

The City General Plan recognizes the existing constraints water resources that exist in supporting future development, as evidenced through its various policies encouraging development of alternative water supplies, promoting conservation and use of non-potable water, and requiring completion of water supply assessments for all projects prior to approval. In addition, the City has a net-zero policy on new development, which requires a proposed development to provide their groundwater allocation to the City (subject to FCGMA approval) or contribute to City programs designed to offset potable water use. The General Plan also includes policies that promote redevelopment of old and/or blighted areas, development of mixed-use urban villages, and/or expansion of existing business and attraction of new business. Such development and investments would undoubtedly require additional water resources to support, and implementation of this GSP is likely to increase existing limitations on water availability. However, as discussed in detail in Section 1.4.3 (Operational Flexibility Limitations) and Chapter 5 (Projects and Management Actions) of the FCGMA, the 820
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City and other jurisdictions within the Oxnard Plain continue to implement projects that increase operational flexibility within the Oxnard Subbasin.

Naval Base Ventura County
Naval Base Ventura County (NBVC) is composed of three main operating areas (Point Mugu, Port Hueneme, and San Nicolas Island) and eight special areas. NBVC Point Mugu is located in unincorporated Ventura County, and NBVC Port Hueneme is located in the City of Port Hueneme.

NBVC plays a vital role in national security missions, supporting approximately 80 tenant commands and over 20,000 direct, indirect, and induced jobs within Ventura County. Water sustainability is critical to military sustainability, resiliency, and compatibility. NBVC’s primary water supply is groundwater extracted from the Forebay by UWCD, blended with imported water from the CMWD, and delivered to NBVC Port Hueneme and NBVC Point Mugu via the Oxnard Hueneme Pipeline, contracted through and in partnership with the Port Hueneme Water Agency.

NBVC also operates one groundwater well on Port Hueneme with limited pumping, listed as a back-up drinking water source, and used primarily for landscaping and water system operations.

NBVC groundwater use currently represents approximately 1 percent of groundwater pumped in the Oxnard Subbasin and Pleasant Valley Basin.

The Channel Islands Air National Guard Station (ANGS) shares the airfield with NBVC Point Mugu, but is housed on property owned by the United States Air Force and is located in unincorporated Ventura County. Channel Islands ANGS supports missions for both the Federal government and the State of California. Channel Islands ANGS is supported by two water sources; a groundwater well, permitted through the County of Ventura, which is used for irrigation only; and a potable water pipeline that is part of the NBVC groundwater pipeline.

All permitting, reporting and other requirements are provided as a matter of comity and in support of good water management.

The SGMA provides that the federal government, appreciating the shared interest in assuring the sustainability of groundwater resources, may voluntarily agree to participate in the preparation or administration of a groundwater sustainability plan, per Water Code Section 10720.3.

Recognizing this shared interest, NBVC has voluntarily engaged in the development of the GSP for the Oxnard Subbasin by FCGMA.

While welcoming federal government participation, SGMA recognizes Federal Reserve Water Rights (FRWR) as distinct from those water rights based in state law and directs that Federal Reserve Water Rights be respected in full, and in case of any conflict between federal and state law, federal law shall prevail. Water Code § 10720.3(d). SGMA also directs that the groundwater sustainability agency consider the interests of all beneficial uses and users of groundwater, listing 821
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the federal government, including, but not limited to, the military and managers of federal lands among those interests. Water Code § 10723.2.

Under U.S. Supreme Court case law defining the FRWR, federal agencies have an implied right to water to support the primary mission for which Congress and the Federal government have designated that land, including a provision of water for growth to support that mission.3It is well established in the Supremacy Clause of the U.S Constitution, Article VI, Clause 2, that the Federal Government is not subject to state regulation, unless Congress clearly and unambiguously waives this sovereign immunity.

Consistent with its proactive and cooperative engagement with FCGMA, NBVC has a vested interest in participating in the SGMA effort to support a groundwater basin that achieves a sustainable yield. NBVC may voluntarily agree to an allocation under the GSP less than its full FRWR. In recognition and acknowledgment of the limits on FCGMA to regulate the federal government, any such allocation shall be directly assigned to the federal agency and shall not be subject to the requirements of any allocation ordinance, including but not limited to allocation carryovers, borrowing, transfers, reductions and/or variances and fees.

Although not subject to formal regulation under SGMA, NBVC is committed to being a good steward of water resources and to exploring partnerships that help to achieve groundwater sustainability, including projects that benefit both the Navy and the community.

Naval Base Ventura County Joint Land Use Study
The NBVC prepared a Joint Land Use Study that includes a discussion of water supply and potential impacts to Naval Base Ventura County water quality and quantity (NBVC 2015). This report, which was prepared in cooperation with the Cities of Camarillo, Oxnard, and Port Hueneme and the County of Ventura, identifies saltwater intrusion and impacts to storm drain flows as potential concerns for adequate supplies of good quality water to Naval Base Ventura County. To avoid these potential impacts, the Joint Land Use Study suggests coordination with the FCGMA GSP efforts (NBVC 2015).

1.7 WELL PERMITTING POLICIES AND PROCEDURES
The three permitting agencies requiring well permits within FCGMA jurisdiction are FCGMA, Ventura County Public Works Agency, and the City of Oxnard. The FCGMA well permit requirements pertain to the entirety of FCGMA’s jurisdiction. The Ventura County ordinances do

3 The FRWR was first recognized by the U.S. Supreme Court in the context of tribal interests (See Winters v. United States, 207 U.S. 564 5090 (1908)) and subsequently expanded to federal agencies (See Cappaert v. United States, 426 U.S. 128 (1976)), Federal Power Commission v. Oregon, 349 US 435 (1955)). 822
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not preclude or supplant any other agency requirements. To construct a well within the City of Oxnard, a permit is required from both FCGMA and the City of Oxnard.

Each well permitting agency, as a minimum standard, implements California’s Water Well Standards, which include requirements to avoid sources of contamination or cross-contamination, proper sealing of the upper annular space (i.e., first 50 feet), disinfection of the well following construction work, use of appropriate casing material, and other requirements. The permitting agencies require wells to meet certain setback criteria (e.g., septic system setback) and specific construction and sealing requirements. In addition, well-drilling activities are required to reduce pollution to the maximum extent practicable using best management practices such as installing a sediment basin to contain runoff, using geotextile fabric to contain sediments and drilling mud, or eliminating the use of drilling foam.

The permitting agencies monitor and enforce these standards by requiring drilling contractors with a valid C-57 license to submit permit applications for the construction, modification, reconstruction (i.e., deepening), or destruction of any well within their jurisdiction. The processing and issuance of a water well permit is currently considered a ministerial action, meaning permits are issued to drillers meeting California Water Well Standards and County sealing requirements, and notwithstanding errors in the application. Certain circumstances, however, such as when installing a well could cause the spread of contaminants to uncontaminated water zones, may prevent FCGMA from issuing a well permit.

The passage of SB 252 added Article 5, Wells in Critically Overdrafted Groundwater Basins, to Chapter 10 of the California Water Code, requiring collection of specific information for water wells proposed in critically overdrafted groundwater basins. The provisions of SB 252 are effective until January 30, 2020.

1.7.1 FCGMA
Since its inception, FCGMA has implemented multiple ordinances and policies related to the extraction and use of groundwater. FGMA did not impose a permit requirement for the Oxnard Subbasin until 2010 (Ordinance 8.2). A complete list of historical policies and ordinances is kept and updated on the FCGMA website (FCGMA 2019c). Those currently pertaining to well permits are described here.

Emergency Ordinance E, adopted April 11, 2014, in response to severe drought, declining water levels, and seawater intrusion, prohibits the issuance of permits for new groundwater wells associated with new or increased groundwater use, and limits extractions from existing wells (FCGMA 2014b). The ordinance limits groundwater extractions for M&I and agricultural users. 823
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Ordinance E temporarily replaced the then-in-use allocation systems (HA and Baseline Allocation [BA]) for M&I well operators with a Temporary Extraction Allocation that uses average annual extractions from the base period 2003 to 2012. The ordinance sets a series of allocation reductions from the base amount to take effect beginning July 1, 2014, with a 10% reduction. The ordinance requires an additional 5% reduction every 6 months through January 2016, resulting in a total reduction of 20%.

Ordinance E requires all agricultural well operators to apply for a 25% reduced Efficiency Allocation. An Efficiency Allocation is based on a well operator demonstrating that water used for agriculturally developed land is at least 80% efficient (FCGMA 2011, Resolution No. 2011-04).

Ordinance E also contains provisions for the FCGMA Board to undertake additional adjustments to irrigation allowances by resolution.

Under Emergency Ordinance E, accounts that are solely associated with domestic wells operate well(s) using a 25% reduced HA (also known as an Adjusted Historical Allocation [AHA]) and/or a BA. An HA is an average of annual extractions from the base period 1985 to 1989. A BA is associated with a parcel and is based on new development after the close of the HA base period.

Since 1983, FCGMA ordinances have required registration of wells, reporting of extractions, and payment of pumping fees. Currently, the FCGMA Ordinance Code continues these requirements.

Additionally, the code (Chapter 2) requires that permits be obtained from FCGMA for new wells prior to construction. For wells installed within the FCGMA area, the applicant must subsequently obtain a permit from the Ventura County Public Works Agency or the City of Oxnard if within the City’s jurisdiction. The FCGMA Ordinance Code requires the installation and maintenance of flow meters, providing proof of flowmeter accuracy, and reporting of all extractions semi-annually (Table 1-11). In 2018, FCGMA adopted an ordinance that will require all wells within the Agency to be equipped with advanced metering infrastructure telemetry by October 1, 2020.

1.7.2 Ventura County
The ordinances relating to groundwater wells in Ventura County are contained in Ventura County Ordinances, Division 4, Chapter 8, Water, Article 1 – Groundwater Conservation, Sections 4811– 4828 (County of Ventura 2016). These ordinances regulate the construction, maintenance, operation, modification, and destruction of groundwater wells. Ventura County requires well permits for any construction, modification, replacement, repair, or destruction of wells. Permit requirements include “information as the Agency may deem necessary in order to determine whether underground waters will be protected” (County of Ventura 2016, Chapter 8, 4813, C8).

Ventura County requires that a well permit application from FCGMA be completed and authorized prior to consideration for a Ventura County permit. Ventura County well construction or destruction activity standards are required to comply with the DWR Well Standards Bulletins Nos. 824
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74-81 and 74-90. New water wells must be equipped with a flow meter and calibrated every 3 years; however, de minimis extractors (those producing less than 2 AFY) are exempt from this requirement. Completion logs are required for all wells, and geophysical logs are required where necessary to prevent cross contamination of pumping zones.

Section 4826 pertains to the Aquifer Protection Program, the purpose of which is to require destruction or repair of wells that are causing groundwater pollution. The provision requires annual reporting of water extractions, time of operation, static water levels, and pump test data if available. Based on these data, all wells are classified with regard to location and operational condition.

Due to pervasive drought conditions, as of October 28, 2014, Section 4826.1 prohibited the construction of new wells within the unincorporated area of Ventura County except under specific circumstances. With the initiation of SGMA, the ordinance was modified to include only basins designated as high or medium priority by DWR, which includes all of the FCGMA basins in the Oxnard Subbasin except the Arroyo Santa Rosa Valley Basin.

1.7.3 City of Oxnard
Chapter 22, Article VII, of the Oxnard City Code includes requirements for the construction, repair, modification, and destruction of wells. The City of Oxnard requires a fee and permit for the construction of water wells. Notable among the permit requirements is a statement confirming that the aquifers underlying the City of Oxnard are no longer in a state of overdraft. Applications for new wells require a public hearing and are considered by City Council (Oxnard City Code, Section 22-101). Permits are also required for the repair, modification, or destruction of existing wells.

1.7.4 Additional Well Permitting Policies and Procedures In addition to State of California, County of Ventura, and FCGMA well permitting policies and procedures, a permit in the form of a well agreement with the City of Ventura is required to construct a well within the City of Ventura’s jurisdictional boundary.

1.8 NOTIFICATION AND COMMUNICATION

1.8.1 Notification and Communication Summary
Notification and communication regarding the development of the Oxnard Subbasin GSP takes place in the following four key phases:

1. Initial Notification

2. GSP Development
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3. Draft GSP Review and Comment

4. GSP Implementation
The Initial Notification was completed with the FCGMA submittal of the Notice of Intent on February 24, 2017, to the DWR to develop a GSP for the Oxnard Subbasin. The GSP Development phase included extensive outreach and engagement with the stakeholders, including beneficial users, as described in more detail in Section 1.8.3, Public Meetings Summary, and Section 1.8.6, Communication.

The Draft GSP Review and Comment phase will include the formal public comment period for the Draft GSP and response to comments, as discussed in Section 1.8.4, Summary of Comments and Responses. The GSP Implementation notification and communication period will begin once FCGMA submits the final GSP to DWR and will include engagement with the public and beneficial users regarding the progress of monitoring and reporting updates on the GSP to DWR, establishment of fees, and the development and implementation of management strategies, including projects as needed.

1.8.2 Summary of Beneficial Uses and Users
Beneficial uses of groundwater from the Oxnard Subbasin include agricultural, M&I, and environmental uses. As discussed in Section 1.3.2.3, Historical, Current, and Projected Land Use, land use on the Oxnard Plain is 47% agriculture, 47% urban, and 6% open space. Of the groundwater produced from the UAS and the LAS, approximately 60% is used for agriculture and the remaining 40% is used for M&I and urban uses. GDEs are the primary environmental users of groundwater in the Subbasin. The GDEs are connected to the semi-perched aquifer, which is separated from the underlying UAS by a clay layer throughout much of the Oxnard Subbasin, and from which there is limited groundwater production.

Beneficial users of groundwater and property interests potentially affected by the use of groundwater are described in the following paragraphs.

Surface Water Users. The primary surface water users within the Oxnard Subbasin are UWCD and CWD, which both operate conjunctive-use programs. The interests of UWCD and CWD are represented on the FCGMA Board, as discussed in Section 1.2.3, Organization and Management Structure. Consultation with UWCD and CWD staff has occurred formally and informally throughout the development of the GSP, including participation in public meetings and the Technical Advisory Group (TAG). UWCD has also contributed data from their monitoring programs. There are also environmental uses of surface water, as discussed in this section under Environmental Users.

All identified surface water users in the Oxnard Subbasin were added to the interested parties list that is sent monthly electronic newsletters and meeting notices regarding the status of the GSP. 826
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Municipal Well Operators and Public and Private Water Purveyors. There are over 40 public and private water purveyors in the Oxnard Plain, as shown on Figure 1-8. A detailed description of each purveyor is included in the VCWPD Inventory of Public and Private Water Purveyors (2006). All of the purveyors in the Oxnard Plain, including all municipal well operators, are supplied water by either UWCD or CMWD. The interests of both UWCD and CMWD are represented on the FCGMA Board, as previously discussed in Section 1.2.3. Staff from both UWCD and CMWD have provided groundwater monitoring data, have participated in public meetings, and regularly collaborate with FCGMA staff. The Cities of Oxnard and Port Hueneme also have direct representation on the FCGMA Board by the representative appointed to serve on behalf of the five incorporated cities within FCGMA jurisdiction. Several of the smaller water districts and mutuals have also participated in FCGMA public meetings and provided comments throughout the development of the GSP.

Agricultural Users. Agricultural users have been identified as key stakeholders since the creation of FCGMA in 1982 and have direct representation through one of five members on the FCGMA Board. The primary crops grown in the Oxnard Plain are strawberries, raspberries, celery, peppers, beans, cabbage, lettuce, spinach, kale, cut flowers, and nursery stock. Agricultural user interests are represented within the Oxnard Plain by the Ventura County Agricultural Commissioner, the Ventura County Farm Bureau, individual pumpers, and groups of pumpers that have organized to advocate for their interests during the GSP development process. The FCGMA Board directed staff to work with pumpers’ groups on the development of proposed allocation systems that will be brought before the FCGMA Board for consideration. FCGMA maintains a database of well owners, including agricultural well owners. Email addresses in the database have been added to the list of interested parties who receive electronic newsletters regarding the status and development of the Oxnard Subbasin GSP.

Domestic Users. The majority of domestic groundwater users in the Subbasin are supplied water from a city, special district, or mutual water company. FCGMA maintains a database of well owners, including domestic well owners. Email addresses in the database have been added to the list of interested parties who receive electronic newsletters regarding the status and development of the Subbasin GSP.

Local Land Use Planning Agencies. FCGMA staff members have reached out to all local land use planning agencies with jurisdiction over the Oxnard Plain, including the County of Ventura, the City of Oxnard, and the City of Port Hueneme. The County of Ventura holds one of five seats on the FCGMA Board. The FCGMA Board also has a member appointed to represent the five incorporated cities, including the cities of Oxnard and Port Hueneme. As discussed in Section 1.6, Land Use Elements or Topic Categories of Applicable General Plans, FCGMA has established working relationships with the land use planning agencies. FCGMA staff has participated on the 827
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Ventura County General Plan Update Water Element Focus Group and continues to work with Ventura County planning staff to ensure that the GSP and General Plan Update are consistent.

Environmental Users. Environmental users of groundwater are concentrated in the four GDEs and two potential GDEs described further in Section 2.3.7, Groundwater-Dependent Ecosystems. These GDEs include aquatic habitat, in-channel wetlands, riparian forest, and coastal marshes. FCGMA has taken steps to incorporate the interests of environmental users in the development of the GSP through appointing an environmental representative to the TAG. The TAG held a special meeting focusing on potential groundwater-dependent ecosystems and accepted comments from the public on the potential impacts to surface water bodies. There are several non-governmental organizations with missions associated with environmental water uses on the list of interested parties who receive electronic newsletters regarding the status and development of the Oxnard Subbasin GSP.

The Federal Government. As discussed in Section 1.3.2.3, the federal government is a landowner and groundwater user in the Oxnard Basin through the Naval Base Ventura County.

Representatives from the U.S. Navy have been coordinating with FCGMA staff regarding the development of the GSP, have participated in FCGMA public meetings, and are on the list of interested parties who receive electronic newsletters regarding the status and development of the Oxnard Subbasin GSP.

California Native American Tribes. According to the U.S. Bureau of Indian Affairs California Tribal Homelands and Trust Land Map, updated in 2011 and available from the DWR website, the entire Oxnard Subbasin is within the Chumash Tribal/Cultural area. There are not currently any federally recognized Indian Tribes, Indian land currently or historically held in trust by the U.S. government, or smaller Reservation or Rancheria areas in the Oxnard Plain. FCGMA recognizes that the Chumash culture and associated cultural resources are important in Ventura County.

Several active local groups and individuals representing the interests of tribal communities in Ventura County have been added to the list of interested parties, including representatives from the Barbareno/Ventureno Band of Mission Indians (Chumash) and the Wishtoyo Chumash Foundation. FCGMA has reached out to the DWR Southern Region Office Tribal Liaison, Jennifer Wong, and added her to the list of interested parties. The San Gabriel Band of Mission Indians has also shown an interest in the groundwater sustainability planning process and has been added to the list of interested parties.

Disadvantaged Communities. The majority of the Disadvantaged Communities (DACs) within the Oxnard Plain receive water from cities, special districts, or mutual water companies. FCGMA works closely with these water agencies and mutuals that represent the interests of the DACs. The Watersheds Coalition of Ventura County has established a DAC Involvement Committee to discuss DAC needs and project opportunities related to Integrated Regional Water Management.

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Regional Water Management and the DAC Involvement Committee have participated in FCGMA public meetings and are on the list of interested parties who receive electronic newsletters regarding the status and development of the Subbasin GSP.

1.8.3 Public Meetings Summary
FCGMA has been discussing the development of a GSP since March 2015. Table 1-12 lists the FCGMA public meetings in which the participants discussed or took action on the Subbasin GSP.

Note that the list will be updated as additional meetings occur.

1.8.4 Summary of Comments and Responses
The FCGMA Board approved release of a Preliminary Draft GSP in January 2018, with a 90-day comment period. An evening public workshop was held on February 8, 2018, to present the Preliminary Draft GSP, answer questions, and solicit comments. Formal comments were accepted in writing only. The comments were submitted in person at the public workshop and electronically via email to [email protected]. A total of 32 comment letters were received by FCGMA on all three GSPs. A summary of the comments was presented to the FCGMA Board at the May 23, 2018, meeting. In consideration of these comments, FCGMA completed an independent peer review of the numerical groundwater models, completed additional analysis for the water quality approach, and extended the timeline for completion of the GSP. Comments on the Preliminary Draft GSP and direction from the FCGMA Board after consideration of public comments have been incorporated in the Draft GSP.

Before completing the Draft GSP, additional information was made available to the public to enhance understanding of the technical information and processes used for the development of the Draft GSP. The following documents were posted on the FCGMA website, discussed in public FCGMA meetings, and sent to the list of interested parties in electronic newsletters:
 Minimum Thresholds and Measurable Objectives Data, March 2019  Peer Review of the United Water Conservation District and Calleguas Municipal Water District Models for the Oxnard Subbasin, Pleasant Valley Basin, and Las Posas Valley Basin, March 2019
 Approach for GSP Modeling of Future Conditions in the Oxnard Subbasin, Pleasant Valley Basin and Las Posas Valley Basin, January 2019
 Minimum Thresholds and Measurable Objectives in the Las Posas Valley Basin, Oxnard Subbasin, and Pleasant Valley Basin, January 2019
 Assessing the Sustainable Yield of the Oxnard Subbasin, Pleasant Valley Basin, and Las Posas Valley Basin, January 2019
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A public workshop was held on March 15, 2019, to discuss the estimated sustainable yield, minimum thresholds, and measurable objectives proposed for the Draft GSP. Comments received at the public workshop were incorporated into the Draft GSP. The Draft GSP was approved by the FCGMA Board and released for a 60-day public comment period on July 29, 2019, during which time FCGMA solicited formal comments on the Draft GSP.

Before completing this Final GSP, the public comments received on the Draft GSP were reviewed and where appropriate incorporated into this Final GSP. Public comments on the Draft GSP are included in Appendix A.

1.8.5 Summary of Initial Information on Relationships between State and Federal Regulatory Agencies
FCGMA has not entered into any formal agreements with the federal government regarding preparation or administration of this GSP or groundwater management pursuant to SGMA, Section 10720.3(c). The U.S. Navy is a current beneficial user of water within the Subbasin and has initiated informal coordination with FCGMA staff, including a presentation to the FCGMA Board on May 24, 2017, detailing the Navy’s interests and operations related to water use within the FCGMA boundaries. There are no federally recognized Indian Tribes within the Subbasin boundaries.

FCGMA recognizes the need for both formal and informal consultation with state and federal regulatory agencies throughout the implementation of the GSP. FCGMA received a formal request from the U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service on October 11, 2016, to be added to the list of interested parties for the development of the GSP. FCGMA has added National Marine Fisheries Service to the list of interested parties, as well as the following state and federal regulatory agencies:
x Los Angeles Regional Water Quality Control Board
x U.S. Fish and Wildlife Service
x California Department of Fish and Wildlife
x California Department of Water Resources

1.8.6 Communication
A public outreach and engagement plan was developed for all of the GSPs that FCGMA is developing (included as Appendix B to this GSP). The purpose of the public outreach and engagement plan was to create a common understanding and transparency throughout the groundwater sustainability planning process, including fulfilling the requirements of SGMA as described in DWR 2016b, Section 354.10.d. The public outreach and engagement plan discusses the FCGMA decision-making process; identifies opportunities for public engagement and 830
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provides a discussion of how public input and response will be used; describes how FCGMA encourages the active involvement of diverse social, cultural, and economic elements of the population within the Subbasin; and describes the method FCGMA shall follow to inform the public about progress implementing the public outreach and engagement plan, including the status of projects and actions.

FCGMA has provided ongoing and innovative opportunities for stakeholders to engage in the GSP development process. FCGMA has provided regular updates to interested parties through monthly electronic newsletters highlighting monthly progress on the GSP development, upcoming meetings, and opportunities for engagement. Monthly updates and opportunities for public comment were provided at FCGMA Regular Board Meetings, FCGMA Special Board Meetings, and TAG Meetings. Meeting agendas and minutes, as well as video recordings of all FCGMA Board Meetings and Workshops, were made available on the FCGMA website. Additional technical information about the GSP development was made available on the FCGMA website including the Preliminary Draft GSP, Technical Memoranda, and TAG Meeting Materials. The Preliminary Draft GSP was available online for more than 120 days, including an official 90-day public comment period. FCGMA encouraged active participation from stakeholders through four public workshops (November 15, 2016; September 20, 2017; February 8, 2019; and March 15, 2019), a survey for input on sustainability indicators, and a public call for project ideas for incorporation into the GSP.

1.9 REFERENCES CITED
Bureau of Reclamation. 2013. Los Angeles Basin Stormwater Conservation Study: Task 3.1.

Development of Climate-Adjusted Hydrologic Model Inputs. U.S. Department of the Interior, Technical Service Center, Bureau of Reclamation. October 2013.

CIMIS (California Irrigation Management Information System). 2018. “Historical climate data provided for the Oxnard weather station” [data]. California Irrigation Management Information System. Accessed 12 Dec. 2018. http://wwwcimis.water.ca.gov/ WSNReportCriteria.aspx.

City of Camarillo. 2016. 2015 Urban Water Management Plan for the City of Camarillo. Final Draft. Prepared by Water Systems Consulting Inc. August 2016.

City of Oxnard. 2011. 2030 General Plan Goals and Policies. October 2011.

City of Oxnard. 2015. City of Oxnard 2015 Urban Water Management Plan. Prepared by MNS Engineers Inc. July 1, 2016.

City of Oxnard. 2016a. Planning Division Quarterly Projects List. Updated October 2016. https://www.oxnard.org/wp-content/uploads/2016/10/October-Project-List.pdf. 831
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City of Oxnard. 2016b. Salt and Nutrient Management Plan (SNMP) for the Oxnard Plain and Pleasant Valley Basins – Preliminary Draft. Prepared by Hydrometrics WRI and Carollo.

July 2016.

City of Port Hueneme. 2016a. “Fact Sheet.” Accessed on October 25, 2016. http://www.ci.port-hueneme.ca.us/index.aspx?nid=919.

City of Port Hueneme. 2016b. City of Port Hueneme 2015 Urban Water Management Plan.

Final. Prepared by Water Consultancy. August 2016.

City of Ventura. 2016. 2015 Urban Water Management Plan for the City of Ventura. Final.

Prepared by Kennedy/Jenks Consultants. June 2016.

CMWD (Calleguas Municipal Water District). 2016. 2015 Urban Water Management Plan.

Final. Prepared by Black and Veatch. June 2016.

County of Ventura. 2016. “Ventura County, California – Code of Ordinances. Division 4, Chapter 8, Article 1, Section 4813 – Well Permits.” September 27, 2016. Accessed November 14, 2016. https://www.municode.com/library/ca/ventura_county/codes/ code_of_ordinances?nodeId=DIV4PUHE_CH8WA_ART1GRCO_4813WEPE.

CWD (Camrosa Water District). 2016. 2015 Agricultural Water Management Plan. Adopted March 10, 2016.

DWR (California Department of Water Resources). 2016a. California’s Groundwater, Bulletin 118. 2016 Interim Update. Accessed May 29, 2019, 2016.
https://water.ca.gov/Programs/Groundwater-Management/Bulletin-118.

DWR. 2016b. “Approved Groundwater Sustainability Plan Emergency Regulations.” May 18, 2016. Accessed November 14, 2016. http://water.ca.gov/groundwater/sgm/pdfs/ GSP_Emergency_Regulations.pdf.

DWR. 2016c. 2015 Urban Water Management Plans Guidebook for Urban Water Suppliers.

Final. March 2016.

DWR. 2019. Sustainable Groundwater Management Act 2018 Basin Prioritization Process and Results. January 2019.
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FCGMA. 2011. “Ordinance No. 8.4. An Ordinance to Amend the Fox Canyon Groundwater Management Agency Ordinance Code Relating to Annual Efficiency Extraction Allocations.” Resolution 2011-04. October 26, 2011. Accessed October 2017. http://www.fcgma.org/images/ordinances_legislation/Ord_8.4_AMENDS_-_ adopted_10-26-2011_web.pdf.

FCGMA. 2014a. “A Resolution Establishing the Conejo Creek Water Pumping Program Involving Camrosa Water District and Pleasant Valley County Water District Using the Conejo Creek Diversion.” Adopted March 26, 2014. Accessed January 15, 2018. http://fcgma.org/images/ordinances_legislation/Resolutions/ Resolution_2014-01_optimized.pdf.

FCGMA. 2014b. “Emergency Ordinance E: An Ordinance Limiting Extractions from Groundwater Extraction Facilities, Suspending Use of Credits and Prohibiting Construction of any Groundwater Extraction Facility and/or the Issuance of any Permit Therefor.” Adopted April 11, 2014. Accessed October 24, 2016. http://www.fcgma.org/ images/ordinances_legislation/Emergency_Ordinance_E_-_Orig._Signed_optimized.pdf.

FCGMA. 2016. “Wells by Water Use Sector.”
FCGMA. 2019a. “Organizational Chart.” Fox Canyon Groundwater Management Agency, About. Accessed May 29, 2019. http://www.fcgma.org/about-fcgma/ organizational-chart.

FCGMA. 2019b. “Board of Directors.” Fox Canyon Groundwater Management Agency, About.

Accessed May 29, 2019. http://www.fcgma.org/about-fcgma/board-of-directors.

FCGMA. 2019c. “Ordinances and Legislation.” Accessed May 29, 2019. http://www.fcgma.org/public-documents/ordinances-legislation.

FCGMA. 2019d. “Fox Canyon Groundwater Management Agency Boundary.” [Map.] http://www.fcgma.org/charts-maps/fcgma-boundary. Accessed June 20, 2019.

FCGMA, UWCD, and CMWD (Fox Canyon Groundwater Management Agency, United Water Conservation District, and Calleguas Municipal Water District). 2007. 2007 Update to the Groundwater Management Agency Groundwater Management Plan. May 2007.

Hanson, R.T., P. Martin, and K.M. Koczot. 2003. Simulation of Ground-Water/Surface-Water Flow in the Santa Clara–Calleguas Ground-Water Basin, Ventura County, California.

U.S. Geological Survey Water-Resources Investigations Report 02-4136. Sacramento:

U.S. Geological Survey.
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MWD (Metropolitan Water District). 2016. 2015 Urban Water Management Plan. June 2016.

PHWA (Port Hueneme Water Agency). 2016. Port Hueneme Water Agency 2015 Urban Water Management Plan. Final. Prepared by Water Consultancy. August 2016.

NBVC (Naval Base Ventura County). 2015. Naval Base Ventura County Joint Land Use Study.

Prepared by Matrix Design Group. September 2015.

SCAG (Southern California Association of Governments). 2005. “land_use_scag_2005.lpk” (GIS Data: Land Use Data [1990, 1993, 2001, 2005]). Accessed October 20, 2016. http://gisdata.scag.ca.gov/SitePages/GIS%20Library.aspx.

SCAG. 2016. 2016–2040 Regional Transportation Plan/ Sustainable Communities Strategy.

Appendix: Demographics and Growth Forecast. Adopted April 2016.

SWRCB (State Water Resources Control Board). 1956. Bulletin No. 12: Ventura County Investigation Volume I. October 1953. Revised April 1956.

U.S. Census Bureau. 2016. 2010 Census [GIS data]. Accessed October 2016. http://www.census.gov/geo/maps-data/.

UWCD (United Water Conservation District). 2014. “Groundwater and Surface Water Conditions Report – 2013.” UWCD Open-File Report 2014-02.

UWCD. 2016. 2015 Urban Water Management Plan for the Oxnard–Hueneme System. Westlake Village, California: MNS Engineering. June 28, 2016.

UWCD. 2018. Administrative Draft Multiple Species Habitat Plan. United Water Conservation District, September 7, 2018.

VCFB (Ventura County Farm Bureau). 2016. Ventura County’s 2015 Crop & Livestock Report.

December 13, 2016. Accessed January 15, 2018. http://www.farmbureauvc.com/ county-crop-data.

VCPD (Ventura County Planning Department). 2005. Final Subsequent Environmental Impact Report for Focused General Plan Update and Related Amendments to the Non-Coastal Zoning Ordinance and Zone Change ZN05-0008. June 22, 2005.

VCPD. 2015. Ventura County General Plan: Goals Policies and Programs. Amended October 20, 2015.
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VCWPD (Ventura County Watershed Protection District). 2006. Inventory of Public and Private Water Purveyors in Ventura County. March 2006.

VCWPD. 2009. Calleguas Creek IWPP Phase II Management Strategy Study. Prepared by CH2MHill. August 19, 2009.

VCWPD. 2015. Lower Santa Clara River Salt and Nutrient Management Plan. Prepared by Larry Walker Associates, Carollo, Hydrometrics WRI, Rincon Consulting, and Dr. Norm Brown. April 2015.

VCWPD. 2016. “VCWPD Mapped Reaches” [shapefile dataset]. Provided by Richard Mendez (VCWPD) to Dudek. August 17, 2016.
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Table 1-1
Estimate of Project Cost and Water Supply for First 5 Years Proposed Project
Estimated
Annual Costs
Estimated AcreFeet of WaterEstimated Cost
per Acre-Foot
Oxnard Groundwater Recovery Enhancement and Treatment
Program Advanced Water Purification Facility
$7,000,000 2,000 $3,500
RiverPark–Saticoy Groundwater Replenishment Reuse Project Recycled Water Project
$6,885,000 4,500 $1,530
Freeman Diversion Expansion $6,426,000 7,400 $870
Temporary Land Fallowing $954,000 530 $1,800
Total $21,265,000 14,430 —
Table 1-2
Groundwater Sustainability Plan Estimated Implementation Cost through 2040 Fiscal
Year
Operations and
Monitoring Costs
Management,
Administration and
Other Costs
5-Year GSP
Evaluationa 10% Contingency Totalb
2020 $1,000,000 $1,455,000 $300,000 $275,500 $3,030,500 2021 $1,028,000 $1,495,740 $308,400 $283,214 $3,115,354 2022 $1,056,784 $1,537,621 $317,035 $291,144 $3,202,584 2023 $1,086,374 $1,580,674 $325,912 $299,296 $3,292,256 2024 $1,116,792 $1,624,933 $335,038 $307,676 $3,384,439 2025 $1,148,063 $1,670,431 $114,806 $293,330 $3,226,630 2026 $1,180,208 $1,717,203 $118,021 $301,543 $3,316,976 2027 $1,213,254 $1,765,285 $121,325 $309,986 $3,409,851 2028 $1,247,225 $1,814,713 $124,723 $318,666 $3,505,327 2029 $1,282,148 $1,865,525 $128,215 $327,589 $3,603,476 2030 $1,318,048 $1,917,759 $65,902 $330,171 $3,631,881
2031 $1,354,953 $1,971,457 $67,748 $339,416 $3,733,573
2032 $1,392,892 $2,026,658 $69,645 $348,919 $3,838,113
2033 $1,431,893 $2,083,404 $71,595 $358,689 $3,945,581
2034 $1,471,986 $2,141,739 $147,199 $376,092 $4,137,016 2035 $1,513,201 $2,201,708 $75,660 $379,057 $4,169,626
2036 $1,555,571 $2,263,356 $77,779 $389,671 $4,286,376
2037 $1,599,127 $2,326,730 $79,956 $400,581 $4,406,394
2038 $1,643,903 $2,391,878 $82,195 $411,798 $4,529,773
2039 $1,689,932 $2,458,851 $168,993 $431,778 $4,749,553 2040 $1,737,250 $2,527,699 $86,862 $435,181 $4,786,992
Totalb $28,067,603 $40,838,363 $3,187,009 $7,209,297 $79,302,272 Notes: GSP = Groundwater Sustainability Plan.

Costs are in 2020 dollars.
a The 5-year update costs include costs for the Oxnard Subbasin as well as the PVB and LPVB, for which FCGMA is the GSA. b Amounts may not sum precisely due to rounding.
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Table 1-3
Groundwater Sustainability Agencies in the Oxnard Subbasin GSA Name
Total Area of GSA
(Acres)
% of GSA area within
Oxnard Subbasin
Acres within
Oxnard Subbasin % of Oxnard Subbasin
Fox Canyon
Groundwater
Management Area
117,280 46.0 53,941 94.1
Camrosa Water
District–Oxnard
Subbasin
3,880 4.4 171 0.3
Oxnard Subbasin
Outlying Areas
(Ventura County)
3,236 100 3,236 5.6
Total 57,348 100
Notes: GSA = Groundwater Sustainability Agency.

Table 1-4
Summary of Land Ownership in the Oxnard Subbasin
Ownership Jurisdiction Description
Acres
within
Subbasin % of Total
Private Land
Private County of Ventura Privately owned land under County jurisdiction, largely agriculture and open space.
31,825 55.5%
Private City of Oxnard Privately owned land under municipal jurisdiction, largely consisting of urban development.
15,959 27.8%
Private Port Hueneme Privately owned land under municipal jurisdiction, largely consisting of urban development.
1,134 2.0%
Private City of Ventura South edge of the City consisting of an office park/warehouse/retail/commercial district (water
served by Ventura Water Department)
407 0.7%
Private City of Camarillo Consists of the western end of the Camarillo Airport and part of a commercial+mobile/pre-fab
home subdivision
281 0.5%
Subtotal (Private Land) 49,606 86.5%
Public Land
Municipal City of Oxnard, City of Ventura,
City of Camarillo, Port
Hueneme
Parks, and/or Golf Courses (Buenaventura Golf
Course uses recycled water for irrigation)
663 1.2%
County County of Ventura Mandalay County Park 8 0.01%
State California Department of Park
and Recreation, California State
University, California
Department of Corrections and
Rehabilitation
State Beaches (McGrath State Beach, Mandalay
State Beach), California State University Channel
Islands, Ventura Youth Correctional Facility
230 0.4%
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Table 1-4
Summary of Land Ownership in the Oxnard Subbasin
Ownership Jurisdiction Description
Acres
within
Subbasin % of Total
Federal U.S. Navy Naval Base Ventura County (Naval Construction Battalion Center Port Hueneme and Point Mugu
Naval Air Station)
6,046 10.5%
Non-Profit The Nature Conservancy Lower Santa Clara River/Ormond Beach 795 1.4% Subtotal (Public Land) 7,742 13.5%
Total 57,348 100%
Table 1-5
Oxnard Plain Stream Gauge Information
Station
Number Station Name
Record
Start
Record
End Active? Latitude Longitude
Elevation
(ft msl) Station Type
Santa Clara River
708 Santa Clara River
at Montalvo
Highway 101
1927 1993 No 34.241944 −119.189 70 Recording Stream
Gauge
708A Santa Clara River
at Saticoy
Highway 118
1967 2004 No 34.278889 −119.141 105 Recording Stream
Gauge
723 Santa Clara River
at Victoria Avenue
2007 N/A Yes 34.234917 −119.217 62 Recording Stream
Gauge
724 Santa Clara River
at Freeman
Diversion
2004 2005 No 34.299222 −119.108 161 Recording Stream
Gauge
Revolon Slough Watershed
776 Revolon Slough at
Laguna Road
1979 2006 No 34.176072 −119.100 11 Recording Stream
Gauge
776A Revolon Slough at
Pleasant Valley
Road
2005 N/A Yes 34.192592 −119.108 20 Recording Stream
Gauge
780 Beardsley Wash
at Central Avenue
1993 N/A Yes 34.2305 −119.112 60 Recording Stream
Gauge
782 Las Posas Estates
Drain
1999 2008 No 34.230816 −119.106 76 Recording Stream
Gauge
Calleguas Creek
805 Calleguas Creek
at California State
University
Channel Islands
1968 N/A Yes 34.179028 −119.040 58 Recording Stream
Gauge
Sources: VCWPD 2009, 2016.

Notes: ft msl = feet above mean sea level. N/A = not applicable, because gauge is active. 838
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-60
Table 1-6
Oxnard Plain Precipitation Station Information
Station
Number Station Name
Record
Start
Record
End Active? Latitude Longitude
Elevation
(ft msl) Station Type
Mean Annual
Rainfall (inches)
for Period of
Record
017 Hueneme Lighthouse near Port
Hueneme
1890 1972 No 34.143333 −119.21 10 Standard Precipitation 13.4 017A Port Hueneme–U.S. Navy 1972 1982 No 34.146389 −119.205 10 Standard Precipitation 15.6 017B Port Hueneme–U.S. Navy 1982 1996 No 34.146389 −119.204 10 Standard Precipitation 14.9 017C Port Hueneme–Oxnard Sewer
Plant
1996 N/A Yes 34.141684 −119.187 10 Recording
Precipitation Gauge

11.4 032 Oxnard–Water Department 1902 2003 No 34.201389 −119.175 53 Standard Precipitation 14.7 032A Oxnard Civic Center 2003 N/A Yes 34.200087 −119.18 53 Recording Precipitation Gauge

10.0 168 Oxnard Airport 1956 N/A Yes 34.201647 −119.208 34 Recording Precipitation Gauge

14.1 156 Oxnard CIMIS Station 2001 N/A Yes 34.2233639 −119.196920 77 CIMIS Station 12.4 177 Camarillo–Pacific Sod 1956 2004 No 34.156446 −119.079 20 Standard Precipitation 12.7 177A Camarillo–Pacific Sod 2004 N/A Yes 34.155471 −119.073 20 Recording Precipitation Gauge

9.9 215 Channel Islands Harbor 1963 N/A Yes 34.162042 −119.223 5 Standard Precipitation 13.4 215A Channel Islands Harbor–Kiddie
Beach
2015 N/A Yes 34.158944 −119.222 15 Recording
Precipitation Gauge

2.5 223 Point Mugu–U.S. Navy 1946 1976 No 34.118333 −119.107 5 Standard Precipitation Midnight

10.0 223A Point Mugu–U.S. Navy 1976 N/A Yes 34.112778 −119.119 12 Standard Precipitation Midnight

13.8 231 El Rio–County Yard 1966 2006 No 34.241111 −119.177 79 Standard Precipitation 16.7 231A El Rio–Riverpark 2006 2008 No 34.245417 −119.181 Unknown (near sea
level)
Recording
Precipitation Gauge

8.8 839
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-61
Table 1-6
Oxnard Plain Precipitation Station Information
Station
Number Station Name
Record
Start
Record
End Active? Latitude Longitude
Elevation
(ft msl) Station Type
Mean Annual
Rainfall (inches)
for Period of
Record
239 El Rio–UWCD Spreading
Grounds
1972 N/A Yes 34.239405 −119.153 105 Recording
Precipitation Gauge

15.2 257 Oxnard South–Vance 1979 1989 No 34.171944 −119.192 27 Standard Precipitation 15.7 261 Saticoy–Recharge Facility 1984 N/A Yes 34.278889 −119.123 145 Standard Precipitation 16.0 267 Ormond Beach–Occidental
Chemical
1989 1993 No 34.140556 −119.171 10 Standard Precipitation 14.1 273A Oxnard NWS 2010 N/A Yes 34.207207 −119.137 63 National Weather Service Site

8.6 403 Silverstrand Alert (Type B) 2008 N/A Yes 34.15271 −119.219 18 Non-Standard Recorder

8.2 412 El Rio–Mesa School APCD 2012 N/A Yes 34.252361 −119.143 131 Recording Precipitation Gauge

6.7 503 Oxnard Plain–Laguna Road
(Type B)
2008 2010 No 34.176072 −119.1 28 Non-Standard
Recorder

6.6 Notes: APCD = Air Pollution Control District; CIMIS = California Irrigation Management Information System; ft msl = feet above mean sea level; N/A = not applicable, because gauge is active; NWS = National Weather Service; UWCD = United Water Conservation District. 840
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-62
Table 1-7
Drought Periods in the Oxnard Plain
Drought Period Duration (years) Cumulative Deficit (inches) 1918–1936 18 −47.2
1944–1951 7 −31.5
1958–1964 6 −25.2
1969–1977 8 −24.8
1986–1991 5 −25.1
2011–2016 5 −27.7
Table 1-8
Past and Present Land Uses within the Oxnard Plain, 1990–2015 Land Use
Category
1990 1993 2001 2005 2015
Acres Percent Acres Percent Acres Percent Acres Percent Acres Percent Agriculture
Orchards and
Vineyards
4,863 8% 5,088 9% 4,438 8% 2,491 4% — —
Cropland and
Improved Pasture
Land
23,080 40% 22,921 40% 21,917 38% 22,188 39% — —
Nurseries 698 1% 743 1% 1,343 2% 1,677 3% — —
Horse Ranches 9 0% 9 0% 5 0% 8 0% — —
Other Agriculture 252 0% 245 0% 271 0% 265 0% — —
Dairy/Livestock 66 0% 66 0% 37 0% 25 0% — —
Total 28,969 51% 29,073 51% 28,011 49% 26,654 47% 26,636 47% Vacant/Open Space
Open Space 5,070 9% 4,713 8% 4,247 7% 4,007 7% — —
Water 358 1% 472 1% 461 1% 533 1% — —
Total 5,429 9% 5,185 9% 4,707 8% 4,540 8% 3,662 6%
Urban/Built-Up
Residential 8,061 14% 8,211 14% 8,810 15% 9,339 16% — — Mixed Commercial
and Industrial
2,399 4% 2,340 4% 2,403 4% 3,156 6% — —
Commercial and
Services
8,136 14% 8,277 14% 8,556 15% 8,795 15% — —
Industrial 1,977 3% 1,835 3% 2,083 4% 2,111 4% — —
Transportation,
Communication,
and Utilities
2,335 4% 2,384 4% 2,734 5% 2,695 5% — —
Total 22,907 40% 23,047 40% 24,586 43% 26,096 46% 26,542 47% Sources: SCAG 2005 (for 1990–2005); VCPD 2015 (for 2015).

Notes: Acres and percentages are rounded to the nearest whole number. The land use data for 2015 is based on the Ventura County General Plan land use map (VCPD 2015), which has a lower geographic resolution and uses fewer land use categories than data provided by SCAG for prior years; therefore, only the total amounts/percentages for the larger land use categories are provided for 2015.

The Naval Base Ventura County is primarily included in the "Commercial and Services” category. 841
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-63
Table 1-9
Past, Current, and Projected Population for Ventura County, the Cities of Oxnard and Port Hueneme, and the Oxnard Plain Population 1990 2000 2010 2012 2015 2040
Ventura County 669,016 756,902 825,378 833,000 853,188 965,210 Oxnard 142,216 170,358 197,899 200,100 206,908 237,300
Port Hueneme 20,322 21,845 21,723 21,800 22,399 22,400
Oxnard Plain — — 237,871 — — —
Sources: SCAG 2016 (for Ventura County 1990–2040, Oxnard 2012 and 2040, and Port Hueneme 1990–2012 and 2040); City of Oxnard 2011 (for Oxnard 1990–2010); City of Port Hueneme 2016a (Port Hueneme 2015); U.S. Census Bureau 2016 (Oxnard Plain 2010); U.S. Census Bureau 2015 (Oxnard 2015).

Note: — = not available or unknown.
842
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-64

INTENTIONALLY LEFT BLANK
843
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-65
Table 1-10
Oxnard Subbasin Existing Water Resources Monitoring Programs Program Program Agency Program Description Parameter Multi-Basin Program Source Link Surface Water Monitoring Programs
Ventura County Precipitation
Monitoring
VCWPD Collection of real-time and historical data from a network of precipitation gauges throughout Ventura County (approximately 22 within the Oxnard Subbasin). Data is available on the Web, along with some statistical reports. Gauge data are available in various time increments, depending on gauge type.

Precipitation LPVB, PVB, ASRVB, Oxnard
Subbasin
VCWPD. 2016. Hydrology Section
Website. Accessed September 15, 2016.
http://vcwatershed.net/hydrodata/gma
p.php?param=rain
Ventura County Streamflow
Monitoring Program
VCWPD, in cooperation with
USGS
Approximately 64 stream locations are monitored county wide (approximately 13 active and inactive gauges in the Oxnard Subbasin). Available data include average daily flow, event hydrographs, and peak flows.

Streamflow LPVB, PVB, ASRVB, Oxnard
Subbasin
VCWPD. 2016. Hydrology Section
Website. Accessed September 15, 2016.
http://vcwatershed.net/hydrodata/gma
p.php?param=rain
Ventura County Stream
Gauging Program
USGS, UWCD Approximately 64 stream locations are monitored county wide. Available data include average daily flow, event hydrographs, and peak flows.

Streamflow Oxnard Subbasin, PVB UWCD. 2014. Groundwater and Surface Water Conditions Report – 2013. UWCD
Open-File Report 2014-12 (p. 31).
http://www.unitedwater.org/images/sto
ries/reports/GW-Conditions-Reports/
2013%20GW%20and%20SW%20
Conditions%20Report%20(UWCD
%202014)%20FINAL.pdf
Surface Water Quality
Monitoring Program
UWCD Monitoring of surface water quality at variable intervals. Parameters monitored include general minerals, temperature, and pH. Data are used to confirm that water quality is acceptable for groundwater recharge and agricultural irrigation.

Streamflow Oxnard Subbasin, PVB UWCD. 2014. Groundwater and Surface Water Conditions Report – 2013. UWCD
Open-File Report 2014-12 (p. 31).
http://www.unitedwater.org/images/sto
ries/reports/GW-Conditions-Reports/
2013%20GW%20and%20SW%20
Conditions%20Report%20(UWCD
%202014)%20FINAL.pdf
Los Angeles Regional Water
Quality Control Board
Surface Water Quality
Sampling
— — — — UWCD. 2014. Groundwater and Surface
Water Conditions Report – 2013. UWCD
Open-File Report 2014-12 (p. 32).
—
Existing Groundwater Monitoring Programs
California Statewide
Groundwater Elevation
Monitoring (CASGEM)
DWR program implemented
by VCWPD
DWR-mandated program (Senate Bill X7-6) to track seasonal and long-term groundwater elevation trends.

Groundwater
Elevation
LPVB, PVB, ASRVB, Oxnard
Subbasin
DWR. 2016. California Statewide
Groundwater Elevation Monitoring
(CASGEM) Program. 2016. Accessed
September 15, 2016.
http://www.water.ca.gov/groundwater/
casgem/
Groundwater Ambient
Monitoring and Assessment
Program (GAMA)
SWRCB SWRCB Program implemented in 2000 (modified by Assembly Bill 599 in 2001) to monitor and assess groundwater basins throughout the state.

Groundwater
Quality
LPVB, PVB, ASRVB, Oxnard
Subbasin
SWRCB. 2016. GAMA – Groundwater
Ambient Monitoring and Assessment
Program Website. Accessed September
22, 2016.
http://www.swrcb.ca.gov/gama/
Ventura County
Groundwater Elevation
Monitoring Program
VCWPD Quarterly measurement of approximately 200 groundwater well elevations (approximately 38 within the Oxnard Subbasin) throughout Ventura County by VCWPD staff.

Groundwater
Elevation
Oxnard Subbasin, LPVB,

PVB, ASRVB
VCWPD. 2015. 2014 Annual Report of
Groundwater Conditions (p. 12.)
http://pwaportal.ventura.org/WPD/
docs/Groundwater-Resources/
2014%20Annual%20Report-Web.pdf
Ventura County
Groundwater Quality
Monitoring Program
VCWPD Approximately 150 wells sampled throughout the County (approximately 46 in the Oxnard Subbasin) and analyzed for general minerals and other constituents.

Groundwater
Quality
Oxnard Subbasin, LPVB,

PVB, ASRVB
VCWPD. 2015. 2014 Annual Report of
Groundwater Conditions (p. 12).
http://pwaportal.ventura.org/WPD/
docs/Groundwater-Resources/
2014%20Annual%20Report-Web.pdf
UWCD Groundwater Quality
Monitoring Program
UWCD Measurement of groundwater water quality throughout the UWCD boundaries to comply with state standards for aesthetics and safety, monitor saltwater intrusion and saline migration, and track changes to water quality. Approximately 120 wells are sampled in the Oxnard Subbasin.

Groundwater
Quality
Oxnard Subbasin, PVB UWCD. 2014. Groundwater and Surface Water Conditions Report – 2013. UWCD
Open-File Report 2014-12 (p. 26).
http://www.unitedwater.org/images/
stories/reports/GW-Conditions-Reports/
2013%20GW%20and%20SW%20
Conditions%20Report%20
(UWCD%202014)%20FINAL.pdf
FCGMA Groundwater
Extraction Reporting
Program (1985)
FCGMA Since 1985, FCGMA has collected extraction records from well operators on a semi-annual basis. Requirements include periodic calibration of meters.

Groundwater
Extraction
Oxnard Subbasin, LPVB,

PVB, ASRVB
FCGMA, UWCD, and CMWD. 2007. 2007
Update to the Fox Canyon Groundwater
Management Agency Groundwater
Management Plan. May 2007 (p. 17).
http://www.fcgma.org/component/
content/article/20-public-documents/
plans/95-groundwater-management-plan
844
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-66
Table 1-10
Oxnard Subbasin Existing Water Resources Monitoring Programs Program Program Agency Program Description Parameter Multi-Basin Program Source Link Basin Management
Objectives Monitoring
FCGMA FCGMA has established a set of Basin Management Objectives that pertain to the overall health of the groundwater basins, including water levels and water quality. Each year, FCGMA publishes a report tracking the progress toward meeting the objectives.

Groundwater
Conditions
Oxnard Subbasin, LPVB,

PVB, ASRVB
FCGMA, UWCD, and CMWD. 2007. 2007
Update to the Fox Canyon Groundwater
Management Agency Groundwater
Management Plan. May 2007 (p. iii).
http://www.fcgma.org/component/
content/article/20-public-documents/
plans/95-groundwater-management-plan
Other Existing Programs
Ventura County Evaporation
Monitoring
VCWPD There is an evaporation gauge that records monthly evaporation from El Rio Spreading Grounds.

Evaporation Oxnard Subbasin VCWPD. 2016. Hydrology Section Website. Accessed September 15, 2016.
http://vcwatershed.net/hydrodata/
gmap.php?param=rain
California Irrigation
Management Information
System (CIMIS)
DWR CIMIS manages a network of over 145 automated weather stations in California. Temperature, Precipitation,
Evapotranspiration
LPVB, PVB CIMIS. 2018. CIMIS Data Website.

Accessed January 15, 2018.
http://www.cimis.water.ca.gov
California Water Rights
Permit 18908
UWCD, Water Rights
Decision
Specifies conditions of release and diversion for habitat conservation. Surface Water, Environmental
— UWCD. 2014. Groundwater and Surface
Water Conditions Report – 2013. UWCD
Open-File Report 2014-12 (p. 18).
http://www.unitedwater.org/images/
stories/reports/GW-Conditions-Reports/
2013%20GW%20and%20SW%20
Conditions%20Report%20(UWCD
%202014)%20FINAL.pdf
Salt Nutrient Management
Plans
VCWPD Complies with the SWRCB Recycled Water Policy. Water Quality Oxnard Forebay VCWPD. 2015. Lower Santa Clara River Salt and Nutrient Management Plan.

Prepared by Larry Walker Associates.

April 2015.
http://www.waterboards.ca.gov/
losangeles/water_issues/programs/
salt_and_nutrient_management/
docs/2015/May/DraftSaltandNutrient
ManagementPlan/Section1Introduction
andGoals.pdf
Notes: ASRVB = Arroyo Santa Rosa Valley Basin; CIMIS = California Irrigation Management Information System; CMWD = Calleguas Municipal Water District; DWR = California Department of Water Resources; FCGMA = Fox Canyon Groundwater Management Agency; LPVB = Las Posas Valley Basin; PVB = Pleasant Valley Basin; SWRCB = State Water Resources Control Board; USGS = U.S. Geological Survey; UWCD = United Water Conservation District; VCWPD = Ventura County Watershed Protection District.

Table 1-11
Oxnard Subbasin Existing Water Resources Management Projects, Programs, and Strategies Program/Project Program Agency Program Description Parameter Conjunctive Use Program? Multi-Basin Program Source Link Existing Surface Water Management Projects, Programs, and Strategies Ventura County
Stormwater Quality
Monitoring Program
Ventura County
Watershed Protection
District, Camarillo,
Moorpark, Oxnard, Port
Hueneme, and others.

Program meets the requirements of the Ventura County
Stormwater Permits. Includes water quality sampling,
watershed assessments, business inspections, and
pollution prevention programs.

Surface Water
Quality
No Oxnard Subbasin, LPVB,

PVB, ASRVB
Ventura Countywide Stormwater
Quality Management Program
Website. Accessed September 15,
2016.
http://www.vcstormwater.org/
State Water Project
Importation
DWR, Ventura County,
UWCD, CMWD, and City
of Ventura
Purchase of up to 5,000 AFY of Ventura County's
20,000 AFY State Water Project allocation for release
and percolation from Lake Piru, the Freeman Diversion,
and surface deliveries to Pleasant Valley through the
PTP. The water reaching the Freeman Diversion is
considered a “foreign water supply” and is credited to
UWCD.

Supplemental
Water
Yes Oxnard, LPVB, PVB,
ASRVB
UWCD. 2014. Groundwater and
Surface Water Conditions Report -
2013. UWCD Open-File Report
2014-12 (p. 36).

FCGMA, UWCD, and CMWD. 2007.
2007 Update to the Fox Canyon
Groundwater Management Agency
Groundwater Management Plan.

May 2007 (p. 50).
http://www.unitedwater.org/images/stories/reports/
GW-Conditions-Reports/2013%20GW%20and%20SW%20
Conditions%20Report%20(UWCD%202014)%20FINAL.pdf
845
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-67
Table 1-11
Oxnard Subbasin Existing Water Resources Management Projects, Programs, and Strategies Program/Project Program Agency Program Description Parameter Conjunctive Use Program? Multi-Basin Program Source Link Importation of
Metropolitan Water
District Water
CMWD Import and deliver water from wholesaler Metropolitan Water District. Water purchased by water retailers such as the City of Oxnard to supplement water supply
instead of pumping groundwater.

Supplemental
Water
Yes Oxnard Subbasin, PVB,
LPVB
CMWD. 2015. Urban Water
Management Plan – Final, pp. 1-1,
4-1, 4-2 (Figure 4-1), 6-1, 6-13.
http://www.mwdh2o.com/Who%20We%20Are%20%20.
2007Fact%20Sheets/Member%20Agency%20Map.pdf
http://www.mwdh2o.com/WhoWeAre/Member-Agencies/.
2007Pages/default.aspx
http://www.mwdh2o.com/WhoWeAre/History/Pages/
default.aspx
http://www.calleguas.com/images/docs-documentsreports/cmwdfinal2015uwmp.pdf Salinity Management
Pipeline
CMWD A brine disposal pipeline that collects brine generated by desalting facilities in the LPVB, PVB, and Oxnard
Subbasin and conveys it to an ocean outfall for disposal.

Future construction of the pipeline is expected to serve additional facilities, including those in the ASRVB.

Surface Water Yes Oxnard Subbasin, LPVB,

PVB, ASRVB
CMWD. 2015. Urban Water
Management Plan – Final, p. 6-1.
http://www.calleguas.com/images/docs-documents-reports/ cmwdfinal2015uwmp.pdf
Existing Groundwater Management Projects, Programs, and Strategies Basin Management
Objective Program
FCGMA FCGMA has established a set of Basin Management
Objectives that pertain to the overall health of the
groundwater basins, including water levels and water
quality. Each year, FCGMA publishes a report tracking
the progress toward meeting the objectives.

Groundwater
Conditions
No Oxnard Subbasin, LPVB,

PVB, ASRVB
FCGMA, UWCD, and CMWD. 2007.
2007 Update to the Fox Canyon
Groundwater Management Agency
Groundwater Management Plan.

May 2007 (p. iii).
http://www.fcgma.org/component/content/article/
20-public-documents/plans/
95-groundwater-management-plan
FCGMA Groundwater
Storage (including InLieu) Credit Program
FCGMA This is a program by which credits are issued to the deliverer in equal amounts to the amount of delivered
“newly available” water, imported water from outside the County, recycled water, or diverted surface water that
would otherwise be wasted to the ocean. Delivered
water used in lieu of pumping.

Groundwater Yes Oxnard Subbasin, LPVB,

PVB, ASRVB
FCGMA. 2015. Fox Canyon
Groundwater Management Agency,
Calendar Year 2014 Annual Report
(p. 23).
http://www.fcgma.org/public-documents/reports
FCGMA Groundwater
Injection Credit
Program
FCGMA This is a program by which credits are issued to
operators that inject “newly available” water, water from outside the County, or recycled water.

Groundwater Yes LPVB, PVB, ASRVB,
Oxnard Subbasin
FCGMA. 2015. Fox Canyon
Groundwater Management Agency,
Calendar Year 2014 Annual Report
(p. 23).
http://www.fcgma.org/public-documents/reports
Salinity Management
Pipeline
CMWD A brine disposal pipeline that collects brine generated by desalting facilities in the LPVB, PVB, and Oxnard
Subbasin and conveys it to an ocean outfall for disposal.

Future construction of the pipeline is expected to serve additional facilities, including those in the ASRVB.

Groundwater Yes Oxnard Subbasin, LPVB,

PVB, ASRVB
CMWD. 2015. Urban Water
Management Plan – Final, p. 6-1.
http://www.calleguas.com/images/docs-documents-reports/ cmwdfinal2015uwmp.pdf
Groundwater Supply
Policy
(Formerly Brackish
Groundwater Policy)
FCGMA The FCGMA Board of Directors adopted Resolution No. 2016-05, a policy for evaluating and authorizing
proposals for groundwater supply projects. It allows for consideration of development of brackish groundwater
for supply projects subject to monitoring requirements
and other constraints and restrictions including
compliance with SGMA.

Groundwater Yes Oxnard Subbasin, LPVB,

PVB, ASRVB
FCGMA. n.d. Draft Brackish
Groundwater Project Pumping
Policy.
http://www.fcgma.org/images/Erin/Draft%20Brackish
%20Groundwater%20Project%20Pumping%20Policy
%20revised%2020160720.pdf
846
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-68
Table 1-11
Oxnard Subbasin Existing Water Resources Management Projects, Programs, and Strategies Program/Project Program Agency Program Description Parameter Conjunctive Use Program? Multi-Basin Program Source Link Extraction Fee
Program
FCGMA Groundwater extractors are assessed fees per acre-foot of extraction. Fees have been used by FCGMA to
finance its management activities since its enabling
legislation in 1983.

Groundwater No Oxnard Subbasin, LPVB,

PVB, ASRVB
Assembly Bill No. 2995, Article 9. http://www.fcgma.org/fcgma.old/publicdocuments/ ordinances/ordinanceAB-2995.pdf
Groundwater
Extraction Limitation
Program
FCGMA FCGMA has implemented a program of reduced
allocations.

Groundwater No Oxnard Subbasin, LPVB,

PVB, ASRVB
FCGMA, UWCD, and CMWD. 2007.
2007 Update to the Fox Canyon
Groundwater Management Agency
Groundwater Management Plan.

May 2007 (p. 45).
http://www.fcgma.org/component/content/article/20-publicdocuments/plans/95-groundwater-management-plan Extraction Surcharge
Program
FCGMA FCGMA charges a fee to well operators for groundwater extractions in excess of annual allocation amounts
Groundwater No Oxnard Subbasin, LPVB,

PVB, ASRVB
FCGMA, UWCD, and CMWD. 2007.
2007 Update to the Fox Canyon
Groundwater Management Agency
Groundwater Management Plan.

May 2007 (p. 45).
http://www.fcgma.org/component/content/article/20-publicdocuments/plans/95-groundwater-management-plan Prohibition of export of
groundwater
FCGMA FCGMA Ordinance requires Board of Directors approval for the export of groundwater from within the FCGMA
boundary for use outside of the boundary
Groundwater No Oxnard Subbasin, LPVB,

PVB, ASRVB
FCGMA Ordinance Code, Chapter 5,

5.2.2.1. http://www.fcgma.org/images/ordinances_legislation/ Ord_Code_FINAL_-_amended_01-09-2015.pdf
Other Existing Programs
IRWM Program WCVC Initiated with Proposition 50 in 2006, the program provides competitive grant funds for projects and studies in accordance with a comprehensive IRWM Plan.

Groundwater,
Surface Water
No Oxnard Subbasin, LPVB,

PVB, ASRVB
Ventura County Watersheds
Coalition. 2016. WCVC. Accessed
September 15, 2016.
http://www.ventura.org/wcvc/IRWMP/2014IRWMP.htm
Oxnard–Hueneme
Pipeline (1954)
UWCD Pumping of Oxnard Forebay wells to supply water to the Cities of Oxnard and Port Hueneme, thus avoiding
coastal pumping and exacerbation of seawater intrusion.

Groundwater
Quality
Yes Oxnard Subbasin UWCD. 2014. Groundwater and
Surface Water Conditions Report –
2013. UWCD Open-File Report 2014-
12 (pp. 7–8).
http://www.unitedwater.org/images/stories/reports/
GW-Conditions-Reports/2013%20GW%20and%20SW
%20Conditions%20Report%20(UWCD%202014)
%20FINAL.pdf
Pumping Trough
Pipeline (1986)
UWCD Supplies agriculture on the Oxnard Subbasin with a combination of surface water diverted from the Santa
Clara River and groundwater, thus reducing the need for groundwater pumpage in the central Oxnard Plain
pumping depression (1986).

Surface/
Groundwater
Yes Oxnard Subbasin and
PVB
UWCD. 2014. Groundwater and
Surface Water Conditions Report –
2013. UWCD Open-File Report
2014-12 (p. 5).
http://www.unitedwater.org/images/stories/reports/
GW-Conditions-Reports/2013%20GW%20and%20SW
%20Conditions%20Report%20(UWCD%202014)
%20FINAL.pdf
The Freeman
Diversion (1991)
UWCD Diversion of Santa Clara River flood flows to Saticoy, El Rio, and Noble Basins for groundwater recharge and
surface deliveries through the PTP and PVP. The
Freeman Diversion allows for surface water supply in
place of groundwater pumping, thus reducing the risk of seawater intrusion.
— Yes Oxnard Subbasin and
PVB
UWCD. 2014. Groundwater and
Surface Water Conditions Report –
2013. UWCD Open-File Report
2014-12 (p. 39).
http://www.unitedwater.org/images/stories/reports/
GW-Conditions-Reports/2013%20GW%20and%20SW
%20Conditions%20Report%20(UWCD%202014)
%20FINAL.pdf
The Noble Spreading
Grounds (1995)
UWCD Diversion of Santa Clara River flows to spreading
grounds recharging both the UAS and LAS.
— Yes — UWCD. 2014. Groundwater and
Surface Water Conditions Report –
2013. UWCD Open-File Report
2014-12 (p. 5).
http://www.unitedwater.org/images/stories/reports/
GW-Conditions-Reports/2013%20GW%20and%20SW
%20Conditions%20Report%20(UWCD%202014)
%20FINAL.pdf
Saticoy Well Field
(2003)
UWCD Draws from the mound beneath the Saticoy Spreading Grounds and allows for additional Santa Clara River
recharge.
— Yes — UWCD. 2014. Groundwater and
Surface Water Conditions Report –
2013. UWCD Open-File Report
2014-12 (p. 5).
http://www.unitedwater.org/images/stories/reports/
GW-Conditions-Reports/2013%20GW%20and%20SW
%20Conditions%20Report%20(UWCD%202014)
%20FINAL.pdf
847
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-69
Table 1-11
Oxnard Subbasin Existing Water Resources Management Projects, Programs, and Strategies Program/Project Program Agency Program Description Parameter Conjunctive Use Program? Multi-Basin Program Source Link Rose and Ferro
Spreading Grounds
UWCD Diversion of Santa Clara River Water to former mining pits for the recharge of groundwater.
— Yes — UWCD. 2014. Groundwater and
Surface Water Conditions Report –
2013. UWCD Open-File Report
2014-12 (p. 6).
http://www.unitedwater.org/images/stories/reports/
GW-Conditions-Reports/2013%20GW%20and%20SW
%20Conditions%20Report%20(UWCD%202014)
%20FINAL.pdf
El Rio Spreading
Grounds
UWCD Diversion of Santa Clara River flows to spreading
grounds recharging both the UAS and LAS.
— Yes — UWCD. 2014. Groundwater and
Surface Water Conditions Report –
2013. UWCD Open-File Report
2014-12 (p. 5).
http://www.unitedwater.org/images/stories/reports/
GW-Conditions-Reports/2013%20GW%20and%20SW
%20Conditions%20Report%20(UWCD%202014)
%20FINAL.pdf
Pleasant Valley
Pipeline
UWCD Water diverted from Santa Clara River is provided to the PVCWD via a pipeline that terminates at the Pleasant
Valley Reservoir. This water is supplied to agricultural users and offsets the need for groundwater pumping.
— Yes Oxnard Subbasin and
PVB
UWCD. 2014. Groundwater and
Surface Water Conditions Report –
2013. UWCD Open-File Report
2014-12 (p. 8).
http://www.unitedwater.org/images/stories/reports/
GW-Conditions-Reports/2013%20GW%20and%20SW
%20Conditions%20Report%20(UWCD%202014)
%20FINAL.pdf
Conejo Creek
Diversion (2002)
CWD PVCWD receives surface water from CWD’s Conejo
Creek Diversion.

Surface Water Yes — UWCD. 2014. Groundwater and
Surface Water Conditions Report –
2013. UWCD Open-File Report 2014-
12 (p. 9).
http://www.unitedwater.org/images/stories/reports/
GW-Conditions-Reports/2013%20GW%20and%20SW
%20Conditions%20Report%20(UWCD%202014)
%20FINAL.pdf
FCGMA M&I Allocation
Program
FCGMA The current M&I allocation program, also known as a Temporary Extraction Allocation, was implemented with
the passage of Ordinance E in 2014. It was
implemented for M&I users, replacing HA and BA.

Groundwater Yes Oxnard Subbasin, LPVB,

PVB, ASRVB
FCGMA. 2015. Calendar Year 2014
Annual Report (p. 10).
http://www.fcgma.org/public-documents/reports
FCGMA Irrigation
Allocation Program
FCGMA Requirement for agricultural irrigation efficiency as compared to FCGMA calculations for required irrigation
for specific crop types with consideration of weather
conditions.

Groundwater
Extractions
Yes Oxnard Subbasin, LPVB,

PVB, ASRVB
FCGMA. 2015. Calendar Year 2014
Annual Report (p. 10).
http://www.fcgma.org/public-documents/reports
Groundwater Recovery
Enhancement and
Treatment (GREAT)
Program – 2013
City of Oxnard A desalination facility, recycled water system, ASR facility, and brine disposal line combine to provide nonpotable M&I water and agricultural irrigation water, to reduce pumping of LAS groundwater.

Groundwater/
Surface Water
Yes Oxnard Subbasin and
Oxnard Forebay
FCGMA, UWCD, and CMWD. 2007.
2007 Update to the Fox Canyon
Groundwater Management Agency
Groundwater Management Plan.

May 2007 (p. 54).
http://www.fcgma.org/component/content/article/20-publicdocuments/plans/95-groundwater-management-plan Various Water
Conservation
Programs
Ventura County, Cities,
and Water Districts
There are numerous conservation programs conducted
by Cities, Ventura County, and other entities within
FCGMA jurisdiction that provide education, incentives,
and regulations to encourage water savings from both
the M&I and agricultural sectors. The exact configuration of these programs change with climate and local and
state requirements.

Surface Water,
Groundwater
No Oxnard Subbasin, LPVB,

PVB, ASRVB
— —
Notes: AFY = acre-feet per year; ASR = aquifer storage and recovery; ASRVB = Arroyo Santa Rosa Valley Basin; BA = Baseline Allocation; CMWD = Calleguas Municipal Water District; CWD= Camrosa Water District; DWR = California Department of Water Resources; FCGMA = Fox Canyon Groundwater Management Agency; HA = Historical Allocation; IRWM = Integrated Regional Water Management; LPVB = Las Posas Valley Basin; M&I = municipal and industrial; PTP = Pumping Trough Pipeline; PVB = Pleasant Valley Basin; PVCWD= Pleasant Valley County Water District; PVP = Pleasant Valley Pipeline; UWCD = United Water Conservation District; WCVC = Watersheds Coalition of Ventura County. 848
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Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-71
Table 1-12
FCGMA Public Meetings on Oxnard Subbasin GSP
Meeting Date
FCGMA Special Board Meeting November 8, 2019
TAG Meeting October 31, 2019
FCGMA Regular Board Meeting August 28, 2019
GSP Work Shops August 21,22, 2019
TAG Meeting August 1, 2019
FCGMA Regular Board Meeting July 24, 2019
FCGMA Regular Board Meeting June 26, 2019
FCGMA Special Board Meeting May 22, 2019
TAG Meeting May 5, 2019
FCGMA Regular Board Meeting April 24, 2019
FCGMA GSP Public Workshop No. 4 March 15, 2019
FCGMA Special Board Meeting March 15, 2019
FCGMA Regular Board Meeting February 27, 2019
Special TAG Meeting February 19, 2019
FCGMA Special Board Meeting February 8, 2019
Special TAG Meeting February 6, 2019
FCGMA Regular Board Meeting January 23, 2019
Special TAG Meeting January 17, 2019
TAG Meeting December 6, 2018
FCGMA Regular Board Meeting December 5, 2018
FCGMA Special Board Meeting November 20, 2018
TAG Meeting November 1, 2018
FCGMA Regular Board Meeting October 24, 2018
FCGMA Special Board Meeting October 12, 2018
TAG Meeting October 4, 2018
FCGMA Regular Board Meeting September 26, 2018
FCGMA Special Board Meeting September 14,2018
TAG Meeting September 6, 2018
FCGMA Special Board Meeting August 29, 2018
FCGMA Special Board Meeting Oxnard and Pleasant Valley Pumping Allocation Workshop July 25, 2018 FCGMA Regular Board Meeting July 25, 2018
TAG Meeting July 5, 2018
FCGMA Special Board Meeting June 20, 2018
Special TAG Meeting June 19, 2018
TAG Meeting June 14, 2018
FCGMA Regular Board Meeting May 23, 2018
TAG Meeting May 3, 2018
FCGMA Regular Board Meeting April 25, 2018
TAG Meeting April 5, 2018
FCGMA Regular Board Meeting March 28, 2018
850
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-72
Table 1-12
FCGMA Public Meetings on Oxnard Subbasin GSP
Meeting Date
FCGMA Special Board Meeting March 9, 2018
TAG Meeting March 1, 2018
FCGMA Regular Board Meeting February 28,2018
FCGMA Special Board Meeting February 26, 2018
FCGMA GSP Public Workshop No. 3 February 8, 2018
TAG Meeting February 1, 2018
Special TAG Meeting January 30, 2018
FCGMA Regular Board Meeting January 24, 2018
TAG Meeting January 4, 2018
FCGMA Special Board Meeting January 3, 2018
Special TAG Meeting December 14, 2018
FCGMA Special Board Meeting November 13, 2017
TAG Meeting November 2, 2017
TAG Meeting October 6, 2017
FCGMA Special Board Meeting October 13, 2017
FCGMA Regular Board Meeting October 25, 2017
FCGMA Regular Board Meeting September 27, 2017
FCGMA GSP Public Stakeholder Workshop No. 2A – Oxnard and Pleasant Valley September 20, 2017 FCGMA Operations Committee Meeting September 14, 2017
TAG Meeting September 7, 2017
FCGMA Special Board Meeting August 11, 2017
FCGMA Operations Committee Meeting August 10, 2017
TAG Meeting August 3, 2017
Special TAG Meeting – Sustainability Objective Concepts July 27, 2017 FCGMA Regular Board Meeting July 26, 2017
FCGMA Fiscal Committee Budget Workshop July 25, 2017
Water Market Pilot Program Ad Hoc Committee Meeting July 24, 2017 FCGMA Board Executive Committee Meeting July 12, 2017
TAG Meeting July 6, 2017
Special TAG Meeting – Groundwater-Dependent Ecosystems June 29, 2017 FCGMA Regular Board Meeting June 28, 2017
FCGMA Board Executive Committee Meeting June 15, 2017
TAG Meeting June 1, 2017
FCGMA Regular Board Meeting May 24, 2017
TAG Meeting May 4, 2017
Special TAG Meeting – Groundwater Models April 27, 2017 FCGMA Regular Board Meeting April 26, 2017
Special TAG Meeting March 24, 2017
Special TAG Meeting – Groundwater Models March 24, 2017 FCGMA Regular Board Meeting March 22, 2017
851
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-73
Table 1-12
FCGMA Public Meetings on Oxnard Subbasin GSP
Meeting Date
TAG Meeting March 3, 2017
FCGMA Regular Board Meeting February 22, 2017
TAG Meeting February 2, 2017
FCGMA Regular Board Meeting January 25, 2017
TAG Meeting December 16, 2016
FCGMA Regular Board Meeting December 9, 2016
TAG Meeting November 18, 2016
FCGMA GSP Public Workshop No. 1 November 15, 2016
FCGMA Regular Board Meeting October 26, 2016
TAG Meeting October 7, 2016
FCGMA Executive Committee October 3, 2016
FCGMA Regular Board Meeting September 28, 2016
TAG Meeting August 26, 2016
TAG Meeting July 29, 2016
FCGMA Regular Board Meeting July 20, 2016
FCGMA Regular Board Meeting June 22, 2016
TAG Meeting May 27, 2016
FCGMA Regular Board Meeting May 25, 2016
FCGMA Special Board Meeting May 13, 2016
TAG Meeting April 29, 2016
FCGMA Regular Board Meeting April 27, 2017
TAG Meeting March 25, 2016
FCGMA Regular Board Meeting March 23, 2016
FCGMA Special Board Meeting March 11, 2016
TAG Meeting February 26, 2016
TAG Meeting January 29, 2016
FCGMA Regular Board Meeting January 27, 2016
TAG Meeting December 18, 2015
FCGMA Regular Board Meeting December 11, 2015
TAG Meeting November 20, 2015
FCGMA Special Board Meeting November 13, 2015
TAG Meeting October 30, 2015
FCGMA Regular Board Meeting October 28, 2015
TAG Meeting September 25, 2015
FCGMA Regular Board Meeting September 23, 2015
TAG Meeting August 28, 2015
FCGMA Special Board Meeting August 13, 2015
TAG Meeting July 30, 2015
FCGMA Regular Board Meeting July 22, 2015
FCGMA Regular Board Meeting June 24, 2015
852
1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-74
Table 1-12
FCGMA Public Meetings on Oxnard Subbasin GSP
Meeting Date
FCGMA Regular Board Meeting May 27, 2015
FCGMA Regular Board Meeting April 22, 2015
FCGMA Regular Board Meeting March 25, 2015
Notes: FCGMA = Fox Canyon Groundwater Management Agency; GSP = Groundwater Sustainability Plan; TAG = Technical Advisory Group. 853
Point Mugu
Naval Air
Station
California
State University
Channel Islands
Naval Construction
Battalion Center
Port Hueneme
Ventura Youth
Correctional
Facility Ventura Rd
Lewis Rd
Central Ave
Hueneme Rd
Pleasant Valley Rd
5th St
232 ?
126 ?
118 ?
?34
?1
P a c i f i c O c e a n
£¤101
Ventura
Oxnard
Port Hueneme
Camarillo
Calleguas Cree
R
k
evolon Slough
Santa Clara River
Santa
Monica
Mountains
Somis
Gap
Camarillo Hills
Vicinity Map for the Oxnard Subbasin
Groundwater Sustainability Plan for the Oxnard Subbasin SOURCE: DWR; County of Ventura; FCGMA
Date: 3/26/2019 - Last saved by: ntucker - Path: Z:\Hydro\Projects\Fox_Canyon_GMA\MXD\FINAL_MXD\OXNARD\CH_1_FIGURES\Figure 1-1.mxd FIGURE 1-1
Revised Bulletin 118 Groundwater Basins
and Subbasin (DWR 2016a)
Arroyo Santa Rosa Valley (4-007)
Las Posas Valley (4-008)
Pleasant Valley (4-006)
Oxnard (4-004.02)
Fox Canyon Groundwater Management Agency
Boundary (FCGMA 2019)
Oxnard Forebay
Bulletin 118 Santa Clara River Valley
Subbasins Adjacent to Oxnard
Mound (4-004.03)
Santa Paula (4-004.04)
Major Rivers/Stream Channels
Urban Land Use
State & Federal Lands
0 0.5 1 2 3 n Miles
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855
Ventura Rd
Lewis Rd
Central Ave
Hueneme Rd
Pleasant Valley Rd
5th St
232 ?
126 ?
118 ?
?34
?1
P a c i f i c O c e a n
£¤101
Ventura
Oxnard
Port Hueneme
Camarillo
Calleguas Creek
Santa Clara River
Revolon Slough
Santa Monica Mou
Camarillo Hills
Administrative Boundaries for the Oxnard Subbasin
Groundwater Sustainability Plan for the Oxnard Subbasin SOURCE: DWR; County of Santa Barbara; FCGMA
Date: 5/6/2019 - Last saved by: ntucker - Path: Z:\Hydro\Projects\Fox_Canyon_GMA\MXD\FINAL_MXD\OXNARD\CH_1_FIGURES\Figure 1-2.mxd Fox Canyon Groundwater Management
Agency
Camrosa Water District-Oxnard Subbasin (GSA
Boundary)
Oxnard Basin Outlying Areas (GSA
Boundary)
Revised Bulletin 118 Groundwater
Basins and Subbasin (DWR 2016a)
Arroyo Santa Rosa Valley (4-007)
Las Posas Valley (4-008)
Pleasant Valley (4-006)
Oxnard (4-004.02)
Historical FCGMA Subbasins
West Las Posas Basin
East Las Posas Basin
South Las Posas Basin
Oxnard Forebay
Oxnard Pressure Plain
Pleasant Valley Basin
Santa Rosa Basin 0 1 2 3
n Miles
FIGURE 1-2
856
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)
)
)
)
")
")
017
017A
017B
017C
032 032A 168
177
177A
215
215A
223
223A
230A
231
231A
239
257
261
267
273A
403
412
503
708
708A
719
723
724
776
776A
780
782
805
Mugu Lagoon
Point Mugu
Freeman Diversion
Conejo Creek
Diversion
Camarillo Sanitary
District Water
Reclamation
Camrosa Water
Reclamation
Plant
232 ?
126 ?
118 ?
?34
?1
P a c i f i c O c e a n
£¤101
Ventura
Oxnard
Port Hueneme
Camarillo
Arroyo LasPosas
Calleguas Creek
Revolon
Slough
Santa Clara River
C o n e j o M o un t
156
152
Cam arill o Hills
Sa nt a M o n i c a M o un t a i ns
Weather Station and Stream Gauge Locations
Groundwater Sustainability Plan for the Oxnard Subbasin SOURCE: DWR; County of Santa Barbara; VCWPD; USGS NHD
Date: 4/29/2019 - Last saved by: ntucker - Path: Z:\Hydro\Projects\Fox_Canyon_GMA\MXD\FINAL_MXD\OXNARD\CH_1_FIGURES\Figure 1-3.mxd FIGURE 1-3
Fox Canyon Groundwater Management Agency Boundary (FCGMA 2019d)
) Diversions and reclamation sites
Revised Bulletin 118 Groundwater Basins and Subbasin
(DWR 2016a)
Arroyo Santa Rosa Valley (4-007)
Las Posas Valley (4-008)
Pleasant Valley (4-006)
Oxnard (4-004.02)
Ventura County Rivers, Streams and Channels (VCWPD 2016) ") CIMIS Stations
Ventura County Gauge Locations (VCWPD 2016; labeled
by station number)
National Weather Service Station
Recording Precipitation Gauge
Standard Precipitation
Storage Precipitation
Non-Standard Precipitation Recorder
Recording Stream Gauge 0 0.5 1 2 3 4 n Miles
858
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Groundwater Sustainability Plan for the Oxnard Subbasin SOURCE: Ventura County Watershed Protection District
Average Daily Flows (ADF) and Monthly Minimum ADF in Oxnard Surface Waters FIGURE 1-4
1920 1940 1960 1980 2000 2020
0 20
40 60
80 100
Western Santa Clara River Average Daily Flows
Average Daily Flows (thousands of cfs)
Station 708
Station 708A
Station 723
Station 724
A
1920 1940 1960 1980 2000 2020
0 200
400
600
800
1000
1200
Western Santa Clara River Average Daily Flows −
Monthly Minimum
Average Daily Flows (cfs)
Station 708
Station 708A
Station 723
Station 724
D
1980 1990 2000 2010
0 500
1000
1500
2000
2500
3000
Revolon Slough Watershed Average Daily Flows
Average Daily Flows (cfs)
Station 776
Station 776A
Station 780
Station 782
B
1980 1990 2000 2010
0 5
10 15
20 25
Revolon Slough Watershed Average Daily Flows −
Monthly Minimum
Average Daily Flows (cfs)
Station 776
Station 776A
Station 780
Station 782
E
1970 1980 1990 2000 2010
0 2000
4000
6000
8000
10000
Calleguas Creek Average Daily Flows
Average Daily Flows (cfs)
Station 805
C
1970 1980 1990 2000 2010
0 20
40 60
80 Calleguas Creek Average Daily Flows −
Monthly Minimum
Average Daily Flows (cfs)
Station 805
F
860
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Groundwater Sustainability Plan for the Oxnard Subbasin SOURCE: Ventura County Watershed Protection District
Oxnard Plain Annual Precipitation
FIGURE 1-5
Water Year
Annual Precipitation (inches)
Note: Annual precipitation values recorded at rain gauges within the Oxnard Plain are shown. The majority of the precipitation records are depicted as gray lines. The two gauges used to create a long-term precipitation record, Stations 032 (Oxnard Water Department) and 168 (Oxnard Airport), are displayed in red and blue, respectively. Records plotted in gray are for Stations 017 (and 017A, B and C), 032A, 177 and 177A, 215 and 215A, 223 and 223A, 231A, 239, 1900 1920 1940 1960 1980 2000 2020
0 10 20 30 40 50
Oxnard Plain Annual Precipitation
257, 261, 267, 273A, 403, 412, and 503.
862
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Groundwater Sustainability Plan for the Oxnard Subbasin SOURCE: Ventura County Watershed Protection District
Long-Term Precipitation Trends in the Oxnard Plain
FIGURE 1-6
140
0 120
100
80 60
40 20
Annual Precipitation (inches) at Stations 032 and 168
40 20
0 -20
-40
-60
-80
Cumulative Departure from the Mean (inches)
1900 1920 1940 1960 1980 2000 2020
Annual Precipitation (inches)
from Stations 032 and 168
Mean Precipitation
(14.4 inches)
Cumulative Departure
from the Mean Falling Limb
60 1880
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P a c i f i c
O c e a n
Ventura Rd
Lewis Rd
Central Ave
Hueneme Rd
Pleasant Valley Rd
5th St
?23
232 ?
126 ?
?34
?1
118 ?
£¤101
Ventura
Oxnard
Port Hueneme
Camarillo
Thousand Oaks
Arroyo Conejo
Arroyo Las Posas
Calleguas Creek
Arroyo Simi
Conejo Creek
ArroyoSant a Rosa
Revolon Slough
Santa Clara River
Mountclef
Ridge
Camarillo Hills
Las Posas Hills
Santa Monica Mountains
Conejo
Mountain
Groundwater Sustainability Plan for the Oxnard Subbasin SOURCE: DWR; County of Ventura; FCGMA
Date: 3/27/2019 - Last saved by: ntucker - Path: Z:\Hydro\Projects\Fox_Canyon_GMA\MXD\FINAL_MXD\OXNARD\CH_1_FIGURES\Figure 1-7.mxd 0 1 2 n Miles
Wells by Water Use Sector (FCGMA 2016)
Agricultural
A Agricultural - Can't Locate/Destroyed/Inactive
Domestic
A Domestic - Can't Locate/Destroyed/Inactive
Municipal/Industrial
A Municipal/Industrial - Can't Locate/Destroyed/Inactive Fox Canyon Groundwater Management Agency Boundary
(FCGMA 2019d)
Revised Bulletin 118 Groundwater Basins (DWR 2016a)
Oxnard Subbasin
Major Rivers/Stream Channels
Ventura County General Plan 2010
Land Use Description
Agricultural
Agricultural - Urban Reserve
Channel Islands Harbor
Existing Community
Existing Community - Urban Reserve
Open Space
Open Space - Urban Reserve
Rural
Rural - Urban Reserve
Rural 5-Acre Minimum
State or Federal Facility
State or Federal Facility - Urban Reserve
Urban
Ventura Harbor
FIGURE 1-7
Land and Water Use
866
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Ventura County Water Purveyors
FIGURE 1-8
Groundwater Sustainability Plan in the Oxnard Subbasin
Z:\Projects\
SOURCE: Ventura County Watershed Protection District;
FCGMA , UWCD, and CMWD. 2007. “2007 Update to the Groundwater Management Agency Groundwater Management Plan.” May 2007. Plate 1. cal-019
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cal-022
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cal-015
u-087
cal-023
cal-016
u-089
cas-049
u-091
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cal-017
u-093
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cal-020
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cas-051
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cas-052
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u-076
cal-004
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Lake Casitas
Lake Piru
Mugu Lagoon
Westlake
Bard Reservoir
Channel Islands Harbor
Ventura Harbor
Lake Sherwood
Port of Hueneme
Matilija Lake
Edison Canal
McGrath Lake
Camino Lake
Lake Eleanor
Pleasant Valley Canal
J
H
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LYNN

SOUTHERN PACIFIC

LOS ANGELES

FOOTHILL
C

TELEGRAPH
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HUENEME
WO
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MARICOPA
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CASITAS PASS

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C

TELEGRAPH
BARD

COCHRAN
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M
O
O
RPA
R
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WOOLEY
C

SATICOY
BARD
LOMA
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SANTA PAULA
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TELEGRAPH

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SANTA PAULA

SOUTHERN PACIFIC

VENTURA COUNTY
J
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BATES
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TELEGRAPH
VEN
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TELEPHONE

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LA
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TELEGRAPH

TELEGRAPH

PLEASANT VALLEY

SANTA PAULA

RALSTON
SYCAM
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A
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P
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SESPE
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MBAL
L
VIC
T
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LOS ANGELES
WOOLEY

DARLING
Ventura County Water Purveyors
W-182
San Nicolas Island Inset

MARICOPA

LOCKWOOD VALLEY

CUDDY VALLEY

FRAZIER MOUNTAIN PARK
Pyramid Lake
Castac lake
w-152
w-154
w-193
w-160
w-159
w-155
w-194
w-170
w-170
w-171
Northern Ventura County Inset
Pacific
Ocean
DISCLAIMER: The information contained herein was created by the Ventura County Watershed Protection District solely for its own use. The VCWPD assumes no liability fordamages incurred directly or indirectly as a result of errors, omissions or discrepancies. Created: Feb 2006 By: JPD Ventura County Watershed Protection District Water & Environmental Resources Division Groundwater Section
800 South Victoria Ave.

Ventura, CA 93009-1600
Ph: (805) 654-2088
Fx: (805) 677-8762
Legend
DWR Bull. 118 GW BasinsFoxCynGMA-bdy
RoadsCalleguas MWD
Casitas MWDUWCD
Water Bodies County Boundary
μ
cal-028
u-184
u-184
u-107
cas-072
u-183
u-183
u-183
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u-127
u-109
cal-028
cal-028
u-134
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u-123
u-104
cal-008
cal-044
u-107
u-126
u-126 u-094
u-094 u-136
w-151
036 1.5
Miles
1:87,500
Inventory of Public & Private
Water Purveyors In Ventura County
Figure 3.0
1 inch equals 3 miles
u-094
cal-008
1 DWR Bulletin 118 Groundwater Basins
1 - Las Posas Valley
2 - Arroyo Santa Rosa Valley3 - Pleasant Valley
4 - Santa Clara River Valley - Santa Paula
5 - Santa Clara River Valley - Mound
6 - Santa Clara River Valley - Oxnard
Plate 1
2 3
4 5
6 1
4 5
62 3
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1 – ADMINISTRATIVE INFORMATION
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 1-90

INTENTIONALLY LEFT BLANK
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CHAPTER 2

BASIN SETTING

2.1 INTRODUCTION TO BASIN SETTING
Physical Setting and Characteristics
The Oxnard Subbasin (Subbasin) of the Santa Clara River Valley Groundwater Basin is located near the western edge of the Transverse Ranges Geomorphic Province, which extends from the San Bernardino Mountains in the east to the San Miguel, Santa Rosa, and Santa Cruz Islands in the west (Figure 2-1, Oxnard Subbasin Vicinity Map; CGS 2002). The Transverse Ranges Geomorphic Province is characterized by a series of east-to-west-trending mountain ranges and valleys that are formed by north–south compression across a restraining bend in the San Andreas Fault (Hadley and Kanamori 1977; Bohannon and Howell 1982; Eberhart-Philips et al. 1990; Nicholson et al. 1994). Compression across this restraining bend is responsible for rapid, ongoing uplift of the mountain ranges (Yeats 1988; Feigl et al. 1993; Marshall et al. 2008) and extensive folding and faulting of the Pleistocene and older geologic formations in the province (Rockwell et al. 1988; Huftile and Yeats 1995).

The Oxnard Subbasin underlies the Oxnard Plain, an approximately 58,000-acre coastal plain formed by deposition of sediments from the Santa Clara River and Calleguas Creek, in southwestern Ventura County (DWR 1965, 2006). The northern boundary of the Oxnard Subbasin is the Oak Ridge Fault, and the southern boundary is the contact between permeable alluvium and semipermeable rocks of the Santa Monica Mountains (SWRCB 1956; DWR 2006).

The eastern boundary of the Oxnard Subbasin lies against the Las Posas Valley Basin (LPVB) and Pleasant Valley Basin (PVB). The western boundary of the Oxnard Subbasin is the Pacific Ocean (SWRCB 1956; DWR 2006).

The stratigraphic sequence underlying the Oxnard Plain comprises an upper unit of younger and older alluvial deposits that unconformably overlies the San Pedro and Santa Barbara Formations (Table 2-1). The San Pedro Formation is a lower to middle Pleistocene shallow marine deposit that grades upward from a white-gray sand and gravel basal layer into an overlying series of interbedded silts, clays, and gravels. The Santa Barbara Formation is a lower Pleistocene marine sand and clay deposit (SWRCB 1956; Weber and Kiessling 1976; Turner 1975). The primary water-bearing units in the Oxnard Subbasin are the alluvial deposits that compose the Oxnard and Mugu Aquifers and the white-gray sand and gravel layer of the San Pedro Formation that composes the Fox Canyon Aquifer (FCA; Table 2-1). In addition, wells in the Oxnard Subbasin also produce water from the Hueneme Aquifer in the Upper San Pedro Formation and the Grimes Canyon Aquifer (GCA) in the Santa Barbara Formation.
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The shallowest aquifer in the Oxnard Subbasin is a semi-perched aquifer comprising sands and gravels deposited by the Santa Clara River. This unit is underlain by a clay layer, commonly referred to as the “clay cap,” that is nearly continuous throughout the Subbasin, with the notable exception of an approximately 10-square-mile area in the northeastern part of the Subbasin, adjacent to and south of the Santa Clara River, referred to as the “Forebay area” (Figure 2-1; Mukae and Turner 1975). In this region, the Oxnard and underlying Mugu Aquifers are unconfined. In the areas where the clay cap separates the semi-perched aquifer from the underlying Oxnard Aquifer, the Oxnard Aquifer is confined. The area in which the Oxnard Aquifer is confined is referred to as the “pressure plain area” of the Oxnard Subbasin (Figure 2-1; Mukae and Turner 1975).

The majority of the Oxnard Subbasin lies within the jurisdiction of the Fox Canyon Groundwater Management Agency (FCGMA), with two exceptions (Figure 2-1). These exceptions include an area in the northeastern corner of the Oxnard Subbasin, at the western end of South Mountain, and along the southeastern edge of the Oxnard Subbasin adjacent to the foothills of the Santa Monica Mountains. The reason for the discrepancy is that the FCGMA boundary was established based on a vertical projection of the FCA as defined by the Fox Canyon Groundwater Management Agency Act in 1982, whereas the Oxnard Subbasin boundary is based on the surface extent of the alluvium in the Oxnard Plain, and the location of both geologic structures and facies changes that impede flow between the Oxnard Subbasin and neighboring groundwater basins (DWR 2006). The geologic and hydrologic descriptions of the Oxnard Subbasin in this Groundwater Sustainability Plan (GSP) are based on the boundaries of the Oxnard Subbasin, including the areas to the northeast and southeast which are outside of the FCGMA jurisdictional boundaries.

2.2 HYDROGEOLOGIC CONCEPTUAL MODEL
The six commonly recognized water-bearing units in the Oxnard Subbasin are the semi-perched aquifer and the Oxnard, Mugu, Hueneme, Fox Canyon, and Grimes Canyon Aquifers (DWR 1965, 2006; Turner 1975). Of the six commonly recognized water-bearing units, five are considered primary aquifers in the Oxnard Subbasin. The semi-perched aquifer is a waterbearing unit, but is not considered a primary aquifer in the Subbasin. The five aquifers are grouped into an Upper Aquifer System (UAS) and Lower Aquifer System (LAS), with the Oxnard and Mugu Aquifers composing the UAS and the Hueneme, Fox Canyon, and Grimes Canyon Aquifers composing the LAS. The UAS primarily comprises recent to upper Pleistocene age alluvial deposits of the Santa Clara River system. The LAS is primarily composed of upper to lower Pleistocene age marine sediments.

The Forebay area is the primary recharge area for the primary aquifers in the Oxnard Subbasin. In this area, the UAS rests directly on the folded and eroded upper surface of the Hueneme Aquifer and FCA.

Water that recharges the UAS in the Forebay area is able to migrate throughout the Subbasin. Both the lithologic units and geologic structures present in the Oxnard Subbasin affect the hydrology of the Subbasin. These features are discussed in more detail in Sections 2.2.1 through 2.2.5. 871
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2.2.1 Geology
Geologic Units and Variation
Tertiary Sedimentary and Igneous Formations
Tertiary sedimentary and igneous rocks that underlie the Oxnard Subbasin are generally considered semipermeable or non-water-bearing (Turner and Mukae 1975). These tertiary formations include the Oligocene/Eocene-age Sespe Formation, the lower Miocene Conejo Volcanics, the upper Miocene Modelo and Monterey Formations, and the Pliocene Pico Formation (Table 2-1; Weber and Kiessling 1976; Dibblee 1992a, 1992b). These formations have been sampled in deep wells drilled in the Oxnard Subbasin (Figure 2-2, Geology of the Oxnard Subbasin; Turner 1975; Weber and Kiessling 1976). These formations are not considered an important source of groundwater in the Oxnard Subbasin (Turner 1975).

Quaternary Sedimentary Formations
Santa Barbara Formation (Lower Pleistocene; Marine)
The Santa Barbara Formation typically comprises laminated, poorly indurated blue-gray marine mud- and siltstone with sand and gravel (Table 2-1; Turner and Mukae 1975). The upper clayrich sediments act as an aquitard between the Santa Barbara Formation and the overlying San Pedro Formation (Weber and Kiessling 1976). The localized basal conglomerate within the upper member of the Santa Barbara Formation hosts the GCA (Weber and Kiessling 1976).

San Pedro Formation (Lower to Middle Pleistocene; Marine and Nonmarine) The San Pedro Formation is an interbedded, poorly lithified fine marine, silty sandstone, shale, and mudstone with local pebble conglomerate and an extensive basal sand unit that unconformably overlies the Santa Barbara Formation in the Oxnard Subbasin (Mukae and Turner 1975; Weber and Kiessling 1976).

The upper and lower parts of the San Pedro Formation are separated by a laterally extensive clay marker bed (Turner 1975). Overlying the clay marker bed are lenticular layers of sand, gravel, and silt (Mukae and Turner 1975). The lenticular deposits of sand and gravel in the Upper San Pedro Formation are known as the Hueneme Aquifer in the Oxnard Subbasin. The sediments of the Upper San Pedro Formation coarsen to the west, with a larger percentage of sand and gravel in the western part of the Subbasin and a larger percentage of fines in the eastern part of the Subbasin, particularly in the area adjacent to the boundary with the LPVB.

In contrast, the basal unit of the San Pedro Formation fines to the west. This unit comprises a 100- to 600-foot-thick continuous white or gray fine to medium marine sand with stringers of gravel 872
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and local silt and clay lenses (Turner 1975).
1 The lower part of the San Pedro Formation is the
FCA, which is an important source of groundwater supply in the Oxnard Subbasin (Turner 1975).

Older Alluvium (Upper Pleistocene; Terrestrial)
The older alluvium, which comprises gravel, sand, silt, and clay, unconformably overlies the Upper San Pedro Formation. The older alluvium can be divided into two units: an upper clay zone and a lower sand and gravel zone (Mukae and Turner 1975). The Mugu Aquifer occurs in the sand and gravel zone at the base of the older alluvium (Mukae and Turner 1975).

Recent Alluvium (Holocene; Terrestrial)
The recent alluvium in the Oxnard Subbasin comprises sands and gravels interbedded with silt and clay (DWR 1965). These sediments, which unconformably overlie the older alluvium, reach a thickness of up to 300 feet. The basal unit includes coarse sands and gravels intercalated with clay layers (Mukae and Turner 1975). Overlying the basal unit throughout much of the Subbasin is a laterally continuous clay layer that reaches a thickness of up to 160 feet locally. The Oxnard aquifer occurs in the sand and gravel layer below the clay. Above the clay is the semi-perched aquifer.

Geologic Structure
Wright Road Fault
The Wright Road Fault is an active oblique right reverse fault that generally parallels the eastern jurisdictional boundary of the Oxnard Subbasin, separating the LPVB to the east from the Oxnard Subbasin to the west (Figure 2-2; DeVecchio et al. 2007). The fault trace is characterized by a 20- meter-high (66-foot-high) topographic scarp with up-to-the-east displacement along the northnorthwest-trending fault (DeVecchio et al. 2007). There is no evidence that the Wright Road Fault impacts groundwater flow between the Oxnard Subbasin and the LPVB.

Oak Ridge and McGrath Faults
The Oak Ridge Fault is a high-angle, south-dipping, left-lateral reverse fault that juxtaposes waterbearing alluvium and older, semipermeable formations in the subsurface (Figure 2-2; SWRCB 1956).

To the east of the Oxnard Subbasin, anticlinal folding in the hanging wall of the Oak Ridge Fault resulted in the Oak Ridge and South Mountain uplift (Yeats 1988). In the Oxnard Subbasin, the western extent of the Oak Ridge Fault is concealed beneath the recent alluvium (Mukae and Turner 1975).

1 This marine sand has been identified as both the Saugus Formation (Kew 1924; Jakes 1979) and the Las Posas Sand (Pressler 1929, as cited in DeVecchio et al. 2012a.; Dibblee 1992a, 1992b; DeVecchio et al. 2012b). The term “San Pedro Formation” is used here for consistency with California Department of Water Resources nomenclature (DWR 2006).
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The McGrath Fault, located approximately 1 mile south of the Oak Ridge Fault along the coast in the Oxnard Subbasin, is a branch of the Oak Ridge Fault system with the same sense of motion (Mukae and Turner 1975). The McGrath Fault defines the northerly limit of the Forebay area (Turner 1975). Together, the McGrath and Oak Ridge Faults limit hydraulic communication between the Oxnard Subbasin to the south and the Mound and Santa Paula Subbasins of the Santa Clara River Valley Groundwater Basin to the north.

Bailey Fault
Along the northern edge of the Santa Monica Mountains, the Bailey Fault Zone trends northeast– southwest through the Oxnard Subbasin (Figure 2-2; Turner 1975). The Bailey Fault is a nearvertical fault with up-to-the-south displacement in the subsurface that offsets quaternary sedimentary formations to the north with older formations to the south (Turner 1975).

Groundwater elevation differences and chloride ion concentration differences across the fault suggest that it is a barrier to groundwater movement (Turner 1975). The FCA is absent to the south of the Bailey Fault.

Las Posas Syncline
The Las Posas syncline has resulted in thickening and downwarping of the San Pedro Formation and older formations in the central part of the Oxnard Subbasin (Figure 2-2). The axis of the Las Posas syncline trends northeast from its western mapped extent at the intersection of West 5th Avenue and Harbor Boulevard, through El Rio, and into the Las Posas Valley (Turner 1975). At the deepest part of the Las Posas syncline, the Upper San Pedro Formation reaches a thickness of approximately 1,150 feet (Mukae and Turner 1975).

Montalvo Anticline
Deformation in the hanging wall of the Oak Ridge and McGrath Faults has resulted in anticlinal structures on the northern boundary of the Oxnard Subbasin, including the Montalvo anticline (Figure 2-2). The Upper San Pedro Formation has been eroded away in the Forebay area of the Oxnard Subbasin along the axis of the anticline (Turner 1975). Erosion of the Upper San Pedro Formation results in direct communication between the alluvium and the white and gray marine sands of the Lower San Pedro Formation that compose the FCA.

2.2.2 Basin Bottom
The bottom of the Oxnard Subbasin generally corresponds to the base of the San Pedro Formation and the base of the FCA in the northern and western parts of the Subbasin, where the Santa Barbara Formation is absent (Figure 2-2 and Figure 2-3, Cross Section A–A′; Turner 1975). In the southern and eastern parts of the Subbasin, where the Santa Barbara Formation is present, the bottom of the 874
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Subbasin is defined by the contact between the upper member of the Santa Barbara Formation, the GCA, and the underlying strata that have poor water quality (Figure 2-4, Cross Section B–B′).

In general, the bottom of the Oxnard Subbasin is shallower in the east and deeper in the west.

Along the eastern margin of the Subbasin, the Subbasin bottom has been mapped at elevations between 0 feet above mean sea level (msl) and −1,200 feet msl (Turner 1975). Along the western edge of the Subbasin, the Subbasin bottom depth ranges from −400 to more than −1,800 feet msl (Turner 1975). The deepest part of the Subbasin occurs along the axis of the Las Posas syncline in the north-central part of the Subbasin.

2.2.3 Principal Aquifers and Aquitards
Semi-Perched Aquifer
River-deposited sands and gravels interbedded with minor silt and clay compose the semi-perched aquifer in the Oxnard Subbasin (DWR 1965; Turner 1975). The term “semi-perched aquifer” is used in this GSP as the name for the uppermost unit of the Oxnard Subbasin, which overlies the extensive clay cap in the pressure plain area of the Oxnard Subbasin (Figure 2-2 and Table 2-1).

This name was used in the State Water Resources Control Board’s Bulletin 12 (SWRCB 1956) to distinguish the water-bearing sedimentary units in the pressure plain area from those in the Forebay area, and this terminology has been adopted by subsequent investigators (Mukae and Turner 1975; Turner 1975; Hanson et al. 2003; DWR 2006). Water-level data indicate that the sediments underlying the semi-perched aquifer are saturated. Therefore, the term “semi-perched aquifer” is used in this GSP to denote the limited migration of water from the uppermost aquifer to the underlying confined aquifer in the pressure plain area. It is not used to denote a discontinuity in saturation. Furthermore, there is limited groundwater production (<50 acre-feet per year [AFY]) from this unit (see Section 2.4, Water Budget). Therefore, although this unit is referred to as the “semi-perched aquifer,” it is not considered to be a principal aquifer in the Subbasin.

The semi-perched aquifer is part of the recent alluvium described in Section 2.2.1, Geology. This aquifer extends from the base of developed soil horizons to a depth of approximately 75 feet throughout most of the Subbasin (Turner 1975). Notably, this aquifer is absent in the Forebay area of the Oxnard Subbasin adjacent to and south of the present course of the Santa Clara River. The permeable sand and gravel deposits of the semi-perched aquifer tend to be continuous in a northeast–southwest orientation, which is similar to the present orientation of the Santa Clara River and lenticular to the northwest and southeast (Turner 1975).

The lenticular shape of the semi-perched aquifer deposits limits flow in the northwest–southeast direction and facilitates flow in the northeast–southwest direction. These deposits have not been affected by faulting or folding in the Subbasin, and there are no structural restrictions to flow through the semi-perched aquifer (UWCD Model Report [2018], provided as Appendix C to this GSP). 875
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Agricultural return flows, saline connate water, and coastal flooding affect both groundwater quality and groundwater elevation in the semi-perched aquifer (Mukae and Turner 1975). The highest water levels in the aquifer, which are typically within a few feet of land surface, are found in heavily irrigated areas (Turner 1975). Tile drains are used throughout the Oxnard Subbasin to alleviate the high groundwater conditions. Agricultural return flows that cause the high water conditions have resulted in high concentrations of total dissolved solids (TDS) and chloride (as high as 23,000 milligrams per liter [mg/L]) in the semi-perched aquifer (Turner 1975; USGS 1996).

Clay Cap
Underlying the semi-perched aquifer is a clay layer that separates the semi-perched aquifer from the Oxnard Aquifer below (Turner 1975). The thickness of the clay cap is approximately 160 feet adjacent to the Pacific Ocean. The clay cap is absent in the Forebay area (DWR 1968; Mukae and Turner 1975). Although the clay cap functions as an aquitard, water can migrate vertically through the clay cap under conditions of differential head (Turner 1975), and in some cases, through casings of wells that have been improperly abandoned.

Oxnard Aquifer
The Oxnard Aquifer is a laterally continuous layer of upper Pleistocene and Holocene nonmarine gravel and cobbles (up to 6 inches in diameter); coarse to fine sand; and interbedded clay, silty clay, and silt lenses (Turner 1975). The deposits that compose this aquifer are part of the recent alluvium and are found beneath the entire Oxnard Subbasin and extend several miles offshore, where they are exposed in the walls of the Hueneme and Mugu submarine canyons (DWR 1965, 1968). The deposits tend to be finer near the coast and coarsen to the east (Turner 1975; DWR 2006). The local silty clay and silt lenses restrict both horizontal and vertical movement of water through the aquifer, and distinct permeable horizons have been identified in logs (DWR 1971).

The top of the Oxnard Aquifer has been shaped by differential erosion and sedimentation of the Santa Clara River (Turner 1975). Throughout much of the Oxnard Subbasin, a clay-rich aquitard that ranges in thickness from 10 to 100 feet separates the Oxnard Aquifer system from the underlying Mugu Aquifer (Mukae and Turner 1975). The basal surface of the clay is more uniform than the upper surface and generally deepens to the west–southwest (DWR 1968). The thickness of the Oxnard Aquifer also generally increases to the west-southwest, with a minimum thickness of less than 50 feet in the vicinity of the Forebay area and reaching a maximum thickness of greater than 150 feet in the vicinity of Point Mugu (DWR 1968; Turner 1975).

Flow of groundwater through the Oxnard Aquifer is controlled by lithologic variability. The only structural feature that restricts flow in this aquifer is the Bailey Fault, in the southern Oxnard Subbasin (Appendix C). The Oxnard Aquifer crops out offshore in the Hueneme and Mugu canyons, making it susceptible to seawater intrusion. The chloride concentration of native water 876
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in the Oxnard Aquifer is approximately 40 mg/L (similar to background values in the Mugu and Hueneme Aquifers), although this concentration varies with geographic location in the Subbasin (USGS 1996). In the vicinity of the Hueneme and Mugu submarine canyons, chloride concentrations have been affected by seawater intrusion. In 2016, the chloride concentration in the vicinity of Hueneme Canyon was as high as 4,800 mg/L, and in the vicinity of Mugu Canyon the chloride concentration was as high as 16,600 mg/L (FCGMA 2016).

The specific yield of the gravels of the Oxnard Aquifer is about 16% in the Forebay area where there are few clay deposits and the aquifer is unconfined (SWRCB 1956; DWR 2006). Wells screened in the Oxnard Aquifer are typically screened in multiple aquifers, including the underlying Mugu Aquifer. (For information on well construction requirements intended to prevent degradation of water quality of the aquifers in the LAS—referred to as requirements for “sealing zone”—see DWR 1968). The California Department of Water Resources (DWR) reports that the average well yield in the Oxnard Aquifer is about 900 gallons per minute (gpm; DWR 2006).

Aquifer test results for two wells screened solely within the Oxnard Aquifer, however, have a higher average well yield, of approximately 1,500 gpm, with an average specific capacity of 47 gpm per foot (Hopkins, pers. comm. 2016). Storage coefficients of 6.18×10−4and 3×10−4 were estimated from pumping test data at these two wells, and the transmissivity was estimated to be approximately 20,400 feet squared per day (Hopkins, pers. comm. 2016). The well yield and specific capacity were measured at three additional wells screened solely in the Oxnard Aquifer, although aquifer tests were not performed at these wells. The average well yield and specific capacity for these wells is 2,450 gpm and 108 gpm per foot. Based on these measurements, the average transmissivity is approximately 32,000 feet squared per day (Hopkins, pers. comm. 2016).

Water quality in the Oxnard Aquifer has been degraded by seawater intrusion and leakage of agricultural return flows through the clay cap separating the Oxnard Aquifer from the overlying semi-perched aquifer (UWCD 2016a). Seawater intrusion has been documented in both the Port Hueneme and Port Mugu areas (Turner 1975; UWCD 2016a). Water produced from this aquifer is used for agricultural and municipal and industrial (M&I) purposes.

Mugu Aquifer
The sediments that compose the Mugu Aquifer are upper Pleistocene age fine to coarse sands and gravels (DWR 1965; Turner 1975). These sand and gravel deposits are laterally extensive throughout the Subbasin and represent the basal deposits of the older alluvium. In general, the sediments of the Mugu Aquifer are finer near the coast and coarsen to the east (Turner 1975). A low-permeability clay deposit that ranges in thickness from 10 to 100 feet separates the Mugu Aquifer from the overlying Oxnard Aquifer throughout much of the Oxnard Subbasin. However, the clay layer is absent in the Forebay area of the Subbasin near the Santa Clara River (DWR 1965; SWRCB 1979; Turner 1975). The Mugu Aquifer ranges in thickness from approximately 30 feet in the Forebay to approximately 270 feet in the vicinity of Point Mugu (DWR 1965; Turner 1975). 877
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The Mugu Aquifer extends several miles offshore and crops out offshore in the Hueneme and Mugu canyons, making it susceptible to seawater intrusion. The chloride concentration of native water in the Mugu Aquifer is approximately 40 mg/L (USGS 1996). In the vicinity of the Hueneme and Mugu submarine canyons, however, chloride concentrations have been affected by seawater intrusion. In 2016, the chloride concentration in the vicinity of Mugu Canyon was as high as 3,200 mg/L (FCGMA 2016).

The base of the Mugu Aquifer was deposited over an irregular surface that has been affected by both folding and erosion (Turner 1975). The extensive folding of the aquifers underlying the Mugu Aquifer, however, has not been documented within the sediments of the Mugu Aquifer. Within the boundaries of the DWR Bulletin 118 basin, the only documented fault that acts as a barrier to flow is the Bailey Fault in the southern part of the Subbasin. Offshore, however, additional faults that act as barriers to flow exist in the vicinity of the Mugu submarine canyon (Hanson et al. 2003; Appendix C).

Wells screened in the Mugu Aquifer are typically screened in multiple aquifers, including the overlying Oxnard Aquifer. DWR does not report aquifer properties specifically for the Mugu Aquifer (DWR 2006). In the Forebay, Well 02N22W36E04S, screened solely within the Mugu Aquifer, has a well yield of 1,500 gpm, a specific capacity of 17.8 gpm per foot, and an estimated transmissivity of 7,900 feet squared per day (Hopkins, pers. comm. 2016). For wells screened in both the Oxnard and Mugu Aquifers, the average yield is 2,300 gpm, the average specific capacity is 110 gpm per foot, and the average estimated transmissivity is 29,000 feet squared per day (Hopkins, pers. comm. 2016). Water produced from this aquifer is used for agricultural and M&I purposes.

Hueneme Aquifer
The Hueneme Aquifer comprises a series of lenticular silts, sands, and gravels in the Upper San Pedro Formation. This aquifer is present in the northern part of the Oxnard Subbasin but is absent to the south of Hueneme Roads (Mukae and Turner 1975). Within the Oxnard Subbasin, the Hueneme Aquifer is up to 1,150 feet thick along the axis of the Las Posas syncline (Turner 1975).

The Hueneme Aquifer extends several miles offshore and crops out in the Hueneme and Mugu submarine canyons.

Changes in lithologic composition, with the aquifer generally containing a higher percentage of fine materials adjacent to the LPVB and PVB, affect flow through the aquifer. The change in composition is accompanied by an increase in the lenticular nature of the deposits that compose the Hueneme Aquifer along the eastern boundary of the Oxnard Subbasin. These changes limit subsurface flow between the Oxnard Subbasin and the LPVB and PVB to the east. 878
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In addition to changes in lithology, structural folding of the Hueneme Aquifer also affects subsurface flow (Turner 1975). Folding, subsequent erosion, and recent deposition have resulted in a direct hydraulic connection between the Hueneme Aquifer and the overlying Mugu Aquifer throughout much of the Oxnard Subbasin (Turner 1975). However, in the southwestern portion of the basin, where seawater intrusion has affected the Mugu Aquifer, the Mugu and Hueneme Aquifers are not in direct hydraulic communication. As a result, water quality in the Hueneme Aquifer has not been affected by seawater intrusion in this area (Turner 1975; Hanson et al. 2003).

Offshore faulting in the Hueneme Aquifer also limits direct seawater intrusion into the aquifer in the vicinity of Mugu Canyon, and faulting along the northern and southern boundaries of the Oxnard Subbasin limit flow out of the Hueneme Aquifer to the Mound Basin or to the south of the Bailey Fault (Hanson et al. 2003; Appendix C).

The chloride concentration of native water in the Hueneme Aquifer is approximately 40 mg/L (USGS 1996). In the vicinity of Point Hueneme, the chloride concentration of the Hueneme Aquifer was as high as 9,900 mg/L in 2016 (FCGMA 2016).

Wells screened solely within the Hueneme Aquifer have an average yield of approximately 2,500 gpm and an average specific capacity of 38 gpm per foot (Hopkins, pers. comm. 2016). Storage coefficients of 2×10−4and 3×10−4 were estimated from pumping test data at two wells and the transmissivity was estimated to be approximately 13,400 feet squared per day (Hopkins, pers. comm. 2016). Water produced from this aquifer is used for agricultural and M&I purposes.

Fox Canyon Aquifer
The FCA is a 100- to 600-foot-thick marine sand and gravel deposit in the Lower San Pedro Formation (Mukae and Turner 1975). The water-bearing deposits of the FCA fine toward the west (Turner 1975). This unit is laterally continuous throughout the Oxnard Subbasin except at the western tip of South Mountain, where the Santa Barbara Formation is in direct contact with the Mugu Aquifer, and in the southwestern part of the Subbasin, where uplift and erosion have removed the FCA (Turner 1975). In the northern and western parts of the Subbasin, the FCA defines the base of the freshwater zone.

In the Oxnard Subbasin, the FCA is thickest along the axis of the Las Posas syncline. In this area, the FCA reaches thickness in excess of 500 feet, and the base of the aquifer is below −2,000 feet msl (Turner and Mukae 1975; Turner 1975). The primary source of freshwater recharge to the FCA is infiltration through the Oxnard and Mugu Aquifer systems in the Forebay area (Turner 1975; FCGMA 2007).

As with the other primary aquifers in the Oxnard Subbasin, the FCA extends several miles offshore and water quality in the FCA has been impacted by seawater intrusion. The native water in the FCA had a chloride concentration of 40 mg/L (USGS 1996). Chloride concentration measured in 879
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2002 from a well in the southeastern part of the Subbasin ranged from 183 to 367 mg/L (Izbicki et al. 2005). However, the concentration of chloride measured in Well 01N21W32Q04, located inland of Mugu Canyon in the southern part of the Subbasin, was 5,070 mg/L in 2015.

Offshore faulting in the vicinity of Mugu Canyon is thought to limit direct seawater intrusion into the FCA (Hanson et al 2003; Appendix C). Instead, increasing concentrations of chloride in the FCA near Mugu Canyon are thought to originate in the aquifers of the UAS and migrate vertically into the FCA.

There are no aquifer-specific hydraulic parameter measurements for the FCA. Several specific capacity aquifer tests have been conducted in the Oxnard Subbasin, but typically these tests occur in wells screened across multiple aquifers (Appendix C). More detail on the limitations of hydraulic parameter measurements is found in the UWCD model documentation report (Appendix C). Well 02N22W20J02S, in the northern Oxnard Subbasin, is screened in both the FCA and overlying Hueneme Aquifer. This well has a yield of 3,030 gpm, a specific capacity of 95.3 gpm per foot, and a transmissivity of 40,100 feet squared per day (Hopkins, pers. comm. 2016). Water produced from this aquifer is used for agricultural and M&I purposes.

Grimes Canyon Aquifer
The GCA comprises lower Pleistocene age sand with minor amounts of gravel. This aquifer corresponds with the basal conglomerate within the upper member of the Santa Barbara Formation and is only found underlying the southern and eastern parts of the Oxnard Subbasin (Turner 1975).

In the southern part of the Subbasin, the GCA is found in a band approximately 5 miles wide along the base of the Santa Monica Mountains from the Pacific Ocean to the boundary with the PVB to the east (Turner 1975). Throughout the rest of the Subbasin, the Grimes Canyon member of the Santa Barbara Formation is absent. As with the other aquifers in the Subbasin, the GCA extends several miles offshore.

The GCA, where present in the Oxnard Subbasin, is in hydraulic communication with the overlying FCA, and there are no production wells perforated solely in the GCA (Turner 1975; VCWPD 2013).

As a result, there is little information on the water quality or aquifer properties of the GCA. Water quality has been sampled in some basal portions of the aquifer, and has been found to have brackish water that is likely a result of limited flushing since deposition and upward migration of brines from underlying formations (Mukae and Turner 1975; Turner 1975; Hanson et al. 2003).2, 3In addition, seawater intrusion may have impacted some wells screened in the GCA (see Section 2.3.3, Seawater Intrusion). Direct seawater flow into the GCA in the vicinity of Mugu Canyon is thought to be limited

2 Brackish water is typically defined as water with a concentration of total dissolved solids (TDS) between 3,000 and 10,000 mg/L.
3 Brines typically have concentrations of TDS greater than 35,000 mg/L. 880
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by offshore faulting (Hanson et al 2003; Appendix C). Concentrations of chloride have been increasing in this area since the 1990s. In 2016 the groundwater concentration measured in a sample collected from Well 01S21W08L03S was 6,428 mg/L (FCGMA 2016). Measured aquifer properties specific to the GCA are not currently available.

2.2.4 Data Gaps and Uncertainty in the Hydrogeologic
Conceptual Model
The primary data gaps in the hydrogeologic conceptual model are as follows:
 Distributed measurements of aquifer properties from wells screened solely in a single aquifer  Distributed measurements of groundwater quality from wells screened solely in a single aquifer  Measurements of groundwater quality that distinguish the sources of high TDS concentrations in the FCA and the GCA
 Temporal limitations on groundwater elevation data
 Spatial limitations on groundwater elevation data
 The relative impacts of production from areas within the Subbasin on seawater intrusion  Connection between the semi-perched aquifer and potential groundwater-dependent ecosystems (GDEs)
 Potential impacts of increased production in the semi-perched aquifer The data gaps listed above create uncertainty in the understanding of the impacts of water level changes on change in storage in the aquifer and on the inland extent of seawater intrusion in the aquifers. Additional aquifer tests, groundwater elevations, and groundwater quality sampling in the future would help reduce the uncertainty associated with these data gaps. Closing the data gaps is discussed further in Chapter 4, Monitoring Networks, of this GSP.

2.3 GROUNDWATER CONDITIONS

2.3.1 Groundwater Elevation Data
Groundwater elevations in the Oxnard Subbasin were first measured in agricultural wells in the 1930s, and multiple entities, including the United Water Conservation District (UWCD), DWR, and the County of Ventura (the County), have recorded water elevations in the Oxnard Subbasin over the intervening decades. In the early 1990s, after the U.S. Geological Survey (USGS) installed a series of nested monitoring wells during the Regional Aquifer System Analysis (Densmore 1996), an annual groundwater monitoring program was initiated in the Subbasin by the County, UWCD, and USGS (FCGMA 2007). The groundwater monitoring programs conducted by the 881
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Ventura County Watershed Protection District and other agencies, including UWCD, include production wells and multiple-completion nested monitoring wells. Many of the production wells included in the monitoring program are screened across multiple aquifers. Historically, the FCGMA annual reports have included potentiometric surface maps for wells screened in the UAS and wells screened in the LAS since 2013 (FCGMA 2015).

To conform with the DWR GSP Regulations, Section 354.16, the following discussion of groundwater elevation is limited to production and monitoring wells screened in a single aquifer. Water level measurements collected between March 2 and March 29, 2015, are used to represent groundwater elevations in spring 2015. Water level measurements collected between October 2 and 29, 2015, are used to represent groundwater elevations in fall 2015.

Because many production wells within the Subbasin are screened across multiple aquifers and there are a limited number of dedicated monitoring wells, the depiction of representative regional potentiometric surfaces in each aquifer is limited. Similarly, the depiction of groundwater trends is also limited by spatial and temporal constraints that are imposed when only using wells screened in a single aquifer. Groundwater pumping data for the year 2015 were mapped to provide context for interpreting the potentiometric surfaces presented in this section (see Figure 2-5, Upper Aquifer System 2015 Extraction [acre-feet] in Oxnard and Pleasant Valley and Figure 2-6, Lower Aquifer System 2015 Extraction [acre-feet] in Oxnard and Pleasant Valley). Self-reported groundwater extraction data for 2015 are shown in Figures 2-5 and 2-6 for wells screened in the UAS and LAS, respectively. In the UAS, the location of the greatest amount of extraction is within the Forebay, with additional extraction areas both west and southeast of the City of Oxnard (Figure 2-5). The majority of the production from the LAS is in the southeastern portion of the Subbasin (Figure 2-6).

The volume of groundwater extracted from the LAS is greater than that extracted from the UAS.

Current and historical groundwater elevations are discussed below by aquifer. Full hydrographs for all Oxnard Subbasin wells in which five or more water level measurements have been recorded are included in Appendix D, Water Elevation Hydrographs. In general, climate cycles, management actions, and the construction of water conservation facilities have impacted water elevations in the Oxnard Subbasin. The Freeman Diversion, completed in 1991, allows UWCD to divert surface water from the Santa Clara River to spreading basins, where it can infiltrate into the aquifers of the UAS and be transported via pipelines to other areas. This additional recharge enhanced aquifer recovery in the 1990s after a period of drought (FCGMA 2007). Additionally, UWCD’s Pumping Trough Pipeline (PTP), constructed in 1986, which delivers diverted Santa Clara River water to agricultural parcels on the Oxnard Plain in lieu of groundwater production from that area, resulted in rising groundwater elevations during the late 1980s. In 1991, Ventura County adopted Ordinance 3991, which provided a temporary prohibition on drilling of new wells in the UAS, which also contributed to water elevation recovery in the UAS in the 1990s. 882
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2.3.1.1 Oxnard Aquifer
Spring and Fall 2015 Groundwater Elevations
In the spring of 2015, recorded groundwater elevations in the Oxnard Aquifer wells ranged from −27.2 to 46.3 feet msl (Figure 2-7, Groundwater Elevation Contours in the Oxnard Aquifer, March 2–29, 2015). In the fall of 2015, recorded groundwater elevations ranged from −30.7 to 37.9 feet msl (Figure 2-8, Groundwater Elevation Contours in the Oxnard Aquifer, October 2–29, 2015).

Groundwater flows from areas of high groundwater elevation to areas of low groundwater elevation. The highest groundwater elevations in the Oxnard Aquifer are found in the Forebay in both the fall and spring of 2015 (Figures 2-5 and 2-7). The hydraulic gradient in the Forebay in the spring of 2015 was approximately 0.005 feet/feet with groundwater flowing to the south and southwest, toward the pumping centers west and southeast of the City of Oxnard. In the fall of 2015, the hydraulic gradient was approximately 0.005 feet/feet with groundwater flowing to the southwest and southeast.

Elsewhere in the Subbasin, groundwater elevations in the Oxnard Aquifer are higher on the western and eastern boundaries of the Subbasin than they are in the center of the Subbasin. In this central area, groundwater elevations are more than −20 feet msl in both the spring and fall of 2015, though the areal extent of lower elevations is much greater in fall than in spring (Figures 2-7 and 2-8). In general, elevations in the UAS in the central Oxnard Subbasin are above sea level during wet climatic periods and fall below sea level during droughts (UWCD 2016a). Artesian conditions can occur in the western Oxnard Subbasin during wet climatic cycles (UWCD 1999).

The central area of low elevations reflects the groundwater production from wells southeast of the City of Oxnard in the central Oxnard Subbasin (Figure 2-5). The hydraulic gradient, directed toward the production wells, was less than approximately 0.001 feet/feet in both the spring and fall of 2015.

Coastal elevations were measured below or near sea level in both spring and fall of 2015, and consequently, the hydraulic gradient was generally landward at the coast (Figures 2-7 and 2-8).

There is uncertainty associated with the groundwater elevation contours, hydraulic gradient, and groundwater flow direction in the Oxnard Aquifer in the spring and fall of 2015. Fewer wells are screened solely within the Oxnard Aquifer than are producing groundwater from the Oxnard Aquifer. The majority of the wells that produce groundwater in the Oxnard Aquifer are screened across multiple aquifers. These wells were not used to create the contour maps in order to conform with the DWR GSP Regulations, Section 354.14. The uncertainty in hydraulic gradient, flow direction, and groundwater elevation within the Oxnard Aquifer is particularly pronounced in the southern Oxnard Subbasin, where there are few wells screened solely within the Oxnard Aquifer but several production wells screened in multiple aquifers (Figures 2-7 and 2-8). 883
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Vertical Gradients
Groundwater elevations in the Oxnard Aquifer are higher than those in the underlying Mugu Aquifer, resulting in a downward vertical gradient from the Oxnard Aquifer to the Mugu Aquifer in all areas of the Oxnard Subbasin for which Mugu-specific elevation data are available (Table 2-2). The magnitude of the vertical gradient varies with distance from the coast. The downward vertical gradient between the Oxnard and Mugu Aquifers was calculated for five wells in the fall of 2015 (Table 2-2). The wells in Table 2-2 were selected from a larger group of nested groundwater monitoring wells to represent the vertical gradient at different geographic locations in the Subbasin.

In the spring of 2015, the vertical gradient from the Oxnard Aquifer to the underlying Mugu Aquifer ranged from 0.004 feet/feet at the coast near Port Hueneme to 0.278 feet/feet inland of Point Mugu (Table 2-2). In the fall of 2015, the vertical gradient from the Oxnard Aquifer to the underlying Mugu Aquifer ranged from 0.002 feet/feet at the coast near Port Hueneme to 0.468 feet/feet inland of Point Mugu (Table 2-2). The vertical gradients along the coast are lower than they are inland, possibly reflecting the influence of seawater in the aquifer, moderating water levels at the coast. Alternatively, the vertical gradients may be lower at the coast because there is less pumping near the coast (Figures 2-5 and 2-6), and gradients may be higher in some inland areas that are closer to the Forebay area, as recharge in the Forebay affects water pressure in the Oxnard Aquifer more than the other aquifers.

The vertical gradient between the Oxnard and Mugu Aquifers was higher in the fall than in the spring, except at the coast where it was the same in the spring and fall (Wells 01N22W20M02S and 01N22W20M03S), and in the Forebay where the gradient was higher in the spring than in the fall (Wells 02N22W23B07S and 02N22W23B08S). The vertical gradient in the Forebay was higher in the spring because of surface water spreading grounds in the Forebay that are primarily used during periods of higher flow in the Santa Clara River.

Vertical gradients within the Oxnard Aquifer were determined from monitoring well clusters 01N21W19L, 02N22W23B, and 01N22W28G, which have two screen intervals within the Oxnard Aquifer (Table 2-2). For each of these locations, the vertical hydraulic gradient within the Oxnard Aquifer was directed downward. The downward vertical hydraulic gradient ranged from 0.009 to

0.278 feet/feet in the spring of 2015. In the fall of 2015, the downward vertical gradient ranged from 0.016 to 0.643 feet/feet. The downward vertical hydraulic gradient was larger in the fall than in the spring, and the largest downward vertical hydraulic gradient was in the Oxnard Forebay (Forebay). The smallest downward vertical hydraulic gradient within the Oxnard Aquifer was adjacent to the coast (Table 2-2; Figure 2-8).
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Historical Groundwater Elevation Trends
Groundwater elevations in the Oxnard Aquifer have declined and recovered over climatic cycles since the 1930s (Figure 2-9a, Groundwater Well Hydrographs in the Oxnard Aquifer – Oxnard Plain). Management policies and the construction and operation of water conservation facilities have also impacted historical groundwater elevations (see Section 2.3.1, Groundwater Elevation Data).

Full hydrographs for Oxnard Subbasin wells with five or more groundwater elevation measurements are included in Appendix D.

Groundwater elevation trends in Well 01N21W07H01S, the well with the longest historical groundwater elevation record in the Oxnard Subbasin, track with the trends observed in the record of cumulative departure from the mean precipitation on the Oxnard Plain (Figure 2-9a). Declines in groundwater elevation occurred between 1941 and 1966, 1970 and 1977, 1984 and 1990, and 2011 and 2016, coincident with periods of drought shown in the declining limb of the cumulative departure from the mean precipitation curve (Figure 2-9a). Groundwater elevations recovered after each historical drought period, but have not yet recovered from the drought beginning in 2011. The amount of historical recovery depended on the length of time between droughts and the amount of precipitation received in each of the water years between the droughts, as well as management measures, including surface water spreading and deliveries, operative during the various periods. By 1980, the groundwater elevation recovered to within 10 feet of the previous maximum measured in 1941, and by 1999, water levels exceeded the 1941 maximum (Figure 2-9a), likely due to several wet years during the 1990s and the influence of management actions taken, and water conservation facilities constructed, in the 1980s and 1990s (see Section 2.3.1). In the late 1990s, artesian conditions were documented in the western Oxnard Subbasin (UWCD 1999). Since 2011, groundwater elevations in this well have declined approximately 40 feet.

The patterns of water level decline and recovery observed in Well 01N21W07H01S are observed in Oxnard Aquifer wells throughout the Oxnard Subbasin, although absolute changes in water level vary geographically within the Oxnard Subbasin (Figure 2-9a and Figure 2-9b, Groundwater Well Hydrographs in the Oxnard Aquifer – Forebay Area). Wells in the Forebay area and northeastern Oxnard Subbasin have experienced water level declines of approximately 90 feet since 2011 (Figure 2-9b), while water levels in wells adjacent to the coast and in wells farther south have declined between 18 and 40 feet over the same period (Figure 2-9a). The larger water level changes observed in the northeastern Oxnard Subbasin reflect the influence of UWCD’s managed aquifer recharge activities in the Forebay area; additionally, water level changes at the coast may be smaller due to the fact that seawater may be intruding and occupying volume within the aquifer as freshwater recedes.
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Although groundwater elevations in the Oxnard Subbasin recover to some degree after each drought period, elevations in coastal wells do not always recover to mean sea level. Historical elevations of coastal wells over time in relation to sea level are discussed in Section 2.3.3.

2.3.1.2 Mugu Aquifer
Spring and Fall 2015 Groundwater Elevations
In the spring of 2015, recorded groundwater elevations in the Mugu Aquifer in the Oxnard Subbasin ranged from −60.7 to 8.2 feet msl (Figure 2-10 Groundwater Elevation Contours in the Mugu Aquifer, March 2–29, 2015). In the fall of 2015, groundwater elevations ranged from −97.7 to −12.1 feet msl (Figure 2-11, Groundwater Elevation Contours in the Mugu Aquifer, October 2–29, 2015).

The highest groundwater elevations in the Mugu Aquifer are found in the Forebay in both the fall and spring of 2015 (Figures 2-10 and 2-11). The hydraulic gradient in the Forebay in the spring of 2015 was approximately 0.003 feet/feet with groundwater flowing to the south and southwest. In the fall of 2015, the hydraulic gradient was approximately 0.002 feet/feet with groundwater flowing to the south and southwest. These gradients are based on the wells that are screened solely within the Mugu Aquifer, which are primarily located in the eastern part of the Subbasin. Groundwater elevations in the Mugu Aquifer are lowest in the southeastern area of the Subbasin. In general, elevations in the UAS in the southernmost corner of the Subbasin tend to be lower than in the central Subbasin (by as much as 40 to 80 feet), regardless of climatic cycles (FCGMA 2013).

In the southeastern area of the Subbasin, groundwater elevations were −30 to −100 feet msl in 2015 (Figures 2-10 and 2-11). The hydraulic gradient, directed toward the area of low groundwater elevations, was approximately 0.002 feet/feet to the southeast in the spring of 2015. In the fall of 2015, the hydraulic gradient directed toward the area of low groundwater elevations ranged from approximately 0.004 to 0.009 feet/feet to the east-southeast. Coastal groundwater elevations were measured below or near sea level in both spring and fall of 2015, creating a presumably landward hydraulic gradient at the coast (Figures 2-10 and 2-11).

There is uncertainty associated with the groundwater elevation contours, hydraulic gradient, and groundwater flow direction in the Mugu Aquifer in the spring and fall of 2015. The gradient is unknown in the northwestern area of the Subbasin, where there are no wells screened solely within the Mugu Aquifer. Additionally, fewer wells are screened solely within the Mugu Aquifer than are producing groundwater from the Mugu Aquifer. The majority of the wells that produce groundwater in the Mugu Aquifer are screened across multiple aquifers. These wells were not used to create the contour maps, in order to conform with the DWR GSP Regulations, Section 354.14. For the central and eastern areas of the Subbasin in which there are well data in the Mugu Aquifer, the uncertainty in hydraulic gradient, flow direction, and groundwater elevation within the aquifer is particularly pronounced. In this area, groundwater appears to flow to the southsoutheast from the Oxnard Subbasin to the PVB (Figures 2-10 and 2-11). 886
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Vertical Gradients
Groundwater elevations in the Mugu Aquifer are lower than those in the overlying Oxnard Aquifer, resulting in a downward vertical gradient from the Oxnard Aquifer to the Mugu Aquifer throughout the Oxnard Subbasin (Table 2-2; Section 2.3.1.1, Oxnard Aquifer). Groundwater elevations in the Mugu Aquifer are higher than those in the underlying Hueneme Aquifer, resulting in a downward vertical gradient from the Mugu Aquifer to the Hueneme Aquifer in the Forebay and adjacent to Port Hueneme (Table 2-2). At monitoring well cluster 01N22W20M, adjacent to Port Hueneme, the downward vertical hydraulic gradient was 0.033 feet/feet in the spring of 2015 and 0.039 feet/feet in the fall of 2015. At monitoring well cluster 02N22W23B, in the Forebay, the downward vertical hydraulic gradient was 0.012 feet/feet in the spring of 2015 and 0.028 feet/feet in the fall of 2015.

Within the Mugu Aquifer, a downward vertical gradient of 0.365 feet/feet was calculated in the spring of 2015 between Wells 01N21W32Q07S and 01N21W32Q05S (Figure 2-10). In the fall of 2015, the downward vertical gradient was 0.560 feet/feet (Table 2-2; Figure 2-11).

Historical Groundwater Elevation Trends
Groundwater elevations in the Mugu Aquifer have declined and recovered over climatic cycles since the 1970s (Figure 2-12, Groundwater Well Hydrographs in the Mugu Aquifer). Management policies and the construction and operation of water conservation facilities have also impacted historical groundwater elevations (see Section 2.3.1). Full hydrographs for Oxnard Subbasin wells with five or more groundwater elevation measurements are included in Appendix D.

Groundwater elevation trends in Well 02N22W24P01S, the well with the longest historical groundwater elevation record in the Mugu Aquifer, track with the trends observed in the record of cumulative departure from the mean precipitation on the Oxnard Plain (Figure 2-12). Declines in groundwater elevation occurred between 1974 and 1977, 1984 and 1990, and 2011 and 2016, coincident with periods of drought shown in the declining limb of the cumulative departure from the mean precipitation curve (Figure 2-12). Groundwater elevations recovered after each historical drought period, but have not yet recovered from the drought beginning in 2011. The amount of historical recovery depends on the length of time between droughts and the amount of precipitation received in each of the water years between the droughts, as well as management measures, including artificial recharge and surface water deliveries, operative during the various periods. In 1996, water levels exceeded the previous maximum in 1980 (Figure 2-12), likely due to several wet years during the 1990s and the influence of management actions taken, and water conservation facilities constructed in the 1980s and 1990s (see Section 2.3.1). In the late 1990s, artesian conditions were documented in the western Oxnard Subbasin (UWCD 1999). Since 2011, groundwater elevations in this well have declined approximately 100 feet. 887
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The patterns of water level decline and recovery observed in Well 02N22W24P01S are observed in Mugu Aquifer wells throughout the Oxnard Subbasin, although absolute changes in water level vary geographically within the Subbasin (Figure 2-12). Well 02N22W24P01S is located near the Forebay area. Other wells in the Forebay area experienced similar water level declines and recoveries to those observed in Well 02N22W24P01S (Figure 2-12). Water levels in wells adjacent to the coast and in wells farther south, however, tend to have larger intra-annual variation (variation that occurs within a single year) in groundwater level, but a smaller drought response (e.g., Wells 01N21W32Q05S and 01N21W19L11S; see Figure 2-12). The groundwater elevation in these wells declined between 20 and 80 feet between 2011 and 2015, whereas the groundwater elevation in wells in the Forebay area declined approximately 100 feet over the same period. The larger groundwater level changes observed in the northeastern Oxnard Subbasin likely reflect the influence of groundwater recharge from spreading basins in the Forebay area; additionally, groundwater level changes at the coast may be smaller due to the fact that seawater may be intruding and occupying volume within the aquifer as freshwater recedes.

Although groundwater elevations in the Oxnard Subbasin recover after each drought period, groundwater elevations in coastal Mugu-specific wells in the southern Subbasin typically remain below mean sea level. Historical elevations of coastal wells over time in relation to sea level are discussed in Section 2.3.3.

2.3.1.3 Hueneme Aquifer
Spring and Fall 2015 Groundwater Elevations
In the spring of 2015, recorded groundwater elevations in the Hueneme Aquifer in the Oxnard Subbasin ranged from −89.4 to 10.2 feet msl (Figure 2-13, Groundwater Elevation Contours in the Hueneme Aquifer, March 2–29, 2015). In the fall of 2015, groundwater elevations ranged from −115.5 to 2.1 feet msl (Figure 2-14, Groundwater Elevation Contours in the Hueneme Aquifer, October 2–29, 2015). There are fewer wells screened solely in the Hueneme Aquifer than are screened in the Oxnard Aquifer, Mugu Aquifer, or FCA in the Oxnard Subbasin. The small number of wells screened solely within the Hueneme Aquifer creates uncertainty in the groundwater elevation contours, hydraulic gradient, and groundwater flow direction (Figures 2-13 and 2-14).

This aquifer is present in the northern part of the Oxnard Subbasin but is absent to the south of Etting and Hueneme Roads (Mukae and Turner 1975).

The highest groundwater elevations in the Hueneme Aquifer are found in the Forebay in both the fall and spring of 2015 (Figures 2-13 and 2-14). The hydraulic gradient in the Forebay in the spring of 2015 was approximately 0.008 feet/feet, with groundwater flowing to the southwest. In the fall of 2015 the hydraulic gradient was approximately 0.007 feet/feet, with groundwater flowing to the south-southwest.
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Groundwater elevations in the Hueneme Aquifer are lowest south of the Forebay and west of Central Avenue (Figures 2-13 and 2-14). In this area, groundwater elevations were −80 to −100 feet msl in 2015 (Figures 2-13 and 2-14). This area of lower groundwater elevations coincides with the location of several production wells that are screened solely within the Hueneme Aquifer (Figure 2-6). The hydraulic gradient, directed toward the area of low groundwater elevations, ranged from approximately 0.003 feet/feet to the southeast in the spring of 2015 to approximately

0.008 feet/feet to the east-southeast in the fall of 2015. Coastal groundwater elevations were below or near sea level in both spring and fall of 2015, resulting in a landward hydraulic gradient at the coast (Figures 2-13 and 2-14).

Vertical Gradients
Groundwater elevations in the Hueneme Aquifer are lower than those in the overlying Mugu Aquifer, resulting in a downward vertical gradient from the Mugu Aquifer to the Hueneme Aquifer (Table 2-2; Section 2.3.1.2, Mugu Aquifer). Groundwater elevations in the Hueneme Aquifer were higher than those in the underlying FCA in both the spring and fall of 2015, except in the Forebay at Wells 02N22W23B03 and 02N22W23B04. In these wells, the groundwater elevation in the Hueneme Aquifer was higher than it was in the FCA in the spring of 2015, and lower than that in the FCA in the fall of 2015 (Table 2-2). In the spring of 2015, the downward vertical hydraulic gradient between the Hueneme Aquifer and FCA ranged from 0.014 feet/feet to 0.040 feet/feet. In the fall of 2015, the vertical hydraulic gradient between the Hueneme Aquifer and FCA ranged from 0.050 feet/feet downward adjacent to the coast, to 0.032 upward in the Forebay (Table 2-2).

Within the Hueneme Aquifer, a downward vertical gradient of 0.017 feet/feet was calculated for Wells 01N22W20M03S and 01N22W20M02S in the spring of 2015 (Figure 2-13). In the fall of 2015, the gradient in these wells was 0.019 feet, which is the same as it was in the spring. Farther north, in Wells 01N23W01C03S and 01N23W01C04S, the vertical gradient within the Hueneme Aquifer was similar to that calculated for Wells 01N22W20M03S and 01N22W20M02S. In the spring of 2015, the downward vertical hydraulic gradient was 0.009 feet/feet in Wells 01N23W01C03S and 01N23W01C04S. In the fall, the downward vertical hydraulic gradient was

0.010 feet/feet between Wells 01N23W01C03S and 01N23W01C04S (Table 2-2).

In Wells 02N22W23B07S and 02N22W23B08S, in the Forebay, the downward vertical gradient is greater in the upper Hueneme Aquifer than in the lower Hueneme Aquifer (Table 2-2). The gradients within the Hueneme Aquifer in the Forebay are similar to those within the Hueneme Aquifer along the coast.

Historical Groundwater Elevation Trends
Groundwater elevations in the Hueneme Aquifer have declined and recovered over climatic cycles (Figure 2-15, Groundwater Well Hydrographs in the Hueneme Aquifer). Management policies and 889
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the construction and operation of water conservation facilities have also impacted historical groundwater elevations (see Section 2.3.1). Full hydrographs for Oxnard Subbasin wells with five or more groundwater elevation measurements are included in Appendix D.

Groundwater elevation trends in Well 02N21W31P03S, the well with the longest historical groundwater elevation record in the Hueneme Aquifer, track with the trends observed in the record of cumulative departure from the mean precipitation on the Oxnard Plain (Figure 2-15). Declines in groundwater elevation occurred between 1974 and 1977, 1984 and 1990, and 2011 and 2016, coincident with periods of drought shown in the declining limb of the cumulative departure from the mean precipitation curve (Figure 2-15). Groundwater elevations largely recovered after each historical drought period, but have not yet recovered from the drought beginning in 2011. The amount of historical recovery depends on the length of time between droughts and the amount of precipitation received in each of the water years between the droughts, as well as the management measures, including artificial recharge and surface water deliveries, operative during the various periods. Since 2011, groundwater elevations in this well have declined approximately 60 feet (Figure 2-15).

The patterns of water level decline and recovery observed in Well 02N21W31P03S are also observed in Hueneme Aquifer Wells 01N22W03F05S and 01N22W26M03S, although the magnitude of the change in groundwater levels varies between the wells (Figure 2-15). Ignoring seasonal variations reflecting pumping, the spring high elevations between 1996 and 2010 were relatively stable in Well 01N22W26M03S and declined by approximately 32 feet in Well 01N22W03F05S. Between 2011 and 2015, during a period of drought, groundwater elevations declined approximately 47 feet in Well 01N22W26M03S and approximately 55 feet in Well 01N22W03F05S (Figure 2-15).

Although groundwater elevations in the Oxnard Subbasin recover after each drought period, groundwater elevations in coastal wells can remain below mean sea level, resulting in a landward gradient near the coast.

2.3.1.4 Fox Canyon Aquifer
Spring and Fall 2015 Groundwater Elevations
In the spring of 2015, recorded groundwater elevations in the FCA in the Oxnard Subbasin ranged from −107.3 to 3.9 feet msl (Figure 2-16, Groundwater Elevation Contours in the Fox Canyon Aquifer, March 2–29, 2015). In the fall of 2015, groundwater elevations ranged from −156.3 to −24.6 feet msl (Figure 2-17, Groundwater Elevation Contours in the Fox Canyon Aquifer, October 2–29, 2015).

The highest groundwater elevations in the FCA are found in the Forebay in both the fall and spring of 2015 (Figures 2-16 and 2-17). The lowest recorded groundwater elevations are found at Well 01N21W06J05S, south of 5th Street, west of Pleasant Valley Road (Figures 2-16 and 890
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2-17). The low groundwater elevations in this well reflects the production from the FCA at this location (Figure 2-6). However, there are several wells in the surrounding areas that produced more groundwater in 2015, but are screened across multiple aquifers in the LAS. The hydraulic gradient in the FCA was directed toward Well 01N21W06J05S in both the spring and fall of 2015. In the spring of 2015, the hydraulic gradient was approximately 0.001 to 0.002 feet/feet.

In the fall of 2015, the hydraulic gradient ranged from approximately 0.002 to approximately

0.005 feet/feet. These gradients may not fully depict the direction and magnitude of flow within the FCA because more production wells are screened across multiple aquifers in the LAS than are screened solely within the FCA, and consequently production is occurring in areas of the aquifer that lack aquifer-specific groundwater elevation data. Coastal groundwater elevations were measured below or near sea level in both spring and fall of 2015, resulting in a landward hydraulic gradient (Figures 2-16 and 2-17).

Vertical Gradients
Groundwater elevations in the FCA are generally lower than those in the overlying aquifers (Figures 2-16 and 2-17; Table 2-2). In the spring of 2015, the downward vertical gradient from the Mugu Aquifer to the FCA ranged from 0.012 feet/feet in the Forebay to 0.390 feet/feet adjacent to Highway 1 (Figure 2-16; Table 2-2). In the fall of 2015, the downward vertical gradient from the Mugu Aquifer to the FCA ranged from 0.620 feet/feet in the Forebay to 0.028 feet/feet south of Hueneme Road.

In the spring of 2015, the downward vertical gradient from the Hueneme Aquifer to the FCA was similar geographically, ranging from 0.014 feet/feet in the Forebay and along the coast north of Port Hueneme to 0.040 feet/feet adjacent to the coast at Port Hueneme (Table 2-2). In the fall of 2015, the vertical hydraulic gradient between the Hueneme Aquifer and FCA ranged from 0.050 feet/feet downward along the coast near Port Hueneme to 0.032 feet/feet upward in the Forebay (Table 2-2).

Within the FCA, a downward vertical gradient of 0.005 feet/feet was calculated for Wells 01N22W36K06S and 01N22W36K07S in the spring of 2015. The vertical hydraulic gradient in these wells, near Point Mugu, was 0.019 feet/feet downward in the fall of 2015. In the Mugu area the vertical flow to the FCA is a major mechanism for seawater intrusion. In the Forebay area, the vertical hydraulic gradient within the FCA was 0.014 feet/feet downward in the spring of 2015 and 0.022 feet/feet upward in the fall of 2015 (Table 2-2; Wells 02N21W07L04S and 02N21W07L06S).

Groundwater elevations in the FCA are higher than those in the underlying GCA, except adjacent to Port Hueneme in Wells 01N22W28G04S and 01N22W28G05S (Table 2-2). 891
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Historical Groundwater Elevation Trends
Groundwater elevations in the FCA have declined and recovered over climatic cycles (Figure 2-18, Groundwater Well Hydrographs in the Fox Canyon Aquifer). Management policies and the construction and operation of water conservation facilities have also impacted historical groundwater elevations (see Section 2.3.1). Full hydrographs for Oxnard Subbasin wells with five or more groundwater elevation measurements are included in Appendix D.

Groundwater elevation trends in Well 01N22W26K04S, the well with the longest historical groundwater elevation record in the FCA, track with the trends observed in the record of cumulative departure from the mean precipitation on the Oxnard Plain (Figure 2-18). Declines in groundwater elevation occurred between 1974 and 1977, 1984 and 1990, and 2011 and 2016, coincident with periods of drought shown in the declining limb of the cumulative departure from the mean precipitation curve (Figure 2-18). Groundwater elevations recovered after each drought period prior to the most recent drought. Groundwater elevations have not yet recovered to pre2011 levels.

The amount of historical recovery depends on the length of time between droughts and the amount of precipitation received in each of the water years between the droughts, as well as management measures, including artificial recharge and surface water deliveries, operative during the various periods. In 1999, water levels exceeded the previous maximum in 1983 (Figure 2-18), likely due to several wet years during the 1990s and the influence of management actions taken, and water conservation facilities constructed, in the 1980s and 1990s (see Section 2.3.1). In the late 1990s, artesian conditions were documented in the western Oxnard Subbasin (UWCD 1999).

The patterns of groundwater level decline and recovery observed in Well 01N22W26K04S are observed in FCA wells throughout the Oxnard Subbasin, although absolute changes in groundwater level vary geographically within the Oxnard Subbasin (Figure 2-18). Well 01N22W26K04S is located south of Hueneme Road. Other wells in this area experienced similar groundwater level declines and recoveries to those observed in Well 01N22W26K04S (Figure 2-18). Wells farther inland tend to have larger intra-annual variations in groundwater level (e.g., Wells 01N21W06J05S and 01N21W09C04S; see Figure 2-18). The groundwater elevation in these wells declines by 40 to 50 feet each year between the spring high and fall low groundwater levels. In contrast, Well 01N23W01C02S, adjacent to the coast, declines approximately 5 feet between the spring high and fall low groundwater level (Figures 2-16, 2-17, and 2-18).

Groundwater level changes at the coast may be smaller due to the fact that seawater may be intruding and occupying volume within the aquifer as freshwater recedes. 892
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Although groundwater elevations in the Oxnard Subbasin recover after each drought period, groundwater elevations in coastal FCA-specific wells in the southern Subbasin typically remain below mean sea level.

2.3.1.5 Grimes Canyon Aquifer
Spring and Fall 2015 Groundwater Elevations
The GCA is only found underlying the southern and eastern parts of the Oxnard Subbasin (Turner 1975). Only six wells in the Oxnard Subbasin are screened solely within the GCA. These wells are located in the southern part of the Subbasin, all located west of Revolon Slough (Figure 2-19, Groundwater Elevation Contours in the Grimes Canyon Aquifer, March 2–29, 2015). In the spring of 2015, recorded groundwater elevations in the GCA ranged from −31.3 to −75.6 feet msl (Figure 2-19). In the fall of 2015, groundwater elevations ranged from −38.6 feet msl to −114.2 feet msl (Figure 2-20, Groundwater Elevation Contours in the Grimes Canyon Aquifer, October 2–29, 2015).

Where measured, groundwater in the GCA flows to the east-northeast from the coast toward the Revolon Slough (Figures 2-19 and 2-20). In the spring of 2015, the hydraulic gradient in the vicinity of Point Mugu was approximately 0.003 feet/feet (Figure 2-19). In the fall of 2015, the hydraulic gradient was approximately 0.008 feet/feet (Figure 2-20).

There is a large degree of uncertainty associated with the groundwater elevation contours, hydraulic gradient, and groundwater flow direction in the GCA in the spring and fall of 2015 because so few wells are screened solely within the GCA. The direction of flow, as contoured by the wells that are screened within the GCA, likely reflects the LAS groundwater production south of Hueneme Road (Figure 2-6). However, no wells are screened solely within the GCA north of Hueneme Road; therefore, the groundwater elevation, hydraulic gradient, and direction of flow in the GCA is unknown for much of the Oxnard Subbasin. Coastal groundwater elevations were measured below or near sea level in both spring and fall of 2015, and consequently the hydraulic gradient was landward at the coast (Figures 2-19 and 2-20).

Vertical Gradients
Groundwater elevations in the GCA are generally lower than those in the overlying FCA, except adjacent to Port Hueneme in Wells 01N22W28G04S and 01N22W28G05S (Table 2-2). The downward vertical hydraulic gradient in the spring of 2015 ranged from 0.047 feet/feet downward at Wells 01N21W32Q04S and 01N21W32Q05S to 0.01 feet/feet upward Wells 01N22W28G04S and 01N22W28G05S (Table 2-2). Vertical hydraulic gradients were similar in the fall of 2015, ranging from 0.044 feet/feet downward to 0.019 feet/feet upward, in the same wells. 893
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Only well cluster 01N21W32Q has two wells screened within the GCA (Wells 01N21W32Q02 and 01N21W32Q03; Figure 2-19). Within the GCA, the vertical hydraulic gradient was 0.084 feet/feet upward in both the spring and fall of 2015 (Table 2-2).

Historical Groundwater Elevation Trends
Groundwater elevations in the GCA have been measured since 1989. Similar to the water levels in the overlying FCA, the groundwater levels in the GCA recovered between 1990 and 1996 (Figure 2-21, Groundwater Well Hydrographs in the Grimes Canyon Aquifer). Between 1996 and 2010, groundwater elevations were relatively stable, with intra-annual variation of up to 80 feet per year, but with inter-annual variation (variation that occurs over a series of years) of 10 feet or less. Between 2011 and 2015 groundwater elevations in the GCA declined, coincident with a period of drought. Groundwater elevations in Wells 01N22W28G01S and 01N22W35E01S vary less than groundwater elevations in other GCA wells, potentially because they are relatively far from major centers of groundwater extraction or because they are adjacent to the coast, and the intrusion of seawater may moderate freshwater elevation changes (Figures 2-19 and 2-21).

Although groundwater elevations in the Oxnard Subbasin recover to some degree after each drought period, elevations in coastal GCA-specific wells in the southern Subbasin remain below mean sea level.

2.3.2 Estimated Change in Storage
Estimated monthly change in storage values for the Oxnard Subbasin were generated by the numerical groundwater flow model prepared by UWCD (Appendix C). Monthly data reported from the model was summed to get the annual change in storage for the period from water year 1986 to water year 2015. There are inherent uncertainties in using any numerical groundwater flow model. The uncertainty associated with the UWCD model estimates is explored in more detail in Appendix E, UWCD Model Peer Review. Model estimated change in storage for the aquifer, the UAS, and the LAS is presented below.

The annual change in storage in the semi-perched aquifer ranged from an increase of approximately 16,300 AF in water year 1995 to a decrease of approximately 11,000 AF in water year 2014. The average annual change in storage in the semi-perched aquifer was a loss of storage of approximately 410 AFY.

In the UAS, the annual change in storage ranged from an increase of approximately 63,000 AF in water year 2005 to a decrease of approximately 34,200 AF in water year 1987. The average annual change in storage in the UAS was a loss of approximately 2,800 AFY. 894
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The LAS had a maximum annual increase in storage of approximately 7,300 AF in water year 2005 and a maximum annual decrease in storage of approximately 8,000 AF in water year 1987.

The average annual change in the LAS was a loss of approximately 220 AFY.

Total average annual change in storage in the Oxnard Subbasin was a decrease in storage of approximately 3,400 AFY. For the entire Oxnard Subbasin, the annual change in storage ranged from an increase of approximately 81,000 AF in water year 2005 to a decrease of approximately 48,700 AF in water year 1987 (Figure 2-22, Oxnard Subbasin Annual Change in Storage).

The cumulative change in storage calculated by the model over the period of record, water years 1986 through 2015, is presented on Figure 2-23, Oxnard Subbasin Cumulative Change in Storage.

For the semi-perched aquifer, the UAS, and the LAS, the cumulative change in storage was a loss of approximately 12,300 AF, 82,500 AF, and 6,600 AF, respectively. The total cumulative loss for the entire Oxnard Subbasin was approximately 101,400 AF (Figure 2-23). Groundwater extraction (pumping) in the FCGMA is reported on a calendar year basis, so pumping and artificial recharge in figures is per calendar year, while change in storage is per water year. Annual change in storage is not strongly correlated to groundwater pumping in the Oxnard Plain (R2 < 0.5). In contrast, artificial groundwater recharge at the UWCD spreading grounds is correlated with change in storage (R
2 > 0.8; see Figures 2-22 and 2-23). Therefore, maintaining the ability to recharge groundwater via the UWCD spreading grounds is critical to maintaining groundwater production in the Subbasin.

The model results illustrated in Figures 2-22 and 2-23 represent the net change in groundwater storage in each of the aquifer systems in the Subbasin. These results, however, include flux of seawater into the coastal areas of the aquifer systems from offshore. The volume of seawater that intruded between 1986 and 2015 was calculated for the UAS and LAS. The volume of seawater calculated does not include coastal flux into or out of the semi-perched aquifer, as few production wells are screened solely in the semi-perched aquifer. In order to assess the change in freshwater storage in the Subbasin, the annual volume of seawater that intruded was subtracted from the annual total storage change discussed above.

In the UAS, the average annual change in freshwater storage is a loss of approximately 6,600 AFY, which is more than two times greater than the total average annual change in storage for the UAS (2,800 AFY), including seawater intrusion (Figure 2-24, Oxnard Subbasin Annual Change in Storage Without Coastal Flux). In other words, approximately 3,800 AFY of seawater intrusion occurred in the UAS between water years 1986 and 2015. The maximum annual increase in freshwater storage was approximately 61,500 AF in water year 2005 and the maximum annual decrease in freshwater storage was approximately 48,500 AF in water year 1990. 895
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The average annual change in freshwater storage in the LAS is a loss of approximately 5,700 AFY, which is 26 times greater than the total average annual change in storage for the LAS (220 AFY), including seawater intrusion (Figure 2-24). Therefore, there was approximately 5,500 AFY of seawater intrusion into the LAS between water years 1986 and 2015. The maximum increase of freshwater in storage in the LAS was approximately 2,820 AF in water year 1998 and the maximum decrease of freshwater in storage was approximately 15,150 AF in water year 1990.

For the entire Oxnard Subbasin, there was an average decrease in freshwater storage of approximately 12,700 AFY, when coastal flux is removed, with a maximum increase in storage of approximately 74,700 AF in water year 2005 and a maximum decrease in storage of approximately 73,500 AF in water year 1990 (Figure 2-24). Cumulatively between 1986 and 2015, the loss of freshwater in storage in the UAS was approximately 197,200 AF and the loss of freshwater in storage in the LAS was approximately 170,200 AF. The cumulative change in freshwater storage for both the UAS and LAS was a loss of approximately 367,400 AF. The cumulative change in storage for the entire Oxnard Subbasin, including the semi-perched aquifer, calculated by the model over the period of record, was a loss of approximately 380,200 AF of freshwater in storage, excluding coastal flux (Figure 2-25, Oxnard Subbasin Cumulative Change in Storage Without Coastal Flux).

Estimates of model changes in storage have a level of uncertainty and are dependent on model input parameters. These parameters include groundwater pumping, artificial aquifer recharge, interbasin flows, recharge from precipitation and irrigation returns, stream leakage and groundwater discharge to streams, and inflows from the ocean. Numbers may also initially be biased due to assumptions about the initial groundwater levels used in the model, which are based on available well locations and measurements that may bias starting groundwater elevations modeled in the aquifers. These inputs were estimated using the best available data and calibrated to groundwater levels in the model to a reasonable extent (Appendix C). Changes in these input values from additional monitoring wells, the filling of data gaps, and model calibration and validation may result in changes in the modeled estimates of change in storage in the future.

2.3.3 Seawater Intrusion
Evidence of seawater intrusion in the Oxnard Subbasin was first documented in the 1930s in the vicinity of Port Hueneme and Point Mugu (DWR 1965). Since that time, the landward extent of the saline water impact front has been monitored and the causes and sources of increasing chloride concentrations have been studied. Table 2-3 lists historical seawater intrusion reports and studies on the Oxnard Subbasin.

An elevated risk of seawater intrusion has been found to exist near Port Hueneme and Point Mugu due to the near shore presence of the groundwater–seawater contact in deeply incised submarine canyons (UWCD 2016a).
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Seawater intrusion has been documented in both aquifer systems, and in each primary aquifer, in the Oxnard Subbasin. Seawater preferentially intrudes the aquifers in permeable sand and gravel beds (UWCD 2016a). As a result, the eastward extent of the saline water impact front varies from north to south along the coastline and within each aquifer (UWCD 2016a). In the Oxnard Subbasin, seawater that has intruded the aquifers in the vicinity of Port Hueneme tends to flow southward toward Point Mugu even after groundwater elevations rise and the landward hydraulic gradient is reversed (UWCD 2016a). As a result, higher groundwater elevations in the aquifer do not tend to flush the seawater back out of the aquifer via the original intrusion pathway (UWCD 2016a).

Consequently, impacts associated with seawater intrusion have not been eliminated during wetterthan-average climatic periods.

2.3.3.1 Causes of Saline Impacts in the Oxnard Subbasin Under seaward groundwater gradients, groundwater in the Oxnard Subbasin generally flows south and west from the Oxnard Forebay area toward the Pacific Ocean and out to sea. When groundwater heads near the coast fall below sea level or, in confined aquifers, the sea-levelequivalent elevation according to the depth of the aquifer outcrop, the gradient reverses. 4 In addition to seawater intrusion, low groundwater heads in confined zones in the Oxnard Subbasin can create conditions under which high-salinity waters from non-marine sources impact freshwater aquifers. These sources include connate (groundwater trapped in sedimentary rocks due their deposition) brines released during compaction of aquitards and older, higher-salinity groundwater upwelling from geologic formations deeper than the lower extent of the freshwater aquifers (Izbicki 1991, 1996; UWCD 2016a; Izbicki et al. 2005).

Thirdly, although the major aquifer units in the Oxnard Subbasin are commonly separated by lowpermeability units, vertical gradients, long-screened wells, and areas of mergence between aquifers can result in vertical groundwater movement between major aquifers (UWCD 2016a). In particular, because water elevations are typically higher in the semi-perched aquifer than in the deeper confined aquifers, higher-salinity water from the semi-perched aquifer may reach confined aquifers via one or more of these mechanisms. Seawater intrusion also enters the FCA from vertical flow from the Mugu aquifer in the Mugu area.

Because zones of low groundwater head cause seawater intrusion and release of connate water from aquitards, and potentially influence non-marine brine migration into freshwater aquifers, distinguishing the source of salts in any given well is not always possible, particularly at chloride concentrations less than 500 mg/L (Izbicki 1996). In the southeastern Subbasin, near the Mugu

4 Because seawater is approximately 1.025 times denser than freshwater (using the Ghyben-Herzberg theory [De Wiest 1998]), the elevation of confined freshwater necessary to counterbalance the pressure of the water in the sea can be several feet above sea level, and depends on the depth at which an aquifer crops out in the ocean (i.e., the deeper the outcrop, the higher the freshwater elevation necessary to counterbalance the pressure of seawater). 897
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submarine canyon, upward migration of brines can cause chloride concentrations to increase before the saline water impact front reaches a well (Izbicki 1996). Because the chloride concentration measured in wells near the Mugu submarine canyon reflect the combined effects of brine migration and seawater intrusion, it is difficult to define the leading edge of the saline water impact front using chloride concentrations in this area (Izbicki 1996). The USGS and UWCD models included faults in the Mugu Lagoon area that limit the hydraulic connection of the LAS in the Oxnard Basin to the Pacific Ocean (Hanson et al. 2003; Appendix C).

2.3.3.2 Current Extent of Seawater Intrusion
The known extent of saline water intrusion in the UAS and LAS in 2015 generally occurred near and southeast of Port Hueneme and in the area surrounding Mugu Lagoon. As of 2015, although seawater intrusion had been reduced in the Oxnard Subbasin due to management actions and wet climatic conditions in the 1990s and 2000s, TDS and chloride concentrations as high as 49,600 and 20,700 mg/L, respectively, were found in wells inland of the southern Oxnard coast (both measured in Well 01N22W07R05S; see Appendix F, Coastal Seawater Intrusion WL vs. CL Plots, and recent water quality data in Section 2.3.4, Groundwater Quality). The extent of saline water intrusion in the Oxnard Subbasin in 2015 is shown in cross section on Figure 2-26 (Approximate 2015 North–South Saline Water Intrusion Extent) and in plan view on Figures 2-27 through 2-32 (Coastal Chloride Concentrations, Fall 2015).5 As discussed, chloride concentrations above 500 mg/L in the area of the Mugu Lagoon can be caused by both seawater intrusion and brine migration. Although this section focuses on areas that are known to be susceptible to seawater intrusion, the precise extent of current seawater intrusion impacts is difficult to separate from the areas that are impacted by release of saline water from connate brines. Therefore, the current area of seawater intrusion is smaller than the area of high chloride concentrations shown in Figures 2-27 through 2-32.

Additionally, the inland extent of seawater intrusion varies by aquifer (see Figure 2-26). Between 1985 and 2015, UWCD groundwater model estimates suggest that approximately 1,800 AFY of groundwater flowed from the semi-perched aquifer to the Pacific Ocean. In the UAS (Oxnard and Mugu Aquifers), in years characterized by relatively high rainfall, groundwater flowed from the aquifers to the ocean in the spring, and the flow reversed in the fall; conversely, in dry years ocean water flowed into the aquifers in all seasons. On average, over the entire model period, there was approximately 3,900 AFY of seawater intrusion into the UAS in the Oxnard Subbasin. In the LAS, the direction of flow varied by aquifer. The direction of flow in the Hueneme Aquifer was primarily from the ocean to the aquifer, though there are some months in which the flow direction was seaward. In the FCA and the GCA, ocean water flowed into the aquifers in every month in the period of record. The average seawater intrusion in the LAS was approximately 5,500 AFY during the model period.

5 Saline water is typically defined as groundwater with a TDS concentration between 10,000 and 35,000 mg/L. 898
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2.3.3.3 Historical Progression of Seawater Intrusion
Chloride concentrations were first measured in the Oxnard Subbasin in the 1920s. Between 1920 and 1929, the chloride concentration in three wells in the UAS ranged from 40 to 81 mg/L, with the lowest chloride concentration detected at the coast near Port Hueneme (FCGMA 2007).

Groundwater elevations at this time ranged from 2 to 22 feet msl (FCGMA 2007). By 1934, when groundwater elevations in the UAS declined to −2 to 9 feet msl, the chloride concentration at a coastal well near Port Hueneme was 1,346 mg/L (FCGMA 2007). This was the first evidence of a potential saline water impact front in the vicinity of Port Hueneme. Between 1935 and 1940, chloride concentrations at the coast declined again and remained below 50 mg/L from 1934 to 1949 (FCGMA 2007). By 1954, however, as groundwater elevations in the UAS had declined to as much as −35 feet msl, seawater intrusion is interpreted to have affected an approximately 1-square-mile area near Port Hueneme, where two UAS wells had chloride concentrations of 1,070 and 1,925 mg/L.

This area of seawater intrusion expanded to the north and east between 1954 and 1959, and by 1959 an additional area of seawater intrusion was identified in the UAS north and east of Point Mugu (FCGMA 2007). Chloride concentrations near Port Hueneme reached 27,350 mg/L and those near Point Mugu reached 11,475 mg/L (FCGMA 2007). As groundwater elevations remained below sea level, the two areas of seawater intrusion continued to expand through the 1960s and 1970s, with the saline water impact front eventually reaching as much as 3 miles inland near Port Hueneme by the early 1980s (Izbicki 1996; FCGMA 2007).

The implementation of management strategies and pumping allocations by the FCGMA, along with increased rainfall in the late 1970s and early 1980s, reduced the area of the UAS affected by seawater intrusion, even as groundwater elevations remained below sea level throughout much of the Subbasin (FCGMA 2007). With the completion of the Freeman Diversion, which allowed for increased aquifer recharge at the spreading basins operated by UWCD, and additional aboveaverage rainfall years, groundwater elevations in much of the UAS rose above sea level and the area of the UAS affected by seawater intrusion decreased in the 1990s (FCGMA 2007).

At the same time that seawater intrusion in the UAS was being managed and mitigated in the 1980s and 1990s, seawater intrusion began to affect the LAS (FCGMA 2007). By 1989, chloride was detected at a concentration of 6,700 mg/L at a well near Port Hueneme (FCGMA 2007). By 1994, chloride concentrations between 1,000 and 7,000 mg/L were detected near both Port Hueneme and Point Mugu (FCGMA 2007). The area impacted by seawater intrusion remained smaller in the LAS than in the UAS throughout the 1980s and 1990s.

Between 2000 and 2013, groundwater elevations in the UAS remained above sea level and there was little change in the extent of seawater intrusion near Port Hueneme (UWCD 2016a). As 899
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groundwater elevations dropped below sea level during the recent drought, however, chloride concentrations in UAS monitoring wells near the coast began to increase and the saline water impact front expanded eastward again (UWCD 2016a). Near the Mugu submarine canyon, the groundwater elevations in the UAS have remained below sea level and chloride concentrations in wells near the coast are close to those of seawater (UWCD 2016a). The current extent of saline water intrusion in both the UAS and the LAS is shown in Figures 2-27 through 2-32.

2.3.3.4 Relationships between Groundwater Elevation and Seawater Intrusion The relationship between groundwater elevations and seawater intrusion, as measured by changes in chloride concentration, is complex. Since the 1950s, water levels in the Oxnard and Mugu Aquifers in coastal areas have historically fallen below sea level in response to increased production and drought cycles (Figures 2-9a and 2-12). Unlike areas farther inland, the water levels below sea level resulted in seasonal seawater intrusion during the fall irrigation season and during droughts in coastal wells in the vicinity of Point Hueneme and Point Mugu (Figure 2-33, Groundwater Flux along the Coast in the Upper Aquifer System). In contrast, as groundwater production increased in the LAS, water levels in the FCA and the GCA near the coast quickly fell below sea level and have remained there since the 1980s, even after periods of above-average precipitation (Figures 2-18 and 2-21). The UWCD model indicates continuous flux from the ocean into these aquifers since 1985 (Figure 2-34, Groundwater Flux along the Coast in the Lower Aquifer System).

Some wells located near Port Hueneme and screened in the Oxnard Aquifer and the Hueneme Aquifer have chloride concentrations that rise as groundwater elevations decline and that decline as groundwater elevations rise. This relationship is shown in Wells 01N22W20M05S and 01N22W29D03S on Figure 2-35 (Selected Historical Records of Water Elevation and Chloride Concentration). All the wells with chloride and groundwater measurements are shown on Figure 2-36 (Locations of Selected Coastal Wells with Historical Measurements of Chloride Concentration and Water Elevation). It should be noted, however, that changes in chloride concentration in groundwater lag behind changes in groundwater elevation by up to 2 years in these wells. This response suggests that by the time the chloride response to declining groundwater elevations is measured, seawater intrusion has already begun.

The relationship between chloride concentration and groundwater elevation observed in Wells 01N22W20M05S and 01N22W29D03S is not universal throughout the Subbasin. In Well 01N22W29D02S, which is located in the same well cluster as Well 01N22W29D03S and is screened deeper in the Hueneme Aquifer, the concentration of chloride increased from 1995 through 2015, independent of groundwater elevation (Figures 2-35[C] and 2-36). The longterm increase in chloride concentration observed in this well suggests that groundwater elevations, even when above sea level, are not limiting the increasing chloride concentrations.

A similar trend is observed in Well 01S21W08L03S, which is screened in the GCA and is 900
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located near Point Mugu; however, in this well groundwater elevations have remained below sea level since 1990 (Figures 2-35[D] and 2-36). One explanation is that the southern flow of groundwater along the coast from Port Hueneme discussed above may limit the ability to flush some areas of saltwater back out of Grimes Canyon.

A complete set of hydrographs for all wells from which both chloride and groundwater elevation data have been collected, showing the relationship between chloride concentration and groundwater elevation, is provided in Appendix F. A summary of the relationship between chloride concentration and groundwater elevation by region within the Oxnard Subbasin is provided below.

North Coast
In the north coastal Oxnard Plains, groundwater elevations in one nested well cluster (01N23W01C02S-05S) screened in the Oxnard Aquifer, the Hueneme Aquifer, and the FCA, were below sea level in the early 1990s, generally remained above or near sea level between the mid1990s and early 2010s, and dropped below sea level between 2013 and 2015 (Appendix F). In spite of the low groundwater elevations in the historical record, the chloride concentration in the four nested wells 01N23W01C02S–01N23W01C05S (Figure 2-36) has not exceeded 55 mg/L since the wells were completed in 1990 (Appendix F). Additionally, recent chloride concentrations in both the UAS and the LAS are typically below 100 mg/L (see Section 2.3.4). The aquifers of the Oxnard Subbasin are believed to crop out on the ocean floor where direct documentation of seawater intrusion cannot be measured.

Port Hueneme
In the vicinity of Port Hueneme, groundwater elevations in confined aquifers were below sea level in the early 1990s, recovered to elevations above sea level, remained there for two decades, and dropped below sea level between 2011 and 2014 after the onset of the recent drought. Records from nested wells 01N22W20M01 through 01N22W20M06 (which are screened in the semiperched aquifer, the Oxnard Aquifer, the Mugu Aquifer, two zones in the Hueneme Aquifer, and the FCA; see Figure 2-36 and Appendix F) underscore the variability in the relationships between groundwater elevation and seawater intrusion in different water-bearing units. Despite the similarity in the five profiles of groundwater elevation over time, seawater preferentially intruded the Oxnard Aquifer in the past, and rising concentrations of chloride are observed in the Oxnard Aquifer, the Hueneme Aquifer, and the FCA in response to the recent decline in groundwater elevations. In this area, offshore outcrops of the older alluvium and the San Pedro Formation occur in the Hueneme submarine canyon. These outcrops provide a direct link between the Pacific Ocean and the freshwater aquifers of the Oxnard Subbasin. This region is susceptible to seawater intrusion, as demonstrated by chloride concentrations and groundwater elevations since the 1950s. 901
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South Coast
In general, groundwater elevations in the Mugu Aquifer, FCA, and GCA in the South Coast Region have remained near or below sea level since the early 1990s (Figure 2-36 and Appendix F).

Elevations in the Hueneme and Oxnard Aquifers largely remained above sea level between the mid1990s and early 2010s. Within the upper Oxnard Aquifer, chloride concentrations have been decreasing, while rising chloride concentrations have been measured in the lower Oxnard Aquifer.

In this area, elevated chloride concentrations in the Oxnard Aquifer likely result from southward migration of seawater that intruded the aquifer in the vicinity of Port Hueneme during earlier periods of low groundwater elevations (UWCD 2016a). This region does not typically experience direct seawater intrusion via offshore outcrops, but rather rising chloride concentrations indicate previous episodes of seawater intrusion via the Hueneme Canyon to the north.

Point Mugu
In all but one case, groundwater elevations in the vicinity of Mugu Lagoon have remained below sea level since the 1990s. Chloride concentrations exceeding 1,000 mg/L are measured in the majority of monitoring wells in this region (Figure 2-36; Appendix F). However, as noted above, some of the elevated chloride concentrations in this area are from the upwelling of connate water and the migration of groundwater to the LAS from the UAS.

2.3.4 Groundwater Quality
FCGMA adopted Basin Management Objectives (BMOs) for nitrate, chloride, and TDS in the Oxnard Subbasin for its 2007 Groundwater Management Plan Update (FCGMA 2007; Table 2-4).

Additionally, the Water Quality Control Plan: Los Angeles Region (Basin Plan) specifies Water Quality Objectives (WQOs) for TDS, chloride, nitrate, sulfate (SO4), boron, and nitrogen (mg/L nitrate) (LARWQCB 2013; Table 2-4). The current and historical distribution of these five constituents are discussed below. There are too few measurements of water quality in wells screened solely within a single aquifer to allow for meaningful discussion of water quality by aquifer. Additionally, as discussed in Section 2.3.1, the majority of the groundwater production in the Oxnard Subbasin occurs in wells that are screened across multiple aquifers. This production has the potential to impact water quality in multiple aquifers simultaneously. Therefore, impacts to groundwater quality in the Oxnard Subbasin are considered based on aquifer system.

Groundwater quality monitoring within the Oxnard Subbasin occurs on different schedules for different wells. In order to assess the current groundwater quality conditions within the Oxnard Subbasin, the most recent concentration of each of the five constituents listed above was mapped for samples collected between 2011 and 2015. Historical groundwater quality hydrographs are presented in Appendix G, Water Quality Hydrographs. Statistics on the most recent sample date, the maximum and minimum concentrations measured, the number of times sampled, and the 902
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number of samples whose concentration exceeded the relevant water quality threshold are presented in Appendix H, FCGMA Water Quality Statistics.

2.3.4.1 Total Dissolved Solids
Sources of high TDS water in the Oxnard Subbasin include seawater and brines migrating via faults or upwelling from older geologic formations (see Section 2.3.3). Additionally, in the UAS, improperly abandoned wells in the semi-perched aquifer and high chloride brines in fine-grained lagoonal deposits in the Oxnard and Mugu Aquifers, can contribute to high concentrations of TDS in the groundwater (Izbicki 1996). The water quality objective for TDS is 1,200 mg/L in the Forebay and confined aquifers, and 3,000 mg/L in the unconfined aquifers (LARWQCB 2013).

The 2007 FCGMA BMO for TDS is 1,200 mg/L for the Forebay (FCGMA 2007). UAS wells with concentrations of TDS greater than 1,200 mg/L are found throughout the Oxnard Subbasin.

Upper Aquifer System
Concentration of TDS in groundwater in the UAS ranged from 652 mg/L to 49,600 mg/L between 2011 and 2015 (Figure 2-37a, Upper Aquifer System – Most Recent Total Dissolved Solids [mg/L] Measured 2011–2015, and Figure 2-37b, Upper Aquifer System, Forebay Area – Most Recent Total Dissolved Solids [mg/L] Measured 2011–2015). Water with TDS concentrations greater than 35,000 mg/L is considered brine. Both the highest and lowest concentrations of TDS were measured adjacent to the coast in Wells 01N22W27R05S and 01N22W27C02S, respectively (Figure 2-37a). The highest concentrations of TDS are found in coastal wells in areas known to be impacted by seawater intrusion (e.g., Well 01S21W08L04S) and release of connate brines from clay layers (e.g., Well 01N22W27R05S). The concentration of TDS in Well 01N22W27R05S has been increasing since 2013, while the concentration of TDS in Well 01S21W08L04S has remained stable over the last 5 years.

In the Forebay, Wells 02N22W23B02S and 02N22W23C05S have been used as BMO wells for TDS. In 2015, the concentration of TDS measured in a sample collected from Well 02N22W23B02S was 1,230 mg/L, and the concentration of TDS measured in a sample collected from Well 02N22W23C05S was 1,070 mg/L. The concentration of TDS in each of these wells has been increasing over the past 5 years (FCGMA 2016).

Lower Aquifer System
In general, TDS concentrations in the LAS are higher in the southern Oxnard Subbasin than in the northern part of the Subbasin (Figure 2-38, Lower Aquifer System – Most Recent Total Dissolved Solids [mg/L] Measured 2011–2015). Concentration of TDS in groundwater in the LAS ranged from 392 mg/L to 37,200 mg/L between 2011 and 2015 (Figure 2-38). The highest concentration was measured in Well 01N21W32Q03S, which is in the southern Oxnard Subbasin, inland from 903
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the coast, and is screened within the GCA (Figure 2-38). The higher concentration of TDS in this area likely resulted from upward migration of brines in deeper formations. This migration may have been induced or exacerbated by lowered groundwater elevations from groundwater production in the LAS, although the concentration of TDS in this well has increased steadily since 1995, even during periods when groundwater elevations were 40 to 100 feet higher than they were in 2015 (Izbicki 1991; Izbicki et al. 2005; UWCD 2016a).

The lowest concentration of TDS was measured in Well 01N22W35E03S, screened in the FCA south of Port Hueneme (Figure 2-38). The concentration of TDS in this well was 392 mg/L in 2015.

TDS concentrations in this well have remained relatively stable over the last 5 years, neither increasing nor decreasing with the onset of the 2011 drought.

2.3.4.2 Chloride
Sources of water high in chloride in the Oxnard Subbasin include modern seawater, groundwater from the semi-perched aquifer, connate water from fine-grained lagoonal deposits in the Oxnard and Mugu formations, and brines migrating via faults or upwelling from older geologic formations (see Section 2.3.3). The UAS has a long history of seawater intrusion, with groundwater elevations below sea level measured as early as the 1930s (see Section 2.3.3; UWCD 2016a). Seawater intrusion affects a smaller area of the LAS than the UAS, and is more pronounced near Point Mugu than near Port Hueneme (UWCD 2016a). Brine migration along faults and from deeper geologic formations also affects the chloride concentration in the LAS (Izbicki 1991).

The water quality objective for chloride is 150 mg/L in the Forebay and confined aquifers, and 500 mg/L in the unconfined aquifers (LARWQCB 2013). The BMO for chloride is 150 mg/L for the UAS and LAS.

Upper Aquifer System
Concentration of chloride in groundwater in the UAS ranged from 23 mg/L to 20,700 mg/L between 2011 and 2015 (Figure 2-39a, Upper Aquifer System – Most Recent Chloride [mg/L] Measured 2011–2015, and Figure 2-39b, Upper Aquifer System, Forebay Area – Most Recent Chloride [mg/L] Measured 2011–2015). Chloride concentrations in the UAS are higher near the coast, from Point Hueneme south to Point Mugu, than inland or north of Port Hueneme (Figure 2-39a). The lowest concentration of chloride was measured in Well 01N22W11C02S in the central Oxnard Subbasin (Figure 2-39a). This well was only sampled one other time, in 1952, and the concentration of chloride measured at that time was 83 mg/L. Between 2011 and 2015, the concentration of chloride was less than 150 mg/L in the Forebay (Figure 2-39b).

The highest concentration of chloride (20,700 mg/L) was measured in Well 01N22W27R05S, adjacent to the coast south of Port Hueneme (Figure 2-39a). Groundwater from this well also had 904
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the highest concentration of TDS. The concentration of chloride in this well has been increasing since 2013. The concentration of chloride in Well 01S21W08L04S, a BMO well near Point Mugu, was 17,500 mg/L in 2015. The concentration of chloride in this well has been stable over the last 5 years (FCGMA 2016). Of the nine BMO wells with chloride concentration objectives in the UAS, three have had increasing chloride concentrations over the past 5 years (Wells 01N22W20J07S, 01N22W20J08S, and 01S22W01H03S), although all of the BMO wells have had water levels below their targets as a result of the drought.

Lower Aquifer System
In general, chloride concentrations in the LAS are higher in the southern Oxnard Subbasin than they are elsewhere in the Oxnard Subbasin (Figure 2-40, Lower Aquifer System – Most Recent Chloride [mg/L] Measured 2011–2015). In the Forebay, the concentration of chloride in groundwater is less than 100 mg/L, while concentrations of chloride south of Port Hueneme exceed 500 mg/L (Figure 2-40).

Concentration of chloride in groundwater in the LAS ranged from 33 mg/L to 14,300 mg/L between 2011 and 2015 (Figure 2-40). The lowest concentration of chloride was measured in Well 01N23W01C02S on the coast, north of Port Hueneme (Figure 2-40). The concentration of chloride in this well has remained stable since it was first measured in 1990.

The highest concentration of chloride was measured in Well 01N21W32Q03S, in the southern Oxnard Subbasin (Figure 2-40). In this well, the concentration of chloride has increased since it was first measured in 1991. At that time the concentration of chloride in the well was 340 mg/L.

BMO Well 01S21W08L03S is also located in the southern Oxnard Subbasin, in the vicinity of Point Mugu. This is the only BMO well in the LAS that has had increasing concentrations of chloride over the past 5 years despite all of the BMO wells having water levels below their targets (FCGMA 2016).

2.3.4.3 Nitrate
Nitrate concentrations above WQOs and BMOs are present in the Forebay of the Oxnard Subbasin (UWCD 2008). These concentrations are likely a legacy of historical septic discharges and agricultural fertilizer application practices.
6 Historical discharges have resulted in concentrations that impact beneficial uses and users of the Oxnard Subbasin. In particular, not all municipal users of groundwater in this area have the ability to blend groundwater with nitrate exceeding the federal maximum contaminant level for nitrate as NO3 of 45 mg/L.

6 Ventura County extended sewer lines into this area in the years between 2000 and 2011 to address additional discharges of nitrate.
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Historical nitrate concentrations in the Forebay are most impacted by the quantity of surface water available for spreading from the Santa Clara River. The river water has lower concentrations of nitrate than the groundwater. Therefore, during periods when Santa Clara River water is used to recharge the Subbasin, groundwater concentrations of nitrate decrease. Conversely, during periods of drought, groundwater concentrations of nitrate in the Forebay tend to increase.

The BMO for nitrate is 22.5 mg/L in the Forebay (FCGMA 2007). The WQO for nitrate as NO3 is 45 mg/L for the entire Oxnard Subbasin (LARWQCB 2013).

Upper Aquifer System
Between 2011 and 2015, concentrations of nitrate as NO3 in groundwater in the UAS ranged from below the detection limit to 240 mg/L (Figure 2-41a, Upper Aquifer System – Most Recent Nitrate [mg/L as Nitrate] Measured 2011–2015, and Figure 2-37B). The highest concentration was measured in Well 02N22W26C01S in the Forebay (Figure 2-41b, Upper Aquifer System, Forebay Area – Most Recent Nitrate [mg/L as Nitrate] Measured 2011–2015). However, the concentration of nitrate measured in a sample collected from the same well in 2011 was only 4.9 mg/L. Similarly, nitrate concentrations in Wells 02N22W23B02 and 02N33W23C05S, which are both BMO wells, increased between 2011 and 2016. The concentration of nitrate in Well 02N22W23B02 was 4.1 mg/L in 2011 and was as high as 127 mg/L in 2015. The concentration of nitrate in Well 02N22W23C05 was 2.8 mg/L in 2011 and was as high as 31.9 mg/L in 2015.

Outside of the Forebay, the concentration of nitrate in the groundwater decreases rapidly and is not correlated with recharge from the spreading basins. In general, nitrate as NO3 concentrations are highest in the southern Forebay and northeastern Oxnard Subbasin. The lowest concentrations are found in the southern Oxnard Subbasin, with the concentration of nitrate below the detection limit in the majority of the wells in the southern Subbasin (Figure 2-41a).

Lower Aquifer System
Concentrations of nitrate as NO3 in groundwater in the LAS are lower than they are in the UAS.

Between 2011 and 2015, the concentration of nitrate as NO3 in wells screened in the LAS ranged from below the detection limit to 57 mg/L. The highest concentration was measured in Well 02N21W19A03S, in the northeastern Oxnard Subbasin. The concentration of nitrate in this well may be influenced by downward migration of water and is not representative of general nitrate concentrations within the LAS. The next-highest concentration of nitrate was measured in Well 01N22W23R02. The concentration of nitrate in the well was 22.1 mg/L (Figure 2-42, Lower Aquifer System – Most Recent Nitrate [mg/L as Nitrate] Measured 2011–2015). The majority of the wells in the LAS have nitrate as NO3 concentrations below the detection limit. In the Forebay, the concentration of nitrate as NO3 is lower in the LAS than it is in the UAS (Figures 2-41b and 2-42).
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2.3.4.4 Sulfate
Sources of sulfate in the Oxnard Subbasin include mineral dissolution in groundwater and seawater intrusion. The majority of the wells in the Oxnard Subbasin have sulfate concentrations below 600 mg/L. Similar to nitrate, wells in the Forebay tend to have higher concentrations of sulfate than wells farther south, with the notable exception of Wells 01N22W27R05S and 01S21W08L04S (Figure 2-43a, Upper Aquifer System – Most Recent Sulfate [mg/L] Measured 2011–2015). The water quality objective for sulfate is 600 mg/L in the Forebay and confined aquifers, and 1,000 mg/L in the unconfined aquifers (LARWQCB 2013).

Upper Aquifer System
Concentrations of sulfate in the UAS ranged from 100 mg/L to 5,740 mg/L between 2011 and 2015 (Figure 2-43a and Figure 2-43b, Upper Aquifer System, Forebay Area – Most Recent Sulfate [mg/L] Measured 2011–2015). High concentrations of sulfate near the coast are generally indicative of seawater intrusion. The highest concentration was measured in Well 01N22W27R05S, which also had the highest concentration of chloride and TDS. The concentrations of each of these constituents has increased since 2013. The lowest concentration was measured in Well 01N22W36K09S in the southern Oxnard Subbasin.

Lower Aquifer System
Concentrations of sulfate in the LAS ranged from below the detection limit to 2,030 mg/L between 2011 and 2015 (Figure 2-44, Lower Aquifer System – Most Recent Sulfate [mg/L] Measured 2011– 2015). High concentrations of sulfate near the coast are generally indicative of seawater intrusion.

The highest concentration was measured in Well 01N21W32Q03S, which also had the highest concentration of chloride and TDS. Only four wells in the LAS had concentrations of sulfate that exceeded 600 mg/L. These wells are distributed throughout the Oxnard Subbasin and do not follow a clear geographic pattern. Similar to nitrate, LAS wells in the Forebay have lower concentrations of sulfate than UAS wells in the Forebay (Figure 2-44).

2.3.4.5 Boron
Sources of boron in the Oxnard Subbasin include seawater intrusion in coastal areas and release of anthropogenic (introduced by human activities) boron from past septic tank uses. The WQO for boron in the Oxnard Subbasin is 1 mg/L (LARWQCB 2013).

Upper Aquifer System
Concentrations of boron in the UAS ranged from 0.05 mg/L to 5.9 mg/L between 2011 and 2015 (Figure 2-45a, Upper Aquifer System – Most Recent Boron [mg/L] Measured 2011–2015, and 907
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Figure 2-45b, Upper Aquifer System, Forebay Area – Most Recent Boron [mg/L] Measured 2011– 2015). The highest concentration was measured in Well 01N22W27R05S, which also had the highest concentrations of sulfate, chloride, and TDS. The lowest concentration was measured in Well 02N22W24A01S, in the northeastern Oxnard Subbasin (Figure 2-45a). Only seven wells in the UAS had boron concentrations greater than 1 mg/L between 2011 and 2015.

Lower Aquifer System
Concentrations of boron in the LAS ranged from 0.3 mg/L to 2.2 mg/L between 2011 and 2015 (Figure 2-46, Lower Aquifer System – Most Recent Boron [mg/L] Measured 2011–2015). The highest concentration was measured in Well 01N21W32Q03S, which also had the highest concentrations of sulfate, chloride, and TDS. Only five wells in the LAS had boron concentrations greater than 1 mg/L between 2011 and 2015.

2.3.4.6 Map of Oil and Gas Deposits
In the database maintained by the County of Ventura (2016), five oil fields entirely or partially fall within the Oxnard Subbasin: Montalvo, W.; Oxnard; El Rio; Santa Clara Avenue; and Saticoy (Figure 2-47, Oil Fields in the Vicinity of FCGMA Groundwater Basins). Petroleum extraction in the FCGMA basins occurs below the deepest freshwater aquifer (Hopkins 2013). While no evidence of impacts of petroleum extraction on beneficial use of groundwater in the FCGMA basins has been identified, there are limited available data. Few wells exist in deep aquifers near oil fields that could be monitored for potential impact. However, trace amounts of organic compounds have been found in deeper wells in southeastern Pleasant Valley (Izbicki et al. 2005), and there have been anecdotal reports of trace petroleum hydrocarbons observed in irrigation wells near some oil fields.

2.3.4.7 Maps of Locations of Impacted Surface Water, Soil, and Groundwater Impacted surface water, soil, and groundwater have been documented in the Oxnard Subbasin, although these impairments tend to be limited to the semi-perched aquifer. This uppermost unit in the Oxnard Subbasin is underlain by a clay cap layer that limits the vertical migration of impaired water to the underlying UAS.

Impaired surface waters (i.e., 303(d) Listed Reaches) that overlie the Oxnard Subbasin include approximately 3 miles of the Santa Clara River, the Revolon Slough, Calleguas Creek, and a number of lined drains serving agricultural areas south of the City of Oxnard (Figure 2-48, Impaired Surface Waters in the Vicinity of FCGMA Groundwater Basins; SWRCB 2004). The names of the reaches used by the State Water Resources Control Board, and the impairments listed for each, are included in tabulated form in Appendix I, Oxnard 303(d) List Reaches. 908
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Locations of impacted soil and groundwater were assessed on a basin-wide scale by reviewing information available on the SWRCB GeoTracker website and the California Department of Toxic Substances Control EnviroStor website. Cases that were closed by the supervisory agency were not considered.

Of the 290 open cases located within the boundaries of the Oxnard Subbasin and Pleasant Valley, groundwater was impacted in 77. Dudek reviewed and catalogued the constituents of concern (COCs) present on site in these 77 cases (Figure 2-49, Constituents of Concern at Open GeoTracker Cases with Impacted Groundwater within FCGMA Groundwater Basin Boundaries).

Case details are included in Appendix J, GeoTracker Open Sites.

Of the 71 open cases in the Oxnard Plain in which groundwater is, or is potentially, impacted, the following COCs were identified as present at the following number of sites (Figure 2-49; Appendix J):
 Chlorinated volatile organic compounds (VOCs), including COCs marked as solvents, VOCs, and chlorinated hydrocarbons, were present at 34 sites.  Gasoline and diesel, including COCs marked TPH and petroleum, were present at 32 sites.  Metals were present at 27 sites.
 Polychlorinated biphenyls (PCBs) were present at 23 sites.  Benzene, toluene, ethylbenzene, and/or xylenes (BTEX) were present at 18 sites.  Pesticides were present at 12 sites.
 Methyl tert-butyl ethylene (MTBE) and/or tert-butyl alcohol (TBA) were present at seven sites.  Two sites listed other COCs.

Many of these sites are located on land administered by the U.S. military (Figure 2-49). Outside of military bases, these sites tend to occur within the city limits of the Cities of Oxnard, Port Hueneme, and Camarillo.

The risk that contamination in the shallow groundwater of the Oxnard Subbasin would reach the UAS is somewhat mitigated by the presence of a confining layer that separates the semi-perched aquifer from the water-bearing units of the UAS throughout much of the Oxnard Plain (Turner and Mukae 1975). However, the vertical gradient is directed downward from the semi-perched aquifer to the underlying Oxnard Aquifer, indicating the potential for groundwater movement from the semi-perched aquifer to the Oxnard Aquifer.

Based on a review of open GeoTracker and EnviroStor cases with impacted groundwater, it does not appear that existing groundwater contamination in the semi-perched aquifer poses a substantial threat to beneficial use of groundwater in the UAS and the LAS. Based on a review of the files 909
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available on GeoTracker for each of the cases in the Oxnard Subbasin that fell outside the bounds of a military base, it appears that in none of the cases were any liable parties required to investigate deeper than 50 feet below ground surface (bgs), indicating that impacts to groundwater in the UAS were not a concern for regulatory agencies.

2.3.5 Subsidence
Inelastic, or irrecoverable, land subsidence (subsidence) can be a concern in areas of active groundwater extraction, including the Oxnard Subbasin. Active causes of land subsidence in the Oxnard Subbasin include tectonic forces, petroleum reservoir compaction, and clay compaction (Hanson et al. 2003). Significant water level declines in the FCGMA groundwater basins since the early 1900s suggest that fluid extraction, rather than tectonic activity, is the major cause of land subsidence (Hanson et al. 2003). Subsidence resulting from any of these sources can cause increased flood risk, well casing collapse, and a permanent reduction in the specific storage of the aquifer (Hanson et al. 2003).

Direct measurement of subsidence within the Oxnard Subbasin is limited. Elevation data from USGS benchmark (BM) E548 in the southern part of the Oxnard Plain indicate subsidence of about

1.6 feet (0.49 meters) during the period from 1939 to 1960, and an additional 1 foot (0.31 meters) of subsidence from 1960 to 1978 (Hanson et al. 2003). The average rate of subsidence for these two periods was similar, averaging approximately 0.07 feet (0.02 meters) per year from 1939 to 1960, and approximately 0.06 feet (0.02 meters) per year from 1960 to 1978 (Hanson et al. 2003).

In contrast, elevation data from USGS BM Z901, located approximately 2.6 miles southeast of BM E548, indicate subsidence of approximately 0.3 feet (0.10 meters) between 1960 and 1978. The average rate of subsidence at BM E548 was 0.02 feet (0.01 meters) per year for this period. The rate of subsidence at BM Z901 decreased to approximately 0.01 feet per year from 1978 to 1992. Data are not available for BM E548 after 1978. The amount of subsidence measured at both BM E548 and BM Z901is the cumulative subsidence from all possible sources, including groundwater pumping, tectonic activity, and petroleum reservoir compaction.

In addition to direct measurement of subsidence in the southern part of the Oxnard Plain, potential subsidence was modeled for the entire Oxnard Plain for different future water production scenarios (Hanson et al. 2003). The scenarios included consideration of proposed water projects and ordinances for the FCGMA Basins. The model results suggest that areas within the Oxnard Plain may experience an additional 0.1 to 1 feet of subsidence by 2040 (Hanson et al. 2003). DWR classified the Subbasin as an area that has a medium to high potential for future subsidence. The amount of future subsidence will depend on whether future water levels decline below previous low levels and remain there for a considerable amount of time (Hanson et al. 2003). Maintaining water levels above the previous low water levels will limit the risk of future subsidence. 910
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From March 2015 to June 2016, the Jet Propulsion Laboratory (JPL) analyzed interferometric synthetic aperture radar (InSAR) data from the European Space Agency’s satellite-borne Sentinel1A and NASA’s airborne UAVSAR, along with similar previous studies from 2006 to 2015, to examine subsidence in areas of California. The study included the south-central coast of California in Ventura and Oxnard (Farr et al. 2017). The map generated from this study for this area of the south-central coast of California (Farr et al. 2017, Figure 23) showed less than 1 foot of subsidence for the Oxnard Subbasin.

2.3.6 Groundwater–Surface Water Connections
The Santa Clara River, Calleguas Creek, Revolon Slough, Mugu Lagoon, Ormond Beach, and McGrath Lake have all been identified as surface water bodies that may have a connection to the semi-perched aquifer in the Oxnard Subbasin (see Section 2.3.7, Groundwater-Dependent Ecosystems). However, groundwater elevation data for the semi-perched aquifer in the Oxnard Subbasin are extremely limited, with no monitoring sites near enough to surface water bodies to establish the extent of the connection between these surface water bodies and underlying groundwater (Figure 2-50, Groundwater Elevation Contours in the Semi-Perched Aquifer, March 2–29, 2015, and Figure 2-51, Groundwater Elevation Contours in the Semi-Perched Aquifer, October 2–29, 2015).The spatial extents of gaining, losing, and dry reaches in the Santa Clara River are seasonally variable (UWCD 2014, 2018).

The best available estimates for groundwater–surface water connections comes from the UWCD numerical model, which simulates the leakage from major surface water bodies in the Oxnard Subbasin using data from stream gauges and estimated aquifer properties (Appendix C). The UWCD model reports stream leakage from the Santa Clara River and Calleguas Creek into the underlying semi-perched aquifer. Numbers from the model represent net stream leakage and do not necessarily indicate direct connection between surface water bodies and groundwater in the semi-perched aquifer.

The UWCD model calculated stream percolation for water years from 1986 to 2015 (Table 2-5).

The Santa Clara River had net recharge to groundwater in 26 of 30 water years, with an average net recharge to groundwater of approximately 5,700 AFY. The recharge to groundwater primarily occurs in the vicinity of the Forebay, where Santa Clara River water percolates into the UAS.

Downstream of the Forebay, some reaches of the Santa Clara River are typically gaining in most years, generally from the semi-perched aquifer. Net groundwater discharge to the Santa Clara River was identified as occurring during 1999, 2002, 2006, and 2013. Calleguas Creek exhibited net recharge to groundwater in all years modeled, with an average net recharge to groundwater of approximately 3,450 AFY.
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2.3.7 Groundwater-Dependent Ecosystems
Six potential GDE units, defined by dominant surface hydrologic features, were identified in the Oxnard Subbasin (Appendix C, UWCD Model Report; TNC 2017 [see Appendix K of this GSP]; Figure 2-52, Groundwater-Dependent Ecosystems for the Oxnard Subbasin). The potential GDE units were identified using the statewide potential GDE map (Appendix K). Of the six potential GDE units identified, the Lower Santa Clara River, McGrath Lake, Ormond Beach, and Mugu Lagoon units were validated using groundwater elevations measured in wells within or adjacent to the unit to confirm the potential hydrologic connection to groundwater in the semi-perched aquifer, as described in The Nature Conservancy’s GDE Guidance Framework (Appendix K). Insufficient well data are available to confirm the depth to groundwater in the Revolon Slough unit or the Lower Calleguas Creek unit. Therefore, in the discussion below, these units remain as potential GDEs. Groundwater elevation in the vicinity of these units will be required in order to confirm whether or not the habitat is supported by groundwater (see Section 4.6.5, Shallow Groundwater Monitoring near Surface Water Bodies and GDEs).

Lower Santa Clara River GDE
The lower Santa Clara River GDE (located downstream of Highway 101 and upstream of the estuary) comprises approximately 750 acres of aquatic habitat, in-channel wetland, and a range of willow–cottonwood riparian forest (Figure 2-53, Lower Santa Clara River GroundwaterDependent Ecosystems; Appendix K, The Nature Conservancy GDE Tech Memo). The GDE is located in the floodplain of the lower Santa Clara River, which undergoes substantial transformations in vegetation composition and distribution due to the dynamic nature of the river flows during winter. The lower Santa Clara River GDE supports habitat for several state- and federally listed species (Table 2-6).

Flow in the lower Santa Clara River downstream of Highway 101 has historically been perennial (SFEI 2011; City of Ventura 2016). The source of the perennial flow in this region is groundwater from the semi-perched aquifer, which is separated from the underlying UAS by a clay cap that limits groundwater migration and allows differences in groundwater elevation between the semiperched aquifer and the Oxnard Aquifer. In the spring of 2015, groundwater elevations in the Oxnard Aquifer were below sea level (Figure 2-7).

Groundwater from the semi-perched aquifer provides the dry summer baseflow, if it exists, and a quarter of the winter flow (City of Ventura 2011). Groundwater flow direction between the semiperched aquifer and the lower Santa Clara River, its estuary, and nearby McGrath Lake, depends on tidal conditions, river stage, and recharge rates due to agricultural irrigation (City of Ventura 2016). Groundwater levels from wells in the vicinity of the lower Santa Clara River GDE generally range between 7 and 11 feet bgs (Figure 2-53). The groundwater depths are within the range 912
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considered necessary for juvenile establishment (<10 feet) and mature vegetation growth (<20 feet) (City of Ventura 2016).

McGrath Lake GDE
The McGrath Lake GDE includes a coastal freshwater back-dune lake, arroyo willow riparian forest, freshwater emergent marsh, and saline emergent marsh (Figure 2-54, McGrath Lake Groundwater-Dependent Ecosystems). The McGrath Lake GDE supports critical habitat for several state- and federally listed endangered species as well as many special-status bird species (Table 2-6).

McGrath Lake is formed by shallow groundwater that remains perched above a clay layer in the semi-perched aquifer (ESA 2003). McGrath Lake operational water surface elevations are maintained between 2.7 and 3.6 feet msl (City of Ventura 2011). Groundwater flows toward the Santa Clara River during open-mouth conditions and towards McGrath Lake when the Santa Clara River Estuary fills following mouth closure (City of Ventura 2011). As measured since 2009, depths to groundwater around the McGrath Lake GDE range from ground surface to 10 feet bgs, depending on the well (Appendix K).

Ormond Beach GDE
The Ormond Beach GDE, which includes isolated patches of southern coastal salt marsh and coastal freshwater/brackish marsh that have been drained, filled, and degraded by past industrial and agricultural use, is part of a larger 1,500-acre coastal dune–marsh system of dunes, lakes, lagoons, and saltwater and freshwater marshes (WRA 2007; CCC 2017; Figure 2-55, Ormond Beach Groundwater-Dependent Ecosystems). The Ormond Beach GDE supports habitat for stateand federally listed species as well as 27 special-status plant species and 42 special-status wildlife species (Table 2-6).

The Ormond Beach GDE is hydrologically connected to the semi-perched aquifer. Shallow groundwater elevations are influenced by rainfall, tidal events, and the surface water elevations of the agricultural drains and flood control channels. Depth to groundwater ranges from ground surface to 15 feet bgs (Appendix K).

Mugu Lagoon GDE
Mugu Lagoon GDE is the largest salt marsh estuary in Southern California (USFWS 2016a). The GDE provides habitat for several state- and federally listed species (Table 2-6; Figure 2-56, Mugu Lagoon Groundwater-Dependent Ecosystems).
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The estimated groundwater depth in the Mugu Lagoon GDE varies between ground surface and 6 feet bgs (Appendix K). Estimated depths to groundwater in the GDE, are based on interpolation of water elevation data from representative wells at Naval Base Ventura County Point Mugu to reference point locations within the Mugu Lagoon GDE. Mugu Lagoon receives groundwater discharge from the semi-perched aquifer along with freshwater from Calleguas Creek, the drainage ditches, primarily Oxnard Drainage Ditch No. 2, and salt water from tidal fluctuations.

Lower Calleguas Creek Potential GDE
The lower Calleguas Creek potential GDE includes aquatic habitat and mulefat and willow riparian forest. This potential GDE may support native special-status species (Table 2-6).

The Lower Calleguas Creek potential GDE overlies the semi-perched aquifer. The channel has been separated from the adjacent floodplain since the 1960s by a riprap and earthen levee countersunk about 3 feet below the surrounding grade. Thus, Calleguas Creek is a losing reach in the Oxnard Plain. Lower Calleguas Creek maintains a perennial streamflow due to a combination of wastewater effluent and pumped tile drain discharge from adjacent agricultural fields, with the addition of natural precipitation and stormwater runoff during winter months. The degree of groundwater recharge and/or discharge has not been studied and groundwater elevation data are not available for this area. Groundwater elevations at semi-perched aquifer monitoring wells (located approximately 1 mile to the southwest at Naval Base Ventura County Point Mugu) indicate typical groundwater elevations range from −1 to 6 feet msl. Extrapolated depths to groundwater at the downstream end of the Calleguas Creek GDE, at approximately 12 feet msl, are between 6 to 13 feet bgs. The extrapolated groundwater depths indicate the potential for the riparian vegetation to access shallow groundwater. Additional data need to be collected within the boundaries of the Calleguas Creek potential GDE in order to determine whether or not the riparian vegetation is accessing shallow groundwater.

Revolon Slough Potential GDE
The Revolon Slough potential GDE comprises aquatic habitat and willow riparian forest. This potential GDE may support native special-status species (Table 2-6). The riparian habitat within this potential GDE is considered “de minimis” because of its poor quality and limited extent adjacent to the waterway. Streamflow in lower Revolon Slough is considered to be a combination of agricultural return flow and precipitation and stormwater runoff. The degree of groundwater recharge and/or discharge has not been studied and groundwater elevation data are not available for this area.

Groundwater elevations at semi-perched aquifer monitoring wells located approximately 1 mile to the southwest at Naval Base Ventura County Point Mugu indicate typical groundwater elevations range from −1 to 6 feet msl. Extrapolated depths to groundwater at the downstream end of the Revolon Slough potential GDE would be between 9 and 16 feet bgs. The extrapolated groundwater 914
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depths indicate the potential for the riparian vegetation to access shallow groundwater. Additional data need to be collected within the boundaries of the Revolon Slough potential GDE in order to determine whether or not the riparian vegetation is accessing shallow groundwater.

2.3.8 Potential Recharge Areas
To evaluate potential future recharge areas within the Oxnard Subbasin, soil types were obtained from the Web Soil Survey, available online at https://websoilsurvey.nrcs.usda.gov/ (USDA 2019).

Soil Ksat rates (saturated hydraulic conductivity rates) for soils of 92 micrometers per second or greater were plotted. Figure 2-57, Oxnard Potential Recharge Areas, shows the results of this evaluation and areas with the most favorable soil recharge rates. The most favorable areas are near the current UWCD spreading grounds, along the Santa Clara River, in sands along the northern coastal areas, and in loamy sands, which may represent old Santa Clara River drainages.

2.4 WATER BUDGET
This section presents the current, historical, and simulated future water budget analysis for the Oxnard Subbasin. This water budget analysis has been completed in accordance with the DWR GSP Regulations. The historical water budget has been prepared for the 31-year period from the beginning of calendar year 1985 through 2015 (the current year for the Sustainable Groundwater Management Act [SGMA]) and is described in units of AF or AFY. The five commonly recognized aquifer units in the Oxnard Subbasin are the Oxnard, Mugu, Hueneme, Fox Canyon, and Grimes Canyon Aquifers (DWR 1965, 2006; Turner 1975). As described in Section 2.2, Hydrogeologic Conceptual Model, these aquifers are grouped into a UAS and an LAS, with the Oxnard and Mugu Aquifers composing the UAS and the Hueneme, Fox Canyon, and Grimes Canyon Aquifers composing the LAS. The UAS primarily comprises recent to upper Pleistocene age alluvial deposits of the Santa Clara River system.

UWCD (2018; Appendix C) developed the “Ventura Regional Groundwater Flow Model (VRGWFM),” a MODFLOW numerical groundwater flow model, for the Oxnard Subbasin, the Mound Basin, the western part of the LPVB, and the PVB. Details of the UWCD modeling effort are included in Appendix C. The groundwater budget analysis for the Oxnard Subbasin is based on the DWR Bulletin 118 basin boundary for the Oxnard Subbasin, and does not incorporate the remainder of the model domain. As with all groundwater flow models, the UWCD model has undergone several revisions and will continue to be revised as additional data are collected and the understanding of the hydrogeologic interactions in the model domain improves. This GSP uses the version of the model finalized in June 2018, which was developed to support the GSP process.

This version of the model was used for the current and historical water budget analysis as well as for the future projected groundwater scenarios discussed in Section 2.4.5, Projected Future Water Budget and Sustainable Yield.
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2.4.1 Sources of Water
Aquifer systems in the Oxnard Subbasin receive water from several sources. Native sources consist predominantly of rainfall infiltration within the Oxnard Subbasin and along its margins (mountainfront recharge), and subsurface inflows from the adjacent basins.

Water sources consist predominantly of streambed seepage from Calleguas Creek where it enters the Oxnard Subbasin from the adjoining PVB; streambed seepage from the Santa Clara River; artificial recharge by the UWCD; deep percolation of a portion of the irrigation water that is applied to agricultural, residential, and commercial lands, and to public open spaces; leakage from water distribution systems; septic system return flows; and wastewater treatment plant (WWTP) percolation ponds. Two small community WWTPs are located adjacent to the Santa Clara River in the Oxnard Subbasin. The Saticoy and the Montalvo WWTPs discharge treated effluent to percolation ponds.

Water supplies for the Oxnard Subbasin consist of locally pumped potable and nonpotable groundwater; imported water provided by UWCD (nonpotable) and Calleguas Municipal Water District (CMWD) (potable); nonpotable surface water provided by UWCD from its Freeman Diversion on the Santa Clara River and delivered to agricultural users in the Oxnard Subbasin via the PTP and to agricultural users in the Oxnard Subbasin and PVB via the Pleasant Valley Pipeline (PVP); the Oxnard Subbasin portion of a nonpotable water supplied provided by the Camrosa Water District (CWD) to the Pleasant Valley County Water District (PVCWD) from a diversion on Conejo Creek; and fully advanced treated recycled water produced by the City of Oxnard (the Groundwater Recovery Enhancement and Treatment (GREAT) Program) that began to be delivered to PVCWD and a few other agricultural users in early 2016.

The predominant municipal water suppliers in the Oxnard Subbasin are the City of Oxnard, the Port Hueneme Water Agency, the City of Ventura, and the Naval Base Ventura County. Water supplies for these municipal users include deliveries by UWCD via the Oxnard–Hueneme Pipeline, which obtains its water exclusively from wells located at the El Rio Spreading Grounds and along Rose Avenue. These municipal users may also receive imported water supplied by the CMWD.

The City of Oxnard has wells within the Oxnard Subbasin. The City of Ventura also has wells in the Oxnard Subbasin, but uses water in their service areas inside and outside of the Oxnard Subbasin. Figure 1-8 shows a map of water purveyors with service areas within the Oxnard Subbasin.

In addition to groundwater pumping, agricultural water supplies are provided by UWCD via its PTP and PVP. The PTP services users in the Oxnard Subbasin, and the PVP services users in both the Oxnard Subbasin and the PVB. UWCD’s water source for the PTP and PVP consists primarily of surface water obtained at the Freeman Diversion, which may include State Water Project water from Lake Piru. Groundwater is also extracted at five LAS wells located along the PTP pipeline 916
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in many years and is included in the water supplied by the PTP. Occasionally, temporarily stored recharge water is pumped from shallow wells at UWCD’s Saticoy Spreading Grounds and included in water supplied by the PVP.7

2.4.1.1 Surface Water
Figure 2-58, Oxnard Subbasin Stream Gauges and Water Infrastructure, shows the locations of streams and primary drainage systems in and around the Oxnard Subbasin, as well as water infrastructure locations including WWTP ponds, stream gauge stations, and the two diversion structures (Freeman and Conejo Creek Diversions) that provide a portion of the water supply for the Oxnard Subbasin.

Santa Clara River
The Santa Clara River interacts with the groundwater system in the Oxnard Subbasin. Reaches of the Santa Clara River in the Oxnard Subbasin range from perennial to intermittent to ephemeral (Appendix C). The river flows through the adjoining Santa Paula Basin into the Oxnard Subbasin in the Forebay area, and then out of the Oxnard Subbasin to the Mound Basin. Climatic and geologic characteristics of the Santa Clara River watershed result in an intermittent flow regime; however, flows can increase rapidly in response to high-intensity rainfall with the potential for severe flooding. During winter months, storm events may cause periods of continuous surface flow to the Pacific Ocean in the Santa Clara River.

Santa Clara River Recharge
The UWCD groundwater model used the MODFLOW STR stream package to simulate stream flow recharge. The stream flow discharge and percolation for the Santa Clara River were estimated using this stream package and the results are provided in Table 2-7a (for the semi-perched aquifer) Table 2-7b (for the UAS), and Table 2-7c (for the LAS). Except for 1998, 1999, and 2006, following the high rains in 1998 and 2005, the net effect of surface-water/groundwater interaction along the Santa Clara River was recharge to the UAS and the semi-perched aquifer in the Oxnard Subbasin (Appendix C). During these years, the net effect of surface-water/groundwater interaction was discharge from the UAS to the Santa Clara River. From 1985 to 2015, the average estimated recharge from the Santa Clara River to the semi-perched aquifer was 661 AFY, and the average estimated recharge to the UAS was 4,848 AFY (Tables 2-7a and 2-7b). These numbers do not include diversions from the Santa Clara River by the UWCD for artificial recharge at their spreading grounds or for direct use, which are discussed below.

7 UWCD extracts limited amounts of temporarily stored water from shallow wells at its Saticoy Spreading Grounds to the PVP during periods of mounding, as authorized by FCGMA Resolution 2011-02. 917
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Santa Clara River Diversions and Recharge
Table 2-8 summarizes the historical diversions of Santa Clara River water by UWCD and deliveries to both the Oxnard Subbasin and the PVB. On average, UWCD diverted 62,467 AFY from the Santa Clara River between 1985 and 2015, although diversion volumes, which depend on local climatic conditions, are highly variable (Table 2-8). These diversions may include State Water Project water held at Lake Piru and then delivered to the UWCD via the Santa Clara River.

UWCD diverts surface water from the Santa Clara River in the Santa Paula Basin, just upstream of the Oxnard Forebay. The majority of this water, on average, is used for groundwater recharge in its spreading basins within the Oxnard Forebay (Table 2-8). Additionally, the water is used as supply for the PTP that services agricultural water users on the Oxnard Plain and as supply for the PVP agricultural water supply line that services agricultural water users in both the PVB and the Oxnard Subbasin. During drought periods, the relative percentage of diverted water used to recharge groundwater in the spreading basins declines, and the relative percentage of groundwater delivered through the PTP increases.

Table 2-9 provides the amounts of diverted water recharged by the UWCD in the three UWCD recharge grounds. Approximately 93% of the diverted water is recharged in the El Rio and Saticoy Spreading Grounds, on average, and the remaining 7% is recharged in the Noble Spreading Grounds (Table 2-9). Figure 2-59, Freeman Diversion and Uses in the Oxnard Subbasin, shows the amounts of diverted water by UWCD, and Figure 2-60, UWCD Groundwater Recharge, shows the annual recharge by UWCD. As shown in Table 2-10, the UWCD supply delivered in the PTP supply line is a mixture of surface water, and groundwater pumped by UWCD from their PTP wellfield, which pumps from the LAS, and less frequently, from their Saticoy wellfield.

Recharge from the UWCD groundwater recharge spreading grounds is included with recharge in Table 2-7a and Table 2-7b, but identified individually in Table 2-11. Of the total average annual recharge shown in Table 2-11 (73,669 AFY), UWCD groundwater recharge accounts for 48,306 AFY, or 65.6%. Recharge related to the PTP/PV system averaged 3,319 AFY from 1985 to 2015 as shown in Table 2-11, this is 4.5% of the total recharge. Of the average 62,467 AFY diverted from the Santa Clara River (Table 2-8), the average of 48,306 AFY (Table 2-11) recharged to the UWCD spreading grounds constitutes 77%.

The water delivered in the Oxnard–Hueneme Pipeline consists of groundwater pumped from the UAS and LAS near the El Rio Spreading Grounds. As shown in Table 2-10, deliveries from the Oxnard–Hueneme Pipeline are primarily used for municipal purposes, but small volumes are occasionally used for agricultural water supply along Hueneme Road on the southern part of the Oxnard Subbasin.
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Calleguas Creek
Calleguas Creek enters the Oxnard Subbasin almost 2 miles upstream of its confluence with Revolon Slough and discharges to the Pacific Ocean at Mugu Lagoon. This reach of Calleguas Creek is perennial, with flow occurring primarily as maintenance flows provided by CWD (6 cubic feet per second required bypass flow at its diversion on Conejo Creek), inflows from agricultural field tile drains, inflows from Revolon Slough, and treated wastewater discharges into the lower reaches of Conejo Creek from the Camarillo Water Reclamation Plant (in the PVB) and the Hill Canyon WWTP in the City of Thousand Oaks. Table 2-12 summarizes the estimated flows in Arroyo Las Posas and Conejo Creek that enter Calleguas Creek, which then flows into the Oxnard Subbasin.

Table 2-12 summarizes the historical diversions of water from Conejo Creek by CWD at the Conejo Creek Diversion near Highway 101 that are supplied to the Oxnard Subbasin via PVCWD (Figure 2-58). The estimated diversions by CWD that are used in the Oxnard Subbasin are shown on Table 2-10. The source of water to Conejo Creek is mostly wastewater discharge from the Hill Canyon WWTP upstream of the Arroyo Santa Rosa Valley Basin. Table 2-10 shows only that portion of this water that is supplied to PVCWD and used in the Oxnard Subbasin.

Calleguas Creek Recharge
The UWCD (2018; Appendix C) groundwater model used the MODFLOW STR stream package to simulate recharge for Calleguas Creek in the Oxnard Subbasin. Calleguas Creek in the Oxnard Subbasin does not have hydraulic communication with the underlying UAS, but modeling indicates recharge to the semi-perched aquifer from 1985 to 2015 averaged 3,394 AFY (Table 2-7a).

Beardsley Wash/Revolon Slough
Beardsley Wash/Revolon Slough is a shallow drainage that captures shallow groundwater and stormwater from agricultural field tile drains and is lying at a similar elevation as the surrounding fields in its lower reaches where it is perennial. Consequently, it is not thought to be a recharge source.

2.4.1.2 Imported Water Supplies
Table 2-13 and Figure 2-61, Water Deliveries to the PVCWD and UWCD, show the historical volumes of water sold to the two water retailers (City of Oxnard and Port Hueneme Water Agency) that have historically purchased imported water from the CMWD. As shown in the table, sales to Port Hueneme Water Agency and to the City of Oxnard have occurred since 1996 and 1964, respectively. Sales have averaged approximately 1,564 AFY (from 1996 to 2015) and 13,500 AFY (from 1985 to 2015) to the Port Hueneme Water Agency and to the City of Oxnard, respectively. 919
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As discussed in Section 2.4.1.1, Surface Water, the UWCD-diverted surface water from the Santa Clara River may include State Water Project water used for groundwater recharge in UWCD spreading basins or water directly delivered to water users by either the PVP or the PTP.

Percolation of Outdoor Irrigation (Urban Return Flows)
In the UWCD (2018; Appendix C) model, an assumed amount of M&I delivered water (5%) is estimated as groundwater recharge. This water is included as recharged water in Tables 2-7a and 2-7b and the total is provided in Table 2-11 by sources. Of the total annual recharge shown in Table 2-11 (73,669 AFY), percolation of applied water accounts for 928 AFY, or 1.3%.

2.4.1.3 Recycled Water Supplies
Two small community WWTPs are located adjacent to the Santa Clara River in the Oxnard Subbasin (Figure 2-58). The Saticoy WWTP and the Montalvo WWTP discharge treated effluent to percolation ponds. According the UWCD (Appendix C, p. 47), the average annual volumes of effluent discharged to the percolation ponds are approximately 80 and 200 AF, respectively, based on reports provided by California’s State Water Resources Control Board online database, GeoTracker (http://geotracker.waterboards.ca.gov/). The Saticoy WWTP is within the Oxnard Forebay, where percolating water can directly recharge the UAS. The Montalvo WWTP is farther downstream, in an area of the Oxnard Subbasin where percolating water recharges the semiperched aquifer, which is not used for water supply. According to UWCD (Appendix C), the Montalvo WWTP ceased operating in 2016, subsequent to the model calibration period.

Recycled water by the City of Oxnard began to be provided to PVCWD and other agricultural users in early 2016. Wastewater effluent generated by the City of Oxnard historically has been treated at the Oxnard WWTP and discharged directly to the Pacific Ocean. However, the first phase of the GREAT Program’s Advanced Water Purification Facility (AWPF) was completed in 2015, which provides this supply to PVCWD and other growers on the southern part of the Oxnard Subbasin.

Recycled Water Recharge
Recharge from the Saticoy and Montalvo WWTPs is simulated in the UWCD model using the recharge package. The monthly percolation volumes reported in the state’s GeoTracker system were added to other areal recharge rates specified for the model grid cells corresponding to the WWTP percolation-pond sites (Appendix C, p. 83).

2.4.1.4 Percolation of Precipitation
Much of the rain that falls in the Oxnard Subbasin quickly returns to the atmosphere via evaporation, or runs off to creeks, storm drains, and ultimately the ocean; the remainder percolates into the soil where it is subject to evapotranspiration (ET), soil absorption, or for plant use. 920
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However, some precipitation can percolate into the soil and downward past the plant root zone and reach an underlying aquifer. This recharge process is referred to as deep infiltration (or percolation) of precipitation.

Deep percolation of precipitation depends on many factors, including: precipitation rate and duration, evaporation rate, ambient temperature, texture and slope of land surface, soil type and texture, antecedent soil moisture, vegetation cover, seasonal plant activity, and others is highly variable over time and location (Appendix C). Thus estimates of the percolation of precipitation is subject to substantial uncertainty.

UWCD downloaded monthly precipitation data for 180 rainfall gauge stations across the model domain from the Ventura County Watershed Protection District (http://www.vcwatershed.net/ hydrodata/) (Appendix C, p. 80). UWCD used the Kriging method of geostatistical analysis to generate monthly precipitation distributions across model area, and the areal recharge from deep infiltration of precipitation was input to the model using the recharge package and was calculated as follows:
 If monthly precipitation is less than 0.75 inches, the precipitation is lost to evapotranspiration.  If monthly precipitation is 0.75 to 1 inch, then recharge is assigned from 0% to 10% of precipitation (on a sliding scale).
 If monthly precipitation is 1 to 3 inches, then recharge is assigned from 10% to 30% of precipitation.
 If monthly precipitation is greater than 3 inches, then recharge is assigned as 30% of precipitation.  Urban (non-agricultural) land use, including residential, commercial, and industrial areas:
5% of the total water precipitation.
 Undeveloped land: 10% of the total water precipitation.

Precipitation Recharge
Recharge from the percolation of precipitation is include with recharge in Tables 2-7a and 2-7b, but identified individually in Table 2-11. Of the total annual recharge shown in Table 2-11 (73,669 AFY), percolation of precipitation accounts for 8,947 AFY, or 12.1%.

2.4.1.5 Basin Groundwater Subsurface Inflow and Outflow UWCD (Appendix C) provided model monthly groundwater inflows and outflows between the Oxnard Subbasin and the Pleasant Valley, Mound, west Las Posas Valley, and Santa Paula Basins, and unincorporated areas, as well asfor three coastal segments adjacent to the Pacific Ocean. These inflows and outflows were combined to generate the annual estimates used for the groundwater budget. Additionally Table 2-7b shows the subsurface flows between the UAS and the semiperched aquifer as well as the UAS and the LAS. 921
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2.4.1.6 Mountain-Front Recharge
UWCD (Appendix C) used the MODFLOW WEL package to input mountain-front recharge specified flux amounts into model grid cells adjacent to each small drainage system (subwatershed) along the margins of the model area, and to the base of elevated bedrock or mountains areas. In the Oxnard Subbasin, mountain-front recharge was applied at the base of the volcanic outcrops adjacent to the southwest side of the CWD Water Reclamation Plant shown on Figure 2-58, and along the Santa Monica Mountains. Recharge rates were calculated from monthly precipitation rates for the area receiving the precipitation. The monthly mountain-front-recharge rate inputs to the model followed the precipitation/recharge-percentage relationship used for agricultural return flows (Section 2.4.1.9, Percolation of Agricultural Irrigation Water [Agricultural Return Flows]). For the Oxnard Subbasin, mountain-front recharge from and to the volcanic outcrops and the Santa Monica Mountains (Unincorporated Areas) are shown in Tables 2-7a and 2-7b.

2.4.1.7 Septic Systems Recharge
The number and location of septic systems in the Oxnard Subbasin were estimated by DBS&A (2017) based on the Ventura County septic database. If septic systems were present within any parcel within a tract, it was assumed that all parcels in the tract contained septic systems. The number of septic systems in the Forebay decreased beginning in 2011 due to a County of Ventura program to phase out septic systems in the area. It was estimated that the number of systems in the Forebay decreased from 1,823 in 1985 to 485 in 2015 (DBS&A 2017).

Household water use and annual disposal was estimated to decrease from 0.21 AFY per household for 1985 to 1997, 0.20 AFY per household for 1988 to 2010, and 0.16 AFY per household from 1998 to 2015 based on DeOreo and Meyer (2012, as cited in DBS&A 2017). The resulting estimated percolation from all septic systems was estimated to decrease from 382 AFY in 1985 to 75 AFY in 2015 (DBS&A 2017). These values are small compared to known recharge values (UWCD spreading) and other estimated recharge values (Santa Clara River recharge; agricultural and municipal return flows).

The UWCD groundwater model assumed that septic system recharge was widespread and small relative to other recharge sources and incorporated septic system return flows implicitly as a component of agricultural and municipal return flows.

2.4.1.8 Distribution Systems Leakage
Distribution system losses from leakage of water-supply pipelines, sewer lines, and storm drains are included with M&I return flows in the UWCD model.
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2.4.1.9 Percolation of Agricultural Irrigation Water (Agricultural Return Flows) Groundwater pumping is discussed in Section 2.4.2.1; only recharge from agricultural return flow is discussed in this section. The UWCD groundwater model used the following water sources that were applied to irrigated land and assumed an agricultural return flow of 14%:
 Extracted groundwater from wells for agricultural use  Groundwater and surface water delivered by the PVCWD pipeline  Surface water diverted from Conejo Creek to PVCWD
If the precipitation is more than 1 inch per month, the agricultural return flow ratio is compared with precipitation recharge ratio. If the precipitation recharge ratio is larger than 14%, the agricultural return flow is replaced by the precipitation recharge ratio.

Agricultural Recharge
Recharge from the agricultural return flow is included with recharge in Tables 2-7a and 2-7b, and identified individually in Table 2-11. Of the total annual recharge shown in Table 2-11 (73,669 AFY), agricultural return flow accounts for 12,169 AFY, or 16.5%.

2.4.2 Sources of Water Discharge
Sources of groundwater discharge predominantly include groundwater pumping, tile drain discharges, and evapotranspiration. However, depending on groundwater levels (as noted in Section 2.4.1.1), groundwater/surface interactions can also discharge groundwater to surface water, which can then either be lost from the Subbasin or recharge elsewhere in the Subbasin.

Likewise, groundwater pumped and used for agricultural, M&I, and domestic purposes can produce return flows (Section 2.4.1.2, Imported Water Supplies; Section 2.4.1.7, Septic Systems Recharge; Section 2.4.1.8, Distribution Systems Leakage; and Section 2.4.1.9). Subsurface groundwater flows (interbasin flows) can discharge groundwater from the Oxnard Subbasin to the adjacent groundwater basins, unincorporated areas, and the Pacific Ocean (Section 2.4.1.5, Basin Groundwater Subsurface Inflow and Outflow).

2.4.2.1 Groundwater Pumping
Table 2-14 shows the amount of groundwater pumped for agricultural, M&I, and domestic uses by aquifer systems from the UWCD model results. UWCD modeled groundwater withdrawals using the multi-node well (MNW2) package. The extraction amounts in Table 2-14 were combined with well types from the FCGMA well database to distinguish the amounts extracted by type.

Figure 2-62, Groundwater Pumping, shows the amounts of agricultural, M&I, domestic, and total groundwater pumped from the Oxnard Subbasin. Groundwater pumping is also shown in the Oxnard Subbasin groundwater budget in Tables 2-7a through 2-7c. 923
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Available data indicate that during the calendar year 2015, a total of 80,814 AF (Table 2-14) of groundwater was extracted from the Oxnard Subbasin, of which, about 69% was for agricultural use (55,973 AF), 30% was for M&I use (24,648 AF), and about 0.2% was for domestic use (193 AF). For the Oxnard Subbasin, the FCGMA groundwater pumping database contains 732 known wells, of which 403 are currently listed as active use, 217 have been destroyed, 106 are inactive, and 6 could not be located. An additional 13 agricultural wells are in the UWCD database outside the FCGMA boundary.

Not all the groundwater produced in the Oxnard Subbasin remains in the Subbasin. Four agricultural users (PVCWD, Coastal Berry Co., Montalvo Water Co., Alta Mutual Water Co., and Guadalasca Mutual Water Co.) may export a portion of the groundwater that they pump from the Oxnard Subbasin to areas inside the PVB. The PVCWD uses a combination of pumped groundwater from the Oxnard Subbasin and the PVB, delivered UWCD water from the PVP, CWD-delivered water from Conejo Creek, and other sources. FCGMA groundwater pumping records indicate that from 1985 to 2015, approximately 41% and 59% of PVCWD’s pumped groundwater has come from the PVB and the Oxnard Subbasin, respectively. A geographic information system (GIS) calculation of the area of the PVCWD in Figure 1-8 indicates that approximately 56% of the PVCWD service area is in the Oxnard Subbasin, and the remaining 44% is in the PVB. For purposes of estimating PVCWD water deliveries, a ratio of 44% PVB and 56% Oxnard Subbasin area was assumed to be a reasonable basis for PVCWD water supplies between the two basins. As shown in Table 2-10, during some years, groundwater pumping by PVCWD in the Oxnard Subbasin is less than this ratio resulting in a net import from the PVB. Conversely, in some years, groundwater pumping in the Oxnard Subbasin is more than this ratio, resulting in a negative import (an export) to the adjacent PVB.

2.4.2.2 Tile Drain Recharge Losses
Tile drains are used beneath many agricultural lands in the Oxnard Subbasin to maintain a sufficiently deep groundwater table where poorly drained soils create shallow groundwater conditions that can negatively affect plant health and crop yields. These conditions prompted the installation of tile drains across most of the Oxnard Plain in the 1900s. Tile drains are present beneath many agricultural land parcels in the PVB as well. These drains discharge to local drainage ditches and then to surface water bodies Revolon Slough and Calleguas Creek. The flows in the tile drains are not metered.

Tile drains were implemented in the UWCD groundwater model using MODFLOW’s drain package (DRN). Model grid cells with simulated tile drains in the uppermost active layer correspond with agricultural areas where tile drains are known or suspected to exist. The UWCD model has calculated losses to tile drains based on groundwater model simulated water levels and the results are provided in Tables 2-7a and 2-7b. Average annual loss to tile drains in the UWCD model is 10,752 AFY. 924
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2.4.2.3 Evapotranspiration (ET)
The UWCD model used the U.S. Fish and Wildlife Service online “Wetlands Mapper” (https://www.fws.gov/wetlands/data/mapper.html) to indicate areas of riparian vegetation along stream channels. These areas, together with parts of the Santa Clara River (including its estuary), Revolon Slough/Beardsley Wash, McGrath Lake, Ormond Beach wetlands, and Mugu Lagoon wetlands were used to estimate evapotranspiration (ET) (Appendix C). ET is the discharge of groundwater from the saturated zone where the water table is present at very shallow depths. Such conditions mostly occur in the Oxnard Subbasin where the semi-perched aquifer interacts with surface water bodies, which is also where riparian vegetation is typically found in the Oxnard Subbasin. These areas are hydraulically connected to, and exchange fresh- to brackish-water with, the semi-perched aquifer near the coast. It should be noted that nearly all of the riparian vegetation that takes up groundwater in the Oxnard Subbasin occurs in land overlying the semi-perched aquifer, which is rarely, if ever, pumped as a source of agricultural or M&I water supply.

Additional discussions about these areas are in Sections 2.3.6 and 2.3.7.

UWCD (Appendix C) applied USGS estimates for ET rates from 1.1 to 5.2 feet per year to calculated long-term annual average groundwater discharge as ET. UWCD implemented ET using MODFLOW’s ET package, EVT. Model grid cells corresponding to areas of mapped wetlands with shallow groundwater were simulated. The maximum ET flux was 0.010 feet per day (3.65 feet per year) for model grid cells subject to ET over their entire area. The maximum ET flux is scaled down proportionally for grid cells that are only partially occupied by wetlands. The ET surface elevation was set at 3 feet bgs, and the ET extinction depth was set at 5 feet bgs (Appendix C, p. 84).

According to UWCD model results, the estimated annual loss from ET is 8,328 AFY, with most coming from the semi-perched aquifer (8,291 AFY, a shown in Table 2-7a) and a small amount from the UAS (37 AFY, as shown in Table 2-7b).

2.4.3 Current and Historical Water Budget Analysis

2.4.3.1 Water Year Types
Water year type is based on the percentage of the water year precipitation compared to the 30-year precipitation average. Types are defined in this GSP as wet (> 150% of average), above normal (> 100% to <150% of average), below normal (> 75% to <100% of average), dry (> 50% to <75% of average), and critical (<50% of average). Figures 2-22 through 2-25 show the water year type from 1986 to 2015. The water type year for 2015 is dry.
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2.4.3.2 Historical Water Budget Analysis
DWR has designated the Oxnard Subbasin as a high-priority basin. The DWR GSP Regulations, Section 354.18, Water Budget, states that, “If overdraft conditions occur, as defined in Bulletin 118, the water budget shall include a quantification of overdraft over a period of years during which water year and water supply conditions approximate average conditions.” According to the DWR Bulletin 118, “A basin is subject to critical overdraft when continuation of present water management practices would probably result in significant adverse overdraft-related environmental, social, or economic impacts” (DWR 2006). Bulletin 118 Interim Update 2016 (October 18, 2016) lists the Oxnard Subbasin (Basin 4-004.02) as being in critical overdraft (DWR 2016).

Because of Bulletin 118’s listing of the Oxnard Subbasin as being in critical overdraft, the DWR GSP Regulations, Section 354.18 (b)(5), requires a quantification of the overdraft over a period of years during which water years and water supply conditions approximated average conditions. Using the water year types discussed in Section 2.4.3.1, and the above normal (> 100% to <150% of average) and the below normal (> 75% to <100% of average) water year types to bracket water supply conditions approximating average conditions, the following years have near average conditions: 1988, 1991, 1992, 1994, 1996, 1997, 2000, 2001, 2003, 2006, 2008, 2010, and 2011.

The change in storage during these years was an increase of 6,045 AFY in the UAS and an increase of 1,029 AFY in the LAS (Tables 2-7b and 2-7c). However, the net seawater intrusion during these years was 4,189 AFY in the UAS, and 5,225 AFY in the LAS (Table 2-7c). Thus, the net change in groundwater storage for the UAS without seawater intrusion was an increase in 1,856 AFY in the UAS and the net change in storage without seawater intrusion in the LAS was a decrease of 4,196 AFY. Total groundwater pumping during these years averaged 47,080 AFY in the UAS and 28,893 AFY in the LAS for a total of 65,973 AFY (Tables 2-7b and 2-7c). This quantification of the overdraft over a period of years during which water years and water supply conditions approximated average conditions would indicate that the Oxnard Subbasin was in overdraft of about 2,340 AFY (4,196 AFY [LAS] − 1,856 AFY [UAS]). It should be noted that except for 2011, Tables 2-7b and 2-7c show net seawater intrusion for the UAS and LAS for each of the years that approximated average conditions. This seawater intrusion analysis suggests that based on the historical pumping patterns and pumping amounts, the Oxnard Subbasin was in overdraft by about 2,340 AFY during average water supply conditions.

GSP regulation Section 354.18 (c)(2) requires that the historical water budget information be used to evaluate availability or reliability of past surface water supply deliveries and aquifer response to water supply and demand trends relative to water year type. Historically, the Oxnard Subbasin has received surface water supply deliveries directly from one main source: the Santa Clara River.

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Subbasin. Table 2-8 shows that the diversion of Santa Clara River from 1985 to 2015 have averaged 62,467 AFY, and leakage from the Santa Clara River has averaged about 5,650 AFY (770 AFY [see Tables 2-7a and 2-7b] + 4,989 AFY [see Table 2-7b] – 109 AFY [see Table 2-7b]).

This indicates a total Santa Clara River supply of approximately 68,117 AFY. In comparison, Calleguas Creek has supplied approximately 3,394 AFY (see Table 2-7a) to the semi-perched aquifer, CMWD has delivered 14,543 AFY of imported water (see Table 2-13), and Conejo Creek diverted flows have averaged 1,159 AFY (see Table 2-10). These last three sources total 19,096 AFY, or 22% of the total surface water deliveries (87,213 AFY) or only 28% of the total Santa Clara River. Tables 2-7a, 2-13, and 2-10 for Calleguas Creek, CMWD imported water, and Conejo Creek (starting in 2002), respectively, suggest that these sources are reliable and not significantly affected by the water year type. However, diversions from the Santa Clara River as shown in Table 2-8 and on Figure 2-59 vary widely depending on climate conditions. The high diversion years of 1993, 1998, and 2005 were wet years (Figures 2-22 and 2-59). The low diversion years of 1990, 2013 and 2014 were critical dry years, and 2015 was a dry year (Figures 2-22 and 2-59). Diversions of surface water by the UWCD from the Santa Clara River are critical to the surface water supplies of the Oxnard Subbasin.

2.4.3.3 Current (2015) Groundwater Conditions
Groundwater level data presented in Section 2.3, Groundwater Conditions, and the change in storage estimates for the calendar year 2015 from Tables 2-7a through 2-7c indicate that the Oxnard Subbasin had greater groundwater outflows than inflows in 2015. The estimated 2015 groundwater change in storage is a loss of about 38,703 AF (Tables 2-7a through 2-7c). This change in groundwater storage would be larger and groundwater storage declines greater if seawater intrusion had not replaced groundwater in the Oxnard Subbasin. Model results in Tables 2-7a through 2-7c indicate a net seawater intrusion in 2015 of approximately 19,200 AF. There was a net outflow of water to the Pacific Ocean in the semi-perched aquifer of approximately 504 AF (Table 2-7a), but a positive inflow (seawater intrusion) in the UAS of approximately 11,633 AF (Table 2-7b) and a positive inflow in the LAS of approximately 8,081 AF (Table 2-7c).

Tables 2-7a through 2-7c show that from 1985 to 2015, seawater intrusion has replaced freshwater in storage in the Oxnard Subbasin in the LAS every year, and 23 of 31 years in the UAS. Tables 2-7a and 2-7b indicate that seawater flows both in and out of the Oxnard Subbasin in the semiperched aquifer and the UAS. However, groundwater generally flows out of the Subbasin from the semi-perched aquifer (which is not currently a usable aquifer), and seawater usually inflows to the UAS and LAS, which affects usable groundwater aquifers. 927
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2.4.3.4 Estimates of Historical Sustainable Yield
Historical estimates for the Oxnard Subbasin sustainable yield8 have also included the PVB. These historical sustainable yield estimates include the following:
 FCGMA, 1985, Groundwater Management Plan
 FCGMA, 2007, 2007 Update to the Fox Canyon Groundwater Management Agency Groundwater Management Plan
 UWCD and CMWD, 2012, Preliminary Draft Yield Analysis (UWCD 2016c)  UWCD, 2016, Proposed Method for Estimating Sustainable Yield (UWCD 2016c) All of these historical estimates for the combined Oxnard Subbasin and PVB sustainable yield are about 65,000 AFY, but do not demonstrate that this groundwater pumping rate prevents seawater intrusion. The UWCD Open-File Report 2017-02 (UWCD 2017a) Scenario D estimated that seawater intrusion would be halted if: (1) there were no groundwater pumping in what the report refers to as an assumed future “seawater intrusion management area,” (2) groundwater pumping were reduced by about 70% in LAS in the Oxnard Plain (excluding the Forebay) and in the PVB, and (3) there were no reduction in UAS pumping. However, this scenario assumed that groundwater for irrigation in the assumed future “seawater intrusion management area” would be supplied by a project to be implemented in the future. The combined estimated sustainable yield under Scenario D was 59,900 AFY for the Oxnard Subbasin (excluding the seawater intrusion management area) and the PVB.

To estimate the sustainable yield under historical conditions where no future project is implemented, the UWCD conducted Scenario F in Addendum Open-File Report 2017-02a (UWCD 2017b). In Scenario F, the assumed seawater intrusion management area was eliminated, and a uniform reduction in groundwater pumping was simulated to achieve sustainable yield. The scenario defined a sustainable yield as maintaining groundwater elevations along the coast at levels sufficiently high to prevent seawater intrusion and other forms of saline water intrusion. In the Port Hueneme area, where the UAS and LAS are believed to have direct hydraulic connection with the Pacific Ocean, UWCD assumed minimum thresholds9as defined in Open File Report 2017-02. However, under Scenario F, UWCD assumes a minimum threshold for the LAS near Mugu Lagoon to be −20 feet msl instead of 18.5 feet msl, as assumed in Open File Report 2017-02. This is because the most recent UWCD Saline Intrusion Update report (UWCD 2016b) interpreted the source of elevated

8 SGMA requires that an estimate of the “sustainable yield” be made for the Oxnard Subbasin based on historical data. However, as used in this section the sustainable yield does not address undesirable results, which are discussed in Chapter 3, Sustainable Management Criteria. 9 “Minimum threshold” used here is in reference to the Open File Report 2017-02 usage and not to the minimum threshold discussed in Chapter 3 of this GSP.
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chloride concentrations in the LAS near Mugu Lagoon to be saline water yielded from marine clays and/or from adjacent Tertiary-age sedimentary rocks, as a result of large declines in potentiometric head in the LAS over the past several decades, and not a direct result of current seawater intrusion.

Additional discussion of saline water and seawater intrusion can be found in Section 2.3.3.

Based on the results from UWCD Scenario F (UWCD 2017b, Table 2-2), the sustainable yield under historical conditions with no changes from the current pumping locations (i.e., without water supply or infrastructure projects) for the Oxnard Subbasin would be a total of 39,000 AFY (27,000 AFY from the Oxnard Plain and 12,000 AFY from the Oxnard Forebay area). The results from UWCD Scenario F (2017b, Table 2-2) would indicate a total of 10,000 AFY for the PVB.

Evaluation of the volume of water entering and leaving the model along the Pacific coastline under Scenario F indicated that there is a net outflow of water from the model to the Pacific Ocean over the 31-year simulation period. Groundwater left the model to the ocean in the UAS, while a smaller amount of seawater intruded the LAS. This suggests that additional production may be possible from the Oxnard Subbasin by reducing groundwater pumping in the LAS and increasing it in the UAS. This shift in pumping may also better protect against seawater intrusion.

2.4.4 General Uncertainties in the Water Budget
There are several limitations and uncertainties associated with other water budget terms used for both the historical and future conditions due to necessary simplifying of assumptions and data gaps. Uncertainties about the groundwater models used are discussed in Section 2.4.5.8. Some of the general water budget limitations and/or uncertainties include the following:

1. The reporting of groundwater pumping outside the boundaries of the FCGMA is limited and there is a possibility of underreporting of pumping within the FCGMA boundaries due to non-reporting, inaccurate reporting, and equipment problems. Additional future data collection is needed to verify the existence and extent of and to eliminate this data gap.

However, the amount of pumping outside the FCGMA boundary is expected to be minor given the limited number of wells (estimated at fewer than 12).

2. The hydrologic base period (calendar years 1985–2015, DWR’s 31-year base period) may not necessarily be representative of long-term average conditions. As shown on Figure 1-6, Long-Term Precipitation Trends in the Oxnard Plain, this was a generally wetter-than-average period. However, the future water budget analysis in Section 2.4.5, which used a model 50-year period with an average precipitation period (1939 to 1979), does not suggest that the historical sustainable yield estimate based on this wetter-thanaverage period is too high. The combined UAS and LAS sustainable yield for the future water budget ranged from 30,000 AFY to 48,000 AFY (Section 2.4.5.9). The estimated historical sustainable yield using UWCD Scenario F (Section 2.4.3.4) of 39,000 AFY is within this range. The uncertainty associated with the future water budget sustainable yield is discussed in Section 2.4.5.8.
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3. Conclusions regarding uncertainties in the UWCD model are discussed in Section 2.4.5.8, Uncertainty Analysis, and in the Dudek peer review of the UWCD model (Appendix E).

4. Subsurface inflows and outflows across basin boundaries are not measurable. The groundwater level data in these areas by themselves do not provide a clear indication of groundwater flow directions because of the limited water level measurements and the variation in time between measurements. The UWCD model provides a significantly improved understanding of these boundary fluxes and their variability under different pumping and recharge conditions in the region, but checking model values with observations and calculating the gradient with three-point groundwater flow problems should be considered to verify model estimates. Attempts to estimate inflows and outflows across basin boundaries using well groundwater level data was attempted for this GSP, but data gaps and limited well locations screened in one aquifer made the results unreliable.

5. Some semi-perched groundwater in the Oxnard Subbasin is potentially captured by tile drains, rather than recharging the UAS. This uncertainty could be reduced through installation of instrumentation and measurement of discharges from the tile drains.

6. Currently, aquifer-specific water level maps are not reliable to estimate aquifer change in groundwater storage due to the limited number and distribution of aquifer-specific water wells. Dedicated monitoring wells could installed and equipped with water-level measuring data loggers in all of the aquifers. This would help decrease uncertainty in estimates of future changes in groundwater storage by enabling use of aquifer-specific water-level maps to check groundwater model change in storage calculations.

2.4.5 Projected Future Water Budget and Sustainable Yield Several model scenarios were developed in accordance with SGMA guidelines to assess the future sustainable yield of the Oxnard Subbasin. Each future scenario covered a 50-year time frame, from 2020 to 2069. In this GSP, the period from 2020 to 2039 is referred to as the implementation period, and the period from 2040 to 2069 is referred to as the sustaining period. The sustainable yield was determined from the model scenarios that did not result in a net flux of seawater into either the UAS or the LAS in Oxnard Subbasin, within the level of the model uncertainty, during the 30-year sustaining period (Figure 2-63, Coastal Flux from the UWCD Model Scenarios).

Because the Oxnard Subbasin is hydraulically connected to the PVB and the WLPMA, the sustainable yield of the Oxnard Subbasin is influenced by groundwater production and projects in these adjacent basins. The UWCD model used to assess the sustainable yield of the Oxnard Subbasin includes both the PVB and the WLPMA in the model domain, and the modeling assumptions associated with each scenario discussed below include the assumptions made for these adjacent basins.
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The model scenarios developed for Oxnard Subbasin, the PVB, and the WLPMA all included existing projects and the 2070 DWR climate-change factor applied to the 1930–1970 historical precipitation and hydrology base period. The model scenarios are the following:
 Future Baseline Simulation (2015–2017 average production rates adjusted by surface water deliveries)
 Future Baseline Simulation With Projects (2015–2017 average production rates adjusted by surface water deliveries; potential future projects that met the DWR conditions for incorporation in the GSP)
 Reduction With Projects (35% reduction of 2015–2017 average production rates adjusted by surface water deliveries for the UAS and LAS in the Oxnard Subbasin, 20% reduction for the UAS and LAS in PVB; and 20% in the LAS in the WLPMA; potential future projects that met the DWR conditions for incorporation in the GSP)  Reduction Without Projects 1 (reduction of 2015–2017 average production rates adjusted by surface water deliveries by 25% in the UAS, 60% in the LAS, and 45% for wells screened in both aquifer systems in the Oxnard Subbasin; 25% reduction for the UAS and the LAS in the PVB; and 25% in the LAS in the WLPMA)
 Reduction Without Projects 2 (reduction of 2015–2017 average production rates adjusted by surface water deliveries by 55% in the UAS and the LAS in the Oxnard Subbasin; 20% reduction for the UAS and the LAS in the PVB; and 20% in the LAS in the WLPMA)  Reduction Without Projects 3 (reduction of 2015–2017 average production rates adjusted by surface water deliveries by 55% in the UAS and the LAS in the Oxnard Subbasin; 0% reduction for the UAS and the LAS in the PVB; and 0% in the LAS in the WLPMA) Two of the model scenarios listed above, the Future Baseline Simulation With Projects Scenario and the Reduction With Projects Scenario, incorporated projects that were approved for inclusion in the GSP model scenarios by the FCGMA Board. The Board’s approval of these projects only indicates that they were sufficiently defined by the project proponent to be analyzed as part of the GSP. It does not indicate that these specific projects will necessarily be constructed or, conversely, that other projects will not be developed in the future. The projects included are discussed in more detail with the description of each scenario below.

An initial set of four modeling simulations were conducted using the future baseline conditions with two 50-year average climate cycles (1930–1979 and 1940–1989), and two DWR climatechange factors (2030 and 2070) applied to each of the 50-year periods. The 1930 to 1979 50-year period with the 2070 DWR climate-change factor was found to be the most conservative and was used for the comparison with the other modeling simulations conducted. Additional details about the selection of the two 50-year average climate cycles is provided in Section 2.4.5.7. 931
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In addition to the initial set of four modeling simulations and the six model scenarios listed above, the Reduction Without Projects Scenario 1 was simulated with the DWR 2030 climate-change factor and with a historical precipitation and hydrology base period from 1940 to 1989. These simulations were conducted to better understand the potential impact of precipitation patterns and climate-change factors on the model results. While the results of these simulations were primarily used as a check on the minimum threshold groundwater elevations discussed in Chapter 3, the predicted impact on seawater intrusion is discussed in Section 2.4.5.7.

Over the next 5 years, as additional projects are developed the model assumptions discussed below will need to be altered and incorporated into the 5-year GSP evaluation.

2.4.5.1 Future Baseline Model Simulation
SGMA requires that the GSP include an assessment of the “future baseline” conditions. In the Future Baseline Scenario, in order to assess whether or not groundwater extractions from the Oxnard Subbasin, PVB, and WLPMA were sustainable at their current rates, the average annual 2015–2017 production rates, adjusted by surface water deliveries, were simulated. Future surface water deliveries were estimated by UWCD using Santa Clara River flows for historical periods, the 1930–1979 climate period adjusted for future DWR climate-change factors, and estimated diversions based on similar historical Santa Clara River flows. UWCD also considered current allowable diversions, which accounts for current environmental restraints and diversion operating conditions, and optimization of water deliveries for the PVP and spreading basins. Additional details about the UWCD future model scenarios are included in Appendix L, UWCD GSP Model Documentation. For the Oxnard Subbasin, this rate is approximately 68,000 AFY without surface diversions, for the combined UAS and LAS (Table 2-15).

Future Baseline Scenario Model Assumptions
The Future Baseline model simulation included the following:
 Constant pumping at the 2015–2017 average rate of approximately 68,000 AFY adjusted for surface water deliveries in the Oxnard Subbasin (39,000 AFY in the UAS; 29,000 AFY in the LAS), 13,000 AFY in the WLPMA, and approximately 14,000 AFY in the PVB  Starting water levels equal to the final 2015 water levels from the historical simulations  Precipitation and streamflow for two 50-year periods (1930–1979 and 1940–1989), with an average precipitation that equaled the average precipitation for the entire historical record  Estimates of Santa Clara River surface water available for diversion prepared by UWCD staff using climate-change factors provided by DWR and historical measured flow in the river for the 50-year periods
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 East Las Posas Management Area outflows to Arroyo Las Posas to the PVB from the CMWD model
 Projects that are currently operating in the Subbasin or currently under development The historical measurements of precipitation for the two 50-year periods were modified using the DWR 2030 and 2070 climate-change factors. Stream flows were estimated using the adjusted rainfall. UWCD estimated Santa Clara River flow and the volume of water diverted to direct delivery and spreading. Pumping was decreased where the water is delivered to account for the surface water delivered. Future streamflow in Conejo and Calleguas Creeks in Pleasant Valley was estimated by regression.

No projects currently under development were identified in the Oxnard Subbasin, but two projects under development in the PVB were incorporated into the future baseline simulation because these projects affect inflows to the Oxnard Subbasin. The two projects in PVB are the City of Camarillo’s North Pleasant Valley Desalter (desalination) Project and Conejo Creek Diversion deliveries to Pleasant Valley County Water District. The North Pleasant Valley Desalter Project was simulated by dividing the total project pumping of 4,500 AFY between project extraction wells 02N20W19L05 and 02N20W19F04. Additionally, pumping from Well 02N21W34C01 increased by 1,300 AFY to reflect a shift in areas of production.

In this scenario, Conejo Creek diversions will increase deliveries to agriculture by an additional 2,200 AFY to make the total deliveries in the PVB 4,500 AFY starting in 2020. The Conejo Creek Project allows CWD to increase pumping by up to 4,500 AFY based on credits for surface water delivered to PVCWD. However, in running the future simulations, it became apparent that the model area identified for production from the CWD wells was not able to extract the full amount.

The amount of simulated CWD pumping that was achievable in the future baseline simulation was therefore limited to 2,816 AFY.

It is important to remember that groundwater extractions are not the only source of water to the Oxnard Subbasin. Surface water deliveries vary between the model scenarios because the model adjusts the deliveries of Santa Clara River water based on simulated groundwater elevations in the Oxnard Subbasin Forebay. Therefore, the total water available to the Oxnard Subbasin in the Future Baseline Scenario is approximately 72,000 AFY. Additionally, although the model calculates the groundwater extractions and surface water deliveries with precision, the values reported in Table 2-15 have been rounded to the nearest 1,000 AFY to reflect the uncertainty in the model calculations.
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Future Baseline Scenario Model Results
Both the modeled flux of seawater and the particle tracks from the Future Baseline Scenario indicate that continuing the 2015–2017 extraction rate for the next 50 years would cause net seawater intrusion in both the UAS and LAS as well as ongoing inland migration of the saline water impact front (Figure 2-63 and Figure 2-64a through 2-64e, UWCD Model Particle Tracks, Future Baseline). The average annual flux of seawater into the UAS during the sustaining period was 4,400 AFY and the average annual flux of seawater into the LAS during the sustaining period was 5,300 AFY. The saline water impact front continued to migrate landward throughout the sustaining period, even during wetter than average climate periods. Based on these factors, the current areal and aquifer-system distribution of groundwater production at the extraction rates modeled in the Future Baseline Scenario was determined not to be sustainable.

2.4.5.2 Future Baseline With Projects Model Simulation
Future Baseline With Projects Scenario Model Assumptions Modeling of future conditions included all of the assumptions incorporated into the Future Baseline simulation, and also incorporated potential future projects approved for inclusion by the FCGMA Board. Incorporation of the potential future projects in the Future Baseline With Projects Scenario neither represents a commitment by FCGMA to impose pumping reductions in the amounts specified at the wells identified below nor a commitment to move forward with each project included in the future model scenarios. Assumptions about projects and project implementation may have changed since the modeling was conducted and will continue to change over the next 5 years. These changes should be incorporated into the modeling for the 5- year GSP evaluation.

In the Oxnard Subbasin simulated future projects included delivery of 4,600 AFY of recycled water to farmers in the vicinity of Hueneme Road, expansion of the GREAT Program to increase groundwater recharge by 4,500 AFY in the Saticoy Spreading Grounds, and a 504 AFY reduction of pumping through temporary fallowing. These projects are discussed in detail in Chapter 5 of this GSP.

To simulate the delivery of 4,600 AFY of recycled water to farmers in the vicinity of Hueneme Road, pumping from wells near the coast in the pumping depression area (UWCD model parameter zone 4; Figure 2-65, UWCD Model Zones) was reduced uniformly and proportionally by 4,600 AFY. Additionally, pumping from Wells 02N22W23C05S and 02N22W23C07S in the Forebay was adjusted to allow the City of Oxnard to pump up to 8,000 AFY of accumulated credits for 2,600 AF recycled agricultural water delivered annually from the GREAT Program (FCGMA 2018).
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To simulate the expansion of the GREAT Program, spreading recharge was increased by 4,500 AFY starting in 2025. To simulate the 504 AFY reduction of pumping through fallowing, pumping from Wells 01N22W26K04S, 01N22W27H02S, 01N22W26M03S, 01N22W26K03S, 01N22W26P02S, 01N22W26Q03S, and 01N22W26D05S was reduced uniformly and proportionally by 504 AFY. It should be noted that these wells were selected for modeling purposes only and use of these wells in the model simulations was not intended to represent any planned pumping restrictions or limitations on these wells.

In the PVB, a proposed temporary fallowing project was simulated near the pumping depression (in model parameter zone 11; Figure 2-65). This project would generate a 2,407 AFY reduction in pumping, however, actual simulated fallowing totaled 2,234 AFY due to considerations of existing contracts for the delivery of surface water from the Santa Clara River. Pumping was preferentially reduced in wells in the LAS within the PVB to the extent possible.

In the WLPMA, future projects included the purchase of 1,762 AFY of water to be delivered to the eastern portion of the WLPMA in lieu of groundwater extraction. Simulated pumping was reduced in Zone Mutual Water Company Wells 02N20W07R03, 02N20W07R02, 02N20W08M01, 02N20W08E01, and 02N20W08F01, as well as Ventura County Waterworks District No. 19 Wells 02N20W06R01 and 02N20W08B01. The pumping reductions of 1,762 AFY were applied uniformly and proportionally across the wells.

After incorporating the potential future projects, the average groundwater production rate for the UAS in the Oxnard Subbasin was 41,000 AFY and the average groundwater production rate for the LAS in the Oxnard Subbasin was 24,000 AFY for the Future Baseline With Projects Scenario.

In the PVB, the average groundwater production rate was 4,300 AFY in the UAS and 7,600 AFY in the LAS. In the WLPMA, the average production rate in the LAS was 11,200 AFY.

Because the projects that were incorporated into the Future Baseline With Projects Scenario included reduction of approximately 500 AFY from temporary fallowing in Oxnard, and deliveries of recycled water from the GREAT Program, the groundwater extractions in the LAS decreased by approximately 4,000 AFY, relative to the Future Baseline Scenario. At the same time, the groundwater extractions from the UAS increased by approximately 2,000 AFY, relative to the Future Baseline Scenario, in the Future Baseline With Projects Scenario (Table 2-15).

Consequently, the effect of incorporating the projects was to shift groundwater extraction from the LAS to the UAS, and reduce overall groundwater extraction by approximately 2,000 AFY. The total water available to the Oxnard Subbasin in the Future Baseline With Projects Scenario was approximately 73,000 AFY, with the reduction in groundwater production being offset by the addition of approximately 3,000 AFY of project water.
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Future Baseline With Projects Scenario Model Results
Although the shift in groundwater extractions from the LAS to the UAS and reduction in the total extractions helped reduce the flux of seawater into the Oxnard Subbasin, overall the Future Baseline With Projects Scenario resulted in approximately 3,000 AFY of seawater flux into the UAS and 2,700 AFY into the LAS during the sustaining period (Figures 2-66a through 2-66e, UWCD Model Particle Tracks, Base Case with Projects). Particle tracks for the Future Baseline With Projects Scenario also showed net landward migration of the saline water impact front during the sustaining period (Figures 2-66a through 2-66e). Based on these factors, the current areal and aquifer-system distribution of groundwater production at the extraction rates modeled in the Future Baseline With Projects Scenario was determined not to be sustainable.

2.4.5.3 Reduction With Projects Scenario
Reduction With Projects Scenario Model Assumptions
The Reduction With Projects Scenario included all of the assumptions incorporated into both the Future Baseline simulation and the Future Baseline With Projects Scenario. The Reduction With Projects Scenario also included a 35% reduction of 2015–2017 average production rates for the UAS and LAS in the Oxnard Subbasin, 20% reduction for the UAS and LAS in the PVB, and 20% in the LAS in the WLPMA. Groundwater production rates were reduced linearly over the implementation period and held constant during the sustaining period. In the Oxnard Subbasin UAS, the simulated groundwater production rate in model year 2020 was 40,000 AFY. The production rate in model year 2040 at the beginning of the sustaining period was 24,300 AFY. 10 The average production from the UAS for the sustaining period was 26,500 AFY. In the LAS, the simulated groundwater production rate in model year 2020 was 28,500 AFY and the simulated groundwater production rate in model year 2040 was 14,000 AFY. The average production rate from the LAS for the sustaining period was 12,800 AFY.

Reduction With Projects Model Scenario Results
Reducing groundwater production in the UAS and LAS, and shifting some groundwater extractions from the LAS to the UAS via the potential future projects in the Reduction With Projects Scenario, resulted in an average flux of groundwater out of the UAS into the Pacific Ocean of approximately 3,300 AFY during the sustaining period. In the LAS, the Reduction With Projects Scenario resulted in an average flux of approximately 1,200 AFY of seawater into the LAS during the sustaining period (Figures 2-67a through 2-67e, UWCD Particle Tracks, Reduction With

10 Modeled extraction rates depend on climate, surface water availability, and simulated groundwater elevations for each model year. The reductions implemented reflect a reduction in overall water demand for the Oxnard Subbasin and are not the exact percentage specified for any given year. Therefore, the extraction rate from the UAS in 2040 is 39% of the extraction rate in 2020 rather than the 35% specified in the model scenario description. 936
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Projects Simulation). Particle tracks for the Reduction With Projects Scenario indicate that the location of the 2015 saline water impact front would likely migrate toward the Pacific Ocean in the UAS as freshwater diluted saline concentrations, while it would experience some landward migration in the LAS (Figures 2-67a through 2-67e). The continued landward migration of the saline water impact front in the LAS suggests that groundwater production in the LAS may need to be reduced further than it was in this model scenario, while at the same time the groundwater production rate in the UAS was likely lower than it needed to be, as groundwater left the aquifers of the UAS and entered the Pacific Ocean.

2.4.5.4 Reduction Without Projects Scenario 1
Reduction Without Projects Scenario 1 Model Assumptions The Reduction Without Projects Scenario 1 included all of the assumptions incorporated into the Future Baseline simulation but did not include the projects that were incorporated into the Future Baseline With Projects and Reduction With Projects Scenarios. In the Oxnard Subbasin, the Reduction Without Projects Scenario 1 also included a 25% reduction of 2015–2017 average production rates for wells screened solely in the UAS, a 60% reduction of the 2015–2017 average production rates for wells screened solely in the LAS, and a 45% reduction of the 2015–2017 average production rates for wells screened in both aquifer systems. The 2015–2017 average pumping rate was reduced by 25% in the UAS and LAS in the PVB, and 25% in the LAS in the WLPMA. Groundwater production rates were reduced linearly over the implementation period and held constant during the sustaining period.

In the Oxnard Subbasin UAS, the simulated groundwater production rate in model year 2020 was 40,300 AFY. The production rate in model year 2040 at the beginning of the sustaining period was 27,300 AFY.
11 The average production from the UAS for the sustaining period was 27,200 AFY.

In the LAS, the simulated groundwater production rate in model year 2020 was 33,100 AFY and the simulated groundwater production rate in model year 2040 was 13,000 AFY. The average production rate from the LAS for the sustaining period was 11,600 AFY. The resulting average combined extraction rate from the two aquifer systems was approximately 39,000 AFY for the 30- year sustaining period (Table 2-15).

Reduction Without Projects Scenario 1 Model Results
The fluxes in the UAS and LAS in the Reduction Without Projects Scenario 1 were similar to those simulated in the Reduction With Projects Scenario (Figures 2-68a through 2-68e, UWCD Model

11 Modeled extraction rates depend on climate, surface water availability, and simulated groundwater elevations for each model year. The reductions implemented reflect a reduction in overall water demand for the Oxnard Subbasin and are not the exact percentage specified for any given year. Therefore, the extraction rate from the UAS in 2040 is 32% of the extraction rate in 2020 rather than the 25% specified in the model scenario description. 937
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Particle Tracks, Reduction Without Projects Scenario (1) Simulation). There was an average flux of groundwater out of the UAS into the Pacific Ocean of approximately 2,800 AFY during the sustaining period in the Reduction Without Projects Scenario 1. In the LAS, the Reduction Without Projects Scenario 1 resulted in an average flux of approximately 1,300 AFY of seawater into the LAS during the sustaining period. Particle tracks for this scenario indicate that the 2015 saline water impact front would likely migrate toward the Pacific Ocean in the UAS as freshwater diluted saline concentrations in the UAS, while it would migrate farther landward in the LAS than in the Reduction With Projects Scenario (Figures 2-68a through 2-68e). As in the Reduction With Projects Scenario, the continued landward migration of the saline water impact front in the LAS suggests that groundwater production in the LAS may need to be reduced further than it was in the Reduction Without Projects Scenario 1, while at the same time the groundwater production rate in the UAS was likely lower than it needed to be, as groundwater left the aquifers of the UAS and entered the Pacific Ocean.

2.4.5.5 Reduction Without Projects Scenario 2
Reduction Without Projects Scenario 2 Model Assumptions The Reduction Without Projects Scenario 2 included all of the assumptions incorporated into the Future Baseline simulation but did not include the projects that were incorporated into the Future Baseline With Projects and Reduction With Projects Scenarios. In the Oxnard Subbasin, the Reduction Without Projects Scenario 2 also included a 55% reduction of 2015–2017 average production rates for the UAS and LAS. The 2015–2017 average pumping rate was reduced by 20% in the UAS and LAS in the PVB, and 20% in the LAS in the WLPMA. Groundwater production rates were reduced linearly over the implementation period and held constant during the sustaining period.

In the Oxnard Subbasin UAS, the simulated groundwater production rate in model year 2020 was 40,000 AFY. The production rate in model year 2040 at the beginning of the sustaining period was 17,600 AFY.
12 The average production from the UAS for the sustaining period was 17,600 AFY.

In the LAS, the simulated groundwater production rate in model year 2020 was 33,100 AFY and the simulated groundwater production rate in model year 2040 was 12,800 AFY. The average production rate from the LAS for the sustaining period was 11,500 AFY. The resulting average combined extraction rate from the two aquifer systems was approximately 29,000 AFY for the 30- year sustaining period (Table 2-15).

12 Modeled extraction rates depend on climate, surface water availability, and simulated groundwater elevations for each model year. The reductions implemented reflect a reduction in overall water demand for the Oxnard Subbasin and are not the exact percentage specified for any given year. Therefore, the extraction rate from the UAS in 2040 is 56% of the extraction rate in 2020 rather than the 55% specified in the model scenario description. 938
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Model results indicate that under this scenario the groundwater flux in the LAS between the PVB and the Oxnard Subbasin is mostly reversed from the above scenarios from model year 2027 to 2055. The groundwater flow during this period (2027 to 2055) in the LAS is from the Oxnard Subbasin to the PVB. This increased the seawater intrusion in the LAS in the Oxnard Subbasin, exacerbating Oxnard Subbasin’s seawater intrusion problem.

Reduction Without Projects Scenario 2 Model Results
There was an average flux of groundwater out of the UAS into the Pacific Ocean of approximately 4,700 AFY during the sustaining period in the Reduction Without Projects Scenario 2 and an average flux of approximately 900 AFY of seawater into the LAS. As in the Reduction Without Projects Scenario 1, the continued inflow of seawater into the LAS suggests that groundwater production in the LAS may need to be reduced further than it was in the Reduction Without Projects Scenario 2, while at the same time the groundwater production rate in the UAS was likely lower than it needed to be, as groundwater left the aquifers of the UAS and entered the Pacific Ocean.

2.4.5.6 Reduction Without Projects Scenario 3
Reduction Without Projects Scenario 3 Model Assumptions The Reduction Without Projects Scenario 3 included all of the assumptions incorporated into the Future Baseline simulation but did not include the projects that were incorporated into the Future Baseline With Projects and Reduction With Projects Scenarios. In the Oxnard Subbasin, the Reduction Without Projects Scenario 3 also included a 55% reduction of 2015–2017 average production rates for the UAS and LAS. The 2015–2017 average pumping rate was not reduced in the UAS and LAS in the PVB or in the LAS in the WLPMA. Groundwater production rates were reduced in the Oxnard Subbasin linearly over the implementation period and held constant during the sustaining period.

In the Oxnard Subbasin UAS, the simulated groundwater production rate in model year 2020, at the beginning of the implementation period, was 40,000 AFY. The production rate in model year 2040 at the beginning of the sustaining period was 18,100 AFY. The average production from the UAS for the sustaining period was 18,100 AFY. In the LAS, the simulated groundwater production rate in model year 2020 was 33,200 AFY and the simulated groundwater production rate in model year 2040 was 13,700 AFY. The average production rate from the LAS for the sustaining period was 12,300 AFY. The resulting average combined extraction rate from the two aquifer systems was approximately 30,000 AFY for the 30-year sustaining period (Table 2-15). 939
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Reduction Without Projects Scenario 3 Model Results
There was an average flux of groundwater out of the UAS into the Pacific Ocean of approximately 3,700 AFY during the sustaining period in the Reduction Without Projects Scenario 3 and an average flux of approximately 1,400 AFY of seawater into the LAS. As in the Reduction Without Projects Scenarios 1 and 2, the continued inflow of seawater into the LAS suggests that groundwater production in the LAS may need to be reduced further than it was in the Reduction Without Projects Scenario 3, while at the same time the groundwater production rate in the UAS was likely lower than it needed to be, as groundwater left the aquifers of the UAS and entered the Pacific Ocean.

Model results indicate that under this scenario the groundwater flux in the LAS between the PVB and the Oxnard Subbasin is reversed from model year 2027 to the end of the model period (2070).

The groundwater flow during this period (after 2027) in the LAS is from the Oxnard Subbasin to the PVB. This significantly increases the seawater intrusion in the LAS in the Oxnard Subbasin exacerbating Oxnard Subbasin’s seawater intrusion problem.

2.4.5.7 Alternative Climate and Rainfall Patterns
To assess the potential impacts on model predictions from alternate climate-change assumptions and precipitation patterns, two additional simulations were conducted using the Reduction Without Projects Scenario 1. These additional simulations changed the scenario assumptions in two ways.

First, the Reduction Without Projects Scenario 1 was simulated using the DWR 2030 climate-change factor, rather than the more conservative 2070 climate-change factor. This revised scenario is referred to as the Reduction Without Projects Scenario 1a. Second, the Reduction Without Projects Scenario 1a was simulated with the DWR 2030 climate-change factor applied to the historical precipitation and hydrology period from 1940 to 1989, rather than the original period from 1930 to 1979. This revised scenario is referred to as the Reduction Without Projects Scenario 1b.

The 50-year periods from 1930 to 1979 and 1940 to 1989 were selected because they were the two periods from the entire historical record with the closest mean, or average, precipitation to the mean precipitation for the entire historical record of 14.4 inches. The mean precipitation for the historical period from 1930 to 1979 is also 14.4 inches and the mean precipitation from the historical period from 1940 to 1989 is 14.6 inches. These periods also have a similar distribution of precipitation years to the historical record and a similar average drought length to the average drought length in the historical record. The primary difference between the two periods is the timing of the dry periods in the records. The period from 1930 to 1979 begins with a 7-year dry period from 1930 to 1936 (model years 2020–2026), while the period from 1940-1989 begins with a 5-year wetter than average period (model years 2020–2024). The differences between these scenarios are discussed below.
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Reduction Without Projects Scenario 1a
The Reduction Without Projects Scenario 1a had approximately 2,200 AFY of freshwater flowing out of the UAS to the Pacific Ocean and 1,500 AFY of seawater intrusion into the LAS during the sustaining period. Compared to the Reduction Without Projects Scenario 1, there was approximately 600 AFY less flow out of the UAS and approximately 200 AFY more flow into the LAS from the Pacific Ocean (Figure 2-63). This is the result of lower water levels in the UAS and LAS under this scenario than the Reduction Without Projects Scenario 1. The 2030 climate-change factor showed lower potential water levels and more seawater intrusion than the 2070 climate-change factor; however, the difference between the simulated fluxes in the two scenarios is within the uncertainty of the model predictions and is not significant compared to other uncertainties in the future simulations, including the actual precipitation pattern that will prevail over the period from 2020 to 2069.

Reduction Without Projects Scenario 1b
The Reduction Without Projects Scenario 1b had approximately 4,300 AFY of freshwater flowing out of the UAS to the Pacific Ocean and 760 AFY of seawater intrusion into the LAS during the sustaining period. Compared to the Reduction Without Projects Scenario 1a, the Reduction Without Projects Scenario 1b had 2,100 AFY more freshwater leaving the UAS and 800 AFY less seawater intrusion in the LAS during the sustaining period (Figure 2-63). The reduced seawater intrusion and increased freshwater outflow are the result of higher simulated groundwater levels during the sustaining period than in the Reduction Without Projects Scenario 1a. The groundwater elevations in the Reduction Without Projects Scenario 1b rise faster in response to the wetter than average precipitation pattern that occurs at the beginning of the model period (model years 2020–2024) and remain higher during the sustaining period (model years 2040–2069) than they do in the Reduction Without Projects Scenario 1a. The differences in seawater intrusion and water levels between the Reduction Without Projects Scenarios 1a and 1b show that the model is more sensitive to actual precipitation patterns than it is to the predicted relative changes in climate between 2030 and 2070. The actual climate and precipitation patterns over the next 5 years should be used to revise the model simulations and refine the estimated potential for net seawater intrusion during the sustaining period.

2.4.5.8 Uncertainty Analysis
A review of the UWCD model was conducted to provide an independent evaluation of the model for use in the context of developing a GSP and to quantify the uncertainty associated with the modeling estimates of the sustainable yield for the basinsin the model domain (Appendix E). UWCD conducted a local sensitivity analysis of its model prior to this review, in order to evaluate how the model input parameters obtained via the model calibration affect the model outputs. The peer review conducted an additional global sensitivity analysis that keys off of their local sensitivity analysis, and allows for a quantitative assessment of uncertainty in seawater flux and sustainable yield. 941
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General Results
Results of the model scenarios discussed above indicate that changes to groundwater production rates or to extraction locations for the Oxnard Subbasin are needed to avoid seawater intrusion in the LAS during the sustaining period. Understanding the uncertainties in the model predictions underscores the desirability of making gradual changes in production rates while additional monitoring and studies help to reduce these uncertainties.

The largest potential sources of uncertainty in the model were found to be hydraulic properties, for a given precipitation pattern. As discussed in Section 2.4.5.7, Alternative Climate and Rainfall Patterns, precipitation and surface water availability are a critical input parameter for predictive simulations. Critical areas of hydraulic properties were constrained in the historical simulations by aquifer testing. In particular, the model parameters that accounted for the most variance (approximately 37% of total variance) in minimizing error between observed groundwater levels and model simulated heads throughout the model were the horizontal hydraulic conductivities assigned to the Oxnard and Mugu Aquifers in the Forebay. The values assigned in the model were consistent with horizontal hydraulic conductivities determined from aquifer testing in that area. The fact that the most sensitive parameter assignments were well constrained by observations reduces uncertainty and provides good confidence in model predictions of groundwater levels overall.

Additionally and importantly, these same zones of horizontal hydraulic conductivity accounted for approximately 24% of total variance in model calculations of seawater flux across the ocean boundary. In contrast, the conductance of the ocean general head boundaries only accounted for approximately 3% of the variance in seawater flux. This indicates that the movement of artificially recharged groundwater from the Forebay to the coast is key in seawater flux. Additionally, the amount of Forebay recharge that enters the WLPMA rather than moving toward the coast was found to affect the seawater flux more than the conductance of the general head boundaries representing the ocean outcrops at the model boundary.

Stream infiltration, a parameter that was estimated based on the correlation between predicted and observed water levels accounted for approximately 5% of the variance in seawater flux and horizontal and vertical hydraulic conductivity of the aquitard separating Layer 5 (Mugu Aquifer) from Layer 7 (the Hueneme Aquifer) in the PVB accounted for approximately 3% of the variance in seawater flux. This sensitivity is associated with the flux across the basin boundary and flow between the UAS and the LAS. Again, these parameters in the PVB accounted for more seawater flux than that accounted for by the conductance of the aquifer outcrops beneath the ocean.

Quantifying Uncertainty
The uncertainty associated with model simulations of seawater flux was calculated by determining the relationship between simulated groundwater levels in wells near the coast and simulated seawater 942
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flux at the ocean boundary for the six model scenarios described in Section 2.4.5. This relationship was established by calculating the mean errors between observed and simulated groundwater levels at the coastal wells and applying the relationship between simulated groundwater levels and seawater flux to determine what the flux would have been had the model exactly reproduced observed groundwater levels. This analysis was conducted for both the entire model period from 2020 to 2069 and the sustaining period from 2040 to 2060. In general the analysis indicated that there is approximately 2,000 AFY uncertainty due to model error in simulated total seawater flux, though this varies depending on which time frame is analyzed. Alternatively, using calculated seawater flux from 121 realizations in a global sensitivity analysis yielded a comparable result of approximately 3,000 AFY uncertainty in seawater flux. The global sensitivity analysis is discussed in Appendix E.

For the sustaining period, the relationship between seawater flux and pumping gives a confidence interval for the sustainable yield of approximately ± 6,000 AFY for the UAS and ± 3,600 AFY for the LAS. For the entire model period from 2020 to 2069, the relationship between seawater flux and pumping gives a confidence interval for the sustainable yield of approximately ± 4,100 AFY for the UAS and ± 2,300 AFY for the LAS. The relationship between seawater flux and water levels will continue to be refined through data collection and analysis over successive 5-year periods for the GSP evaluations, and these uncertainty estimates are anticipated to contract accordingly.

2.4.5.9 Estimates of Future Sustainable Yield
The sustainable yield for Oxnard Subbasin was assessed by examining the modeled flux of seawater into the Subbasin over the 50-year model period and 30-year sustaining period predicted by the UWCD model for the Subbasin, the PVB, and the WLPMA. The sustaining period was assessed because SGMA recognizes that undesirable results may occur during the 20-year implementation period, as basins move toward sustainable groundwater management. In addition to the flux of seawater, particle tracks from the model runs were analyzed to evaluate the potential migration of the current extent of saline water impact in the UAS and the LAS. The particles were placed along the approximate inland extent of the zone of saline water impact in 2015. Scenarios that minimize the net flux of seawater into the Oxnard Subbasin and the landward migration of the saline water impact front over the 30-year sustaining period are sustainable for Oxnard, while those that allow for net seawater intrusion and landward migration of the saline water impact front are not.

None of the model scenarios described in Section 2.4.5 successfully eliminated seawater intrusion in the LAS during the 50-year model period or the 30-year sustaining period, while the majority of the model scenarios resulted in net freshwater loss from the UAS to the Pacific Ocean.

Therefore, none of the direct model scenarios was used to estimate the sustainable yield of the Oxnard Subbasin. Instead, the relationship between seawater flux and groundwater production from the model scenarios for both the 50-year period and the 30-year period were plotted graphically and the linear relationship between the seawater flux and groundwater production was used to predict the quantity of groundwater production that would result in no net seawater 943
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intrusion over the periods in either the UAS or the LAS. This method is also discussed in Appendix E, Section 2.3.2.2, and the seawater flux and groundwater production plots are provided in Appendix E as Figures 4 and 5. In order to provide separate estimates for the two aquifer systems, independent relationships between groundwater production and seawater intrusion were developed for the UAS and LAS. It was possible to develop relationships for each aquifer within the UAS and LAS, but in general wells in the Oxnard Subbasin are screened in multiple aquifers in each aquifer system. Therefore, for management purposes, the sustainable yield estimates were developed for the aquifer systems rather than for independent aquifers.

The sustainable yield of the UAS was calculated to be approximately 32,000 AFY for both the entire 50-year model period and the 30-year sustaining period. The uncertainty in the estimated sustainable yield for the UAS is lower if only the sustaining period is used. For the entire model period, the uncertainty in the sustainable yield is approximately ± 6,000 AFY, whereas for the sustainable period the uncertainty in the sustainable yield is approximately ± 4,100 AFY.

Consequently, this analysis suggests that the sustainable yield of the UAS may be as high as 38,000 AFY or as low as 26,000 AFY.

The sustainable yield of the LAS was calculated to be approximately 7,000 AFY for both the entire 50-year model period and the 30- year sustaining period. The uncertainty in the estimated sustainable yield for the LAS is lower if the entire model period is used. For the entire model period, the uncertainty in the sustainable yield of the LAS is approximately ± 2,300 AFY, whereas for the sustainable period the uncertainty in the sustainable yield is approximately ± 3,600 AFY. Consequently, this analysis suggests that the sustainable yield of the LAS may be as high as 10,600 AFY or as low as 3,400 AFY.

It is anticipated that the analysis for the 5-year update to the GSP will focus on differential extractions on the coast and inland, particularly in the LAS. Additional modeling is recommended for the 5-year update process to understand how changes in pumping patterns can increase the overall sustainable yield of the Oxnard Subbasin. As this understanding improves, projects to support increases in the overall sustainable yield can be developed.

2.5 MANAGEMENT AREAS
In order to sustainably manage the groundwater resources of the Oxnard Subbasin, the Subbasin has been divided into five management areas (Figure 2-69, Oxnard Subbasin Management Areas). These areas are the Forebay Management Area, the West Oxnard Plain Management Area, the Oxnard Pumping Depression Management Area, the Saline Intrusion Management Area, and the East Oxnard Plain Management Area (EOPMA). These areas are separated by hydrogeologic and water quality characteristics.
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The Forebay Management Area is in the northeastern Oxnard Subbasin. In this area of the Subbasin, the semi-perched aquifer and clay cap are absent, resulting in direct communication between the alluvium and the underlying aquifer systems. The majority of surface water recharge to the Oxnard Subbasin occurs within the UWCD spreading grounds located in the Forebay Management Area.

The West Oxnard Plain Management Area lies within the Oxnard Subbasin jurisdictional boundaries. The West Oxnard Plain Management Area, which includes the City of Oxnard, is south and west of the Forebay Management Area.

The Oxnard Pumping Depression Management Area is south and east of the West Oxnard Plain Management Area. The boundaries of the Oxnard Pumping Depression Management Area include are Highway 101 to the north, North Rice Avenue and North Rose Avenue to the west, East Hueneme Road and Highway 1 to the south, and the Bailey Fault and the PVB to the east.

This management area was established based on the low groundwater elevations historically recorded in both the UAS and the LAS in the area.

The Saline Intrusion Management Area lies to the west of the Oxnard Pumping Depression Management Area, and south of the West Oxnard Plain Management Area. The Saline Intrusion Management Area includes both Port Hueneme and Point Mugu, where saline intrusion has occurred historically and has impacted wells in both the UAS and LAS.

The EOPMA lies to the east of the Bailey Fault and is predominantly within the jurisdiction of the County of Ventura. A small area on the northern boundary between the EOPMA and the PVB is covered by the Camrosa Water District–Oxnard Subbasin GSA (see Figure 1-2).The FCGMA jurisdictional boundary extends into the EOPMA along the boundary with the Oxnard Pumping Depression Management Area (Figure 2-69). This management area was established based on groundwater elevation and chloride concentration differences across the Bailey Fault, which acts as a barrier to groundwater flow (Turner 1975; Section 2.2.1).

This GSP has been prepared for the entire Oxnard Subbasin and management areas defined in this GSP will be managed by the FCGMA. The minimum thresholds and measurable objectives developed in Chapter 3 are based on the data available in the Forebay Management Area, the West Oxnard Plain Management Area, the Oxnard Pumping Depression Management Area, and the Saline Water Intrusion Management Area. Comparable historical data on groundwater elevation, storage, production, and quality are not available for the EOPMA. Therefore, the minimum thresholds and measurable objectives for the West Oxnard Plain and Oxnard Pumping Depression Management Areas, which are adjacent to the EOPMA, will be applied to age and/or depth equivalent hydrostratigraphic units in the EOPMA. As additional data are collected in the EOPMA, separate minimum thresholds and management objectives may be developed. If changes to the minimum thresholds and management objectives are warranted, justification will be provided in the 5-year GSP updates.
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2.6 REFERENCES CITED
Bohannon, R.G., and D.G. Howell. 1982. “Kinematic Evolution of the Junction of the San Andreas, Garlock, and Big Pine Faults, California.” Geology 10:358–363. https://doi.org/10.1130/0091-7613(1982)10<358:KEOTJO>2.0.CO.

CCC. 2017. “Ormond Beach Wetlands Restoration Project.” Accessed April 2017. http://scc.ca.gov/2010/01/07/ormond-beach-wetlands-restoration-project/.

CDFW (California Department of Fish & Wildlife). 2016. California Natural Diversity Database (CNDDB), Rarefind, Version 3.1.1 (Commercial Subscription). Sacramento, California:

CDFW, Biogeographic Data Branch. Accessed October 2016.

CGS (California Geological Survey). 2002. Note 36: California Geomorphic Provinces. Revised December 2002.

City of Ventura. 2011. City of Ventura Special Studies: Estuary Subwatershed Study Assessment of the Physical and Biological Condition of the Santa Clara River Estuary, Ventura County, California. Final Synthesis Report. Prepared by Stillwater Sciences, Berkeley, California for City of Ventura, California. March 2011.

City of Ventura. 2016. Groundwater data collected by Stillwater Sciences in support of City of Ventura Special Studies compiled from Bailard Landfill monitoring program.

County of Ventura. 2016. Shapefile data of oil fields in Ventura County. Oil Fields.shp.

December 22, 2016.

Densmore, J.N. 1996. Lithologic and ground-water data for monitoring wells in the Santa ClaraCalleguas ground-water basin, Ventura County, California, 1989-1995. U.S. Geological Survey Open-File Report 96-120.

DeVecchio, D.E., R.V. Heermance, M. Fuchs, and L.A. Owen. 2012b. “Climate-Controlled Landscape Evolution in the Western Transverse Ranges, California: Insights from Quaternary Geochronology of the Saugus Formation and Strath Terrace Flights.” Lithosphere 4(2): 110–130. https://doi.org/10.1130/L176.1.

DeVecchio, D.E., E.A. Keller, M. Fuchs, and L.A. Owen. 2012a. “Late Pleistocene Structural Evolution of the Camarillo Fold Belt: Implications for Lateral Fault Growth and Seismic Hazard in Southern California.” Lithosphere 4(2): 91–109. https://doi.org/10.1130/L136.1.
946
2 – BASIN SETTING
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 2-78
DeVecchio, D.E., E.A. Keller, L.A. Owen, and M. Fuchs. 2007. “Earthquake Hazard of the Camarillo Fold Belt: An Analysis of the Unstudied Fold Belt in Southern California Hot Zone.” Final. U.S. Geological Survey/National Earthquake Hazards Reduction Program Award Number 07HQGR0040.

De Wiest, R.J.M. 1998. “Ghyben–Herzberg Theory.” In Encyclopedia of Hydrology and Water Resources, edited by R.W. Herschy and R.W. Fairbridge. Encyclopedia of Earth Science series. Dordrecht, Netherlands: Springer. Accessed January 17, 2018. https://link.springer.com/referenceworkentry/10.1007%2F1-4020-4513-1_104.

Dibblee, T.W., Jr. 1992a. “Geologic Map of the Moorpark Quadrangle, Ventura County: Santa Barbara California, Dibblee Geological Foundation” [map]. 1:24,000.

Dibblee, T.W., Jr. 1992b. “Geologic Map of the Simi Quadrangle, Ventura County: Santa Barbara California, Dibblee Geological Foundation” [map]. 1:24,000.

DWR (California Department of Water Resources). 1965. Bulletin No. 63-1: Seawater Intrusion Oxnard Plain of Ventura County. October 1965.

DWR. 1968. Bulletin No. 74-9: Well Water Standards, Ventura County. August 1968.

DWR. 1971. Bulletin No. 63-4: Sea-Water Intrusion: Aquitards in the Coastal Ground Water Basin of Oxnard Plain, Ventura County. September 1971.

DWR. 2006. California’s Groundwater Bulletin 118: Santa Clara River Valley Groundwater Basin, Oxnard Subbasin. Last updated January 20, 2006. Accessed October 2016. http://www.water.ca.gov/pubs/groundwater/bulletin_118/basindescriptions/4-4.02.pdf.

DWR. 2016. Bulletin 118 Interim Update 2016: California’s Groundwater—Working Toward Sustainability. December 22, 2016. www.water.ca.gov/groundwater/bulletin118/index.cfm.

Eberhart-Phillips, D., M. Lisowski, and M.D. Zoback. 1990. “Crustal Strain near the Big Bend of the San Andreas Fault: Analysis of the Los Padres–Tehachapi Trilateration Networks, California.” Journal of Geophysical Research 95(B2): 1139–1153.

ESA (Environmental Science Associates). 2003. McGrath State Beach Natural Resources Management Plan. Prepared for California Department of Parks and Recreation. April 2003.

Farr, T.G., C.E. Jones, and Z. Liu. 2017. “Progress Report: Subsidence in California, March 2015–September 2016.” California Institute of Technology, Jet Propulsion Laboratory.

FCGMA (Fox Canyon Groundwater Management Agency). 1985. Groundwater Management Plan. 947
2 – BASIN SETTING
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 2-79
FCGMA. 2007. 2007 Update to the Fox Canyon Groundwater Management Agency Groundwater Management Plan. Prepared by FCGMA, United Water Conservation District, and Calleguas Municipal Water District. May 2007.

FCGMA. 2013. Water Elevation Maps, 1972–2012, Adopted by the FCGMA Board. Item 7, FCGMA Board Meeting, December 4, 2013.

FCGMA. 2015. Annual Report for Calendar Year 2015. Prepared by FCGMA.

FCGMA. 2016. Basin Management Objectives Report Card.

FCGMA. 2018. “Full Agenda Package: Special Board Meeting of August 29, 2018.” Meeting agenda, minutes, and preliminary project descriptions for GSPs currently in progress.

August 29, 2018.

Feigl, K.L., D.C. Agnew, Y. Bock, D. Dong, A. Donnellan, B.H. Hager, T.A. Herring, and D.D.

Jackson. 1993. “Space Geodetic Measurement of Crustal Deformation in Central and Southern California, 1984–1992.” Journal of Geophysical Research 98(B12): 21677–21712.

GreenInfo Network. 2016. California Protected Areas Data Portal. Accessed August 8, 2017. http://www.calands.org/.

Hadley, D., and H. Kanamori. 1977. “Seismic Structure of the Transverse Ranges, California.” Geological Society of America Bulletin 88:1469–1478.

Hanson, R.T., P. Martin, and K. Koczot. 2003. Simulation of Ground-Water/Surface-Water Flow in the Santa Clara–Calleguas Ground-Water Basin, Ventura County, California. U.S.

Geological Survey Water Resources Investigation Report 2002-4136.

Hopkins (Hopkins Groundwater Consultants Inc.). 2013. Preliminary Hydrogeological Study:

Anterra Energy Services, Inc. Fluid Disposal Wells, Injection Well Construction and Injection Practices Review. Prepared for the City of Oxnard, California. October 2013.

Hopkins, C. 2016. Oxnard Plain and Vicinity Aquifer Properties Data Request. Email from C. Hopkins (Hopkins Groundwater Consultants Inc.) to M. Naftaly (Dudek). October 18, 2016.

Huftile, G.J., and R.S. Yeats. 1995. “Convergence Rates across a Displacement Transfer Zone in Western Transverse Ranges, Ventura Basin, California.” Journal of Geophysical Research 100(B2): 2043–2067.
948
2 – BASIN SETTING
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 2-80
Izbicki, J.A. 1991. “Chloride Sources in a California Coastal Aquifer.” In: American Society of Civil Engineers Symposium on Groundwater in the Pacific Rim. Honolulu, Hawaii, July 22-26, 1991. Proceedings, p. 71-77.

Izbicki, J.A. 1996. “Use of 
18O and D to Define Seawater Intrusion.” In North American Water Congress, Anaheim, California, June 23–28, edited by C.T. Bathala. Proceedings: New York American Society of Civil Engineers.

Izbicki, J.A., A.H. Christensen, M.W. Newhouse, G.A. Smith, and R.T. Hanson. 2005. “Temporal Changes in the Vertical Distribution of Flow and Chloride in Deep Wells.” Groundwater 43(4): 531–544.

Jakes, M.C. 1979. “Surface and Subsurface Geology of the Camarillo and Las Posas Hills Area:

Ventura County, California.” Master’s thesis; Oregon State University.

Kew, W.S. 1924. “Geology and Oil Resources of a Part of Los Angeles and Ventura Counties California.” In United States Geological Survey Bulletin 753.

LARWQCB. 2013. “Chapter 3: Water Quality Objectives.” In Water Quality Control Plan: Los Angeles Region Basin Plan for the Coastal Watersheds of Los Angeles and Ventura Counties.

Updated April 19, 2013. Accessed February 20, 2017. https://www.waterboards.ca.gov/ losangeles/water_issues/programs/basin_plan/electronics_documents/ Final%20Chapter%203%20Text.pdf.

Marshall, S.T., M.L. Cooke, and A.E. Owen. 2008. “Effects of Nonplanar Fault Topology and Mechanical Interaction on Fault-Slip Distributions in the Ventura Basin, California.” Bulletin of the Seismological Society of America 98(3): 1113–1127. https://doi.org/

10.1785/0120070159.

Mukae, M.M., and J.M. Turner. 1975. “Geologic Formations, Structures and History in the Santa Clara–Calleguas Area.” In Compilation of Technical Information Records for the Ventura County Cooperative Investigation: Volume I, 1–28. Prepared by the Ventura County Public Works Agency Flood Control and Drainage Department for the California Department of Water Resources.

Nicholson, C., C.C. Sorlien, T. Atwater, J.C. Crowell, and B.P. Luyendyk. 1994. “Microplate Capture, Rotation of the Western Transverse Ranges, and Initiation of the San Andreas Transform as a Low-Angle Fault System.” Geology 22:491–495.

Rockwell, T.K., E.A. Keller, and G.R. Dembroff. 1988. “Quaternary Rate of Folding of the Ventura Avenue Anticline, Western Transverse Ranges, Southern California.” Geological Society of America Bulletin 100:850–858.
949
2 – BASIN SETTING
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 2-81
SFEI (San Francisco Estuary Institute). 2011. Historical Ecology of the Lower Santa Clara River, Ventura River, and Oxnard Plain: An Analysis of Terrestrial, Riverine, and Coastal Habitats. SFEI Publication No. 641. A report of SFEI’s Historical Ecology Program prepared for the State Coastal Conservancy. Oakland, California: San Francisco Estuary Institute.

SWRCB (State Water Resources Control Board). 1956. Bulletin No. 12: Ventura County Investigation Volume I. October 1953. Revised April 1956.

SWRCB. 2004. Resolution No. 2004-0063: Adoption of the Water Quality Control Policy (Policy) for Developing California’s Clean Water Act Section 303(d) List.

Turner, J.M. 1975. “Aquifer Delineation in the Oxnard–Calleguas Area, Ventura County.” In Compilation of Technical Information Records for the Ventura County Cooperative Investigation: Volume I, 1–45. Prepared by the Ventura County Public Works Agency Flood Control and Drainage Department for the California Department of Water Resources.

Turner, J.M., and M.M. Mukae. 1975. “Effective Base of Fresh Water Reservoir in the Oxnard– Calleguas Area.” In Compilation of Technical Information Records for the Ventura County Cooperative Investigation: Volume I, 1–15. Prepared by the Ventura County Public Works Agency Flood Control and Drainage Department for the California Department of Water Resources.

USDA (U.S. Department of Agriculture). 2019. Web Soil Survey. USDA Natural Resources Conservation Service, Soil Survey Staff. Accessed January 2019. http://websoilsurvey.nrcs.usda.gov/.

USFWS (U.S. Fish and Wildlife Service). 2016a. National Wetlands Inventory. Accessed August 2016. fws.gov/wetlands/NWI/index.html.

USFWS. 2016b. Endangered Species Program, ECOS Joint Development Team. 2016. Critical Habitat Polygons and Lines. https://ecos.fws.gov/ecp/report/table/critical-habitat.html in December 2016.

USGS (U.S. Geological Survey). 1993. A Study of Seawater Intrusion Using Direct-Current Soundings in the Southeastern Part of the Oxnard Plain, California. USGS Open-File Report 93-524. Prepared by A.A.R. Zohdy, P. Martin, and R.J. Bisdorf.

USGS. 1996. Seawater Intrusion in a Coastal California Aquifer. U.S. Geological Survey Fact Sheet 125-96.
950
2 – BASIN SETTING
Groundwater Sustainability Plan for the Oxnard Subbasin 9837 December 2019 2-82
UWCD (United Water Conservation District). 1999. Surface and Groundwater Conditions Report, Water Year 1998. July 1999.

UWCD. 2007. Mugu Seawater/Saline Water Intrusion Monitoring Program: AB303 Grant, Agreement No. 4600004100. Exhibit U41. Prepared by P. Dal Pozzo, D. Detmer, and K.

Turner (UWCD, Groundwater Resources Department). April 2007.

UWCD. 2008. Nitrate Observations in the Oxnard Forebay and Vicinity, 1995–2006. Prepared by D. Detmer. Santa Paula, California: UWCD. July 2008.

UWCD. 2010. Oxnard Plain Time Domain Electromagnetic Study for Saline Intrusion. UWCD Open-File Report 2010-003. Prepared by UWCD, Groundwater Resources Department.

October 2010.

UWCD. 2014. Groundwater and Surface Water Conditions Report – 2013. United Water Conservation District Open-File Report 2014-02. May 2014.

UWCD. 2016a. Saline Intrusion Update, Oxnard Plain and Pleasant Valley Basins. United Water Conservation District Open-File Report 2016-04. October 2016.

UWCD. 2016b. United Water Conservation District Multiple Species Habitat Conservation Plan Study: Effects of Freeman Diversion on Riparian Vegetation in the Santa Clara River.

Prepared by Stillwater Sciences, Berkeley, California for United Water Conservation District, Santa Paula, California.

UWCD. 2016c. “Technical Advisory Group: UWCD Groundwater Model.” Presentation by J. Sun (UWCD) to the Fox Canyon Groundwater Management Agency Technical Advisory Group. December 16, 2016.

UWCD. 2017a. Preliminary Evaluation of Impacts of Potential Groundwater Sustainability Indicators on Future Groundwater Extraction Rates – Oxnard Plain and Pleasant Valley Groundwater Basins. Open-File Report 2017-02. April 2017.

UWCD. 2017b. Addendum to Preliminary Evaluation of Impacts of Potential Groundwater Sustainability Indicators on Future Groundwater Extraction Rates – Oxnard Plain and Pleasant Valley Groundwater Basins. Open-File Report 2017-02a. November 2017.