Carlsbad City Council
September 27, 2022

CA Review _RMC_
Meeting Date:

To:

From:

Staff Contact:

Subject:

Districts:

Sept. 27, 2022
Mayor and City Council/President and Board Members
Scott Chadwick, City Manager/Executive Manager
Vicki Quiram, Utilities Director
[email protected], 442-339-2722
Authorize City and Carlsbad Municipal Water District Support for the Encina Wastewater Authority’s One Water North San Diego County Water Reuse Studies
All
Rec
ommended Actions

1. Receive a report from Encina Wastewater Authority General Manager Scott McClelland on “One Water North San Diego County,” a potable water reuse project being studied by the wastewater authority

2. Adopt resolutions authorizing the City Manager/Executive Manager to sign the principles of understanding document, committing the city and the Carlsbad Municipal Water District to be advocacy agencies of the One Water North San Diego County water reuse project for 2022-23
Executive Summary
In June 2021, Mayor Pro Tem Keith Blackburn requested a presentation by the Encina Wastewater Authority to update the City Council on its developing innovative projects.

With the scarcity of potable water in Southern California, the Encina Wastewater Authority with its member agencies, including the City of Carlsbad, have been studying the potential of reusing the portion of effluent from its wastewater treatment plant that is treated and still discharged to the ocean. This project, called One Water North San Diego County, would further improve the quality of the water through an advanced treatment process so that it could be used for local potable water supply.

Encina Wastewater Authority staff will give the City Council a presentation on the following topics:
• Outcomes of its 2018 Potable Water Reuse Feasibility Study • Update on EWA’s One Water North County water reuse project and pilot study • Upcoming Potable Reuse Strategic Plan
• Information on becoming an advocacy agency for the project Sept. 27, 2022
Item #10 Page 1 of 279

A regional approach to this future potable reuse project represents the best opportunity for success. Encina Wastewater Authority is asking interested agencies to sign a principles of understanding document to become advocacy agencies for the project. This document is intended to establish a framework for the wastewater authority activities through 2022-23 and set expectations for those agencies willing to advocate for the project, and to participate in future project phases.

There are no financial commitments associated with this agreement.

Discussion
Background
The City of Carlsbad provides wastewater collection service to 74% of the city through six interceptor pipelines, 265 miles of collection and conveyance pipelines, 6,000 manholes and 11 lift stations. All wastewater flows to the Encina Water Pollution Control Facility for treatment.

Treated wastewater is disposed through the ocean outfall pipe or sent to the Carlsbad Water Recycling Facility for additional treatment and reuse as recycled water by the Carlsbad Municipal Water District, which provides water and recycled water to approximately 82% of the city.

The Encina Water Pollution Control Facility is governed by a joint powers authority, the Encina Wastewater Authority. The joint powers authority is made up of six north San Diego County public agencies, including the city. (The other member agencies are the cities of Encinitas and Vista, the Buena Sanitation District, Vallecitos Water District and Leucadia Wastewater District.

The authority is governed by a 10-member board consisting of council members or directors from the member agencies. The city holds two seats on the Encina Wastewater Authority Board of Directors, with Mayor Pro Tem Blackburn and Councilmember Acosta currently serving in those roles. Mayor Pro Tem Blackburn also serves on the board’s newly established Water Reuse Executive Steering Committee.

The first phase of CMWD’s recycled water program began in 1994. Today, 22% of the water that the district serves to its customers is recycled water. This water goes through advanced treatment at the Carlsbad Water Recycling Facility and is delivered to customers for irrigation and some light industrial use. CMWD’s water recycling reduces the amount of treated wastewater the Encina Wastewater Authority must discharge to the ocean and offsets the use of potable water in the CMWD service area. The One Water North San Diego County project would have no effect on CMWD’s production or distribution of recycled water.

One Water North San Diego County – water reuse project
With the severity of the current long-term drought and the scarcity of potable water in California, it is more important than ever to not only provide safe and reliable potable water service but also to develop local reliable and renewable water supplies. The wastewater authority and its member agencies have one of the largest untapped local water supplies in the region: the treated wastewater now being discharged into the sea.

The Encina Wastewater Authority not only has access to this water, it has land available for the site of an advanced wastewater treatment facility and staff with the expertise needed to implement and operate one.

Sept. 27, 2022
Item #10 Page 2 of 279

Although there are considerations that need more analysis, this water reuse project could provide a significant local supply of water for Carlsbad and surrounding cities. This resource also has the potential to provide greater local control of the cost of water and may be cost competitive with water imported from elsewhere.

The estimated potable water demand from the currently interested participating agencies in the year 2035 totals 18,500 acre feet1 per year. This demand closely matches the potential supply available from the Encina Wastewater Authority of 20,000 acre feet per year. CMWD estimates that it may use up to 3,500 acre-feet per year in potable reuse local supply water if the project is economically feasible and comes to fruition.

This reuse project would require an even more advanced treatment facility than the Encina Pollution Control Facility and Carlsbad’s Water Recycling Facility. The discussion among the authority and its member agencies became more robust a few years ago when state legislation was introduced that would have required wastewater treatment plants to eliminate all discharges to the ocean. Although the legislation was not successful, similar proposals will likely reappear in the future.

The “One Water North San Diego County” water reuse project was included as a conceptual project in both the Carlsbad Municipal Water District and the San Diego County Water Authority’s 2020 Urban Water Management Plans for a new water supply in 2035. However, because the project is still considered conceptual, the additional water supply amounts are not included in the 2020 plans as future local supply.

I
n April 2018, the first Water Reuse Feasibility Study was presented to the Encina Wastewater Authority Board of Directors (Exhibit 3). The study identified high-l evel options for potable
reuse and recycled water, or non-potable, projects to ensure year-r ound beneficial use of the
effluent from the Encina Water Pollution Control Facility, which is currently discharged through the ocean outfall pipe.

Me
mber agency staff, including City of Carlsbad staff, have continued to work with wastewater authority staff on the potable water reuse concept and have met with potential project partners to discuss high-level concepts. The parties that have currently expressed interest in receiving potable water from such a project are CMWD, Olivenhain Municipal Water District, San Dieguito Water District, Vallecitos Water District and the City of Poway. Others may become interested as more details on the feasibility and cost of the project become available.

Proposed Advocacy Agreement
The Encina Wastewater Authority recently began asking interested agencies to sign a principles of understanding document to become an advocacy agency for the project. The principles of understanding define the role of an advocacy agency as follows:
• Cooperate with Encina Wastewater Authority in refining project concepts and costs • Review and provide feedback on any documentation produced by Encina Wastewater Authority for distribution
• Advocate for the project and solicit additional regional partners, both wholesale and retail

1 An acre foot is the amount of water it takes to submerge one acre of land one foot deep. An average California household uses between one-half and one acre-foot of water per year for indoor and outdoor use.

Sept. 27, 2022
Item #10 Page 3 of 279

• Participate in stakeholder meetings to discuss project concepts, regulatory issues and funding strategies
• Participate in pursuit of funding opportunities
• Engage with regional stakeholders regarding potential institutional arrangements • Consider financial participation in future phases of the project With City Council and CMWD Board approval, the City Manager/CMWD Executive Manager will be authorized to sign the documents on behalf of the city and CMWD.

Strategic planning
On May 5, 2021, the Encina Wastewater Authority Board voted unanimously to move the potable water reuse project into the strategic planning phase, approving the following recommendations:

1. Direct staff to develop the Water Reuse Strategic Plan

2. Direct staff to initiate pilot testing efforts with Trussell Technologies to develop treatment technologies for wastewater so it can be reused

3. Direct staff to continue to advance the One Water North San Diego County project

4. Discuss and take other action as appropriate
The Water Reuse Strategic Plan will include:
• A funding strategy
• Partner outreach and development of the One Water North San Diego County project • A regulatory strategy
• Refined needs and approach to Encina Water Pollution Control Facility improvements

The Water Use Strategic Plan is expected to be complete by 2024.

Options
Staff recommend the City Council and the Board of Directors authorize the city and the CMWD, respectively, to each be a signatory to the principles of understanding document, thereby becoming advocacy agencies of the water reuse project. The city and the CMWD will incur no financial commitments by signing this document.

If the city and the CMWD’s project advocacy for this project is not authorized, regional conversations will continue about the future of water reuse and local supply within the city’s jurisdiction, but the City of Carlsbad and the CMWD will not have as strong a voice in those discussions.

Staff have identified no drawbacks to becoming an advocacy agency.

Fiscal Analysis
No additional appropriations in fiscal year 2022-23 are being requested at this time. Potential future fiscal year impacts will be incorporated into future budgets. Estimated Encina Wastewater Authority costs related to the Water Use Strategic Plan are included in the wastewater rate-setting process, which is based on budgeted wastewater authority amounts.

The wastewater authority costs are allocated and paid for by the city based on a percentage share of ownership, which is approximately 24%.

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Item #10 Page 4 of 279
Next Steps
With City Council and CMWD Board approval, staff will continue to participate in Encina Wastewater Authority’s exploration of the One Water North San Diego County and will support the efforts outlined in the principles of understanding as an advocacy agency. Staff will return to the City Council and the CMWD Board upon completion of the Water Reuse Strategic Plan.

Environmental Evaluation
This action does not constitute a project within the meaning of the California Environmental Quality Act under California Public Resources Code Section 21065. It has no potential to cause either a direct physical change in the environment or a reasonably foreseeable indirect physical change in the environment.

Public Notification
This item was noticed in keeping with the Ralph M. Brown Act and it was available for public viewing and review at least 72 hours before the scheduled meeting date.

Exhibits

1. City Council resolution

2. CMWD Board resolution

3. Water Reuse Feasibility Study
Sept. 27, 2022
Item #10 Page 5 of 279
RESOLUTION NO. 2022-228

A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF CARLSBAD,

CALIFORNIA, AUTHORIZING THE CITY MANAGER TO SIGN THE PRINCIPLES

OF UNDERSTANDING DOCUMENT COMMITTING THE CITY TO BE AN

ADVOCACY AGENCY OF THE ONE WATER NORTH SAN DIEGO COUNTY WATER REUSE PROJECT FOR 2022-2023
WHEREAS, the State of California and the western United States are presently experiencing an unprecedented drought; and
WHEREAS, conservation of current water supplies and minimization of the effects of water supply shortages that are the result of drought are essential to the public health, safety and welfare; and
WHEREAS, support of projects that develop more local renewable water sources further these public health, safety, and welfare interests; and
WHEREAS, the City Council of the City of Carlsbad, California has determined it necessary and in the public interest to cooperate with the Encina Wastewater Authority in refining project concepts and costs for the One Water North San Diego County Project, or Project; and WHEREAS, the City of Carlsbad wishes to be an advocacy agency for the Project as described in the Principles of Understanding for Advocacy Agency.

NOW, THEREFORE, BE IT RESOLVED by the City Council of the City of Carlsbad, California, as follows:

1. That the above recitations are true and correct.

2. That the City of Carlsbad will be a signatory to the Principles of Understanding for Advocate Agency, attached hereto as Attachment A.

3. That the City Manager is authorized to sign the Principles of Understanding for Advocacy Agency on behalf of the City of Carlsbad.

Exhibit 1
Sept. 27, 2022 Item #10 Page 6 of 279
PASSED, APPROVED AND ADOPTED at a Regular Meeting of the City Council of the City of Carlsbad on the 27th day of September, 2022, by the following vote, to wit:

AYES:

NAYS:

ABSENT:

Hall, Blackburn, Bhat-Patel, Acosta, Norby.

None.

None.

MATT HA[L, Mayor
fJvC Af'--'FAVIOLA MEDINA, City Clerk Services Manager
. Y. (SEAL)
Sept. 27, 2022 Item #10 Page 7 of 279

BACKGROUND

ENCINA WASTEWATER AUTHORITY

ONE WATER NORTH SAN DIEGO

PRINCIPLES OF UNDERSTANDING

ADVOCACY AGENCY
March 2022
Attachmen t A
The wastewater flows and facilities at the Encina Water Pollution Control Facility (EWPCF) represents a unique opportunity for large-scale production of purified water. EWPCF is estimated to produce approximately 20,000 acre­ feet per year of purified water for potable reuse in North San Diego County. Key assets available at the EWPCF site to support a potable reuse project include an ocean outfall, available land for advanced treatment facility, treated secondary effluent, and technically capable staff. A regional approach to this future potable reuse project represents the best opportunity for success.

The purpose of this Principles of Understanding is to establish a framework for activities through 2022 - 2023 and set expectations for those agencies that are willing to advocate for the project and would likely desire to participate in future phases of the project.

BENEFITS OF PROJECT
Wastewater Benefits
• Embraces Encina Wastewater Authority (EWA) Core Mission and Values • Reduced ocean discharges
• Position for future treatment requirements (potential avoided costs flow and nutrients) • Consistent with goals and commitments of Climate Change Action Plans Water Supply Benefits
• Increase water supply reliability (locally controlled source) • Addresses sustainability and resiliency objectives of local agencies • Environmental and Political benefits from reduced ocean discharges • Address future water efficiency regulations
• Reduced staffing for Advanced Treatment
• Cost competitive compared with imported water
• Further reduce Metropolitan Water District purchases

ROLE OF ADVOCACY AGENCY
Role of Advocacy Agency during 2022 - 2023
• Cooperate with EWA in refining project concepts and costs • Review and provide input on any documentation produced by EWA for distribution • Advocate for the project and solicit additional regional partners (wholesale and retail) • Participate in stakeholder meetings to discuss project concepts, regulatory, and funding strategies Participate in pursuit of funding opportunities
Engage with regional stakeholders regarding potential institutional arrangements Consider financial participation in future phases of the project Advocate Agency
Scott Chadwick, City Manager, City of Carlsbad
Sept. 27, 2022 ONE WATER NORTH SAN DIEGO
Encina Wastewater Authority (22-14954a)
Date
Item #10 Page 8 of 279
RESOLUTION NO. 1684

A RESOLUTION OF THE BOARD OF DIRECTORS OF THE CARLSBAD

MUNICIPAL WATER DISTRICT, AUTHORIZING THE EXECUTIVE MANAGER TO

SIGN THE PRINCIPLES OF UNDERSTANDING DOCUMENT COMMITTING THE

DISTRICT TO BE AN ADVOCACY AGENCY OF THE ONE WATER NORTH SAN DIEGO COUNTY WATER REUSE PROJECT FOR 2022-2023
WHEREAS, the State of California and the western United States are presently experiencing an unprecedented drought; and
WHEREAS, conservation of current water supplies and minimization of the effects of water supply shortages that are the result of drought are essential to the public health, safety and welfare; and
WHEREAS, support of projects that develop more local renewable water sources further these public health, safety, and welfare interests; and
WHEREAS, the Carlsbad Municipal Water District, or CMWD, Board of Directors have determined it necessary and in the public interest to cooperate with the Encina Wastewater Authority in refining project concepts and costs for the One Water North San Diego County Project, or Project; and
WHEREAS, the CMWD wishes to be an advocacy agency for the Project as described in the Principles of Understanding for Advocacy Agency.

NOW, THEREFORE, BE IT RESOLVED by the Carlsbad Municipal Water District Board of the City of Carlsbad, California, as follows:

1. That the above recitations are true and correct.

2. That the CMWD will be a signatory to the Principles of Understanding for Advocacy Agency, attached hereto as Attachment A.

3. That the Executive Manager is authorized to sign the Principles of Understanding for Advocacy Agency on behalf of the CMWD.

Exhibit 2
Sept. 27, 2022 Item #10 Page 9 of 279
PASSED, APPROVED AND ADOPTED at a Regular Meeting of the Board of Directors of the Carlsbad Municipal Water District on the 27th day of September, 2022, by the following vote, to wit:

AYES:

NAYS:

ABSENT:

Hall, Blackburn, Bhat-Patel, Acosta, Norby.

None.

None.

MATT 1tb{/!(L
k1M/ --fovFAVIOLA MEDINA, City Clerk Services Manager
(SEAL)
Sept. 27, 2022 Item #10 Page 10 of 279

BACKGROUND

ENCINA WASTEWATER AUTHORITY

ONE WATER NORTH SAN DIEGO

PRINCIPLES OF UNDERSTANDING

ADVOCACY AGENCY
March 2022
Attachment A
The wastewater flows and facilities at the Encina Water Pollution Control Facility (EWPCF) represents a unique opportunity for large-scale production of purified water. EWPCF is estimated to produce approximately 20,000 acre­ feet per year of purified water for potable reuse in North San Diego County. Key assets available at the EWPCF site to support a potable reuse project include an ocean outfall, available land for advanced treatment facility, treated secondary effluent, and technically capable staff. A regional approach to this future potable reuse project represents the best opportunity for success.

The purpose of this Principles of Understanding is to establish a framework for activities through 2022 - 2023 and set expectations for those agencies that are willing to advocate for the project and would likely desire to participate in future phases of the project.

BENEFITS OF PROJECT
Wastewater Benefits
• Embraces Encina Wastewater Authority (EWA) Core Mission and Values • Reduced ocean discharges
• Position for future treatment requirements (potential avoided costs flow and nutrients) • Consistent with goals and commitments of Climate Change Action Plans Water Supply Benefits
• Increase water supply reliability (locally controlled source) • Addresses sustainability and resiliency objectives of local agencies • Environmental and Political benefits from reduced ocean discharges • Address future water efficiency regulations
• Reduced staffing for Advanced Treatment
• Cost competitive compared with imported water
• Further reduce Metropolitan Water District purchases

ROLE OF ADVOCACY AGENCY
Role of Advocacy Agency during 2022 - 2023
Cooperate with EWA in refining project concepts and costs Review and provide input on any documentation produced by EWA for distribution Advocate for the project and solicit additional regional partners (wholesale and retail) Participate in stakeholder meetings to discuss project concepts, regulatory, and funding strategies Participate in pursuit of funding opportunities
Engage with regional stakeholders regarding potential institutional arrangements Consider financial participation in future phases of the project ~~'l!ti gency
Scott Chadwick, Executive Manager, Carlsbad Municipal Water District Sept. 27, 2022 ONE WATER NORTH SAN DIEGO
Encina Wastewater Authority (22-14954a)
Date
Item #10 Page 11 of 279
Encina Wastewater Authority

WATER REUSE FEASIBILITY STUDY
Final Report | July 2018
Prepared by Woodard & Curran
In Association with:

Carollo Engineers | Trussell Technologies Inc.

Ken Weinberg Water Resources Consulting, LLC | Michael R. Welch, Ph.D., P.E.

Exhibit 3
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EWA Water Reuse Feasibility Study
Final Report

Prepared by:

In Association with:

Trussell Technologies Inc.

Carollo Engineers Inc.

Ken Weinberg Water Resources Consulting, LLC
Michael R. Welch, Ph.D., P.E.

July 2018
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EWA Water Reuse Feasibility Study
Executive Summary
July 2018
i
Table of Contents
Executive Summary ...................................................................................................................................... 1 ES-1 Introduction .............................................................................................................................. 1 ES-2 Background of Potable Reuse in California (TM 1) ................................................................ 1 ES-3 Stakeholder Involvement Plan (TM 6) ..................................................................................... 2 ES-4 Portfolio of Options (TM 2) ..................................................................................................... 3 ES-5 Preferred Project Identification (TM 3) ................................................................................... 7 ES-6 Project Phasing (TM 4) .......................................................................................................... 10 ES-7 Funding Opportunities (TM 5) ............................................................................................... 14 ES-8 Conclusions and Next Steps ................................................................................................... 15

List of Figures
Figure ES-1: Projected 2040 Monthly Flows and Potential for Potable Reuse ............................................ 3 Figure ES-2: Reuse Opportunities using EWPCF Effluent and Potential Flows .......................................... 4 Figure ES-3: Regional Context for Reuse Project and Potential Receptors of EWPCF Effluent ................. 5 Figure ES-4: Capital Cost Summary for Options F, G, and H ...................................................................... 7 Figure ES-5: Unit Cost Summary for Options F, G, and H .......................................................................... 8 Figure ES-6: Conceptual Pipeline Alignment for Option H ....................................................................... 10 Figure ES-7: Proposed AWTF Treatment Train for RWA ......................................................................... 10 Figure ES-8: EWRFS Project Treatment Facilities Footprint (16 mgd RWA) ........................................... 11 Figure ES-9: Sensitivity of Unit Costs with Increased Water for RWA and Outside Funding1 ................. 13 Figure ES-10: Comparative Cost of Water for Option H and Regionally Available Alternatives ............. 13 Figure ES-11: Implementation Schedule for EWA’s Potable Reuse Project (Phase 1) .............................. 14

List of Tables
Table ES-1: Portfolio of Options Summary .................................................................................................. 6 Table ES-2: Summary of Key Considerations for EWA’s Potable Reuse Options ...................................... 9 Table ES-3: Cost Summary for Option H at 16 mgd .................................................................................. 12 Table ES-4: Funding Program Ranking ...................................................................................................... 15

Attachments
Attachment 1 - TM1: Background of Potable Reuse in California Attachment 2 - TM2: Portfolio of Options
Attachment 3 - TM3: Preferred Project Identification
Attachment 4 - TM4: Phasing of Preferred Project
Attachment 5 - TM5: Funding Opportunities
Attachment 6 - TM6: Stakeholder Involvement Plan

\\wc\shared\Projects\RMC\IRV\0305 - Encina Wastewater Authority\59 - Water Reuse FS\B. Project Work\8. Final Report\EWRFS_ExecSummary_Final.docx

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EWA Water Reuse Feasibility Study
Executive Summary
July 2018
ii
List of Abbreviations
AADF annual average daily flow
AF acre-feet
AFY acre-feet per year
AOP advanced oxidation process
AWT advanced water treatment
AWTF advanced water treatment facility
BAF biologically activated filtration
CEQA California Environmental Quality
Act
CDP Carlsbad Desalination Plant
DDW State Water Resources Control
Board Division of Drinking Water
DPR direct potable reuse
EWA Encina Wastewater Authority
EWPCF Encina Water Pollution Control
Facility
FAT full advanced treatment
gpd gallons per day
gpm gallons per minute
GWA Groundwater augmentation
HGL hydraulic grade line
HP horsepower
IPR indirect potable reuse
IRWM Integrated Regional Water
Management
LF Linear feet
LRP Local Resources Program
LWSIP Local Water Supply Incentive
Program
LWSD Local Water Supply Development
mgd million gallons per day
mg/L milligram per liter
MF microfiltration
MWD Metropolitan Water District
NDN nitrification/denitrification
NPDES National Pollutant Discharge
Elimination System
NPR non-potable reuse
NSDRC North San Diego Reuse Coalition
O3 ozone
O&M operations and maintenance
OMWD Olivenhain Municipal Water District
psi pounds per square inch
RRT response retention time
RO reverse osmosis
ROWD Report of Waste Discharge
RWA raw water augmentation
RWQCB Regional Water Quality Control
Board
SDCWA San Diego County Water Authority
SDWD San Dieguito Water District
SEJPA San Elijo Joint Powers Authority
SFID Santa Fe Irrigation District
SRF State Revolving Fund
SWA surface water augmentation
SWRCB State Water Resources Control
Board
TDWA treated drinking water augmentation
TM technical memorandum
UF ultrafiltration
UV ultraviolet irradiation
VWD Vallecitos Water District
WDR Waste Discharge Requirements
WIIN Water Infrastructure Improvements
for the Nation
WRF Water Reclamation Facility
WRFP Water Recycling Funding Program
WRR water recycling requirements
WTP water treatment plant
WWTP wastewater treatment plant
Sept. 27, 2022
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EWA Water Reuse Feasibility Study
Executive Summary
July 2018 1
Executive Summary
ES-1 Introduction
As required by Encina Wastewater Authority’s (EWA) 2020 Business Plan, this Water Reuse Feasibility Study (Study) identifies a path to maximize benefici al reuse of effluent from the Encina Water Pollution Control Facility (EWPCF)—which by 2040 is projected to reach an average of approximately 31 million gallons per day (mgd). Ultimately, the Study serve s to advance EWA’s mission of resource recovery and contributing to sustaining and enhancing the region’s water resources.

A series of technical and regulatory issues were analyzed, and alternative project concepts were developed during the Study. The analysis is documented in a series of technical memoranda (TM):
• TM 1 – Background of Potable Reuse in California
• TM 2 – Portfolio of Options
• TM 3 – Preferred Project Identification
• TM 4 – Phasing of Preferred Project
• TM 5 – Funding Opportunities
• TM 6 – Stakeholder Involvement Plan
This Executive Summary provides an overview of the water reuse opportunities for EWA, identifies the Preferred Project along with a recommended approach and schedule for implementation that will help EWA chart a path forward. The complete TMs referenced above are attached to this Executive Summary, which together constitute the Study’s final report.

ES-2 Background of Potable Reuse in California (TM 1)
Non-potable reuse (NPR) can be a vital component of a diverse water supply portfolio. In Southern California, non-potable reuse systems often serve to offset imported water by providing recycled water for irrigation demands. This is an important function, particularly in semi -arid San Diego Cou nty where approximately 84 percent of the water supply is imported from hundreds of miles away via the State Water Project and the Colorado River Aqueduct1. However, NPR does have limitations compared to potable water reuse. These include the fact that non -potable water has limited applications due to its quality ; the cost of constructing, operating, and maintaining dedicated "pur ple pipe" infrastructure in parallel with potable water infrastructure; and the limited ability to maximize use given the seasonal nature of irrigation demands.

Indirect Potable Reuse (IPR) is the incorporation of recycled water into the drinking water supply system after storage in an environmental buffer , such as an aquifer or reservoir , and, in some cases, additional treatment steps. The two primary types of IPR are Groundwater Augmentation (GWA) and Surface Water Augmentation (SWA)2. There are currently several State regulations that govern IPR.

The State Water Resources Control Board (SWRCB) Division of Drinking Water (DDW) has specific regulations for Groundwater Replenishment Reuse Projects (GRRPs) included in Title 22. These were last revised in July 2015. There are currently two types of regulated GRRPs: surface application and subsurface application. For surface application, additional treatment can be provided through percolation and dilution of the recycled water with groundwater in the groundwa ter basin. Subsurface application (injection) of

1 Source: SDCWA 2016, http://www.sdcwa.org/san-diego-county-water-sources, Accessed 11/8/16. 2 The terms “surface water augmentation” and “reservoir water augmentation” may be used interchangeably.

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EWA Water Reuse Feasibility Study
Executive Summary
July 2018 2
recycled water directly into the groundwater basin requires full advance d treatment that includes reverse osmosis (RO) and an advanced oxidation process (AOP).

Regulations for SWA were adopted by SWRCB on Ma rch 6, 2018. The new regulations set requirements for the quality of treated recycled water that can be added to a surfac e water reservoir that is used as a source of drinking water. The regulations also specify the percentage of recycled water that can be added and how long it must reside there before being treated again at a surface water treatment facility and provided as drinking water.

DDW is also developing regulations for Direct Potable Reuse (DPR). DPR is differentiated from IPR based on the absence of an environmental buffer. SWRCB defines DPR as the planned introduction of recycled water either directly into a public water system (Treated Drinking Water Augmentation [TDWA]), or into a raw water supply immediately upstream of a water treatment plan t (Raw Water Augmentation [RWA]).

No uniform regulations have been established within the State of California or national ly for DPR.

However, AB 574 requires SWRCB to establish a framework for the regulation of DPR projects by June 1, 2018 and to adopt uniform water recycling criteria for RWA by 2023. SWRCB published a Draft Proposed Framework for Regulating Direct Potable R euse in California in April 2018. The two DPR facilities globally that are currently operating (one in Windhoek, Namibia and the other in Big Spring, Texas) have site-specific permits and treatment requirements set forth by regional regulatory agencies.

The following considerations can facilitate the determination of timing and feasibility of various reuse options for EWA:
• There is significant experience with successful non-potable water reuse projects in North San Diego County, which are expected to expand over the next 10 to 20 years and continue providing a well- recognized valuable resource to the community.
• Final regulations allow fo r confident implementation of IPR projects, supported by decades of successful groundwater recharge project operations in California. • DPR has been determined to be feasible in California by DDW. Regulations related to RWA are expected by 2023 after further research, expert consultation, and public engagement to ensure the regulations protect public health while increasing drinking water supplies. No timeframe has been established for development of regulations related to TDWA. • Nationally, there are several established and very successful IPR projects. Some of these projects have been in operation for over 40 years.

ES-3 Stakeholder Involvement Plan (TM 6)
A stakeholder involvement plan was developed early in the project to identify stakeholder activities to be carried throughout the Study. The plan is presented in TM 6. At this stage, EWA has taken a leadership role by developing this Water Reuse Feasibility Study ; however, EWA’s role for future work will need to be carefully defined. Although EWA would likely b e the producer of recycled wate r, local water purveyors and others will ultimately control the end beneficial use. Developing the roles and responsibilities of EWA in a large -scale beneficial reuse project is critical to the formation of a business case an d structure to implement a project.

The initial outreach activity was directed at EWA Member Agencies through a letter from EWA’s General Manager to each individual Member Agency. The North San Diego Water Reuse Coalition (NSD WRC) was a convenient stakeho lder group to approach next because it was already an established structure that included most of the northern San Diego County retail water agencies. In addition, the City of San Diego and San Diego County Water Authority ( SDCWA) were included due to thei r ownership in some of the facilities being considered in the Reuse Study Options.

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EWA Water Reuse Feasibility Study
Executive Summary
July 2018 3
Several presentations were made to the various stakeholder groups throughout the Study to:
• Obtain feedback from the local water purveyors to develop the best alternatives possible, • Build on work done by NSDWRC,
• Discuss options for cost responsibility assumptions, ownership of facilities , and permit responsibilities, and
• Seek a consensus through group discussion on the initial screening criteria and the highest ranked alternatives.

ES-4 Portfolio of Options (TM 2)
An update of the futu re flow projections to the EWPCF was performed as part of the EWPCF Process Master Plan (EWA 2016). This update was deemed necessary because of the significant drop in wastewater flows during the 2011-2016 drought. This analysis resulted in a range of estimated flows by 2040 between 26 mgd and 31 mgd, revised down from previous projections of 40.5 mgd.

Any new reuse project being considered by EWA must be compatible with other current and planned reuse efforts being undertaken by the EWA Member Agencies. Based on a survey of these agencies, demand of EWPCF effluent for NPR is projected to be as high as 12.5 mgd by 2040, as shown in Figure ES-1. This projection includes 10 mgd to supply the City of Carlsbad’s Water Reclamation Facility (WRF) and 2.5 mgd to supply Leucadia Wastewater District’s Gafner WRF. Assuming reverse osmosis (RO) would be part of the treatment train for all potable reuse projects, approximately 20 mgd is estimated to be available for year-round potable reuse after accounting for projected NPR and RO concentrate losses.

Figure ES-1: Projected 2040 Monthly Flows and Potential for Potable Reuse

TM 2 presents a wide range of opportunities for potable reuse projects within the North San Diego County region. Each potential receptor of EWPCF effluent was categorized by form of reuse —including NPR, GWA, SWA, RWA, and TDWA ( Figure ES-2). The initial estimates of potential potable reuse f lows account for reserving a baseline of 12.5 mgd for NPR by EWA Member Agencies. The existing regional water and wastewater facilities that may be involved in options for reuse are shown in Figure ES-3. 0 5
10 15
20 25
30 35Flow (mgd, average)
Available for
Potable Reuse
EWPCF Effluent
Effluent Available
Year-Round
Projected NPR
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Figure ES-2: Reuse Opportunities using EWPCF Effluent and Potential Flows

Note: Flows denoted with an asterisk (*) require further evaluation (beyond the scope of this Study) to confirm reuse flows.

Based on the various potable reuse opportunities described in TM 2, nine options were identified as EWA’s Portfolio of Options for this Reuse Study, summarized in Table ES-1, by combining opportunities considering peak demand requirements. A qualitative set of criteria was developed to allow for an initial screening of the nine options in EWA’s Portfolio of Options prior to embarking on a more detailed quantitative evaluation to include capital and operating costs. For each criterion, a weighting factor was assigned and scoring levels were selected based on the expected range and relative impact on project feasibility. The nine options were then screened based on the criteria identified. The five criteria consisted of the following:
• Anticipated regulatory and permitting effort;
• Treatment and engineered storage requirements;
• Operational considerations;
• Conveyance infrastructure needed; and,
• Stakeholder input and potential institutional challenges.

Based on the results from the screening evaluation, the following were identified as the three most favorable options that were carried forward for further analysis to determine the preferred project:

1. Option F: San Dieguito Reservoir (SWA) and CDP Product Water (TDWA) (Ranked 3rd)

2. Option G: San Dieguito Reservoir (SWA) and Second Aqueduct (RWA) (Ranked 1st)

3. Option H: Second Aqueduct (RWA) and San Marcos Basin (GWA) (Ranked 2nd) Non-Potable
Reuse
(NPR)
Carlsbad WRF
10 mgd
Gafner WRF

2.5 mgd
Meadowlark
WRF

6.5 mgd
Groundwater
Augmentation
(IPR)
San Dieguito
Basin &
San Elijo Basin
Up to 2 mgd*
San Marcos
Basin
Up to 2 mgd*
Surface Water
Augmentation
(IPR)
Olivenhain &
Hodges
Reservoirs

15.7 mgd
San Dieguito
Reservoir

3.1 mgd
Raw Water
Augmentation
(DPR)
Twin Oaks
WTP

15.7 mgd
Carlsbad
Desalination
Plant

15.7 mgd
Second
Aqueduct
(Raw Water)

15.7 mgd
Treated
Drinking
Water
Augmentation
(DPR)
SDCWA
Carlsbad
Desalination
Plant
(Finished
Water)

11.1 mgd
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Figure ES-3: Regional Context for Reuse Project and Potential Receptors of EWPCF Effluent

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Table ES-1: Portfolio of Options Summary

NPR
Recycled
Water
Ground-
water
Large
Res.

Small
Res.

Source
Water
Treated
Water SE Brine
A Carlsbad Desalination Plant (CDP) Influent 12.5 - - - 11.1 - 0 7.4 11.1 23.6 B CDP Product Water 12.5 - - - - 15.7 0 2.8 15.7 28.2
C Olivenhain Reservoir 12.5 - 15.7 - - - 0 2.8 15.7 28.2 D San Dieguito Reservoir + Olivenhain Reservoir 12.5 2.0 10.6 3.1 - - 0 2.8 15.7 28.2 E San Dieguito Reservoir + CDP Influent 12.5 2.0 - 3.1 7.5 - 0 5.9 12.6 25.1 F San Dieguito Reservoir + CDP Product Water 12.5 2.0 - 3.1 - 10.6 0 2.8 15.7 28.2 G San Dieguito Reservoir + 2nd Aqueduct (Raw) 12.5 2.0 - 3.1 10.6 - 0 2.8 15.7 28.2 H Second Aqueduct (Raw) + San Marcos Basin 12.5 2.0 - - 13.7 - 0 2.8 15.7 28.2 I Twin Oaks WTP Influent + San Marcos Basin 12.5 2.0 - - 13.7 - 0 2.8 15.7 28.2 Option Description DPR
Total
Potable
Reuse
(mgd)
Option
ID
Total
Reuse
(mgd)
IPR
Projected 2040 Peak Production (mgd)
Ocean Disposal
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ES-5 Preferred Project Identification (TM 3)
In TM3, t he three highest ranked project options are evaluated based on unit cost and non -cost factors including potential implications to EWPCF operations, advanced treatment requirements, anticipated timeframe for regulatory acceptance , project implementation timeline, and expected stakeholder support.

The capital costs for the three options are summarized under three main categories and are shown on Figure ES-4:
• EWPCF Treatment Improvements: consisting primarily of primary effluent flow equalization, aeration basin retrofits for nitrifi cation-denitrification, increased secondary clarifier capacity, and addition of tertiary filtration.
• Advanced Water Treatment Facility ( AWTF): development of a new treatment facility on EWA’s South Parcel to provide a level of treatment based on current and/or expected regulations that is protective of human health and can be achieved with available technologies. o Option G for SWA would require an AWTF providing full advanced treatment (FAT) consisting of membrane filtration (MF/UF), reverse osmosis (RO), and an ultraviolet light/advanced oxidation step (UV/ AOP).
o In addition to an AWTF providing FAT, Option H and Option G for RWA would also require ozonation (O ₃) with BAF as pretreatment before U F to provide further pathogen removal and enhanced water quality.
o In addition to an AWTF providing FAT with O3/BAF, Option F for TDWA would require further treatment by a tailored Water Tr eatment Plant (WTP) consisting of an Engineered Storage Buffer (ESB) with chlorination (Cl 2) and a high -flux UF system. This treatment train is anticipated to be required for integration with the potable water system. • Conveyance Concepts: based on a prelim inary hydraulic evaluation, the approximate conveyance pipe sizes, pressure requirements, pumping requirements, and alignment options were determined to convey the advanced treated water from the proposed AWTF to the receptor(s) associated with each option.

Figure ES-4: Capital Cost Summary for Options F, G, and H

$89 $89 $89
$284 $234 $234
$143 $287
$180
$516
$611
$504
$-
$100
$200
$300
$400
$500
$600
$700
Option F
Carlsbad Desal.

TDWA
Option G
San Dieguito SWA
+ RWA
Option H
RWA + San Marcos
GWA
Capital Cost (millions)
Conveyance
AWTF
EWPCF
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The annual O&M costs are summarized for the three options under the following categories:
• Power for treatment (including both the incremental power requirements at the EWPCF and the requirements for the AWTF)
• Power for conveyance (pumping)
• Other O&M costs: this includes equipment rehabilitation/replacement, consumables (across all improved and new facilities), and labor for the AWTF and the conveyance system (pipeline and pump station maintenance)
Unit costs for water produced were developed for each option, including O&M costs plus annualized capital costs, to assist with identification of the preferred project option (see Figure ES-5).

Figure ES-5: Unit Cost Summary for Options F, G, and H

Note: Annualized capital costs assume 100% financing at a 2.0% annual interest rate over a 30-year term.

In evaluating the relative merits of the three options, the following criteria were considered in selecting the preferred option (as summarized in Table ES-2):
• Unit Cost of water
• Likely timeframe for regulatory acceptance and project implementation • Complexity of operations and compliance
• Anticipated stakeholder support
$1,310 $1,540 $1,270
$428
$438
$386
$320
$304
$304
$896
$871
$752
$2,960
$3,160
$2,720
$-
$500
$1,000
$1,500
$2,000
$2,500
$3,000
$3,500
Option F
Carlsbad Desal. TWA
Option G
San Dieguito SWA + RWA
Option H
RWA + San Marcos GWA
Cost of Water ($/af)
Power
(Conveyance)
Power
(Treatment)
Other O&M
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Table ES-2: Summary of Key Considerations for EWA’s Potable Reuse Options Option F: Carlsbad
Desal, TDWA
Option G: San Dieguito
SWA + RWA
Option H: RWA + San
Marcos GWA
Cost of Water
(at 20.5 mgd
influent)
$2,960/af $3,160/af $2,720/af
Time to
Implement 15-20+ years 10-15 years 10+ years
Regulatory
Considerations Timeframe uncertain Expected by 2023 Expected by 2023 Complexity of
Operations &
Compliance
AWTF + ESB +
Blending & Pumping at
CDP
AWTF +
Up to three forms of
potable reuse (reservoir +
groundwater + raw water)
AWTF +
Up to two forms of potable
reuse (raw water +
groundwater)
Key
Stakeholders
SDCWA,
Poseidon

SEJPA, SDWD, SFID,

OMWD, SDCWA
Vallecitos,
SDCWA

Based on the considerations identified in Table ES-2, Option H was selected as the Preferred Project for further refinement under this Study. Relative advantages include lower cost of water than Options F and G, an earlier timeframe for implementation considering the regulatory requirements and coordination required with other key stakeholders, and simpler operations. EWPCF tertiary effluent would undergo advanced water treatment to produce water suitable for RWA. The facilities required for the RWA portion of the Preferred Project would include:
• Upgrades to the EWPCF, including primary effluent flow equalization, conversion of the secondary process to nitrification-denitrification and tertiary filters for the flow directed to the AWTF. • AWTF (FAT with O3 + BAF) that produces up to 16 mgd of advanced treated recycled water • Pump station and conveyance pipeline to the SDCWA Second Aqueduct, Pipeline No. 5.

If, under Option H, Vallecitos Water District (VWD) pursues GWA in the San Marcos groundwater basin (within its service area), additional facilities required include two groundwater injection wells, conveyance pipeline to the injection wells, and two gro undwater extraction wells with wellhead treatment (note that costs for these facilities are included in Figure ES-5 above). Because the GWA project facilities would be downstream of the connection point to the SDCWA Aqueduct (see conceptual alignment in Figure ES-6 below), the water for GWA would be treated to the same standards as for RWA.

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Figure ES-6: Conceptual Pipeline Alignment for Option H

ES-6 Project Phasing (TM 4)
TM 4 presents the approach to phasing the implementation of the Preferred Project. This TM provides the initial recommendations for the secondary improvements and advanced treatment facilities, evaluation of AWTF size and future expansion capability, and a framework implementation plan and schedule.

The recommended phased approach consists of improvements to the EWPCF and construction of a new 16 mgd AWTF for potable reuse, using the treatment train shown in Figure ES-7. This would require a total area of approximately 286,100 ft2 (6.6 acres) for the AWTF alone, in addition to the other facilities shown on Figure ES-8. A future expansion phase could increase the production to 25 mgd depending on flows available, with the AWTF footprint increasing to approximately 8.9 acres. Therefore, it is recommended to reserve adequate space on EWA’s South Parcel to accommodate the expand ed footprint within the 22.9 acres currently available.

Figure ES-7: Proposed AWTF Treatment Train for RWA

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Figure ES-8: EWRFS Project Treatment Facilities Footprint (16 mgd RWA) Sept. 27, 2022
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Excluding the GWA aspec t, the initial phase of the Preferred Project at 16 mgd product water (20.5 mgd influent, minus brine losses) has a capital cost of $481m and annual operations and maintenance cost of $22m. The Preferred Project’s annualized cost over 30 years equates to $2,450/AF, as summarized in Table ES-3.

Table ES-3: Cost Summary for Option H at 16 mgd
Option H: RWA to Second Aqueduct (16 mgd) Cost Notes
EWPCF Secondary Improvements $89,000,000 at 31 mgd flow rate Advanced Treatment (FAT + O3/BAF) $234,400,000 at 20.5 mgd influent rate Conveyance - East $157,000,000 at 20.5 mgd influent rate Total Capital Cost $480,400,000
Annual O&M Costs
Power - Treatment (EWPCF + AWTF) $5,403,000 24/7/365 operations Power - Conveyance $9,864,000 24/7/365 operations
Equipment Rehabilitation/Replace, Consumables $5,537,000 All new facilities (incl. EWCPF) Labor $1,134,000 AWTF + Conveyance
Total Annual O&M Cost $21,938,000
Cost of Water
Annualized Capital Cost $21,450,000 2.0% rate, 30-yr term Total Annual Cost $43,388,000 for first 30 years
Annual Yield 17,800 acre-feet
Unit Cost of Water $2,450 per acre-foot

Unit Cost of Water Sensitivity Analysis
The unit cost of water for Option H were initially developed based on reserving 12.5 mgd year -round for NPR by EWA Member Agencies , assumes there is no outside funding and it includes the VWD GWA project facilities. A sensitivity analysis (Figure ES-9) of the unit costs, excluding the GWA project facilities (i.e., RWA project only), was developed considering the following:
• Amount of water reserved for NPR water reduced to 8.0 mgd (more likely), resulting in an increased RWA project yield of 20 mgd (vs. 16 mgd baseline)
• Inclusion or exclusion of potential funding opportunities, including 20 percent outside funding and production incentives (local rebates) that would reimburse the participating agencies $500 per acre- foot for the first 25 years of operation.

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Figure ES-9: Sensitivity of Unit Costs with Increased Water for RWA and Outside Funding1

Note: Costs shown are based on Option H excluding GWA by VWD.

The anticipated cost of untreated (raw) water purchased from the SDCWA between 2025 and 2045 is shown in comparison with the projected range of costs for Option H on Figure ES-10. The range of costs for Option H as shown are with capital costs inflated at 2.5 percent per year and O&M cost escalated at 1.5 percent annually. As can be seen fro m Figure ES-10, the projected cost of water derived from Option H would match the cost of untreated SDCWA water by 2040 or earlier depending on flow available and level of outside funding.

Figure ES-10: Comparative Cost of Water for Option H and Regionally Available Alternatives

$1,210
$547
$1,140
$451
$375
$375
$368
$368
$304
$304
$279
$279
$554
$554
$552
$552
$2,450
$1,780
$2,340
$1,660
$-
$500
$1,000
$1,500
$2,000
$2,500
$3,000
Option H
16 mgd RWA
Option H
16 mgd RWA
+ Funding
Option H
20 mgd RWA
Option H
20 mgd RWA
+ Funding
Cost of Water ($/af)
Power
(Conveyance)
Power
(Treatment)
Other O&M
Annualized
Capital
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Implementation Schedule
Additional planning, pilot studies, environmental review, public outreach and regulatory coordination are needed to refine the selected Preferred Project c oncept and verify econo mics. In addition, regulations related to RWA are not expected until at least 2023 after further research is completed. By laying out an implementation schedule for the initial phase of the Preferred Project, it was estimated that steady progress toward implementation would require approximately 10 years until the start of project operations (Figure ES-11).

Figure ES-11: Implementation Schedule for EWA’s Potable Reuse Project (Phase 1)

ES-7 Funding Opportunities (TM 5)
TM 5 identifies local, state, and federal funding opportunities for the Project, including funding program objectives, eligibility criteria, cost share requirements, and activities that could be funded based on funding programs that existing today. It is likely that in the future additional funding programs may be available.

Five of the funding programs described in TM 5 were determined to be the most applicable to EWA’s water reuse project and were ranked as shown in Table ES-4.

Planning
EWPCF Improvements
AWTF
Pilot Testing
Pipeline Alignment
Funding
Funding Plan
State
Federal
Regulatory
Strategy
Engineering Report
Permitting
Environmental
CEQA
Design/Construction
EWPCF Improvements
AWTF
Conveyance
Stakeholder/Public Outreach
Stakeholder Outreach
Public Outreach
Start of Project Operations
TASKS 9 105 6 7 841 2 3
YEARS
●
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Table ES-4: Funding Program Ranking
Rank Program Explanation
1 SWRCB Water
Recycling Funding
Program (WRFP)
WRFP planning grant funds are currently available and could support development of a Feasibility Study with up to $75,000 at a 50% match. 2 San Diego Integrated
Regional Water
Management (IRWM)
Program
IRWM funding is a strong option because the competition occurs at the regional scale, where local water agency partners can be an advocate for the EWA Project. Planning activities can be paired with other “shovel-ready” capital projects to secure grant funding (using the capital project costs as match) or phased to allow for work to proceed in stages.
3 USBR Water
Infrastructure
Improvements for the
Nation (WIIN)
Program
WIIN funding could be used to fund planning, design, and/or construction of all potential project components. Construction activities can be phased to pursue construction of different components of the Project in each 2-year funding cycle until the $20 million grant is achieved.
4 SWRCB Clean Water
State Revolving Fund
(SRF) Loan Program
EWA and partnering agencies would likely qualify for low-interest financing through the Clean Water SRF Program, which would cover construction activities up to the full project cost. Extensive application materials are necessary, including completion of CEQA and all permits.
5 MWD Local
Resources Program
(LRP) / SDCWA Local
Water Supply
Incentive Program
(WSIP)
The LRP and LWSIP are likely to become available to SDCWA member agencies again; however, the timeline or availability of funds is uncertain. Further, these funds only apply to the cost of delivered water, so they may only be awarded after all construction and start-up activities are complete.

Several water supply agencies within the region have capitalized on multiple grant and loan programs. In the near-term, pursuit of the SWRCB’s Water Recycling Funding Program and the San Diego Integrated Regional Water Management Program grants coul d provide funding for further planning activities. In the long-term, the Federal Water Infrastructure Improvements for the Nation, State Revolving Fund Program, and MWD’s Local Resource Program / SDCWA’s Local Water Supply Development funding should be pursued if available. To increase the chances of receiving funding for any future phases of EWA’s water reuse p roject, it is recommended that EWA and any partnering agencies pursue all funding options available.

ES-8 Conclusions and Next Steps
EWA’s wastewater flows and facilities represent a unique opportunity and a centralized location for large- scale production of recycled water that could capture economies of scale to the benefit of the region. EWA’s experience in water treatment and water quality may well m ake it suitable to take on the responsibility for the AWTF required for potable reuse. The presence and avai lable capacity of a deep ocean outfall is conducive to siting the AWTF near the EWPCF for disposal of reject streams.

Demand for non -potable reuse i n the region is not projected to be sufficient to fully utilize the available effluent at the EWCPF, especially considering the seasonal nature of irrigation demands. Therefore, potable reuse would be necessary to minimize discharges of EWPCF effluent to t he Pacific Ocean. Although the cost of water estimated for EWA’s RWA option is higher than current SDCWA untreated water rates (like other recycled water projects being implemented in the region), SDCWA’s costs are projected to rise over Sept. 27, 2022
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time and EWA’s RWA project may become cost-competitive by the time it could begin delivering water in the mid to late 2020s.

Because the production of a new water supply by EWA is not required to comply with its NPDES permit or any other state or federal requirement, the co st of the RWA option beyond wastewater treatment and disposal would be the responsibility of water purveyors . As such, future planning and implementation activities should be pursued on a cost share basis with participating local and regional water supplie rs.

However, it should be noted that the draft Amendment to the Recycled Water Policy released by the SWRCB on May 9, 2018 identified the following:
• Goal: Increase the use of recycled water from 714,000 afy in 2015 to 1.5 million afy by 2020 and to 2.5 million by 2030.
• Goal: Minimize the direct discharge of treated municipal wastewater to […] ocean waters, excep t where necessary to maintain beneficial uses. Under this goal, treated municipal wastewater does not include brine discharges from recycled water facilities or desalination facilities. • The State Water Board will evaluate progress toward these goals and re vise the goals or establish mandates as necessary.

As reflected by the RWA project Implementation Schedule (Figure ES-11), the activities identified during the initial phases of the project are focused on:
• Identifying the potential impacts on the EWPCF.
• Refining the design criteria for the AWTF and pilot testing. • Strategizing the approach to defining the regulatory requirements for RWA. • Developing a funding plan to maximize the opportunities for outside funding. • Determining a likely corridor for the conveyance pipeline to the SDCWA raw water pipeline.

If EWA’s Board of Directors authorizes staff to continue planning and permit ting activities beyond th is Study, future stakeholder outreach should focus on developing a formal partnership with the water purveyor(s) that would use the purified raw water produced from EWPCF effluent. The cost of the initial activities identified in the implementation schedule could be shared by local and regional water purveyors interested in continuing to refine the costs and partnering on the project.

Defining EWA’s role after the Feasibility Study will be key to any implementation plan of wider reu se of EWA’s valuable wate r resources. EWA should invite continued discussions with its potential partners (retail water agencies), and the next steps could also involve significant policy and financial deliberations by its Board and Member Agencies.

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Attachment 1 - TM1: Background of Potable Reuse in
California

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July 2018 1

Technical Memorandum No. 1
EWA Water Reuse Feasibility Study
Subject: Background of Potable Reuse in California
Prepared for: Encina Wastewater Authority
Prepared by: Andrea F. Corral, Ph.D., Andrew Salveson, P.E. | Carollo Engineers Nathan Chase, P.E. | Woodard & Curran
Bryan Trussell, P.E. | Trussell Technologies, Inc.

Reviewed by: Eva Steinle-Darling, Ph.D., P.E. | Carollo Engineers Scott Goldman, P.E. | Woodard & Curran
Shane Trussell, Ph.D., P.E. | Trussell Technologies, Inc.

Date: July 2018 (Draft issued: November 2016)

Table of Contents
1 Introduction ........................................................................................................................................... 3

1.1 Feasibility Study Background ....................................................................................................... 3

1.2 Objectives ..................................................................................................................................... 3 2 Water Reuse Regulatory Setting ........................................................................................................... 4

2.1 Non-Potable Reuse ........................................................................................................................ 4

2.2 Indirect Potable Reuse .................................................................................................................. 5

2.3 Direct Potable Reuse ..................................................................................................................... 8 3 Non-Potable Water Reuse in North San Diego County ...................................................................... 14

3.1 Carlsbad Water Reclamation Facility ......................................................................................... 14

3.2 Leucadia Wastewater District Gafner Water Reclamation Facility ............................................ 14

3.3 Vallecitos Water District Meadowlark Water Reclamation Facility .......................................... 14

3.4 San Elijo Water Reclamation Facility ......................................................................................... 15 4 Potable Water Reuse Case Studies ...................................................................................................... 16

4.1 Existing Indirect Potable Water Reuse in California .................................................................. 18

4.2 Planned Direct Potable Water Reuse Projects in California ....................................................... 20

4.3 Existing Potable Reuse Projects Outside of California ............................................................... 22 5 Conclusions ......................................................................................................................................... 25 6 References ........................................................................................................................................... 25

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TM1: Background of Potable Reuse in California
July 2018 2
List of Figures
Figure 2-1: SWA Project Schematic Process Flow Diagram ........................................................................ 6 Figure 2-2: Small Reservoir DPR ............................................................................................................... 11 Figure 2-3: RWA ........................................................................................................................................ 11 Figure 2-4: TDWA (“Flange-to-Flange” DPR) .......................................................................................... 11 Figure 2-5: DPR Treatment Train Example without RO ............................................................................ 12 Figure 4-1: Existing and Planned Potable Reuse Projects in California ..................................................... 17 Figure 4-2: GWRS RO Membranes ............................................................................................................ 18 Figure 4-3: Rio Hondo Spreading Grounds, located off-channel ............................................................... 18 Figure 4-4: City of Los Angeles Terminal Island AWPF RO Train ........................................................... 19 Figure 4-5: San Diego Pure Water Demonstration Facility ........................................................................ 20 Figure 4-6: City of Ventura DPR Demonstration Facility .......................................................................... 21 Figure 4-7: Lake Lanier, Georgia ............................................................................................................... 22 Figure 4-8: Colorado River Municipal Water District’s Raw Water Production Facility .......................... 23 Figure 4-9: CEC Comparison between DPR Product Water and Existing Source (Moss Creek Lake) ..... 23 Figure 4-10: Potable Reuse Safety Demonstration Using Understandable Methods (Beer) ...................... 24

List of Tables
Table 2-1: California Recycled Water Classifications .................................................................................. 4 Table 2-2: Criteria for Potable Reuse via Groundwater Augmentation ........................................................ 5 Table 2-3: SWA Pathogenic Microorganism Control ................................................................................... 7 Table 3-1: Recycled Water Projections ...................................................................................................... 14 Table 4-1: Operational Potable Reuse Projects in California (as of 2016) ................................................. 16

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EWA Water Reuse Feasibility Study
TM1: Background of Potable Reuse in California
July 2018 3
1 Introduction

1.1 Feasibility Study Background
As required by the Encina Wastewater Authority (EWA) 2020 Business Plan, this Water Reuse Feasibility Study (Study) identifies a path to maximize beneficial reuse of effluent from the Encina Water Pollution Control Facility (EWPCF)—which by 2040 is projected to r each an average of approximately 31 million gallons per day (mgd).

Within the context of potable reuse in California, the Study’s focus was on developing of a broad portfolio of options for reuse projects using EWPCF effluent ; screening the portfolio down to a short list for feasibility evaluation and conceptual cost analysis ; identifying a preferred reuse project and phasing approach for implementation; determining applicability and timing of potential funding opportunities; preparing a stakeholder involv ement plan; and coordinat ing with EWA ’s Member Agencies and other stakeholders to engage with the Study development and recommendations. Ultimately, the Study is intended to serve to advance EWA’s mission of resource recovery and contribut e to sustaining a nd enhancing the region’s water environment.

1.2 Objectives
The purpose of this Technical Memorandum (TM) is to present a brief background on non-potable water reuse and potable water reuse in California , review select potable water reuse projects nationally, and provide regional context for the portfolio of water reuse options to be developed in this Study. The TM is organized as summarized below:
• Water Reuse Regulatory Setting: For each form of water reuse, this section provides a summary of the regulatory status in California.
• Non-Potable Water Reuse in North San Diego County: this section presents a summary of recycled water facilities operating in the region and their plans for expansion, with particular focus on the facilities that currently utilize EWPCF effluent. • Potable Water Reuse Case Studies: a summary of indirect potable reuse (IPR) and direct potable reuse (DPR) projects in California and elsewhere that are in operation or advanced planning stages—where possible, focusing on projects in the region that may be most relevant to EWA. • Conclusions: the final section presents conclusions regarding the feasibility of the various forms of water reuse, along with a discussion of challenges and lessons learned from other successful water reuse projects that can be applied to EWA’s Study.

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2 Water Reuse Regulatory Setting

2.1 Non-Potable Reuse
Non-potable reuse (NPR) can be a vital component of a diverse water supply portfolio. In Southern California, non-potable reuse systems often serve to offset imported water by providing recycled water for irrigation demands. This is an important function, particularly in semi -arid San Diego County where approximately 84 percent of the water supply is imported from hundreds of miles away via the State Water Project and the Colorado River Aqueduct1. However, NPR does have limitations compared to potable water reuse. These include the fact that non -potable water has limited applications due to its quality; the cost of constructing, operating, and maintaining dedicated "purple pipe" infrastructure in parallel with potable water infrastructure; and the limited ability to maximize use given the seasonal nature of irrigation demands.

In California, Title 22 Code of Regulations related to recycled water establishes the treatment requirements for recycled water and the approved uses based on the level of treatment. Title 22 defines four classifications of recycled water , which are determined by the level of treatment process , virus removal achieved, total coliform (TC) bacteria, and turbidity levels. The four classifications of non-potable recycled water that are currently permitted by the State Water Resources Control Board (SWRCB) Division of Drinking Water (DDW) under Title 22 §60304 are summarized in Table 1 (SWRCB DDW, 2015).

Table 2-1: California Recycled Water Classifications
Treatment Level Approved Uses
Total Coliform
(TC) Standard
(median)
Disinfected Tertiary
Recycled Water
Spray Irrigation of Food Crops
Landscape Irrigation(1)
Non-restricted Recreational Impoundment

2.2 MPN/100 mL(4)
Disinfected Secondary-2.2
Recycled Water
Surface Irrigation of Food Crops
Restricted Recreational Impoundment 2.2 MPN/100 mL
Disinfected Secondary-23
Recycled Water
Pasture for Milking Animals
Landscape Irrigation(2)
Landscape Impoundment
23 MPN/100 mL
Undisinfected Secondary
Recycled Water
Surface Irrigation of Orchards and Vineyards(3)
Fodder and Fiber Crops and Pasture for non-
Milking Animals
N/A
Footnotes:
(1) Includes unrestricted access golf courses, parks, playgrounds, school yards, and other landscaped areas with similar access. (2) Includes restricted access golf courses, cemeteries, freeway landscapes, and landscapes with similar public access restrictions. (3) No fruit is harvested that has come in contact with irrigation water or the ground. (4) In addition to the TC requirements, disinfected tertiary recycled water must also meet the following criteria:
a. Filtered such that this water does not exceed: an average of 2 NTU within a 24-hour period; 5 NTU more than 5 percent of the time within a 24-hour period; and 10 NTU at any time (Title 22 §60301.320). b. Disinfected by one of the two following methods:
• Chlorine disinfection with a minimum product of chlorine residual (C) and contact time (t), or Ct, of 450 mg-min/L with a modal contact time of at least 90 minutes, or • An alternative disinfection process, that, when combined with the filtration process, has been demonstrated to inactivate and/or remove 5-log virus (Title 22 §60301.230).

1 Source: SDCWA 2016, http://www.sdcwa.org/san-diego-county-water-sources, Accessed 11/8/16.

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2.2 Indirect Potable Reuse
Indirect Potable Reuse (IPR ) is the incorporation of tertiary or advanced treated recycled water into the water supply system after storage in an envi ronmental buffer such as an aquifer or a reservoir. There are currently several State regulations that govern the use of IPR, as described in the following sections.

2.2.1 Groundwater Augmentation
DDW has promulgated regulations for Groundwater Replenishment Re use Projects (GRRPs) in Title 22 , which were last revised in July 2015 . There are currently two types of regulated GRRPs: surface and subsurface application. General requirements for groundwater augmentation (GWA) are listed in Table 2.

Table 2-2: Criteria for Potable Reuse via Groundwater Augmentation Selected Parameters Criteria
Pathogenic Microorganisms
Enteric virus 12-log reduction
Giardia cyst 10-log reduction
Cryptosporidium oocyst 10-log reduction
Chemicals
Total Organic Carbon (TOC) Maximum 0.25 mg/L in 95% of samples within first 20 weeks Maximum 0.5 mg/L in 20-week running average
1,4-Dioxane 0.5-log reduction in the advanced oxidation process (2) Total Nitrogen (TN) 10 mg/L maximum
Notes:
(1) Log reductions are from the point of raw wastewater to the point of finished water for drinking. (2) Requirement for 1,4-dioxane removal applies to subsurface application (i.e., injection) projects only.

Surface Application (Spreading)
For surface application, additional treatment is provided through percolation and dilution of the recycled water with groundwater in the groundwater basin. Surface spreading projects can use tertiary recycled water if treatment through the soil (“soil aquifer treatment”) is shown to be sufficient. Regulations establish that surface application projects can use up to 20 percent of recycled water initially and 80 percent of other acceptable dilution water, as long as the specific recycled water contribution of TOC in the blended water is below the values listed in Table 2. Per the regulations, "acceptable dilution water" is a water that meets drinking water standards. If only tertiary water is used, the recharge water should remain in the groundwater basin for a m inimum of six months to meet the retention time target based on tracer tests or conservative hydraulic modeling.

Subsurface Application (Injection)
Subsurface application (injection) of recycled water directly into the groundwater basin requires full advanced treatment that includes reverse osmosis (RO) and an advanced oxidation process (AOP). Under these conditions, no dilution water is required. Additionally, a minimum of two months of subsurface travel time is required before extraction for potable use. These two months provides "Response Retention Time" (RRT), which provides time to monitor water quality and respond to water quality concerns.

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AOP systems, including the City of Los Angeles' new (12 mgd) ultraviolet light (UV) AOP that uses sodium hypochlorite (NaOCl) instead of hydrogen peroxide (H2O2) as the oxidant.

2.2.2 Surface Water Augmentation
State Bill 918 require d DDW to develop and promulgate regulations for surface water augmentation (SWA), which were adopted on March 6, 2018. SWA projects are similar to GRRPs in that they also u se an environmental buffer in between treatment and distribution ; however, for SWA, the buffer is provided by a reservoir ahead of an existing surface water treatment plant. The following discussion is based on early drafts of the regulations (released in 2015) made available as a result of the dialogue between the Expert Panel and DDW. Key elements of the SWA regulations include pathogen and chemical control at the advanced water treatment facility (AWTF) and retention time and dilution requirements in the reservoir.

Figure 2-1: SWA Project Schematic Process Flow Diagram

The following are key requirements for SWA:

1. Advanced Treatment - The SWA regulations require full advanced treatment of the recycled water prior to delivery to the surface water reservoir. An advanced treatment train for SWA must include reverse osmosis (RO) and oxidation that achieves at least 0.5-log reduction of 1,4-dioxane.

2. Dilution Requirement - The SWA regulations stipulate dilution requirements for recycled water discharged into the reservoir. The basis of these requirements is that any 24-hour input of recycled water to the reservoir must be mixed such that water withdrawn for use as drinking water will never contain more than 1% of this input (or 10% with an additional log of pathogen treatment). The intent of this requirement is to provide a buffer against off -specification water that enters the reservoir; pathogen concentrations will be reduced by 2 logs, either through 100:1 dilution or 10:1 dilution with 1 -log treatment (see pathogenic microorganism control requirements discussion below for log removal requirements).

To demonstrate compliance with this requirement, the regulations require hydrodynamic modeling that verifies the ability of the reservoir to meet this requirement under all conditions, as well as completion of a tracer study with added tracer prior to the end of the first six months of operatio n.

The achievable dilution of a 24-hour input can be estimated using a simplifying assumption of complete mixing in the reservoir. Under this assumption, dilution is related to the theoretical retention time (τ) and the duration of the input (Δt):
dilution factor = τ / ∆t

3. Retention Time - The SWA regulations continue to incorporate the concept of retention time, albeit taking into account the differences in hydrodynamics between an aquifer and a reservoir. The regulations currently available stipula te that a reservoir used for SWA must ha ve a minimum theoretical retention time (τ) of 180 days, to be measured on a monthly basis as follows:
τ = 𝑉𝑡𝑜𝑡𝑎𝑙
𝑄𝑜𝑢𝑡
≥ 180 𝑑𝑎𝑦𝑠
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the V/Q is at least 60 days (i.e., within the “gap” between SWA and DPR —which is expected to include projects with V/Q of less than 60 days).

4. Pathogenic Microorganism Control - The treatment requirements in the SWA regulations look very similar to those for a GRRP, particularly with regard to pathogenic microorganism control. If at least a 100:1 dilution is achieved in th e reservoir, then the log removals for ente ric virus, Cryptosporidium, and Giardia are the same as in the GRRP regulations. If less than 100:1 but at least 10:1 is dilution achieved in the reservoir, then an additional 1 -log of pathogen treatment is required by an additional process. If there is less than 10:1 dilution available in the reservoir, then the project will likely be considered immediately upstream of a drinking water treatment plant and will be defined as DPR (see Section 0 below for more details) . Table 3 illustrates the required removal criteria for enteric virus, Cryptosporidium, and Giardia.

Table 2-3: SWA Pathogenic Microorganism Control
Dilution
Enteric Virus
Removal
Cryptosporidium
Removal Giardia Removal
Dilution ≥ 100:1 12-log 10-log 10-log
100:1 ≥ Dilution ≥ 10:1 13-log 11-log 11-log
Dilution < 10:1 Not classified as surface water augmentation

GRRPs have the benefit of receiving log removal credit from the retention time underground, whereas SWA projects do not. Instead, SWA projects allow treatment credits from the conventional drinking water treatment plant downstream of the reservoir. The original surface water treatment rule (SWTR) promulgated by the U.S. Environmental Protection Agency (EPA 1989), required the surface water treatment plant to provide treatment to remove 4 -log virus and 3 -log Giardia. This rule has since been updated to include 2 -log Cryptosporidium removal as well. SWA projects can combine the treatment credit achieved prior to the reservoir and at the conventional drinking water treatment plant to achieve the required pathogen reductions.

A primary goal in the design of the treat ment train will be to design an overall system that has enough credit to achieve the required log removals in the SWA regulations.

5. Regulated Contaminant Limits - As with the GRRP regulations, the recycled water must meet all current regulatory limits. The inclusion of a RO system will ordinarily keep the product water quality well below any current regulatory limits; however, it is possible that the San Diego Regional Water Quality Control Board ( RWQCB) may require strict nutrient limits for environmental reasons, lowering the total nitrogen discharged.

Water Code section 13561 defines Direct Potable Reuse (DPR) as "the planned i ntroduction of recycled water either directly into a public water system, as defined in Health and Safety Code section 116275, or into a raw water supply immediately upstream of a water treatment plant." This definition provides a potential “gap” between SWA and DPR, as certain projects may use a reservoir that is too small to qualify for the SWA regulations. The adopted SWA regulations address this via an alternatives clause that can allow for a reduced minimum theoretical retention time of less than 180 days, but no less than 60 days.

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2.3 Direct Potable Reuse
DPR projects are differentiated from IPR based on the absence of an environmental buffer. SWRCB defines DPR as the planned introduction of recycled water either directly into a public water system (Treated Drinking Water Augmentation [TDWA]) , or into a raw water supply immediately upstream of a water treatment plant (Raw Water Augmentation [RWA]). No uniform regulations have been established within the State of California or nationally for DPR. However, AB 574 requires SWRCB to establish a framework for the regulation of DPR projects by June 1, 2018 and to adopt uniform water recycling criteria for RWA by 2023. SWRCB published a Proposed Framework for Regulating DPR in California in April 2018. The two DPR facilities globally that are currently operating (on e in Windhoek, Namibia and the other in Big Spring, Texas) have site -specific permits and treatment requirements set forth by regional regulatory agencies.

2.3.1 Feasibility of DPR Regulations in California
Senate Bill (SB) 918 directed SWRCB to investigate the feasibility of developing uniform water recycling criteria for DPR, convene an Expert Panel to study the technical and scientific issues, and provide a final report to the California State Legislature by December 31, 2016. SB 322 further required that the SWRCB convene an Advisory Group comprised of utility stakeholders to advise SWRCB and its Expert Panel on the development of the feasibility report. SB 322 also amended the scope of the Expert Panel to include identification of research gaps that should be filled to support the development of uniform water recycling criteria for DPR. The SWRCB DDW released a draft report on the feasibility of DPR in C alifornia on September 8, 2016.

Summary of SWRCB Draft Report
In general, SWRCB found that regulations for DPR projects are attainable and that a common framework across the various forms of DPR will help avoid discontinuities in the risk assessment and management approach. The SWRCB clearly indicated that f urther quantification of reliability is necessary to d evelop criteria for DPR. The SWRCB stated that the process for developing criteria for DPR can be initiated as projects move forward, with a parallel analysis of the knowledge gaps.

The SWRCB outlines recommendations that must be addressed to successfully adopt uniform water recycling criteria for DPR that are protective of public health . These recommendations were derived in large part from the Expert Panel report, and are briefly summarized as follows:

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The SWRCB also adopted the Expert Panel and Advisory Group recommendations for non -treatment barriers, including the following:
•Develop uniform water recycling criteria for DPR concurrently with the six Expert Panel research recommendations to inform the development of criteria.

Concurrent Uniform Criteria Development
•To continue to improve on source control and final water quality monitoring, carry out an ongoing literature review to identify new compounds that may pose health risks from short term exposures, particularly to fetuses and children.

Targeted monitoring for source control and final water quality •Implement a probabilistic method (Quantitative Microbial Risk Assessment, QMRA) to confirm the necessary removal values for viruses, Cryptosporidium and Giardia, based on a literature review and new pathogen data collected, and apply this method to evaluate the performance and reliability of DPR treatment trains.

Use of QMRA for DPR
•Require monitoring of pathogens in raw wastewater to develop better empirical data on concentrations and variability.

Pathogen Monitoring in Raw Wastewater
•Investigate the feasibility of collecting raw wastewater pathogen concentration data associated with community outbreaks of disease, and implement where possible.

Outbreak Monitoring
•Identify suitable options for final treatment processes that can provide some “averaging” with respect to potential chemical peaks, particularly for chemicals that have the potential to persist through advanced water treatment.

Control of Chemical Peaks
•Develop more comprehensive analytical methods to identify unknown contaminants, particularly low molecular weight compounds in wastewater that may not be removed by advanced treatment and are not detectable with existing monitoring approaches.

Identification of Unknown Contaminants
•Convene technical workgroups to address the knowledge gaps regarding resiliency to assist in developing uniform water recycling criteria for DPR.

Addressing Knowledge Gaps
•SWRCB will continue to work with WE&RF on its DPR Research initiative. SWRCB will serve as an advisor to prioritize projects and serve in its Project Advisory Committees.

DPR Research Initiative
•The SWRCB will partner with other relevant agencies within CalEPA, university research centers, and water and wastewater research foundations to develop research projects that will advance knowledge relevant to DPR.

Partnering Approach to Research
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1. Advanced training and certification of operators for potable reuse treatment facilities

2. Optimizing wastewater treatment plant performance

3. Enhancing source control/ pretreatment programs

4. Technical, managerial, and financial (TMF) capacity to ensure the success and safety of the project

The Expert Panel report , which is included as an appendix to the SWRCB report , includes the following specific findings:
• It “is technically feasible to develop uniform water recycling criteria for DPR in California, and that those criteria could incorporate a level of public health protection as good as or better than what is currently provided by conventional drinking water supplies and IPR." • Increasing the reliability of mechanical systems and treatment plant performance will address the absence of an environmental buffer and the level of protection th at it provides in IPR projects.

Several reliability features should be incorporated into DPR projects:
o Providing multiple, independent barriers
o Ensuring the independent barriers represent a diverse set of processes o Using parallel independent treatment trains
o Providing diversion of inadequately-treated water
o Providing a final treatment step to attenuate any remaining short-term chemical peaks o Incorporating frequent monitoring of surrogate parameters at each step to ensure treatment processes are performing properly
o Developing and implementing rig orous response protocols, such as a fo rmal Hazard Analysis Critical Control Point (HACCP) system

Key Findings
The SWRCB made several statements in the draft report that could have implications to the path forward for DPR projects in California:

1. Timing: the SWRCB plans to further address knowledge gaps related to reliability prior to finalizing uniform water recycling criteria for DPR. This indicates that any planned DPR projects may need to seek site-specific approval from the SWRCB in the absence of a St ate-wide framework.

2. Framework for criteria: each form of DPR will have its own unique set of criteria that are possibly captured within a common framework to avoid discontinuities in the risk assessment. Thus, how a DPR project is defined could have implic ations to permitting requirements. The DDW acknowledges at least three forms of DPR:

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a) Small Reservoir Augmentation: a project delivering recycled water to a surface water reservoir, with the reservoir providing some benefit s, but not the full complement of benefits provided by SWA. This could include a relatively small reservoir that provides less than 60 days of “V/Q” retention time.

Figure 2-2: Small Reservoir DPR

b) Raw Water Augmentation (RWA): a project delivering recycled water directly to a surface water treatment plant or a surface water reservoir that does not provide benefits.

Figure 2-3: RWA

c) Treated Drinking Water Augmentation (TDWA): a project delivering finished water directly to a public water system's distribution system . T he advanced water treatment facility would also be permitted under the Surface Water Treatment Rule (SWTR) as a drinking water plant.

Figure 2-4: TDWA (“Flange-to-Flange” DPR)

3. Raw water pathogen monito ring, including during outbreaks and recommendation to consider incorporating QMRA. The SWRCB approach on establishing pathogen log inactivation / removal requirements will directly impact treatment requirements and costs. The language in the draft report suggests that rather than setting uniform values as with the groundwater replenishment requirements, the log inactivation / removal requirements could be based on site-specific raw water pathogen concentrations, or a more robust set of raw water pathogen concentrations for California that encompasses outbreak data. Those site-specific or worst-case raw water pathogen data would be used to calculate the required log removal / inactivation requirements to achieve a target finished water quality, potentially derived from QMRA. Depending on the database of raw water pathogen data, this approach could result in similar or more stringent requirements for log inactivation / removal than those established for IPR us ing injection into the groundwater aquifer as an environmental buffer.

4. Monitoring and control of ongoing projects. The Expert Panel suggests that a new formal process be established by the SWRCB to administer periodic review of treatment performance data o f permitted potable reuse projects. This proposed p rocess is not unlike the process for ongoing monitoring and review of surface water treatment plant operation through surface water monthly Wastewater
Treatment
Full Advanced
Water
Treatment
Small
Reservoir
Surface
Water
Treatment
Drinking Water
Distribution
System
Wastewater
Treatment
Full Advanced
Water
Treatment
Surface
Water
Treatment
Drinking Water
Distribution
System
Wastewater
Treatment
Advanced Water
Treatment
Drinking Water
Distribution
System
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operating reports (SWMORs), annual reports (e.g., consumer confid ence reports), and California DDW inspections. The SWRCB also indicates a plan to review the state of the science on chemicals of emerging concern every five years.

5. Start-up and commissioning. The Expert Panel cautioned that the introduction of DPR water into a public water system be staged to demonstrate reliability before contribution is increased. This language, if adopted by the SWRCB, has potential implications on the approach for starting up new DPR facilities.

6. Approach to fill knowledge gaps and incorporate new research findings. Outcomes of ongoing research and future blue-ribbon panel discussions will influence the criteria for DPR and should be carefully tracked by any DPR project planning to ensure that the facility design reflects any updated requirements that are expected to be incorporated in the DPR regulations.

7. DPR projects without reverse osmosis (RO) treatment. The Expert Panel recommended that the SWRCB consider proposals for DPR projects that do not employ RO. While RO provides a robust barrier for protozoa, viruses, nitrate, nitrite, TDS, and multiple metals and chemical micro - constituents, it produces a concentrate stream of up to 20% or more of the raw water production rate that requires disposal with environmental implications. The SWRCB's approach to establishing criteria for alternatives to RO will have significant ramifications for the feasibility of DPR projects that may be unable to readily manage RO concentrate or have other drivers that make RO unattractive. Figure 5 shows an example of a DPR treatment train without RO as a proces s, taken from the Expert Panel report.

Figure 2-5: DPR Treatment Train Example without RO

8. Provision of a final treatment step to "average" out any chemical pe aks. The Expert Panel recommendation for research to identify suitable op tions for final treatment processes that can provide some "averaging" with respect to chemical peaks, and any resulting incorporation of that language in the criteria, will have important implications to the design, cost, and operation of DPR projects. This point should be carefully considered:
a) If the Expert Panel is concerned with chemicals that pose a chronic health impacts, "averaging" may or may not result in a health benefit.

Biological Nutrient
Removal + Tert.

Filtration
Ozonation Biological
Activated Carbon Ultrafiltration
UV/H2O2
Biological Aerated
FilterWater StabilizationDisinfection
Chlorine
Drinking Water
Distribution
System
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b) Large storage volumes following chlorine disinfection can result in a risk t radeoff of increased formation of halogenated disinfection by-products (DBPs). c) Alternate approaches to "averaging" can result in the same desired benefit. For example, if the motivati on for "averaging" is to reduce peak concentrations in organic chemical concentrations, a granular activated carbon (GAC) or biologically -active carbon (BAC) polishing step can further reduce concentrations of these chemicals, rather than simply averaging. If the motivation for "averaging" is in part to provide additional time to detect and respond to off -specification water, Salveson et al. (2016) outlines several recommended approaches to provide that engineered buffer.

9. Consideration and incorporation of non-treatment barriers. The Expert Panel and the SWRCB recommend incorpor ation of non -treatment barriers, including: optimization of wastewater treatment plant operation (WWTP), source control, technical, managerial and financial capacity (TMF), and operator training and certification. The SWRCB approach to incorporating these non- treatment barriers in any uniform water recycling criteria for DPR could have implications to:
o WWTP capital improvement projects (CIP) and operational costs; o Pre-treatment program requirements for monitoring, management, and local limits; o Industrial discharge options and costs;
o Water utility investment in technical, managerial, and financial capacity; and o Staffing and training costs for operation of a new DPR facility.

Generally, these non-treatment factors reflect best practices for DPR and are recommended within the potable reuse industry. However, their potential adoption within State criteria for DPR projects highlights the importance of planning in advance to ensure that they are addressed as part of a comprehensive DPR project requiring State of California approval.

10. Research on low molecular weight organics . One of the SWRCB recommendations is that research be conducted to develop more comprehensive methods to identify low molecular weight unknown compounds for DPR, including non -targeted analysi s as a screening tool. How the SWRCB proceeds with this may impact monitoring requirements at a minimum for DPR projects, but could also affect treatment requirements and incorporation of processes that address low molecular weight compounds. Low molecular weight compounds are perhaps the most challenging to remove through established treatment processes (e.g., membrane filtration, membrane desalination, advanced oxidation, granular activated carbon adsorption, biologically active filtration, and chemical d isinfection). Requirements to mitigate these compounds could include source control strategies as one of the more effective approaches to reduce concentrations in DPR projects.

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3 Non-Potable Water Reuse in North San Diego County
Recycled water serves as an important local water resource to Southern California, including the North San Diego County area. Information is provided below on the facilities that receive flows from EWPCF and/or may be part of the portfolio of options to be developed in this Study. In addition, plans for expansion to the facilities are also identified based upon the efforts of the North San Diego Water Reuse Coalition (NSDWRC). This information is summarized in Table 3-1 below.

Table 3-1: Recycled Water Projections
Recycled Water (RW)
Production Facility
Planned Tertiary Treatment
Capacity (mgd)
Projected Peak Summer
Demand, Max. Month (mgd)
2015 2025 2040 2015 2025 2040
Carlsbad WRF 4.0 7.0 7.0 4.0 8.0 10.0
Gafner WRF 1.0 2.5 3.7 0.5 1.0 2.5
Meadowlark WRF 5.0 5.0 7.0 4.0 5.0 6.5
San Elijo WRF 3.0 3.5 3.5 3.0 3.5 3.5

3.1 Carlsbad Water Reclamation Facility
The Carlsbad Municipal Water District (MWD) recycled water system includes the 7.0 mgd Carlsbad Water Reclamation Facility (CWRF) operated by EWA , 79 miles of pipeline, three booster pumping stations, three storage tanks, three pressure regulating systems, and two supply sources with pump stations.

Secondary effluent flows from EWPCF are currently sent to CWRF where they are treated to tertiary levels and recycled . By 2040, the projected peak summer recycled water demand for the City of Carlsbad is expected to be 10 mgd. The City of Carlsbad’s treatment capacity ownership at EWPCF is 10.26 mgd out of the total 40.51 mgd liquid capacity (as of the Phase V expansion).

3.2 Leucadia Wastewater District Gafner Water Reclamation Facility Leucadia Wastewater District ( LWWD) wholesales recycled water to the City of Carlsbad for use at the Omni La Costa Resort and Spa. LWWD owns and operates the Forest R. Gafner WRF, which has a 1 mgd capacity to treat water to tertiary levels. Secondary effluent is provided to Gafner WRF from EWPCF. In the short-term, Gafner WRF could be expanded to provide up to an additional 1.5 mgd of recycled water, increasing its total capacity to 2.5 mgd by 2025. By 2040, the Gafner WRF’s capacity could be increased to 3.7 mgd for recycled water depending on demands . This expansion would allow LWWD to meet additional recycled water demands identified through NSDWRC planning effo rts. LWWD’s treatment capacity ownership at EWPCF is 7.11 mgd out of the total 40.51 mgd liquid capacity (as of the Phase V expansion).

3.3 Vallecitos Water District Meadowlark Water Reclamation Facility Vallecitos Water District (VWD) provides water, wastewater, and reclamation services to San Marcos, the community of Lake San Marcos, parts of the cities of Carlsbad, Escondido and Vista, and other unincorporated areas in north San Diego County, but does not currently retail recycled water to any customers. VWD owns and operates the 5 mgd Meadowlark WRF and wholesales recycled water to other agencies (Carlsbad MWD and Olivenhain MWD). However, wastewater flows currently limit production of recycled water to just under 4 mgd on an average daily basis. Projections show that the average daily flow will increase to approximately 4.5 mgd in the future. To meet short-term potable reuse demands, VWD is considering improvements to Meadowlark WRF to provide 1.0 mgd of advanced treatment capacity , Sept. 27, 2022
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which may be used for a groundwater replenishment reuse project in the San Marcos Basin . VWD’s treatment capacity ownership at EWPCF is 7.67 mgd out of the total 40.51 mgd liquid capacity (as of the Phase V expansion); however, VWD has requested to increase their ownership to 10.06 mgd in the future.

3.4 San Elijo Water Reclamation Facility
San Elijo Joint Powers Authority (JPA) owns and operates San Elijo WRF and approximately 19 miles of recycled water distribution pipelines and two covered reservoirs. San Elijo WRF is a tertiary tre atment facility that has a design capacity of 5. 25 mgd through secondary treatment and a disinfected tertiary treatment capacity of 3.0 2 mgd. Secondary -treated wastewater that is not treated to tertiary levels is discharged to the ocean through the San Elijo Ocean Outfall. The tertiary treatment train at San Elijo WRF includes microfiltration and rev erse osmosis processes. To meet increased recycled water demands, San Elijo JPA anticipates the need to increase its tertiary treatment capacity by 0.5 mgd (fro m 3.0 to 3.5 mgd) by approximately 2025.

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4 Potable Water Reuse Case Studies
A summary of the potable reuse projects in California that were operational as of late 2106 is provided in Table 4-1. Brief descriptions of the Groundwater Replenishment System, Montebello Forebay Groundwater Recharge Project, and the Terminal Island Advanced Water Purification Facility are provided in the following sections.

Table 4-1: Operational Potable Reuse Projects in California (as of 2016) Agency Project Name
Facility
Start-
up
Potable
Reuse
Type
Current Treatment
Current
Capacity
(mgd)

LACSD, WRD,
LACDPW
Montebello Forebay
Groundwater Recharge
Project
1962 Spreading
Tertiary
(biological, GMF,
disinfection)
50 Orange
County Water
District
Groundwater
Replenishment System 1978 Spreading,
Injection
Purification
(biological, MF, RO,
UV/H2O2)
100
West Basin
Municipal
Water District
West Coast Basin
Seawater Intrusion
Barrier
1992 Injection
Purification
(biological, MF, RO,
UV/H2O2)

17.5 Inland Empire
Utilities
Agency
Chino Basin 2005 Spreading
Tertiary
(biological, GMF,
disinfection)
19 Water
Replenishment
District
Alamitos Barrier 2005 Injection
Purification
(biological, MF, RO,
UV/H2O2)
10 Los Angeles
Bureau of
Sanitation
Dominguez Gap
Seawater Intrusion
Barrier (Terminal Island
AWPF)
2006 Injection
Purification
(biological, MF, RO,
disinfection)
12 Cambria
Community
Services
District
Sustainable Water
Facility at the San
Simeon Well Field and
Percolation Pond
System
2015 Injection
Purification
(biological, MF, RO,
disinfection)

0.5 TOTAL 208

In addition to these operational projects, the map shown in Figure 4-1 also includes the planned potable reuse projects in California as of July 2018. Notably, three of the five planned SWA projects shown are located in San Diego County.

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Figure 4-1: Existing and Planned Potable Reuse Projects in California

Source: (WateReuse California, July 2018)

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4.1 Existing Indirect Potable Water Reuse in California

4.1.1 Groundwater Replenishment System
The Orange County Water District's (OCWD) Groundwater Replenishment System (GWRS) is the world's largest potable water reuse project, producing 100 mgd of purified water that is injected into the local groundwater basin. Since starting up in the late 1970s, this project has injected more than 188 billion gallons of purified water into the groundwater basin, later to be extracted for potable water use. Currently, OCWD is pursuing a final expansion of the GWRS to a total production to 130 mgd.

Figure 4-2: GWRS RO Membranes

4.1.2 Montebello Forebay Groundwater Recharge
The Water Replenishment District (WRD) and the Los Angeles County Sanitation Districts (LACSD) are partners in the Montebello Forebay Groundwater Recharge Project Tertiary recycled water is recharged into the local groundwater basin via spreading. Over the last 30+ years, more than 1.45 million acre-feet of reclaimed water has been placed into sprea ding basins and percolated down into the aquifer, later to b e extracted for potable water use.

Figure 4-3: Rio Hondo Spreading Grounds, located off-channel

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4.1.3 Terminal Island Advanced Water Purification Facility The LA Sanitation (LASAN) Terminal Island Advanced Water Purification Facilities (AWPF) provides highly-purified water to recharge the Dominguez Gap Barrier. Currently the facility is undergoing an expansion that will increase the plant's capacity from 6 to 12 mgd and will add UV/AOP (UV plus sodium hypochlorite) for disinfection. The project's expansion will allow Terminal Island AWPF to continue supplying water to the Dominguez Gap Barrier, as well as to supply reclaimed water to various Los Angeles Harbor area industrial users and replenish the evaporation losses at Machado Lake.

Figure 4-4: City of Los Angeles Terminal Island AWPF RO Train

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4.2 Planned Direct Potable Water Reuse Projects in California Within California , multiple agencies are eager to move ahead with direct potable reuse projects. Two notable examples described below are the San Diego Pure Water program and the VenturaWaterPure DPR Demonstration Facility.

4.2.1 San Diego Pure Water
As part of its 2015 Point Loma WWTP National Pollutant Discharge Elimination System (NPDES) permit approval application, the City of San Diego worked with environmental stakeholders to develop a potable reuse strategy to reduce ocean discharges. This effort resulted in the development of a phased approach for the San Diego Pure Water Program that is intended to ultimately produce approximately 83 mgd of purified water by 2035. The initial phase of the Program will produce up to 30 mgd of purified water from the City's North County Water Reclamation Plant (NCWRP) to augment Miramar Reservoir.

Based on interactions with the i ndependent advisory panel (IAP) and the Division of Drinking Water (DDW), the City of San Diego has develop ed an enhanced treatment train concept to ensure reliabilit y of the purified water discharged to Miramar Reservoir. In a related effort, a Prop. 84 state-funded project, led by the WateReuse Research Foundation, has been on-going at NCWRP with a 1 mgd demonstration facility to quantify the reliability of the following potential DPR treatment train:

Ozone → Biologically Activated Carbon → Microfiltration and Ultrafiltration → RO → UV AOP As part of its first phase of the Pure Water Program, the City is moving forward with the design of this treatment train for augmenting Miramar Reservoir. Additionally, the project includes conveyance and discharge of the advanced treated water to Miramar Reservoir, as well as consideration of the integration of this new supply into the Miramar drinking water treatment plant, a Surface Water Treatment Rule compliant drinking water filtration plant that will then further treat this recycled water prior to distribution to consumers.

The Miramar Reservoir is relatively small and has a retention time of approximately two months. According to early drafts of the SWA regulations, this reduced retention time would have been within the 'gap' between DPR and SWA. Through significant coordination between the City of San Diego and DDW (e.g., via weekly meetings through key project development phases), a Draft Engineering Report for the North City Pure Water Project was submitted in J une 2018 with the project defined as SWA and having at least 60 days of retention time in the reservoir . This was in line with the Expert P anel's recommendation to allow “gap” projects within the SWA regulations via an alternatives clause.

Figure 4-5: San Diego Pure Water Demonstration Facility

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4.2.2 VenturaWaterPure
The goal of the City of Ventura and Ventura Water's VenturaWaterPure demonstration facility was to document the high quality of purified reclaimed water through extensive wa ter quality testing, and to understand the impact of blending this purified water with the conventional finished potable water.

Additionally, this demonstration facility provided an educational opportunity for the community.

The VenturaWaterPure demonstra tion facility was designed to have multiple barriers for both pathogens and trace pollutants in excess of the treatment required for subsurface (injection) GWA and the anticipated requirements for DPR. The ~20 gallon per minute process train took filtered secondary effluent from the Ventura Water Reclamation Facility and treated it through pasteurization, UF, RO, and a UV light advanced oxidation process using hydrogen peroxide ( Figure 4-6). In addition, the RO system was tested wit h an online control system using fluorescent tracers to demonstrate a minimum of 3-log removal credit for virus.

Moving forward, a granular activated carbon (GAC) process may be added after RO for an additional barrier to trace pollutants, and an engineered storage buffer may be added to the treatment train after the UV AOP to allow for appropriate system monitoring and water quality assurance.

Figure 4-6: City of Ventura DPR Demonstration Facility

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4.3 Existing Potable Reuse Projects Outside of California Potable water reuse projects have been successfully implemented nationally using a broad range of treatment and monitoring technology. Three examples of IPR and DPR projects across the United States are reviewed here.

4.3.1 IPR – SWA in Gwinnett County, Georgia
Gwinnett County Georgia is responsible for the advanced treatment of wastewater prior to discharge into Lake Lanier. The latest treatment process modifications to the F. Wayne Hill Water Resources Center were completed in 2005, allow ing the advanced treatm ent of secondary effluent at up to 150 mgd using microfiltration, pre -ozone, biofiltration, and post -ozone. Water from Lake Lanier is then treated at a conventional water treatment plant and distributed to customers throughout Gwinnett County.

Figure 4-7: Lake Lanier, Georgia

4.3.2 DPR in Big Spring, Texas
The Colorado River Municipal Water District (CRMWD) is a regional water agency in Texas, serving the cities of Big Springs, Odessa, Snyder, and others, with a cu rrent combined population of about 500,000.

Extreme drought in Texas led the CRMWD to construct the Raw Water Production Facility (RWPF) in Big Spring, Texas. The RWPF started operating in May 2013, with a production capacity of 2 mgd. The RWPF uses the same advanced treatment processes as OCWD ’s GRWS: MF, RO, and UV advanced oxidation.

After purification, the water from the RWPF is fed into a raw water supply line which blends with other raw water (up to 50 percent) and is then subjected to treatment at a standard water treatment plant (media filtration and chlorine disinfection). The City of Big Spring’s surface water treatment plant (SWTP) is the first downstream user to withdraw from the pipeli ne. The cities of Snyder, Odessa, Stanton, and Midland also operate SWTPs that take water downstream of that pipeline.

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Figure 4-8: Colorado River Municipal Water District’s Raw Water Production Facility

A two-year, third-party evaluation of the water qua lity produced at this facility was recently completed.

Water quality was tested across the treatment train at four major sample events, with test parameters including enteric virus, Giardia, Cryptosporidium, bacterial indicators, a large suite of CECs (pharmaceuticals, personal care products, consumer chemicals, flame retardants, steroid hormones, perfluorinated alkyl substances, conventional and emerging disinfection byproducts) and many other constituents. The study concluded that the product water met public health standards and was fit to drink without the additional treatment that occurs at the downstream conve ntional water treatment plants. The product water was found to generally be of a better quality than the conventional water supply from Moss Creek Lake, which has served the CRMWD's customers for many decades (Figure 14).

Figure 4-9: CEC Comparison between DPR Product Water and Existing Source (Moss Creek Lake)

0 1
10 100
1,000
ng/L
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4.3.3 DPR High Purity Water Project Demonstration Facility, Oregon Clean Water Services (CWS) is a water resources management utility in Washington County, Oregon. CWS has Oregon’s largest water reuse program and is exploring further options to address water needs within the Tualatin River Watershed. As part of their water reuse program, CWS funded, designed and constructed a High Purity Water Project DPR Demonstration Facility to purify municipal disinfected secondary effluent to various levels which would be sufficient for use in a variety of purposes, including semiconductor processing, agriculture and food crops, product manufacturing, and human consumption. The end goal was not to immediately produce a purified water for potable use, but to elevate the discussion of water in Oregon and to allow for a future potable reuse project.

Included in the overall process design were the following advanced water treatment technologies, which, when combined, provided robust pathogen and pollutant treatment:

Ultrafiltration → RO → UV / AOP → Granular Activated Carbon These processes were used in series to purify disinf ected secondary effluent from CWS’s Forest Grove Facility (FGF). The testing demo nstrated that the FGF effluent provides a very high-quality water absent of trace pollutants and/o r pathogens. As a result, the purified water was deemed suitable for potable use, public consumption was confirmed, and a single use DPR permit was obtained from the Oregon Department of Environmental Quality. As a public outreach tool, annual Sustainable Water Challenge/Pure Water Brew competitions have been held since 2014, in which local brewers enter their beers made with the high purity water produced by the advanced treatment system (Figure 4-10).

Figure 4-10: Potable Reuse Safety Demonstration Using Understandable Methods (Beer)

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5 Conclusions
As EWA considers opportunities for increasing the reuse of its secondary effluent, the following considerations drawn from the discussion in this TM can facilitate the determination of timing and feasibility of various reuse options:
• There is significant experience with successful non-potable water reuse projects in North San Diego County, which are expected to expand over the next 10 -20 years and continue providing a well - recognized valuable resource to the community.
• Final regulations allow for confident implementation of indirect potable water reuse (IPR) projects using groundwater recharge, supported by decades of successful project operations in California. • Regulations for IPR surface water augmentation (SWA) projects were finalized in 2018, and earlier drafts provided sufficient information to move forward with planning for these types of projects. • Direct potable water reuse (DPR) has now been determined to be feasible in California by DDW.

Regulations related to RWA are expected by 2023 after further research, expert consultation, and public engagement to ensure the regulations protect public health while increasing drinking water supplies. No timeframe has been established for development of regulations related to TDWA. • Nationally, the re are several established and very successful IPR projects, both groundwater recharge and SWA. Some of these projects have been in operation for over 40 years. • The most watched potable water reuse project in the U.S. is the CRMWD facility in B ig Spring Texas, where they have been now performing DPR successfully for over three years. • In the San Diego region, it is expected that the San Diego Pure Water project and the East San Diego County surface water augmentation project will be one of the pioneers in advancing potable reuse regulations and public acceptance.

Considering the context of water reuse in California and elsewhere presented in this TM, subsequent TMs under this Study explore the feasibility of NPR, IPR, and DPR options to allow EWA flexibili ty to move forward with one or more options as the regulatory landscape evolves over time. 6 References
Expert Panel on the Development of Water Recycli ng Criteria for Indirect Potable Reuse through Surface Water Augmentation and the Feasibility of Developin g Criteria for Direct Potable Reuse (Expert Panel) (2015). Final Panel Meeting Report #5: Surface Water Augmentation – IPR Criteria Review.

Salveson, A., Steinle -Darling, E., Trussell, S., Pecson, B., & Macpherson, L. (2016). Guidelines for Engineered Storage for Direct Potable Reuse. Water Intelligence Online, 15.

State Water Resources Control Board (SWRCB) (2016). "Investigation on the Feasibility of Developing Uniform Water Recycling Criteria for Direct Potable Reuse" Public Review Draft.

State Water Resources Control Board (SWRCB), Division of Drinking Water (DDW) (2015). "(Water Recycling Criteria. Title 22, Division 4, Chapter 3, California Code of Regulations). California State Water Resources Control Board Division of Drinking Water.

Tchobanoglous, G., J. Cotruvo, J. Crook, E. McDonald, A. Olivieri, A. Salveson, R. S. Trussell. (2015).

Framework for Direct Potable Reuse, WateReuse, American Water Works Association, Water Environment Federation, and National Water Research Institute.

WateReuse California. (2018). Potable Use Projects Map.

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July 2018 1

Technical Memorandum No. 2
EWA Water Reuse Feasibility Study
Subject: Portfolio of Options
Prepared for: Encina Wastewater Authority
Prepared by: Nathan Chase, P.E. | Woodard & Curran
Reviewed by: Scott Goldman, P.E., BCEE | Woodard & Curran Date: July 2018 (Draft issued: July 2017)

Table of Contents
1 Introduction ........................................................................................................................................... 3

1.1 Feasibility Study Background ....................................................................................................... 3

1.2 Objectives ..................................................................................................................................... 3 2 Project Feasibility Requirements .......................................................................................................... 3

2.1 General Requirements ................................................................................................................... 3

2.2 EWA-Specific Requirements ........................................................................................................ 3 3 Wastewater Flow Projections................................................................................................................ 4

3.1 Phase V Flow Projections ............................................................................................................. 4

3.2 Updated EWPCF Flow Projections ............................................................................................... 5 4 Treated Effluent Available for Additional Reuse ................................................................................. 6

4.1 Member Agency Recycled Water Demand Projections ................................................................ 6

4.2 Available EWPCF Effluent for Potable Reuse ............................................................................. 6 5 Potential Types of Reuse and Receptors of Advanced Treated Water ................................................. 8

5.1 Groundwater Augmentation Opportunities ................................................................................... 8

5.2 Reservoir Augmentation Opportunities ........................................................................................ 9

5.3 Raw Water Augmentation ........................................................................................................... 10

5.4 Treated Water Augmentation ...................................................................................................... 12 6 Development of Options ..................................................................................................................... 12 7 Qualitative Evaluation of Options ....................................................................................................... 15

7.1 Scoring and Ranking Methodology ............................................................................................ 15

7.2 Feasibility Screening Criteria ...................................................................................................... 15

7.3 Results of Options Screening ...................................................................................................... 16 8 Conclusions ......................................................................................................................................... 18 9 References ........................................................................................................................................... 19

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List of Figures
Figure 3-1: EWPCF Flow Projections to 2040. ............................................................................................ 5 Figure 4-1: Projected 2040 Monthly Flows and Potential for Potable Reuse ............................................... 7 Figure 4-2: Proposed 2040 Peak Summer Flow Schematic .......................................................................... 7 Figure 5-1: Regional Map of SDCWA Aqueduct System and Emergency Storage Project ....................... 11

List of Tables
Table 3-1: EWPCF Liquid Ownership and Current Flow Contribution by Member Agency ...................... 5 Table 4-1: EWA Member Agency Recycled Water Projections to 2040 ..................................................... 6 Table 6-1: Portfolio of Options Summary .................................................................................................. 14 Table 7-1: Feasibility Screening Criteria with Weighting Factors and Scoring Levels .............................. 15 Table 7-2: Scoring and Ranking of Potable Reuse Options ........................................................................ 17 Table 8-1. Most Favorable Options for Further Analysis ........................................................................... 18

Appendices
Appendix A – EWA Member Agency Correspondence
Appendix B – SDCWA Water System Planning Schematic

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1 Introduction

1.1 Feasibility Study Background
As required by Encina Wastewater Authority’s (EWA) 2020 Business Plan, this Water Reuse Feasibility Study (Study) will identify a path to maximize beneficial reuse of effluent from the Encina Water Pollution Control Facility (EWPCF)—which by 2040 is projected to reach an average of approximately 3 1 million gallons per day (mgd).

This Study will focus on developing a portfolio of options for potential reuse projects; identify and analyze a short list of options; develop an approach to phasing of the preferred water reuse project; identify funding opportunities; develop a stakeholder involvement plan; and coordinate with EWA member agencies and other stakeholders to engage with the Study development and recommendations. Ultimately, the Study will serve to advance EWA’s mission of resource recovery and contri bute to sustaining and enhancing the region’s water environment.

1.2 Objectives
The purpose of this Technical Memorandum (TM) is to define EWA’s portfolio of potential water reuse options, perform a qualitative evaluation of each option, and define a shortlist of options to be analyzed in further detail under subsequent TMs in this Study. This TM is organized as follows:
• Project Feasibility Requirements
• Wastewater Flow Projections
• Treated Effluent Available for Additional Reuse
• Potential Types of Reuse Projects and Receptors of Advanced Treated Water • Development of Options
• Qualitative Evaluation of Options
• Conclusions
2 Project Feasibility Requirements

2.1 General Requirements
In general, a water reuse project is considered feasible when it meets the following overall requirements1:
• Technical: project must be technically feasible, produce high quality water, and achieve sustainable local supply.
• Regulatory: project must be feasible to permit, protect public health, provide multiple treatment barriers, and use enhanced monitoring.
• Socioeconomic: project must be accepted by the public, supported by stakeholders , and funded adequately for capital investments and ongoing operations.

2.2 EWA-Specific Requirements
In addition to generally accepted feasibility requirements , a reuse project must make sense for EWA and fit within its core functions. As a model of excellence and innovation, EWA is committed to sound planning

1 Adapted from WateReuse DPR Framework Summary Report.

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and investment, protecting public health and the Pacific Ocean, and efficiency and fiscal responsibility .

From EWA’s perspective , for a r euse project to be feasible , it must satisfy the following specific requirements:

1. Maximize use of available EWPCF effluent year-round: the reuse project must be large enough to achieve economies of scale, to significantly reduce E WA’s ocean discharges, and to noticeably advance the sustainability of water resource management in the region.

2. Project cost neutrality (or better) for EWA : the reuse project must ensure fiscal responsibility to EWA’s Member Agencies and must generate sufficient revenue to offset any costs incurred that extend beyond EWA’s core functions. To do this, the reuse water must be produced and delivered at a competitive cost of water with respect to alternatives for the region.

3. Maximize benefits for EWA Member Agencies and Service Area: the reuse project must ensure that existing and projected recycled water demands for EWA’s Member Agencies will continue to be met, and that new reuse projects within EWA’s service area will be prioritized if possible.

4. Centralized Advanced Treatment: any potable reuse project will require advanced treatment of effluent from the EWPCF. For the purposes of this study, it is assumed that any new advanced treatment facilities will be located on existing EWA property because this provides the most synergies with existing operations and staff and is consistent with the planned uses for the 28 acres available at EWA’s South Parcel . Consideration will also be given to locating the advanced treatment of EWPCF flows at the San Elijo JPA’s Water Reclamation Plant (SEJPA WRP) because there has been interest expressed by that agency . Other wastewater facilities in North San Diego County have been excluded, such as the Oceanside San L uis Rey Wastewater Treatment Plant (SLR) and the Escondido Hale Av enue Res ource Recovery Facility (HARRF) , because those facilities have sufficient wastewater and no interest was expressed by those agencies.

5. Maintain EWPCF Sewershed Intact: No consideration was given to diversion of wastewater into or out of the existing EWA service area. For example, diversion of wastewater away from the EWPCF and towards the SEJPA WRF was not considered. In addition, diversion of wastewater to an upstream scalping WRP was also not considered in this study. Whil e these options might be viable concepts, it is expected that they could only be feasible at a small scale and not maximize the use of the available local water resources. Therefore, only effluent conveyed from the EWPCF, or advanced treated water from any new EWA facilities , were considered in the development of the reuse options.
3 Wastewater Flow Projections

3.1 Phase V Flow Projections
The Phase V Expansion, completed in 2008, was the last major expansion of the EWPCF. Prior to the Phase V Expansion, EWA spent a great deal of time wor king with the Member Agencies to project future wastewater flows and loadings. The results of this effort is a Phase V design influent flow of 40.5 mgd, and a corresponding solids loading equivalent flow of 43.3 mgd. The difference between the two capaciti es is a result of the solids loading from the upstream Meadowlark WRF, which only has a liquid treatment train.

The breakdown of Phase V EWPCF liq uid ownership and existing flow contributions from each Member Agency is shown in Table 3-1.

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Table 3-1: EWPCF Liquid Ownership and Existing Flow Contribution by Member Agency Agency Phase V Ownership 2017 Average Flows
(mgd) (percent) (mgd) (percent)
Vista 10.67 26.3% 5.88 24.5%
Carlsbad 10.26 25.3% 6.30 26.6%
Buena 3.00 7.4% 1.77 6.7%
Vallecitos 7.67 18.9% 3.51 21.8%
Leucadia 7.11 17.6% 3.82 16.4%
Encinitas 1.80 4.4% 0.97 4.0%
Total 40.51 22.25

3.2 Updated EWPCF Flow Projections
A recent update of the future flow projections to the EWPCF was performed as part of the EWPCF Process Master Plan (EWA 2016). This update was deemed necessary because of the significant drop in wastewater flows during the 2011-2017 drought. Population projections were obtained from the San Diego Association of Governments (SANDAG). An updated unit wastewater generation rate and annual growth rate was estimated based SANDAG data. This analysis resulted in a range of estimated flows b y 2040 between 26 mgd and 31 mgd, which is significantly less than the Phase V design capacity (see Figure 3-1).

Figure 3-1: EWPCF Flow Projections to 2040.

Source: EWA 2016.

A projected annual average daily flow (AADF) of 31.0 mgd by 2040 will be used for th is Reuse Study.

Using the higher end of the range of flows assumes that water conservation efforts during the recent drought may decrease if drought conditions subside in the future, leading to a resumption of a flow growth trend.

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4 Treated Effluent Available for Additional Reuse
Any new reuse project being considered by EWA must be compatible with other current and planned reuse efforts being undertaken in the region. As an early coordination step, each of the EWA Member Agencies were contacted to provide input on projected demands. Copies of the letters that were sent to each Member Agency and their responses are provided in Appendix A – EWA Member Agency Correspondence . It is assumed that the EWA Member Agencies have determined th e maximum amount of cost effective non - potable reuse within the region, and that a new EWA reuse project will involve some type of potable reuse.

4.1 Member Agency Recycled Water Demand Projections
Based on the responses received, EWA’s Member Agency proje ctions to 2040 include a total of approximately 12.5 mgd of non-potable recycled water demand to be supplied from the EWPCF, as shown in Table 4-1. This projection includes 10 mgd to supply the City of Carlsbad’s WRF and 2.5 mgd to supply Leucadia Wastewater District’s Gafner WRF. It should be noted that Vallecitos Water District’s Meadowlark WRF obtains its source flow from wastewater diversion upstream of the EWPCF, and thus is already accounted for in the flow projections for th e EWPCF and does not require additional EWPCF effluent.

Table 4-1: EWA Member Agency Recycled Water Projections to 2040 Recycled Water
Production Facility
Planned Tertiary Treatment
Capacity (mgd)
Projected Peak Summer
Demand, Max. Month (mgd)
2015 2025 2040 2015 2025 2040
Carlsbad WRF 4.0 7.0 10.0 4.0 8.0 10.0
Gafner WRF 1.0 2.5 3.7 0.5 1.0 2.5
Meadowlark WRF 5.0 5.0 7.0 4.0 5.0 6.5
TOTAL (sourced by
EWPCF effluent) 5.0 9.5 13.7 4.5 9.0 12.5

The option s developed as part of this Study will allocate flow from the EWPCF to meet the Member Agency’s 2040 projection of 12.5 mgd of recycled water demands. The remaining flow will be considered available flow for new potable reuse projects.

4.2 Available EWPCF Effluent for Potable Reuse
Based on the projections to 2040 for EWPCF flows and EWA Member Agency recycled water demands, it is anticipated that the summertime minimum flow available for potable reuse will be 20.5 mgd. The summertime minimum was selected t o allow the project to operate at capacity year -round, which will increase the potential to identify a cost effective and feasible project. Assuming typical recovery values for a conventional full advanced treatment train (i.e., microfiltration with 90% re covery and reverse osmosis with 85% recovery), this would result in approximately 15.7 mgd of advanced treated water year-round and approximately 2.8mgd of brine for disposal (as shown on Figure 4-1 and Figure 4-2). Note that this also assumes that the microfiltration backwash can be added to the nonpotable reuse supply.

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Figure 4-1: Projected 2040 Monthly Flows and Potential for Potable Reuse

Figure 4-2: Proposed 2040 Peak Summer Flow Schematic

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5 Potential Types of Reuse and Receptors of Advanced Treated Water
This section presents the wide range of opportunities for potable reuse projects within the North San Diego County region. These are categorized by the potable reuse regulatory framework that would be applicable for a potential project using EWPCF effluent.

5.1 Groundwater Augmentation Opportunities

5.1.1 San Elijo and San Dieguito Basins
The San Dieguito Valle y groundwater basin lies beneath Osuna Valley and San Dieguito Valley in San Diego County. The basin is naturally recharged by percolation in the San Dieguito River, underflow from Hodges Dam, percolation from the valley, and underflow from the La Jolla Gr oup Sediments. The groundwater storage capacity for the basin is e stimated to be approximately 50,000 acre-feet. Salinity concentrations range from up to 3,000 mg/L of total dissolved solids (TDS) in the upper and middle portions of the basin, to as high a s 10,000 mg/L in the lower portion of the basin. The basin primarily overlays the Olivenhain Municipal Water District (OMWD) service area, as well as part of the SFID/SDWD service area.

The San Elijo Valley groundwater basin underlies two valleys with Escondido Creek intermittently flowing through the upper valley and discharging into the San Elijo Lagoon. The basin’s natural recharge source is primarily percolation in Escondido Creek, with additional smaller recharge contributed by direct precipitation, u nderflow from surrounding marine sedimentary units, and percolation of urban runoff.

Groundwater storage capacity for the basin is estimated to be 8,500 acre-feet. This is a narrow and shallow basin, with average TDS of 1,550 mg/L. Deeper formations have higher TDS of up to 5,000 mg/L.

OMWD is studying the San Elijo/San Dieguito Valley basins for siting of a brackish groundwater desalter facility near San Elijo Lagoon that could produce up to 1-2 mgd. For San Elijo Valley Basin in particular, a recent study determined that the feasibility for a groundwater desalter was low due to the thin alluvium and number of private wells located within the basin (OMWD 2015).

Therefore, for the purpo ses of this Reuse Study, the San Dieguito Basin will be considered as a potential location for groundwater augmentation with up to 1 mgd of advanced treated recycled water from the EWPCF.

5.1.2 San Marcos Basin
The San Marcos Valley groundwater basin lies beneath San Marcos Valley in northwestern San Diego County, spanning 3.3 square miles. The basin is recharged predominantly by rainfall percolation in the valley and ephemeral stream flow. TDS levels range between 500 and 750 mg/L, and groundwater quality is better in the northern part of the basin than in the south (DWR 2003).

Vallecitos Water District has previously studied the San Marcos Valley Groundwater Basin for possible development. It was estimated in a study done by Todd Engineers in 2005 that the recharge capacity of the San Marcos Basin is about 4,600 AFY. Development of groundwater in the San Marcos area is constrained by limited storage, relatively low well yields and poor water quality. Nonetheless, for purposes of this reuse study the San Marcos Basin will be considered as a potential location for groundwater augmen tation with up to 1 mgd of advanced treated recycled water from the EWPCF.

5.1.3 Mission Basin
The City of Oceanside is investigating the Mission groundwater basin, which runs along the San Luis Rey River, for groundwater augmentation opportunities using highly treated water from the San Luis Rey WRF.

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The goal is to improve groundwater quality, and thereby also improve the water produced by the Mission Basin Groundwater Purification Facility (a brackish groundwater desalter), which currently has a capacity of 6.2 mgd and provides 15% of the City of Oceanside’s water supply . Although this is the largest coastal basin in the region, it is expected to be fully utilized by the City of Oceanside and therefore will be excluded from the EWA reuse study’s portfolio of options.

5.2 Reservoir Augmentation Opportunities

5.2.1 Hodges and Olivenhain Reservoirs
Hodges Reservoir was created in 1918 with the construction of Hodges Dam on San Dieguito Creek. The reservoir and dam are owned by the City of San Diego (since 1925 ). Hodges Reserv oir has a storage capacity of approximately 30,000 acre -feet, and services the San Dieguito Water District and Santa Fe Irrigation District. A 21 cfs pipeline carries water from Hodges to the San Dieguito Reservoir, as discussed in Section 5.2.2 below. In addition, Hodges Dam has historically discharged water from its spillway during large storm events, which has contributed to groundwater recharge in the San Dieguito basin.

Olivenhain Reservoir is owned by the SDCWA and has a storage capacity of 24,000 acre -feet. A 600 cfs pump station serves to lift water from Hodges to Olivenhain, with a maximum total design head (TDH) of 800 feet. Energy recovery facilities are used to capture the hydraulic energy when transferring water f rom Olivenhain to Hodges. Thus, water is typically moved between the two reservoirs daily to optimize energy usage in the region. Olivenhain Reservoir can also be filled directly from the Second Aqueduct.

The San Diego County Water Authority (SDCWA) Emergency and Carryover Storage Project consists of a system of reservoirs, pipelines, and pump stations designed to provide water to the San Diego service area in an event of an inter ruption of imported water deliveries (e.g., due to a major earthquake) . The p roject connects the City of San Diego’s Hodges Reservoir and SDCWA’s Olivenhain Reservoir to store up to 20,000 acre-feet of water in Hodges for emergency use.

Due to water quali ty concerns in Hodges Reservoir, water from Olivenhain Reservoir must meet DD W conditions for the blended water quality at the point of connection to the Second Aqueduct raw water pipeline no. 5, which can restrict the allowable flow from Olivenhain Reserv oir. Based on input from the SDCWA and the City of San Diego, f or purposes of this Reuse Study, reservoir augmentation is only considered for the Olivenhain Reservoir. Hodges and Olivenhain function as a single reservoir and all water must be conveyed through the Olivenhain reservoir to be distributed to the region. The potential that Hodges could be full for months at a time eliminated it as a potential receptor of advanced treated water. The reservoir system is considered large enough to receive all the available advanced treated water from the EWPCF.

5.2.2 San Dieguito Reservoir
The S an Dieguito Reservoir is jointly owned by SFID and SDWD and serves as a raw water storage reservoir and pretreatment facility for the R.E. Badger Water Filtration Plant (WFP). The reservoir storage capacity has decreased over time due to decayed plant material build up, solids sent from the Badger WFP, and sediments from urban and storm water runoff. The current capacity of the reservoir is approximately 800 acre-feet. Based on recent analysis (Trussell, 2015), a n existing 30-inch low-pressure pipeline from SEWRF to the San Dieguito Reservoir could be rehabilitated and used to convey up to 5 mgd or 3,472 gallons per minute (gpm).

The Badger WFP is jointly owned by SFID and SDWD. The plant can treat local water supplied from Lake Hodges, which is conveyed through the San Dieguito Reservoir for pretreatment, or raw water directly from the SDCWA Second Aqueduct. The plant was first constructed in 1970 and upgraded in 1993 for a total treatment capacity of 40 mgd.

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A study performed for SFID, SDWD and SEJPA iden tified the potential for up to 4 mgd of reservoir augmentation could be implemented based on the anticipated regulations (Trussell 2016). However, based upon the expected requirements for surface water augmentation projects, it is anticipated that a maximum of approximately 3.1 mgd could be accommodated. For purposes of this Reuse Study, the San Dieguito Reservoir will be considered for Reservoir Augmentation up to 3.1 mgd.

5.2.3 Additional Reservoirs in the Region
Although other reservoirs in the region have been considered in past studies for potable reuse opportunities (e.g., Lake Wohlford, Lake Dixon), these are not considered feasible for a project using EWPCF effluent.

5.3 Raw Water Augmentation

5.3.1 SDCWA Aqueduct System
SDCWA provides both raw and treated water to serve its member agencies using large-diameter pipelines that are grouped in two north-south aqueduct alignments (see Figure 5-1 below; for additional detai l, see Appendix B – SDCWA Water System Planning Schematic):
• First Aqueduct consists of the 48-inch diameter Pipelines 1 and 2, which are operated as a single unit. The northern portion of the First Aqueduct serves to deliver 180 cubic feet per second (cfs) of treated water from Metropolitan Water Distr ict’s (MWD) R.A. Skinner Water Treatment Plant (WTP). At the connection point with the Crossover Pipeline, the First Aqueduct is refilled with raw water and provides 190 cfs to various agencies, terminating at the San Vicente Reservoir. • Second Aqueduct con sists of three high pressure (400 psi) pipelines, identified as Pipelines 3, 4, and 5, which are operated independently. All three pipelines run from the MWD Delivery Point, six miles south of the county boundary, to the Twin Oaks Valley WTP, and continue south to a point where the Second Aqueduct crosses Interstate 15 in the Mira Mesa area. Their design characteristics are summarized below:
o Pipeline 3: 72-inch diameter, 280 cfs, terminates at the Lower Otay Reservoir o Pipeline 4: 90-inch diameter, 470 cfs, terminates at the Lower Otay Reservoir o Pipeline 5: 96-inch diameter, 500 cfs, terminates just north of I-15 Pipelines 3, 4, and 5 operate differently between different reaches of the aqueduct, as summarized below:
• Pipeline 3 conveys treated water in the reach from the Twin Oaks Valley Diversion Structure to the Interstate 15 (south of the Miramar Vent). North of San Marcos, 5.5 miles of Pipeline 3 have been re-purposed to convey water from the Carlsbad Desalination Plant to the Twin Oaks Valley Diversion Structure. South of San Marcos , Pipeline 3 continues as a gravity flow treated water pipeline at 200 cfs until it reaches its connection with the Ramona Pipeline. • Pipeline 4 conveys treated water from its initial MWD delivery point to the Miramar Vent; south of the Miramar Vent, it branc hes off to provide treated water to South County, and also interconnects with Pipeline 3 to provide raw water.
• Pipeline 5 is used for raw water only. It conveys 636 cfs of raw water to the R.E. Badger and David C. McCollom WTPs.

For purposes of this Study, Pipeline 5 will be considered an option for raw water augmentation up to the full amount of advanced treated water that is available from EWPCF. It is assumed that sufficient blend water would be available within Pipeline 5 based on SDCWA’s current operations.

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Figure 5-1: Regional Map of SDCWA Aqueduct System and Emergency Storage Project

Source: Civil Engineering Magazine, November 2016.

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5.3.2 Twin Oaks Valley Water Treatment Plant
The Twin Oaks Valley WTP was completed in 2008 as the first treatment plant built by SDCWA. The plant is located adjacent to SDCWA’s Second Aqueduct north of San Marcos, with a treated water capacity of 100 mgd. The Twin Oaks Valley WTP primarily treats raw imported water delivered from the State Water Project or Colorado River. In addition, the Twin Oaks WTP is one of the locations where SDCWA can blend and distribute the desalinated product water from the Carlsbad Desalination Plant throughout the region.

For purposes of this reuse study , Twin Oaks Valley will not be considered an option for raw water augmentation using advanced treated water that is available from EWPCF. The distance to the Twin Oaks Valley WTP is further than the raw water aqueducts and offers little to no advantage over the pipeline.

5.3.3 Carlsbad Desalination Plant
Poseidon Water owns the Claude “Bud” Lewis Carlsbad Desalination Plant (CDP), a 54 mgd desalination plant adjacent to the Encina Power Station in Carlsbad. Potable water produced at the CDP is delivered to the SDCWA at the property boundary of the treatment facility. SDCWA has responsibility for distribution of the potable water, which is first pumped from the desalination pump station into the desalinated wat er conveyance pipeline. From there, the desalinated water can be delivered to Pipelines 3, 4, and/or the Tri - Agency Pipeline (serving Vallecitos Water District, Vista Irrigation District, and Carlsbad Municipal Water District, as well as the City of Oceanside).

For purposes of this reuse study , the CDP will be considered an option for raw water augmentation up to the full amount of advanced treated water that is available from EWPCF. For raw water augmentation, this would involve blending the advanced treated water from the EWPCF with the o cean water prior to the desalination treatment step.

5.4 Treated Water Augmentation

5.4.1 SDCWA Desalinated Water Pipeline
The Carlsbad desalinated water conveyance pipeline is considered an east -west branch of the Second Aqueduct. It is 10 miles long and has a 54-inch diameter. Since the CDP started operations in late 2015, an average of approximately 50 mgd has been supplied to the SDCWA and its Member Agencies. Additional pipeline capacity is available up to a total of approximately 83 mgd.

At the location where the desalinated water pipeline ties into the Second Aqueduct, the minimum HGL in Pipelines 3 and 4 is approximately 979 ft (equal to the invert elevation of the San Marcos Vents).

For purposes of this reuse study, the SDCWA Desalinated Water pipeline will be considered an option for treated water augmentation using advanced treated water that is available from EWPCF.

5.4.2 SDCWA Second Aqueduct Pipelines 3-4
For purposes of this Reuse Study, the Second Aqueduct treated water pipelines in the vicinity of the EWPCF (Pipelines 3 and 4) will not be considered an option for treated water augmentation because the distance from the EWPCF to Pipeline 3 is further than that to the Desalination Pipeline and is not expected to offer any significant advantage.
6 Development of Options
Based on the various potable reuse opportunities described in the previous section, t he following nine options were identified as EWA’s Portfolio of Options for this Reuse Stu dy. Note that all options include the baseline assump tion of reserving 12.5 mgd for nonpotable reuse by EWA Member Agencies. Brine Sept. 27, 2022
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losses are also accounted for, depending on whether the reverse osmosis treatment step includes seawater (assumed 60% recovery and 40% brine) or not (assumed 85% recovery and 15% brine).

A. Carlsbad Desalination Plant (CDP) Influent
• 11.1 mgd of potable reuse through raw water augmentation of the CDP source water B. CDP Product Water
• 15.7 mgd potable reuse through treated water augmentation of the CDP finished water C. Olivenhain Reservoir
• 15.7 mgd potable reuse through reservoir augmentation of the Olivenhain Reservoir D. San Dieguito Reservoir and Olivenhain Reservoir
• 15.7 mgd potable reuse through the following:
o Groundwater augmentation of the San Dieguito Valley groundwater basin (up to 2 mgd) o Reservoir augmentation of the San Dieguito Reservoir (up to 3.1 mgd) o Reservoir augmentation of the Olivenhain Reservoir (9.7 mgd to 15.7 mgd) E. San Dieguito Reservoir and CDP Influent
• 12.6 mgd potable reuse through the following:
o Groundwater augmentation of the San Dieguito Valley groundwater basin (up to 2 mgd) o Reservoir augmentation of the San Dieguito Reservoir (up to 3.1 mgd) o Raw water augmentation of the CDP source water (7.5 mgd to 12.6 mgd) F. San Dieguito Reservoir and CDP Product Water
• 15.7 mgd potable reuse through the following:
o Groundwater augmentation of the San Dieguito Valley groundwater basin (up to 2 mgd) o Reservoir augmentation of the San Dieguito Reservoir (up to 3.1 mgd) o Treated water augmentation of the CDP finished water (9.7 to 15.7 mgd) G. San Dieguito Reservoir and Second Aqueduct
• 15.7 mgd potable reuse through the following:
o Groundwater augmentation of the San Dieguito Valley groundwater basin (up to 2 mgd) o Reservoir augmentation of the San Dieguito Reservoir (up to 3.1 mgd) o Raw water augmentation of the Second Aqueduct, Pipeline No. 5 (9.7 to 13.7 mgd) H. Second Aqueduct and San Marcos Basin
• 15.7 mgd potable reuse through the following:
o Groundwater augmentation of the San Marcos groundwater basin (up to 2 mgd) o Raw water augmentation of the Second Aqueduct, Pipeline No. 5 (13.7 to 15.7 mgd) I. Twin Oaks WTP Influent and San Marcos Basin
• 15.7 mgd potable reuse through the following:
o Groundwater augmentation of the San Marcos groundwater basin (up to 2 mgd) o Raw water augmentation of the Twin Oaks WTP source water (13.7 to 15.7 mgd)

Table 6-1 summarizes the portfolio of options and the associated 2040 peak summer production.

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Table 6-1: Portfolio of Options Summary

Footnotes

1. Assumed available secondary effluent flow from EWPCF: 31.0 mgd

2. Assumed secondary effluent sent to AWPF as source water: 20.5 mgd

3. Assumed recovery from MF process: 90%

4. Assumed recovery from AWT RO process: 85%

5. Assumed recovery from seawater desalination process: 60%

6. Assume that all potable reuse options require MF and RO (at AWT or at desalination plant), and assume that MF backwash can be recovered for NPR.

NPR
Recycled
Water
Ground-
water
Large
Res.

Small
Res.

Source
Water
Treated
Water SE Brine
A Carlsbad Desalination Plant (CDP) Influent 12.5 - - - 11.1 - 0 7.4 11.1 23.6 B CDP Product Water 12.5 - - - - 15.7 0 2.8 15.7 28.2
C Olivenhain Reservoir 12.5 - 15.7 - - - 0 2.8 15.7 28.2 D San Dieguito Reservoir + Olivenhain Reservoir 12.5 2.0 10.6 3.1 - - 0 2.8 15.7 28.2 E San Dieguito Reservoir + CDP Influent 12.5 2.0 - 3.1 7.5 - 0 5.9 12.6 25.1 F San Dieguito Reservoir + CDP Product Water 12.5 2.0 - 3.1 - 10.6 0 2.8 15.7 28.2 G San Dieguito Reservoir + 2nd Aqueduct (Raw) 12.5 2.0 - 3.1 10.6 - 0 2.8 15.7 28.2 H Second Aqueduct (Raw) + San Marcos Basin 12.5 2.0 - - 13.7 - 0 2.8 15.7 28.2 I Twin Oaks WTP Influent + San Marcos Basin 12.5 2.0 - - 13.7 - 0 2.8 15.7 28.2 Option Description DPR
Total
Potable
Reuse
(mgd)
Option
ID
Total
Reuse
(mgd)
IPR
Projected 2040 Peak Production (mgd)
Ocean Disposal
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7 Qualitative Evaluation of Options

7.1 Scoring and Ranking Methodology
A set of criteria was developed to allow for an initial screening of each option in EWA’s Portfolio of Options prior to embarking on a more detailed evaluation of the top preferred option s, which will include capital and operating cost analyses. For each c riterion, a weighting factor was assigned and scoring levels were selected based on the expected range and relative impact on project feasibility. The weighting and scoring methodology is summarized as follows:

1. Assign a Weighting Factor to each Criterion (on a scale of 1 -10), where a h igher weight means higher impact on project feasibility.

2. Define Scoring Levels within each Criterion (on a scale of 0 -4), where a h igher score means the project is more feasible.

3. Select appropriate scoring for each option across all criteria.

4. Multiply scores by their associated weighting factors to obtain Option total score.

5. Rank Options by total score.

For options wit h multiple potable reuse types (e.g. , Option E contains both D PR and IPR), points are allocated to each project based on the criteria and are weighted by flow.

7.2 Feasibility Screening Criteria
The five feasibility screening criteria used are shown in Table 7-1 below, along wi th key considerations and associated weighting and scoring.

Table 7-1: Feasibility Screening Criteria with Weighting Factors and Scoring Levels Screening Criteria Weight Score Description of Scoring Levels Regulatory Certainty and Permitting Effort
Considerations:
-Status of regulations in California and
expected future requirements.
-Ease of approval and precedents to follow.
6 4 IPR (groundwater or surface water)
3 DPR - Source Water (for SWTP)
2 N/A
1 DPR - Source Water (for desalination)
0 DPR - Treated Water (flange-to-flange)
Treatment and Engineered Storage
Considerations:
-Knowledge of advanced treatment and
engineered storage requirements.
-Operational complexity and potential impacts
to EWPCF.
5 4 FAT for IPR (groundwater or surface water)
3 FAT for DPR (source water augmentation)
2 N/A
1 FAT for DPR (treated water augmentation)
0 FAT for DPR (for desalination)
Operations
Considerations:
-Regional demand for raw/treated water
(considering seasonality).
-Integration with reservoir operations and
groundwater management.
-Brine management and disposal for
desalination.
5 4 No seasonal limitations
3 Seasonal limitations (e.g., demand for treated water) 2 Wet-weather limitations (e.g., reservoir freeboard)
1 Integration with desalination facilities & increased
brine disposal
0 Groundwater recharge facilities/operations
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Screening Criteria Weight Score Description of Scoring Levels Conveyance Infrastructure
Considerations:
-Pipeline length, alignment constraints,
pumping facilities, pumping requirements.
10 4 <5 miles
3 5-15 miles | <500 ft ΔHGL
2 5-15 miles | >500 ft ΔHGL
1 >15 miles | <500 ft ΔHGL
0 >15 miles | >500 ft ΔHGL
Stakeholders and Institutional Challenges
Considerations:
-Benefits to EWA member agencies.
-Institutional challenges related to quantity and
type of stakeholders.
-Public acceptance of regional IPR/DPR option.
3 4 EWA Member Agencies only
3 EWA + 1 stakeholder group
2 EWA + 2 stakeholder groups
1 EWA + 3 stakeholder groups
0 EWA + 4 stakeholder groups

7.3 Results of Options Screening
Based upon the methodology described above, each of the nine options within EWA’s Portfolio of Options was scored. This led to the ranking of options by score, as shown in Table 7-2.

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Table 7-2: Scoring and Ranking of Potable Reuse Options

Footnote

1. For options with multiple potable reuse types, points are allocated to each project based on the criteria and are weighted by flow.

CDP
Influent
CDP
Product
Water
Olivenhain
Reservoir
San
Dieguito
Res. +
Olivenhain
Res.

San
Dieguito
Res. + CDP
Influent
San
Dieguito
Res. + CDP
Product
Water
San
Dieguito
Res. + 2nd
Aqueduct
(Raw)
Second
Aqueduct
(Raw) + San
Marcos
Twin Oaks
WTP
Influent +
San Marcos
Screening Criteria Weight Score Description of Scoring Levels A B C D E F G H I 4 IPR (groundwater or surface water)
3 DPR - Source Water (for SWTP)
2 N/A
1 DPR - Source Water (for desalination)
0 DPR - Treated Water (flange-to-flange)
4 FAT for IPR (groundwater or surface water)
3 FAT for DPR (source water augmentation)
2 N/A
1 FAT for DPR (treated water augmentation)
0 FAT for DPR (for desalination)
4 No seasonal limitations
3 Seasonal limitations (e.g., demand for treated water) 2 Wet-weather limitations (e.g., reservoir freeboard)
1 Integration with desalination facilities & increased brine disposal 0 Groundwater recharge facilities/operations
4 <5 miles
3 5-15 miles | <500 ft ΔHGL
2 5-15 miles | >500 ft ΔHGL
1 >15 miles | <500 ft ΔHGL
0 >15 miles | >500 ft ΔHGL
4 EWA Member Agencies only
3 EWA + 1 stakeholder group
2 EWA + 2 stakeholder groups
1 EWA + 3 stakeholder groups
0 EWA + 4 stakeholder groups
57 69 60 67 68 74 87 81 60
9 4 8 6 5 3 1 2 7
6 Operations 5
3 2.13
Stakeholders and
Institutional
Challenges
Regulatory
Certainty and
Permitting Effort
1 Conveyance
Infrastructure 10
4 5
Treatment and
Engineered
Storage
2 2
3 4 1.6 2.0 3.1

2.8 3.5
1 2

1.6 3.3

3.5 2.6
2 1
1 4 0
4 0
Total Weighted Score
Rank
4 0
2 3.1
4 2.2 3.1

1.0 3.6 3.7 2.0

3.1 2.6

1.3 3.3
Portfolio of Options Scoring

0.4 3
1 3
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8 Conclusions
Based on the results from the screening evaluation, the following are the three most favorable options that will be carried into TM3 for further analysis to determine feasibility and identify the preferred project:

1. Option F: San Dieguito Reservoir and CDP Product Water

2. Option G: San Dieguito Reservoir and Second Aqueduct (Raw Water Pipeline 5)

3. Option H: Second Aqueduct (Raw Water Pipeline 5) and San Marcos Basin

Table 8-1 summarizes key aspects of each of these options , including the projected flows considered for each of the potable reuse receptors selected for this Reuse Study (as described in Section 5 above).

Table 8-1. Most Favorable Options for Further Analysis
Potable Reuse
Receptor
Key
Stakeholders
Form of
Potable Reuse Option F Option G Option H
San Dieguito
Groundwater Basin
Olivenhain
MWD
Groundwater
Augmentation 2 mgd 2 mgd -
San Marcos
Groundwater Basin Vallecitos WD Groundwater
Augmentation - - 2 mgd
San Dieguito
Reservoir

SEJPA/ SFID/
SDWD
Surface Water
Augmentation 3.1 mgd 3.1 mgd -
Olivenhain and
Hodges Reservoirs
SDCWA, City
of San Diego
Surface Water
Augmentation - - -
Second Aqueduct
(Pipeline 5) SDCWA Raw Water
Augmentation - 10.6 mgd 13.7 mgd
Carlsbad Desalination
Plant Finished Water SDCWA Treated Water
Augmentation 9.7 mgd - -
Twin Oaks Valley
WTP SDCWA Raw Water
Augmentation - - -
Carlsbad Desalination
Plant Influent
Poseidon,
SDCWA
Raw Water
Augmentation - - -
Potential Phase 1 Potable Reuse

TOTAL POTABLE REUSE

5.1 mgd

15.7 mgd

5.1 mgd

15.7 mgd
N/A

15.7 mgd

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9 References

DWR, 2003. Bulletin 118: California’s Groundwater. October 2003.

EWA, 2016. Process Master Plan for the EWPCF. Prepared for Encina Wastewater Authority. Prepared by Carollo Engineers. November 2016.

OMWD, 2015. San Elijo Valley Groundwater Project. Prepared for Olivenhain Municipal Water District.

Prepared by Stoney-Miller Consultants, Inc. February 2015.

SDCWA, 2014. Final 2013 Regional Water Facilities Optimization and Master Plan Update. Prepared for San Diego County Water Authority. Prepared by CH2MHill/Black & Veatch. March 2014.

Trussell, 2016. Santa Fe Irrigation District, San Dieguito Water District, and San Elijo Joint Powers Authority Potable Reuse Feasibility Study. Trussell Technologies, Inc. in association with RMC Water and Environment, March 2016.

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Appendix A – EWA Member Agency Correspondence

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Attached is a request for confirmation of water reuse projections for the City of Vista and the Buena Sanitation District. As we move forward with this water reuse feasibility study we want to make sure we capture all potential water reuse for each of EWA’s member agencies and key stakeholders to ensure compatibility and alignment. Thanks in advance for your help! Hard copy to follow.

Best,
Mike
Michael F. Steinlicht
General Manager
Encina Wastewater Authority
From: Brian Smith [mailto:[email protected]]
Sent: Thursday, November 3, 2016 7:08 AM
To: '[email protected]'
Cc: '[email protected]'; Scott Goldman; Don Smith; Randy Whitmann Subject: FW: Confirmation of Water Reuse Projections
Mike,
I am Brian Smith, Director of Engineering at the Vista Irrigation District. I am responding to an email you sent to Don Smith at our office.

We do not have any immediate plans for any reuse or recycled water projects. All potential recycled projects for our District are included in the North San Diego Water Reuse Coalition’s Facilities Plan.

If you have any questions or need additional information please feel free to contact Randy Whitman or myself.

Sincerely,
Brian Smith
Director of Engineering
Vi
sta Irrigation District
1391 Engineer St.

Vista, CA 92081
(760) 597-3113
[email protected]
From: Mike Steinlicht [mailto:[email protected]]
Sent: Monday, October 31, 2016 8:16 AM
To: Don Smith
Cc: Scott Goldman; Nathan Chase; 'Elmer Alex ([email protected])' Subject: Confirmation of Water Reuse Projections
Good Morning Don,
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From: Paul Bushee <[email protected]>
Sent: Monday, October 31, 2016 9:37 AM
To: Mike Steinlicht
Cc: Scott Goldman; Nathan Chase
Subject: RE: Confirmation of Water Reuse Projections

Mike:

Th
anks for forwarding the information. All the flow numbers look accurate for LWD. I don’t this would impact EWA’s study, but the only discrepancy I could see was that we would have to build a pump station and pipeline to OMWD or Carlsbad if we increase our capacity to 2.5 mgd in 2025.

Thanks,

Paul

Paul J. Bushee
General Manager
L
eucadia Wastewater District
19 60 La Costa Avenue
Carlsbad, CA 92009
Ph: (760) 753-0155
Fax: (760) 753-3094
Email: [email protected]
Web: www.lwwd.org

From: Mike Steinlicht [ma ilto:[email protected]]
Sent: Friday, October 28, 2016 11:01 AM
To: Paul Bushee <[email protected]>
Cc: Scott Goldman <[email protected]>; Nathan Chase <[email protected]> Subject: Confirmation of Water Reuse Projections

Good Morning Paul,

Attached is a request for confirmation of water reuse projections for the Leucadia Wastewater District. As we move forward with this water reuse feasibility study we want to make sure we capture all potential water reuse for each of EWA’s member agencies to ensure compatibility and alignment. Thanks in advance for your help!

Hard copy to follow.

Best,

Mike

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From: Terry Smith <[email protected]>
Sent: Tuesday, November 22, 2016 12:48 PM
To: Mike Steinlicht
Cc: Scott Goldman; Nathan Chase; Wendy Chambers
Subject: RE: Confirmation of Water Reuse Projections

Mike,
I
have reviewed the attached letter and agree with the projections you have shown for the City of Carlsbad. I have no additional comments.

Thanks,

Terry L. Smith, PE
Engineering Manager / District Engineer

Public Works – Utilities Engineering
City of Carlsbad
5950 El Camino Real
Carlsbad, CA 92008
www.carlsbadca.gov

Direct Line 760.603.7354
[email protected]

From: Mike Steinlicht [ma
ilto:[email protected]]
Sent: Friday, October 28, 2016 11:01 AM
To: Terry Smith <[email protected]>; Wendy Chambers <[email protected]> Cc: Scott Goldman <[email protected]>; Nathan Chase <[email protected]> Subject: Confirmation of Water Reuse Projections

Good Morning Terry, Wendy,

Attached is a request for confirmation of water reuse projections for the City of Carlsbad. As we move forward with this water reuse feasibility study we want to make sure we capture all potential water reuse for each of EWA’s member agencies to ensure compatibility and alignment. Thanks in advance for your help!
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EWA Water Reuse Feasibility Study
TM2: Portfolio of Options
Appendix B – SDCWA Water System Planning Schematic
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CAPITAL IMPROVEMENT

PROGRAM

WATER SYSTEM PLANNING SCHEMATIC

AQUEDUCTS, FLOW CONTROL FACILITIES
A

ND GRADIENT CONTROL STRUCTURES
STATUS: AS OF DECEMBER 2016
NOTES

SYMBOLS

ABBREVIATIONS
LEGEND

LAKE MORENA
50,200 ACRE-FEET
EL. 3039.4

LOVELAND

RESERVOIR
25,400 ACRE-FEET
EL. 1355.0

LOWER OTAY

RESERVOIR
49,500 ACRE-FEET
EL. 484.7

LAKE MURRAY
4,820 ACRE-FEET
EL. 536.5

EL CAPITAN RESERVOIR
113,000 ACRE-FEET
EL. 750.00

LAKE CUYAMACA
8,190 ACRE-FEET
EL. 4635.6

LAKE JENNINGS
9,790 ACRE-FEET
EL. 700.00

STARVATION

MOUNTAIN

RESERVOIR
RMWD
30 ACRE-FEET

LAKE RAMONA
12,000 ACRE-FEET
EL. 1341.00

LAKE POWAY
3,320 ACRE-FEET
EL. 938.00

SWEETWATER

RESERVOIR
27,700 ACRE-FEET
EL. 237.00

SUTHERLAND

RESERVOIR
29,700 ACRE-FEET
EL. 2057.00

LAKE DIXON
2,610 ACRE-FEET
EL. 1043.50

LAKE WOLHFORD
6,940 ACRE-FEET
EL. 1480.21

ESCONDIDO
CANAL 60 CFS

SAN LUIS

REY RIVER

HENSHAW

RESERVOIR
53,400 ACRE-FEET
EL. 2690.00
TURNER

RESERVOIR
1,730 ACRE-FEET
EL. 1071.00

OLIVENHAIN RESERVOIR
24,700 ACRE-FEET
SPILLWAY EL. 1080.50

LAKE HODGES
30,250 ACRE-FEET
EL. 315.00

SAN VICENTE RESERVOIR
249,350 ACRE FEET
EL. 766.00

LAKE MIRAMAR
7,180 ACRE-FEET
EL. 714.00

RED MOUNTAIN

RESERVOIR
1,335 ACRE-FEET
EL. 1140.00

SAN DIEGUITO

RESERVOIR
883 ACRE-FEET
EL. 250.00

BARRETT LAKE
37,900 ACRE-FEET
EL. 1607.0
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EWA Water Reuse Feasibility Study

Attachment 3 - TM3: Preferred Project Identification
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July 2018 1
Technical Memorandum No. 3
EWA Water Reuse Feasibility Study
Subject: Preferred Project Identification
Prepared For: Encina Wastewater Authority
Prepared by: Nathan Chase, P.E.; Kraig Erickson, P.E. | Woodard & Curran Samantha Bear; Brett Faulkner, P.E. | Trussell Technologies Andrea F. Corral, Ph.D. | Carollo Engineers
Michael Welch, Ph.D., P.E.

Reviewed by: Sunny Huang, P.E. and Scott Goldman, P.E., BCEE | Woodard & Curran Shane Trussell, Ph.D., P.E., BCEE | Trussell Technologies Andrew Salveson, P.E. | Carollo Engineers
Date: July 2018 (Draft: January 2018)

Table of Contents
1 Introduction ........................................................................................................................................... 5 Feasibility Study Background ....................................................................................................... 5 Objectives ..................................................................................................................................... 5 2 Wastewater Treatment Plant Improvements ......................................................................................... 7 EWPCF Treatment Upgrades ........................................................................................................ 7 Preliminary Layout of Improvements ......................................................................................... 13 Conceptual Costs for EWPCF Improvements ............................................................................. 15 3 Advanced Water Treatment Concepts ................................................................................................ 17 Overview ..................................................................................................................................... 17 Treatment Technologies .............................................................................................................. 17 Proposed Treatment Trains ......................................................................................................... 21 Unit Process Monitoring ............................................................................................................. 23 Facility Planning and Conceptual Layouts ................................................................................. 26 Conceptual Costs for Advanced Treatment ................................................................................ 51 4 Conveyance Concepts ......................................................................................................................... 53 Introduction ................................................................................................................................. 53 Option F – North ......................................................................................................................... 55 Option G – South ........................................................................................................................ 58 Option H - East ........................................................................................................................... 62 Sept. 27, 2022
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Conceptual Costs for Conveyance .............................................................................................. 65 5 Purified Water Receptor Integration Concepts ................................................................................... 67 Groundwater Augmentation ........................................................................................................ 67 Surface Water Augmentation ...................................................................................................... 68 Raw Water and Treated Drinking Water Augmentation ............................................................. 69 6 Permitting Considerations and Brine Disposal ................................................................................... 73 Permitting Overview ................................................................................................................... 73 Groundwater Augmentation ........................................................................................................ 77 Surface Water Augmentation ...................................................................................................... 78 Raw Water Augmentation ........................................................................................................... 86 Brine Disposal ............................................................................................................................. 87 7 Conceptual Cost Analysis ................................................................................................................... 89 Cost Opinion Methodology ......................................................................................................... 89 Costs by Option ........................................................................................................................... 91 8 Conclusions ......................................................................................................................................... 95 References ................................................................................................................................................... 96 Appendix A – Conceptual Cost Analysis Tables ...................................................................................... 101

List of Figures
Figure 2-1: Projected EWPCF Diurnal Flow Curve and Flow Equalization Volume .................................. 8 Figure 2-2: Preliminary site layout for new facilities at EWPCF ............................................................... 14 Figure 3-1: Advanced Treatment Train Options. ........................................................................................ 22 Figure 3-2: Representative Layout of the FAT AWTF on EWA’s South Parcel. ...................................... 34 Figure 3-3: Representative Layout of the O₃/BAF + FAT AWTF on EWA’s South Parcel (Far View). .. 46 Figure 3-4: Representative Layout of the O₃/BAF + FAT + WTP on EWA’s South Parcel (Far View). .. 49 Figure 3-5: Representative Layout of the O₃/BAF + FAT AWTF Expansion (25 mgd) on EWA’s South Parcel. ................................................................................................................................................. 51 Figure 4-1: Pumping Requirements Summary ............................................................................................ 54 Figure 4-2: Option F - Carlsbad Desalination Plant Augmentation Alignment .......................................... 56 Figure 4-3: Option F - Carlsbad Desalination Plant Augmentation HGL ................................................... 57 Figure 4-4: Option G Alignment Analysis .................................................................................................. 59 Figure 4-5: Option G - San Dieguito Reservoir, Groundwater Basin & SDCWA Second Aqueduct Augmentation HGLs .......................................................................................................................... 60 Figure 4-6: Option H Alignment. ................................................................................................................ 63 Figure 4-7: Option H - San Marcos Groundwater Basin & SDCWA Aqueduct #2 Augmentation HGL .. 64 Sept. 27, 2022
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Figure 7-1: Capital Cost Summary for Options F, G, and H. ..................................................................... 91 Figure 7-2: Cost of Water Summary for Options F, G, and H. ................................................................... 92

List of Tables
Table 2-1: Average Influent and Primary Effluent Strength for 2011 - 2012 and 2016 ............................... 9 Table 2-2: Modeling Results Summary ...................................................................................................... 10 Table 2-3: Aeration Basin Retrofit .............................................................................................................. 12 Table 2-4: Dimensions of Proposed Facilities ............................................................................................ 14 Table 2-5: Preliminary Estimate of Increase in O&M Cost with NDN ...................................................... 16 Table 3-1: Potable Reuse Pathogen Reduction Requirements (from source water to potable water). ........ 23 Table 3-2: Expected Performance of Treatment Train “a” for Groundwater Augmentation. ..................... 23 Table 3-3: Expected Performance of Treatment Train “a” for Surface Water Augmentation. ................... 24 Table 3-4: Expected Performance of Treatment Train “b” for Raw Water Augmentation. ....................... 24 Table 3-5: Expected Performance of Treatment Train “c” for Treated Drinking Water Augmentation. ... 25 Table 3-6: CCPs for an AWTF. .................................................................................................................. 26 Table 3-7: UF System Design Parameters .................................................................................................. 26 Table 3-8: RO System Design Parameters .................................................................................................. 30 Table 3-9: UV/AOP Design Parameters ..................................................................................................... 32 Table 3-10: FAT AWTF Footprint. ............................................................................................................ 34 Table 3-11. Ozone Design Parameters. ....................................................................................................... 35 Table 3-12: BAC Design Parameters .......................................................................................................... 37 Table 3-13: UF Design Parameters ............................................................................................................. 38 Table 3-14: RO Design Parameters. ........................................................................................................... 42 Table 3-15: UV/AOP Design Parameters ................................................................................................... 43 Table 3-16: Footprint of FAT + O3/BAF AWTF ........................................................................................ 45 Table 3-17. Design Criteria for ESB-Cl2 + UF System .............................................................................. 47 Table 3-18: O₃/BAF + FAT + WTP for Treated Drinking Water Augmentation Footprint ....................... 47 Table 3-19. Footprint of FAT + O3/BAF AWTF at 25 mgd ....................................................................... 50 Table 4-1: Pipeline Velocity and Headloss – Option F ............................................................................... 55 Table 4-2: Pumping Requirements – Option F ........................................................................................... 55 Table 4-3: Pipeline Velocity and Headloss – Option G .............................................................................. 58 Table 4-4: Pumping Requirements – Option G .......................................................................................... 58 Table 4-5: Pipeline Velocity and Headloss – Option H .............................................................................. 62 Table 4-6: Pumping Requirements – Option H .......................................................................................... 62 Sept. 27, 2022
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Table 4-7: Conveyance & Receptor Integration Costs by Option ............................................................. 65 Table 6-1: Anticipated RWQCB and DDW Permits for TM3 Reuse Options. .......................................... 76 Table 6-2: Basin Plan Groundwater Quality Objectives. ............................................................................ 78 Table 6-3: Basin Plan Surface Water Quality Objectives for San Dieguito Reservoir ............................... 80 Table 6-4: California Toxic Rule Standards for the Protection of Aquatic Habitat .................................... 82 Table 6-5: California Toxics Rule Standards for the Protection of Human Health .................................... 83 Table 6-6: Recommended Criteria for Chlorine for the Protection of Freshwater Aquatic Life ................ 86 Table 7-1: Cost Summary for Option F. ..................................................................................................... 92 Table 7-2: Cost Summary for Option G. ..................................................................................................... 93 Table 7-3: Cost Summary for Option H. ..................................................................................................... 93 Table 8-1: Summary of Key Considerations for EWA’s Potable Reuse Options. ...................................... 95

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1 Introduction
Feasibility Study Background
As required by Encina Wastewater Authority’s (EWA) 2020 Business Plan, this Water Reuse Feasibility Study (Study) will identify a path to maximize beneficial reuse of effluent from the Encina Water Pollution Control Facility (EWPCF) —which by 2040 is projected to reach an average annual daily flow of approximately 31 million gallons per day (mgd).

The Study will focus on developing a portfolio of options for potential reuse projects; analyze a shortlist of options (focus of this technical memorandum (TM)); develop an approach to phasing of the preferred water reuse project; identify funding opportunities; develop a stakeholder involvement plan; and coordinate with EWA member agencies and other potential stakeholders. Ul timately, the Study will serve to advance EWA’s mission of resource rec overy and contribute to sustaining and enhancing the region’s water resources.

1.1.1 Preferred Options for Analysis
Through prior work on this Study, three preferred options have been identified for further analysis. Each option includes improvements to the EWPC F and construction of a new Advanced Water Treatment Facility (AWTF) to produce approximately 16 mgd of advanced treated water (or purified water) for potable reuse. Additional details on each option are presented in this TM. The options are listed below, along with the associated designation that will be used throughout this TM:
• Option F: 15.8 mgd of potable reuse through the following:
o Groundwater augmentation in the San Dieguito Valley groundwater basin (up to 2 mgd) o Surface water augmentation in the San Dieguito Reservoir (up to 3.1 mgd) o Treated drinking water augmentation introduced at the Carlsbad Desalination Plant finished water pump station (ranging from 10.7 to 15.8 mgd) • Option G: 16.0 mgd of potable reuse through the following:
o Groundwater augmentation in the San Dieguito Valley groundwater basin (up to 2 mgd) o Surface water augmentation in the San Dieguito Reservoir (up to 3.1 mgd) o Raw water augmentation in the Second Aqueduct, Pipeline No. 5 (ranging from 10.9 to 14 mgd)
• Option H: 16.0 mgd of potable reuse through the following:
o Groundwater augmentation in the San Marcos groundwater basin (up to 2 mgd) o Raw water augmentation in the Second Aqueduct, Pipeline No. 5 ( ranging from14 to 16 mgd)
Objectives
This TM includes conceptual analysis leading to a preliminary opinion of probable construction costs and annual operational costs for each of the three preferred options at the projected 2040 flow levels (as described in TM2) . The analysis includes estimation of the unit cost of water produced (i.e., dollars per acre-foot) to allow for comparison of existing and planned water resources expected to be available in the region. The TM is organized as summarized below:
• Wastewater Treatment Plant Improvements: With a goal of pr oviding improved source water to a future AWTF, this section examines raw wastewater source control and improvements to the Sept. 27, 2022
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existing EWPCF secondary treatment process. Key outcomes include expected AWTF source water quality and quantity.
• Purified Water Rec eptor Integration Concepts: For the surface water augmentation option, a concept will be presented for diffusing the purified water into the reservoir and meeting the anticipated regulatory requirements for dilution a nd retention time. For the groundwater augmentation option, a concept w ill be presented for injection wells and extraction wells to meet anticipated retention time requirements. For the treated drinking water augmentation option, a concept will be presente d for engineered storage and blending facilities to combine the purified water with the desalination plant effluent.
• Advanced Water Treatment Concepts: To meet the requirements for potable reuse in California, an AWTF will need to be constructed to deliver purified water to the specific receptor(s) in e ach option. This section will pr esent potential treatment trains tailored to each form of potable reuse contemplated in the top options, as well as conceptual facility layouts for the AWTF options. • Conveyance Concepts: Various pipeline alignment routes were considered for conveying purified water from the AWTF to the proposed receptor(s). This section will present conceptual pipeline alignments and pump station requirements for each option. • Permitting Conside rations and Brine Disposal : Based on the prop osed modifications to the EWPCF, the proposed AWTF, and the proposed forms of potable reuse , this section outlines the associated considerations for permitting based on available information . Furthermore, permit ting requirements are outlined for disposal of RO concentrate (brine) generated at the proposed AWTF via the Encina Ocean Outfall.
• Conceptual Cost Analysis: For each option, a feasibility-level Opinion of Probable Construction Costs is provided. In turn, operational cost rates are added to each option to develop a cost of water that can be compared across options, as well as to other water sources in the region. • Conclusions: Based on the analysis in this TM and feedback from stakeholders, a recommendation is provided to carry forward in the Study regarding project phasing analysis and funding opportunity identification.

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2 Wastewater Treatment Plant Improvements
EWPCF Treatment Upgrades
No changes to the EWPCF treatment are expected to be required by current regulations to provide secondary effluent to source non -potable reuse projects w ith EWA’s Member Agencies. However, current best practice suggests that the source water for an AWTF should include biological nutrient removal (e.g., nitrification-denitrification [NDN]) and tertiary fi ltration. These modifications may also be required by future potable reuse regulations. The following aspects of the EWPCF treatment upgrades and how they pertain to potable reuse will be addressed in this section:
• Source control and industrial pretreatment
• Primary effluent flow equalization
• Conversion of secondary process to NDN
• Tertiary filters
• Management of sludge dewatering sidestreams

2.1.1 Source Control and Industrial Pretreatment
Effective source control and industrial pretreat ment management programs are important for maintaining consistent feed water qua lity for potable reuse. Source control and industrial pretreatment will help minimize concentrations of chemicals of concern and illegal dumping events that can cause wastewate r treatment upsets.

EWA maintains a robust source control program in which they permit and monitor all industrial users in the sewershed. The most recent data from their source control program is from 2015, at which time EWA had 59 permitted industrial users, four of which were considered significant. As of the end of 2015, EWA had no incidents of “upset, interference or pass -through” attributed to industrial users and industrial users were contributing only 0.84% of the average daily influent flow (Encina Wastewater Authority 2017). All regular sampling at both the ocean outfall and in receiving waters showed that EWA’s effluent quality met or exceeded compliance standards.

In addition to the regulation of industrial users, EWA also implements a range of best management practices (BMPs) aimed at reducing the level of pollutants entering the system. The BMP program involves working with non -significant industrial users to iden tify specific pollution prevention strategies and follow -up sampling and inspection to ensure the effective ness of the program. Since its inception in 1999, the BMP program has reduced th e level of pollutants entering the treatment plant and has resulted i n a decrease of non-significant industrial user permits, including a decrease from 304 to 35 by the end of the second year of the program (Encina Wastewater Authority 2017) . Increased wastewater flows to EWA’s s ervice area are expected to result from increased residential development and should have little to no effect on the level of industrial sources in the sewershed. If new indust rial users enter the sewershed, EWA is well -equipped to ensure that proper indus trial source control and pretreatment is implemented to safeguard the influent flows to the treatment plants.

2.1.2 Primary Effluent Flow Equalization
Primary effluent flow equalizat ion stabilizes the organic and nitrogen load to the biological treatment process, making the biological treatment, as well as each subsequent treatme nt step, easier to operate and manage. The constant flow allows the processes to become more stable and reliable. It also allows for more appropriate sizing of subsequent treatment proces ses, including membrane processes at the AWTF, preventing over-design due to sizing for peak flows.

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Currently, EWPCF utilizes Aeration Basin No. 4 for primary flow equalizatio n; however, this required modifications to the basin and addition of manual controls. Converting the EWPCF to an NDN facility will require additional aeration basin volume; thus, Basin No. 4 is likely to be needed for its original purpose in the future.

A flow equalization simulation was performed to estimate the volume required to equalize an average daily flow of 31 mgd assuming a typical diurnal fl ow pattern ( Figure 2-1). Based on the simulation, approximately 4.5 MG of equalization volume is required. A 20% safety factor was assumed resulting in a total volume of 5.4 MG. Based on this analysis, two new 2.7 MG circular tanks are assumed to provide primary flow equalization.

Figure 2-1: Projected EWPCF Diurnal Flow Curve and Flow Equalization Volume

2.1.3 Conversion of Secondary Treatment to NDN
Currently, EWPCF operates in a non -nitrifying mode which has the primary goals of reducing the biochemical oxygen demand (BOD), total suspended solids (TSS) and turbidity of the secondary effluent for ocean discharge . Howeve r, as mentioned, biological nutrient removal such as nitrification - denitrification (NDN) is recommended for waters used as source waters for an AWTF. Running the EWPCF as an ND N facility, specifically using the Modified Ludzack -Ettinger Process (MLE) , will lead to more consistent and better water quality with respect to BOD, TSS, turbidity, TOC and contaminants of emerging concern (CECs). It will also reduce the downstream capit al costs of filtration at the AWTF and reduce fouling of the membranes. Typicall y, ML E requires greater aeration basin capacity than non -nitrifying facilities. However, EWPCF currently uses only two of four aeration basins and can potentially Sept. 27, 2022
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accommodate MLE in the existing aeration basins so recent water quality data and biological modeling was utilized to evaluate MLE at EWPCF.

The strength of the influent wastewater to the EWPCF has increased in recent years due to drought and water conservation efforts. Table 2-1 presents and compares average influent and primary effluent strength from 2011-2012 and 2016.

Table 2-1: Average Influent and Primary Effluent Strength for 2011 - 2012 and 2016 Parameter Units 2011-2012 2016 Percent
Change
Influent Flow mgd 23.2 21.0 -11%
Influent TSS mg/L 299 380 21%
Influent BOD mg/L 288 406 29%
Primary Effluent TSS mg/L 71 57 -25%
Primary Effluent BOD mg/L 159 203 22%
TSS Removal % 76 85 11%
BOD Removal % 44 50 12%

As shown in Table 2-1, the average influent TSS and BOD have increased by 21% and 29%, respectively, since the sampling in 2011 -2012. The primary effluent BOD also increased similarly (by 22%), but the primary effluent TSS decreased. Though TSS removal was already quite high during the first sampling (76% removal), it increased to 85% removal in 2016 leading to a decrease of 25% in primary effluent TSS.

Therefore, although influent TSS increased 21% from 2011-2012 to 2016, primary effluent TSS decreased by 25% over this same interval. Th is could be explained by chemical enhancement of the primary sedimentation, or perhaps by increases in chemical dosing or hydraulic residence time.

Overall, increases in influ ent TSS and BOD are dampened by primary sedimentation and do not affect secondary processes as much as influent concentrations would suggest. Influent ammonia is not measured but would follow the same trends as TSS and BOD, though ammonia would not be remo ved by primary sedimentation. While increased ammonia concentrations do not impa ct conventional treatment, they are a significant factor in NDN. Limited data is available on nitrogen in influent or primary effluent flows, so additional sampling and profili ng of the influent and primary effluent should be performed to further develop the conversion to NDN.

Modeling of the EWPCF was conducted using GPS -X, a dynamic wastewater treatment simulator. The model was calibrated using 2016 operational data as it is most representative of recent wastewater strength.

Table 2-2 presents the average historical conditions (January - December 2016) and the calibrated model results. Once the model was calibrated to closely simulate the average conditions, it was used to simulate NDN conditions at 2040 design flows, peak flows, and peak concentrations and sludge volume index (SVI) assuming primary flow equalization and steady state conditions.

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Table 2-2: Modeling Results Summary

Parameters a Units
Existing
Average
Conditions
(2016)
Calibrated
Model
Results
NDN Modeling Results Typical Design Values
Current
Flow
Projected
2040
Flow
Peak
Flow c
Peak
Conc. &
SVI c, d
Conventional NDN
Flow mgd 21.0 21.0 21.0 31.0 40.3 31.0 --
Primary Clarifiers
Primary Clarifiers in Operation No. 6 6 6 9 10 9 --
Primary Overflow Rate gpd/sf 1094 1094 1094 1076 1259 1076 800 – 1000 Primary Detention Time hours 1.5 1.5 1.5 1.5 1.3 1.5 1.5 – 2.5 Primary Effluent TSS mg/L 57 57 57 57 57 70 --
Primary Effluent BOD mg/L 203 203 203 203 203 226 --
Primary Effluent TKN mg/L 46 46 46 46 46 50 --
Aeration Basins (Bioreactors)
Aeration Basins Online No. 2 2 3 3 4 4 --
Active Bioreactor Volume MG 4.68 4.68 7.02 7.02 9.36 9.36 -- Anaerobic/Anoxic Volume % 17 17 33 33 33 33 20 - 40
Bioreactor Detention Time hours 5.3 5.3 8.0 5.4 5.6 7.2 2.5 – 5.0 5.0 – 12 SRT days 1.88 1.88 8.0 8.0 8.0 8.0 <2.5 >8
Mixed Liquor Recycle Flow mgd 0 0 100 120 120 120 0 2Q – 4Q RAS Flow g %Q 37 37 75 75 75 100 50 – 100
MLSS mg/L 1413 1415 2960 4313 4140 3940 1000 –
2500
2500 -
5000
Alpha factor e -- -- 0.6 0.4-0.6 0.4-0.6 0.4-0.6 0.4-0.6 0.4 – 0.6 SOTE f % -- 16 16 16 16 16 30
Dissolved Oxygen (Zones 3&6) mg/L 1.4/1.8 1.4/1.8 1.4/1.8 1.4/1.8 1.4/1.8 1.4/1.8 2 OUR (1st Aerobic Zone) mgO2/(L.h) NA 39 61 91 87 74 <100 Total Airflow scfm 10213 8465 29600 43300 55900 47000 -- Sept. 27, 2022
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Table 2-2: Modeling Results Summary (Continued)
Secondary Clarifiers
Secondary Clarifiers in Service No. 5 5 5 7 8 8 --
SVI mL/g 150 150 150 150 150 180 --
WAS Rate mgd 0.74 0.74 0.39 0.38 0.51 0.66 --
WAS Concentration mg/L 4992 4764 6736 9903 9690 7700 -- 2 Overflow Rate gpd/sf 485 485 476 505 575 440 400 – 700 2 Solids Loading Rate lb/(sf.d) 7.8 7.8 21.0 32.2 35.5 29.4 <35 2 BOD mg/L -- 5.7 5.0 6.0 6.0 5.0 --
2 TSS mg/L 7.56 9.00 9.00 12.00 12.00 10.00 --
2 Ammonia mg/L 33.7 34.0 0.2 0.2 0.2 0.2 >30 <1
2 Nitrite + Nitrate mg/L 0 0 15.0 15.0 14.3 14.3 0 <10 2 TKN mg/L -- 35.4 1.5 1.7 1.7 1.5 >30 <5
Footnotes:
a. SRT = solids retention time, RAS = return activated sludge, MLSS = mixed liquor suspended solids, OUR = oxygen uptake rate, WAS = waste activated sludge b. Peak flow is assuming a peaking factor of 1.3
c. Peak conditions assume 4th aeration basin is in service and 8th clarifier is equipped and operational d. Peak concentrations/SVI assume 90th percentile primary effluent BOD, TSS and TKN concentrations and SVI from 2016 e. Alpha factor based on low concentration MLSS and assumed to be lower for higher MLSS concentration; tapered through the aeration basin for NDN scenarios f. SOTE calibrated to target approximate total aeration airflow assuming some of the existing airflow used for channel mixing g. Higher RAS rate required for peak concentration/SVI condition to keep secondary clarifier blankets low Parameters a Units
Existing
Average
Conditions
(2016)
Calibrated
Model
Results
NDN Modeling Results Typical Design Values
Current
Flow
Projected
2040
Flow
Peak
Flow c
Peak
Conc. &
SVI c, d
Conventional NDN
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The NDN model results for the 2040 projected flows sh ow that NDN with the MLE process is possible with the existing tanks/footprint at EWPCF; however, there is limited redundancy as three of four aeration basins and seven of eigh t secondary clarifiers are in use at that condition. To ensure that current tank age could handle peak storm events or other challenging circumstances (e.g., peak concentrations and reduced sludge settleability), additional scenarios were modeled. The NDN m odel results at peak flows show that existing tankage can treat up to 40.3 mgd, though all four aeration basins and all eight secondary clarifiers would be in use. This is also the case for the peak concentration and SVI condition, for which the 90 th percentile primary effluent BOD, TSS, TKN and SVI values from 2016 were used as model inputs. There is a significant increase in aeration demand and associated energy requirements for all NDN scenarios, which is described in more detail in Section 2.3 below. The solids loading rate to the secondary clarifie rs appears to be the most limiting factor for all NDN conditions, and due to the lack of redundancy at 2040 peak conditions, two additional secondary clarifiers are recommended.

The biological modeling results for NDN at the projected 2040 flow are compared to the current operating conditions of the City of San Diego’s North City Water Reclamation Plant (WRP) in Table 2-3. North City WRP is designed to treat and reclaim up to 30 mgd of wastewater, though it currently receives only 15.4 mgd of influent flow. Recycled water produced at the North City WRP supplements the water supply of the northern region of the City of San Diego, used primarily for industrial and agricultural purposes. The North City WRP is an NDN facility that has been running successfully since 1996 and is similar in many ways to the proposed EWPCF at 2040 design flows utilizing MLE.

Table 2-3: Aeration Basin Retrofit
Parameter Encina WPCF (2040) North City WRP a
Influent Flow 31.0 mgd 15.4 mgd
Aeration Basins
Duty/Total Number of Units 3/4 3/7
Sludge Retention Time (SRT) 8 days 10 days
Mixed Liquor Suspended Solids (MLSS) 4,313 mg/L 4,500 mg/L Hydraulic Retention Time (HRT) 5.4 hours 5.1 hours
Secondary Clarifiers
Duty/Total Number of Units 7/8 8/14
Overflow Rate 505 gpd/sf 538 gpd/sf
Solids Loading Rate 32.2 lbs/sf-d 33.6 lbs/sf-d
Footnotes:
a) Based on operational data from July 1, 2016 through February 22, 2017.

Table 2-3 shows clear similarities between the estimated operational parameters for the EWPCF running as an MLE facility and those employed at the North City WRP. EWPCF is closer to its full tre atment capacity than the North City WRP, but the similarity in operations suggests that the designs for the EWPCF with MLE at 2040 flows are reasonable and yield results similar to the well-functioning North City WRP.

It is important to note that there are other treatment options available for achieving nutrient removal, such as the u se of a membrane bioreactor (MBR) in the secondary treatment process or using the secondary effluent as source water for an MBR. Retrofitting the EWPCF with an MBR system would be a m ajor capital investment and would also carry high operating expenditures, including additional energy for air scouring, chemicals for membrane cleans, and routine membrane replacements every 5 -7 years. An MBR treating a non-nitrified secondary effluent will also require a supplemental carbon source, such as methanol, for denitrification. Based on the increased associated cost, MBR was not assessed in this Reuse Study.

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2.1.4 Tertiary Filters
Filtration is recommended to reduce the particulate matter in the secondary effluent prior to the AWTF.

Lower particulate levels will help improve the effectiveness of downstream membrane treatment processes and reduce the maintenance requirements for the online meters. The filters will also provide a significant buffer to any process upsets in the upstream wastewater treatment plant and redundancy of treatment processes, which is ideal for potable reuse schemes.

Six granular media filters, each with a surface area of 440 ft2, are assumed to filter the 19 mgd of secondary effluent to be treated by the AWTF. A waste wash water equalization basin is also required to equalize the granular media filter and membrane filtration backwash flows. The filtrate from the tertiary filters will feed the AWTF and does not need to adhere to Title 22 filtration requirements, so these filters can exceed 5 gpm/ft2. The predicted flow rate through all six filters is 5 gpm/ft 2, increasing to 7.50 gpm/ft 2 with two filters offline.

2.1.5 Management of Sludge Dewatering Sidestreams
The dewatering of dig ested s ludge results in liquid sidestreams that contain high concentrations of ( 1) nutrients (ammonia and phosphorus), (2) polymers and organic components that are known precursors of NDMA (a carcinogenic disinfection byproduct known to breach RO systems), and (3) recalcitrant organics that behave as strong membrane foulants. Currentl y, EWPCF treats sludge dewatering sidestreams in the plant with the rest of their water. It is critical to manage and dilute these sidestreams effectively to ensure reliable nitrification, minimize NDMA formation, provide consistent treatment, and protect the downstream membranes.

The best option for the management of sludge dewatering streams at EWPCF is to have separate treatment for the sidestreams (e.g., a membrane bioreact or), and discharge the effluent into the ocean at the Encina Ocean Outfall. This option will need to be assessed further to ensure that EWPCF can still meet their ocean- discharge permits with the inclusion of these sidestreams. With this configuration, the treated effluent from the sidestreams is not recycled through the treatment pla nt, which is ideal for both maintaining consistent conditions for the biological processes and for improving effluent quality.

Alternatively, the sidestreams can be returned to primary flow equalization basins. By returning the sludge dewatering sidestreams to primary flow equalization basins, these concentrated liquid streams are diluted and slowly brought back into the biological treatment process when the BOD and ammonia load are lowest.

Preliminary Layout of Improvements
The modifications to the EWPCF and the proposed AWTF could be sited in the area south of the treatment plant designated for expansion (except for the additional secondary clarifiers, which could fit in the current EWPCF footprint) (Figure 2-2). Refer to Table 2-4 for the dimensions of the proposed facilities.

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Figure 2-2: Preliminary site layout for new facilities at EWPCF

Table 2-4: Dimensions of Proposed Facilities
Description Dimensions (ft)
Primary Flow EQ Tanks (2) 140 (dia.)
Tertiary Filters (6) 20 x 22 x 7 (L x W x D)
Waste Wash Water Basin 40 x 40 x 25 (L x W x D)
Tertiary Filter Perimeter 200 x 100 (L x W)

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Conceptual Costs for EWPCF Improvements

2.3.1 Capital Costs
Preliminary cost estimates were performed for the following EWPCF treatment improvements:
• Primary effluent flow equalization
• Conversion of the secondary process to MLE
• Tertiary filters
Estimates for sidestream t reatment of the centrifuge centrate are not included in this preliminary cost estimate associated with the EWPCF but should be further evaluated.

Primary effluent flow equaliz ation assumes two concrete storage tanks, piping, a pump, flow meter, and control valve. The costs of excavation and installation are included in the estimate as well.

Conversion of the secondary process to MLE will require the following modifications:
• Internal mixed liquor recycle (IMLR)
o Pumps
o Piping
• Anoxic Zones
o Baffling
o Mixing
o Scum and Foam Removal
• Aeration
o Larger blowers
o Larger air piping
o Additional fine bubble diffusers
• Clarification
o Two additional secondary clarifiers

The preliminary cost estimate (see Appendix A) assumes that NDN will take place in the existing aeration basins with the retrofits listed above. Larger air piping, new blowers, and enhanced mixing make up the bulk of the estimated additional capital associated with the aeration basin re trofit for MLE. It is assumed that the existing blower building is adequate for accommodating the new blowers. If the existing aeration piping is large enough for the anticipated airflow rates for nitrification, then the additional capital associated with MLE could be considerably less than what is shown in Appendix A . Installation co sts for this equipment are listed separately.

Two additional circular secondary clarifiers are assumed wit h the same dimensions as the existing secondary clarifiers. This cost estimate includes the cost of two new secondary clarifier structures and the equipment for three clarifiers (i.e., to also equip the existing Secondary Clarifier No. 8 that is currently unequipped). The costs of equipment, excavation and installation for the new clarifiers are included in the estimate for the structures, while the equipment cost for the unequipped existing clarifier is listed as its own line item. Installation for the unequipped secondary clarifier equipment is listed separately, in combination with the installation of the aeration basin retrofit.

Six granular media f ilters are assumed with surface areas of 440 ft 2, as well as a waste wash water equalization tank with a ca pacity of 264,000 gal. The waste wash water tank was sized to hold th ree Sept. 27, 2022
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backwash volumes (estimated as 200 gal/sf filter surface area); this is a conservative sizing approach that should also be sufficient to accommodate backwash water from membrane processes at the AWTF as well.

The cost estimates for the tertiary filters include excavation, piping and installation.

2.3.2 O&M Costs
The operations and maint enance (O&M) costs associated with NDN are also higher than non-nitrified treatment. The cost increases ove r “status quo” EWPCF operating conditions are presented in Table 2-5 (based upon a rate of $0.15 per kWh), and are also included in Appendix A.

Table 2-5: Preliminary Estimate of Increase in O&M Cost with NDN O&M Item Difference in Cost
Power
Aeration Blowers $2,013,000
IMLR Pumps $122,000
Anoxic Zone Mixers $47,000
Subtotal Power Costs $2,182,000
Equipment
Equipment Rehabilitation and Replacement $71,500
Estimated Annual O&M Increase $2,254,000

The O&M cost estimates assume that EWPCF is runn ing at the design flow of 31 mgd. The difference in O&M costs scale with flow should EWPCF not operate at the design condition. The principal driver for the increase in O&M costs is the power demand associated with the increased aeration demand for nitrification.

It was assumed that no additional labor would be required over EWA’s bas eline operations and that there would be no increase in chemical costs as additional coagulant/polymer is not expected to be necessary.

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3 Advanced Water Treatment Concepts
Overview
In implementing potable reuse at the EWPCF , protection of public health req uires adequate treatment to remove pathogens and chemicals, a system of multiple barriers for reliability and redundancy, system atic monitoring to ensure compliance, proper ope ration and maintenance, careful source control, a nd qualified operator training. Combining treatment processes into a series of multiple barriers provides effective pathogen and chemical pollutant reduction.

While the pathogen and chemical pollutant remov al goals are the same for all types of potable reuse, the actual combination of treatment processes can vary, depending on the end use. The major concerns of using treated wastewater as a feed source for puri fication are the presence of pathogens and trace -level constituents in secondary effluent (Rose et at., 2004, Olivieri et al., 2007, and Trussell et al., 2015).

Additional processes beyond secondary or tertiary treatment, defined as A dvanced Water Treatment , are used to produce advanced treated water ( ATW) (Tchobanoglous et al., 2015). ATW must protect human health, as well as surface water quality and groundwater quality, depending upon the use of the water . To serve as a new water source, ATW must meet federal, state, and local regulations. A description of the regulatory requirements and a review of water reuse projects in Calif ornia and Nationally is provided in this Study’s TM1: “Background of Potable Reuse in California".

From a risk reduction standpoint, minimization of both chronic and acute ris k to consumers is the goal of advanced treatment. From a p ublic health perspective, potable water reuse depends on the combined performance of various processes to remove pathogens and pollutants. These processes can only produce water reliably if the overall treatment train is robust, redundant, and resilient (known as the “4 Rs”, Pecson et al., 2015).

Each treatment process operates within a performance range , of ten normally or close to normally distributed. This means that, for a small percentage of time, the performance of that process may be below or above the expected value. Fro m a treatment train perspective, should the low level of performance (equating to lesser water quality) for one key process occur at the same time as the low level of performance for another key process, there may be an increased risk to public health. Thi s risk is minimized through coupling reliability and redundancy. To make processes redundant, treatment processes are designed with multiple barriers to provide effective patho gen and chemical pollutant reduction. While the pathogen removal and chemical pollutant goal is the same for all types of potable reuse, the types and combinations of treatment processes can vary based on the source water, end use, and other project-specific factors.

Treatment Technologies
Potable reuse treatment technologies have be en documented in both demonstration and full -scale applications through years of re search and performance monitoring. This section summarizes accepted treatment technologies that would be appropriate for producing ATW from EWPCF effluent.

3.2.1 Ozonation with Biologically Active Filtration
Ozonation (O 3) with biologically active filtration (BAF) is a treatment combination used to break down organic matter and trace pollutants into smaller molecules through chemical oxidation by ozone, so that the biofilm developed in the biofilter can more readily biodegrade the oxidized organic matter. O3/BAF can be installed ahead of microfiltration (MF) or ultrafiltration (UF) membranes, enhancing their operation. There are three primary benefits of O3/BAF treatment:

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• reduction of TOC, both the bulk TOC and trace pollutants, • reduction of pathogens, and
• removal of nutrients (e.g., ammonia removal through nitrification).

Results from two recent O ₃/BAF demonstration projects for potable water reuse are summarized in this section.

Pilot at Reno-Stead Water Reclamation Plant, Las Vegas, NV An O₃/BAF demonstration project was completed as part of WRRF Project 11 -02, and documented by Trussell et al. ( 2015). The O3/BAF pilot plant used an O3 system from MiPro, advanced oxidation pilot system from Xylem, and the BAF from Leopold Biofiltration. The O 3/BAF was studied on a very high quality secondary effluent, with and without microfiltration as pretreatment. Feed TOC was approximately 5 mg/L. TOC removal percentages were higher for MF filtered water (29 -40 %, average 34 %) compared to secondary effluent (26-33 %, average 30%). Substantial destruction and degradation of trace pollutants (e.g., hormones and pharmaceuticals) was seen as part of this study.

Pilot at Santa Clara Valley Water District
An O₃/BAF demonstration project was completed at the Santa Clara Valley Water District (SCVWD ) (2015) using the same O3/BAF pilot plant as in Trussell et al. (2015). Two water qualities were used with the O3/BAF setup (tertiary recycled water and secondary effluent) at O₃/TOC values of <1, and with BAF empty bed contact times (EBCTs) of 20 to 30 minutes, based on Trussell et al. (2015). The goal of testing the different operational scenarios was to maxim ize TOC reduction , destroy or reduce trace organic constituents, and destroy pathogens, all while minimizing the construction cost of a future O3/BAF system.

Influent water quality plays an important role in O 3 demand and O3 dosing costs. A stable influent water quality lessens operational effort with a streamlined dosing system for both O3 and BAF. Overall, the TOC removal for this study's O3/BAF pilot was approximately 20% when treating blended tertiary recycled water, and 25 % when treating secondary effluent. The effluent TOC from the O3/BAF pilot ranged from 2 to 7 mg/L. Reduced performance on the tertiary recycled water was potentially due to the variability in feed water quality, particularly due to the changing chlorine concentration and type (free or combined). Periodic breakthrough of chlorine to the BAF could hinder the biological activity within the BAF. O₃/BAF showed good reduction of ammonia through BAF (from ~1 mg/L to below detection [0.1 mg/L]), but nitrate levels, as expected, remained high (~11 to 15 mg/L as nitrate-N). The BAF would need to be run in an entirely different mode to provide denitrification.

Disinfection byproduct formation, particularly bromate, chlorate, and NDMA, is also a concern due to the use of O₃, and thus was measured through the O3/BAF process at SCVWD (2015). O3 was shown to form bromate, for which BAF was an effective removal technology. Higher O 3/TOC ratios resulted in higher bromate formation, as expected. In all tested cases, the O3/BAF finished water bromate concentration was less than the MCL. Chlorate levels were low in the feed to the O 3/BAF, with no measurable increase by ozonation or decrease through BAF. The O3/BAF finished water chlorate concentration for all tests was less than the notification level of 800 µg/L (NL). Consistent with other work, ozonation increases NDMA formation, and BAF reduces NDMA concentrations. The key to meeting NDMA targets (such as 10 ng/L) is to minimize NDMA levels upstream of o zonation (e.g., by separating sludge dewatering centrate sidestream flows as described in Section 2.1.5 above).

Overall Performance for Pathogen Reduction : No log removal credit is obtained by BAF, though the U.S. Environmental Protection Agency’s (USEPA) Long Term 2 Enhanced Surface Water Treatment Rule could be used to obtain pathogen credit based upon filtered effluent turbidity va lues (USEPA, 2006).

However, log removal credit can be achieved by ozonation . Assuming a temperature of 15 ºC or higher, Giardia is reduced by 3 log at a CT of 0.95 mg/min/L. At the same temperature, 4 -log reduction of virus occurs at a CT of 0.6 mg/min/L. A 5-log virus disinfection approval for O ₃ disinfection is based upon a Sept. 27, 2022
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minimum CT of 1.0 mg/min/L. Trussell et al. (2015) documented similar virus kill. Both projects consistently demonstrated 7+ log reduction of seeded MS2. Such log reduction of MS2 is conservatively equivalent to 5-log reduction of poliovirus (Tchobanoglous et al., 2015).

3.2.2 Membrane Filtration - Microfiltration/ Ultrafiltration Microfiltration (MF) and Ultrafiltration (UF) are both types of physical filtration processes. Membranes used for MF applications have a pore size that r anges from 0.1 to 10 µm, while UF membrane pore sizes are smaller, in the range of 0.001 to 0.1 µm. MF/UF is a robust technology that has proved to be effective to remove Giardia oocysts and Cryptosporidium cysts, algae, and some bacterial species. However, MF is not an effective barrier to viruses. On the other hand, UF have proven to be effective in removing viruses.

MF/UF processes have not been shown to remove a significant amount of chemical pollutants. A primary function of the MF/UF system in a potab le reuse treatment train is to provide adequate pretreatment for sustainable operation of the RO process.

Recent DPR demonstration testing with Clean Water Services (CWS) (Oregon) indicates that a well - functioning UF membrane (0.01 µm nominal pore size in this case) can attain 4.7-log reduction of seeded virus (CWS, 2014) without chemical use (such as alum or polymer) ahead of the membrane. Equivalent or greater reduction of protozoa can be assumed based upon this data, and is directly supported by NSF (2012).

Furthermore, MF or UF membrane integrity testing (MIT) confirms system performance and demonstrates how MIT data can be used to track and ensure continued membrane performance (CWS, 2014).

Overall Performance for Pathogen Reduction: Both MF and UF memb ranes can be relied upon for 4+ log reduction of protozoa. System performance monitoring (to provide regulators confidence in the removal credit) is accomplished by precise and accurate filtrate turbidity monitorin g coupled with daily pressure hold tests a nd MIT. Innovative methods to track MF or UF performance includes the use of bench -scale particle counting and the use of adenosine triphosphate (ATP) to daily verify bacteria removal . ATP provides a near real -time microbial monitoring tool that could allow better diagnosis and mitigation of threats as compared to the more conventional MIT and turbidity monitoring.

3.2.3 Reverse Osmosis (RO)
The RO process in a potable reuse treatment train provides for removal of salt (measured as TDS and electrical conductivit y (EC)), organics (measured as total organic carbon (TOC)), and pathogens. RO removes ~95 percent of incoming salt. Depending on the feed water quality, RO permeate can have a total dissolved solids (TDS) concentration lower than 50 mg/L. Along with salt and TOC removal, RO removes trace level pollutants as hormones, pharmaceuticals, and personal care products.

Studies have found virus removal by RO to be from 3 to >6 -log (Reardon et al., 2005, NRMMC/EPHC/NHMRC 2008, CWS 2014). Equal or greater removal is expected for protozoa based upon size differences (protozoa being much larger than virus). However, the log removal value for RO pathogen rejection is not governed by the ability of an intact membrane to rejec t pathogens; it is governed by the ability to mo nitor process integrity (Reardon et al., 2005 and Schäfer et al., 2005). The monitoring tools currently used, EC meters and TOC meters, can measure 99 percent or less removal of both parameters through the RO process. Recently, the DDW granted 1.5 -log reduction credit for all pathogens for RO (WRD, 2013), based upon a requirement to continuously monitor TOC reduction across RO. The Orange County Water District currently attains 2-log pathogen credit using online TOC meters.

Alternative technologies, such as online fluorescent dye monitoring, have been shown to have higher accuracy in assessing membrane efficiency (Steinle -Darling et al., 2016, Kitis et al., 2003, Henderson et al., 2009, Pype et al., 2013). The proprietary Trasar® fluorescent dye (Nalco) is s table over a range of temperature and is not impacted by pH in the range of 4 to 10. At 600 g/mol, this compound is larger than Sept. 27, 2022
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the openings in the RO membrane, but smaller than the size of any target pathoge n, making the Trasar technology a potentially valuable tool for RO system performance monitoring.

The Trasar technology's efficiency to detect any flaw in a RO membrane was tested as part of the Ventura Water Pure demonstration testing. The test included monitoring the removal of seeded virus MS2, EC, and Trasar for different RO operational conditions, including "normal" operation, a cut O -ring condition, and two chlorine oxidized RO membranes. The performance was tracked across both the first stage of RO a nd for the entire RO. Results from this research demonstrate the ability to conservatively monitor 3 to >4 -log removal of virus using Trasar, compared to ~1.5 -log removal of other monitoring surrogates (Steinle - Darling et al., 2016).

Overall Performance for Pathogen Reduction : RO provides a robust remov al for all pathogens and substantial removal of trace level chemical pollutants. For the purposes of this Study, we are assuming 1.5- log reduction for all pathogens, with an increase to 3.0 -log reduction if t he Trasar technology is used.

California DDW has stated that they are willing to approve the Trasar technology once a utility applies for credit.

3.2.4 Advanced Oxidation Process (AOP)
In the event of pathogens passing through RO, the AOP process provides additional disinfection and removal of trace organics . An ultraviolet irradiation (UV) dose of 235 mJ/cm 2 will result in 6+ log reductions of all target pathogens (USEPA 2006; Hijnen et al., 2006, Rochelle et al., 2005), including Cryptosporidium, Giardia, and adenovirus. Potable water reuse UV AOP systems wi ll commonly operate at UV doses greater than 900 mJ/cm 2; thus, higher reductions are theoretically possible, but DDW allows only a maximum of 6-log reduction credits per any one treatment technology (CDPH, 2014).

Adding an oxidant before a high UV dose results in the generation of hydroxyl radicals during treatment, providing an advanced oxidation process (AOP). The UV AOP provides destruction of a range of pollutants that may pass through RO. Either Hydrogen peroxide (H2O2) or sodium hypochlorite (NaOCl) can be used as an oxidant for this application. H2O2 is a more common oxidant than NaOCl for UV AOP applications.

Both the NaOCl and H 2O2 UV AOPs are controlled by oxidant dose and UV dose (UV intensity, UV transmittance, or power). However, the NaOCL UV process is also controlled by the influent pH to the UV reactor and is sensitive to ammonia residual through the RO process , which has a high NaOCl demand, thereby requiring a higher oxidant dose. Free chlorine concentration and pH should be closely monitore d to ensure the UV AOP design dose is met.

DDW requires the UV AOP to provide at least 0.5 -log reduction of 1,4-dioxane, a conservative surrogate for destruction of trace pollutants (CDPH, 2014). Additional ly, NDMA, with a DDW notification level (NL) of 10 ng/L, can pass through RO at low concentrations (typically 20 to 100 ng/L), requiring destruction by UV photolysis (Sharpless and Linden, 2003). Therefore, it is common to set the UV dose at 900 mJ/cm2 or higher. This high UV dose photolyzes NDMA as well as many other smaller chemicals that may have passed through the RO train. NDMA is particularly photolabile.

Overall Performance for Pathogen Reduction: UV/AOP reliably provides at least 6 -log disinfection of both protozoa and virus. The same system will reduce NDMA to <10 ng/L and destroy at least 0.5 -log of 1,4-dioxane, thus also reducing other trace level pollutants. Online dose monitoring systems, using real time inputs of UV, UV intensity, flow, and o xidant dosing, is recommended for continuous confi dence in UV AOP performance.

3.2.5 High-Flux Water Treatment Plant
To meet the anticipated regulations for direct potable reuse (following the Quirk Bill), in particular for “treated drinking water augmentation”, a separate water treatment plant consisting of en gineered storage buffer (ESB), chlorination, and a high-flux UF system will be used to treat the purified water produced by Sept. 27, 2022
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the AWTF. The UF system will be able to achieve high fluxes (~120 gfd) due to the high quality of the water.

For this case, the ESB has been designed to have a residence time of two (2) hours. This time will provide response time to identify treatment and monitoring system failures and implement appropriate corrective actions. Should t he hold time of two hours pass without an “overrid e” by the responsible operator (i.e., indicating successful resolution of any problems and return to required treatment quality) , the “off-spec” water would be diverted to waste, followed by continued diversion until all issues are remedied.

Proposed Treatment Trains
The proposed treatment trains for this Study’s Options combine the available technologies for advanced water treatment of pathogens and pollutants in accordance with current California state reg ulations for potable water reuse through groundwater injection and surface water augmentation. The proposed treatment trains (Figure 3-1 below) include RO for reduction of salts as well as the removal of pollutants and pathogens. The brine from the RO process will be disposed via the Encina Ocean Outfall. Backwash water for the MF/UF will be directed to the Carlsbad Water Reclamation Facility (CWRF) to augment non-potable reuse supplies.
a. Full Advanced Treatment (FAT) AWTF: this widely accepted treatment train includes membrane filtration (MF/UF), reverse osmosis (RO), and an ultraviolet light/advanced oxidation step (UV/ NaOCl AOP). NaOCl as an oxidant for AO P presents benefits such as increased disinfection due to the presence of free chlorine, lower chemical cost, and operator familiarity. An additional benefit of the UV/NaOCl AOP is a more efficient generation of hydroxyl radicals at a low pH (<6), because RO permeate is typically in this pH range and can be readily controlled within this range . This treatment trai n is tailored to groundwater and surface water (reservoir) augmentation projects.
b. FAT with O 3/BAF AWTF: this treatment train adds ozonation (O ₃) with biologically active filtration (BAF) as pretreatment before MF/UF. These additional treatment steps provide further pathogen removal and enhance d water quality, improving the performance of downstream technologies. This treatment train is anticipated to be appropriate for raw water augmentation projects, based on currently available information (DDW regulations are pending). c. FAT with O₃/BAF AWTF plus WTP: in addition to the FAT with O3/BAF advanced treatment train, an additional barrier and treatment would be provided by a tailored Water Treatment Plant (WTP) consisting of an Engineered Storage Buffer (ESB) with chlorination (Cl2) and a high-flux UF system. This treatment train is anticipat ed to be appropriate for integration with the potable water system, based on currently available information (DDW regulations are pending).

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Figure 3-1: Advanced Treatment Train Options.

Raw Water
Pipeline or WTP
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Unit Process Monitoring
The performance of each treatment process is measured by log reduction of pathogens and removal of chemical compounds. Because a system of multiple barriers is added up to meet the total log reduction criteria established by regulations, it is important to understand the log reductions that occur across each process. The log reduction credit (LRC) of each process is subject to the ability to accurately monitor system performance, either online or periodically. In California, the potable reuse goals (from source to drinking water) to meet regulatory criteria are defined in Table 3-1, better known as the 12/10/10 rule.

Table 3-1: Potable Reuse Pathogen Reduction Requirements (from source water to potable water).

Applicable Potable Reuse Form Virus Giardia Crypto.

Groundwater Augmentation
Surface Water Augmentation (standard: Dilution  100:1) 12 10 10 Surface Water Augmentation (reduced dilution: 100:1  Dilution  10:1) 13 11 11 Raw Water and Treated Drinking Water Augmentation* 14+ 12+ 12+ Footnotes:
* It is expected that the State will increase several LRC for raw water augmentation and treated drinking water augmentation projects. This increase does not imply an increase in health protection, but rather risk minimization to mitigate the potential of process failure without an environmental buffer.

3.4.1 Expected Performance of Proposed Treatment Trains The anticipated total performance of a proposed treatment train will depend upon the coupled treatment processes, which in turn depends upon the planned type of potable water reuse. Tables 3-2 through 3-5 summarize the treatment performance for the proposed treatment trains described in Section 3.3 above.

Table 3-2: Expected Performance of Treatment Train “a” for Groundwater Augmentation.

Parameter Primary/Secondary
Treatment UF1 RO2 UV/AOP3 Underground
Travel Time4
Total
Credits Goal
Virus (log) 1.9 0 1.5 6 2.6 12.0 12
Giardia cysts
(log) 0.8 4 1.5 6 0 12.3 10
Crypto. oocysts
(log) 1.2 4 1.5 6 0 12.7 10
1,4-dioxane X 0.5-log
by AOP
NDMA X X <10
ng/L
Turbidity X <0.2
NTU
TOC X <0.5
mg/L
Drinking Water
MCLs X X X Varies
Footnotes:

1. Although UF can achieve greater than 2 LRC for virus, no regulatory credit is expected to be granted.

2. Online TOC monitoring can conservatively obtain 1.5 LRC.

3. Assumes NaOCl as oxidant can achieve comparable results to H2O2 as oxidant for 6 LRC.

4. DDW regulations set a minimum time of 2 months. Virus removal can be correlated with time at 1-log removal per month. For this example, 2.6 months is needed to obtain the full credit. Alternatively, Trasar® technology could be used for the RO process to demonstrate 3 LRC instead of 1.5 LRC with online TOC monitoring.

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Table 3-3: Expected Performance of Treatment Train “a” for Surface Water Augmentation.

Parameter Primary/Secondary
Treatment UF RO1 UV/AOP2 WTP Total
Credits Goal3
Virus (log) 1.9 0 1.5 6 4 13.4 13
Giardia cysts (log) 0.8 4 1.5 6 3 15.3 11
Crypto. oocysts (log) 1.2 4 1.5 6 3 15.7 11
1,4-dioxane X X 0.5-log
by AOP
NDMA X X <10
ng/L
Turbidity X X <0.2
NTU
TOC X X <0.5
mg/L
Drinking Water MCLs X X X X Varies
Footnotes:

1. Online TOC monitoring can conservatively obtain 1.5 LRC.

2. Assumes NaOCl as oxidant can achieve comparable results to H2O2 as oxidant for 6 LRC.

3. Assumes reduced dilution credit requirements.

Table 3-4: Expected Performance of Treatment Train “b” for Raw Water Augmentation.

Parameter
Primary/
Secondary
Treatment
O₃ BAF UF RO1 UV/AOP2 WTP Total
Credits Goal
Virus (log) 1.9 5 0 0 3.0 6 4 19.9 14+
Giardia
cysts (log) 0.8 3 0 4 3.0 6 3 19.8 12+
Crypto.
oocysts
(log)

1.2 0 0 4 3.0 6 3 17.2 12+
1,4-
dioxane
X X 0.5-log by
AOP
NDMA X X X <10 ng/L
Turbidity X X X <0.2 NTU
TOC X X X X <0.5 mg/L
Drinking
Water
MCLs
X X X X X X Varies
Footnotes:

1. Use of Trasar® technology for 3 LRC.

2. Assumes NaOCl as oxidant can achieve comparable results to H2O2 as oxidant for 6 LRC.

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Table 3-5: Expected Performance of Treatment Train “c” for Treated Drinking Water Augmentation.

Parameter
Primary/
Secondary
Treatment
O₃ BAF UF RO1 UV/AOP2 ESB/
Cl2 UF Total
Credits Goal
Virus (log) 1.9 5 0 0 3.0 6 6 1 22.9 14+
Giardia
cysts (log) 0.8 3 0 4 3.0 6 3 4 23.8 12+
Crypto.
oocysts
(log)

1.2 0 0 4 3.0 6 0 4 18.2 12+
1,4-
dioxane
X X 0.5-log by
AOP
NDMA X X X <10 ng/L
Turbidity X X X <0.2 NTU
TOC X X X X <0.5 mg/L
Drinking
Water
MCLs

X X X X X

X Varies
Footnotes:

1. Use of Trasar® technology for 3 LRC.

2. Assumes NaOCl as oxidant can achieve comparable results to H2O2 as oxidant for 6 LRC.

3.4.2 Critical Control Points
Operation, maintenance, and monitoring of each the processes used in advanced water treatment is of critical importance to ensure that the finished water is protective of public health. End-of-pipe compliance monitoring and performance-based monitoring are used to ensure that the AWTF continuously and reliably meets the regularity criteria. The benefit of a performance -based monitoring approa ch is to identify and implement Critical Control Points (CCPs) where hazards to human health risks can be reduced, prevented, or eliminated (Mosher et al., 2016).

NWRI defines a CCP as "a point in advanced water treatment where control can be applied to an individual unit process to reduce, prevent, or eliminate process failure and where monitoring is conduc ted to confirm that the control point is functioning correctly. The goal is to reduce the risk from pathogen and chemical constituents." (Tchobanoglous, 2015).

The CCP is intended to effectively monitor process performance, and hence relies upon the consistency of the monitoring system. Monitoring system failures can be gradual (sensor drift), slight (sensor bias), result in a loss in sensitivity, false positives, and false negatives, and even result in outright failure. Table 3-5 shows examples of CCPs for an AWTF and the corresponding monitoring requirements (Tchobanoglous, et al., 2015).

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Table 3-6: CCPs for an AWTF.

CCP Monitoring Tool
O3 / BAF Online ozone dose, empty bed contact time (EBCT); control dose based on the ozone-to-TOC ratio and ozone CT.

MF / UF Daily pressure decay testing (PDT). Values in accordance with membrane supplier recommendations and validation to demonstrate membrane integrity RO
Online EC or online TOC or online fluorescence. Log reduction of EC or TOC or fluorescence across the RO process to demonstrate a minimum level of pathogen removal.

UV-AOP Intensity sensors. Following USEPA 2006 or other methods, online intensity monitoring demonstrates disinfection dose delivery.

Footnote: Adapted from Tchobanoglous et al., 2015 and Mosher et al., 2016 Facility Planning and Conceptual Layouts
The purification systems described here are intended to receive effluent from the EWPCF ’s proposed tertiary filters. It is assumed that the existing Secondary Effluent Equalization Pumps (SEEPs) capacity could be used to pump EWPCF effluent to the potential future AWT site, and thus there would be no added cost or engineering required for this effort. The UF and RO recoveries are estimated at 93% and 85% 1, respectively. The UV/AOP process uses sodium hypochlorite (NaOCl) as oxidant. The process is designed for an available EWPCF effluent flow of 20.5 mgd.

The conceptual facility layouts are intended to accommodate the additional staff required to operate the facility (including administration offices, maintenance shops, and vehicle access and parking), as well as accommodating public tour groups (including additional parking area and a large meeting room).

Furthermore, the conceptual layouts ha ve been configured to avoid conflicts with other planned uses for the South Parcel, including future Interstate 5 expansion, widening and re -alignment of Avenida Encinas, and additional secondary flow equalization facilities.

3.5.1 AWTF for Groundwater and Surface Water Augmentation The preliminary design parameters used for the conceptual design of the AWTF for potable reuse via groundwater augmentation and surface water augmentation are shown in Table 3-7 through Table 3-9.

Table 3-7: UF System Design Parameters
System Component Design Value Unit
UF Feed Tank
Number of tanks 1
Volume for operational equalization, minimum 130,000 gal Total residence time, minimum 11.5 min
Total water volume 163,000 gal

UF Feed Pump
Pump type Vertical Turbine
Number of duty pumps 4

1 These estimated recoveries can be refined in the future with additional analysis of EWPCF water quality and specific treatment equipment.

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System Component Design Value Unit
Number of standby pumps 1
Capacity per pump 5.1 mgd
Drive type VFD

Automatic Strainer
Manufacturer/model Amiad Omega, SP Kinney: AF, Eaton 2596, Fluid Engineering Model 723, or equal
Type Auto-backwash strainer
Design flow 20.5 mgd
Clean head loss, minimum <1 psi
Duty units 4
Standby units 1
Excess capacity required 25 %
Capacity per strainer 6.41 mgd
Screen pore size, minimum 3 m
Strainer recovery 99.93 %

Automatic strainer backwash residuals estimates
Backwash average waste flow 3,000 - 33,000 gpd
Backwash duration per unit, per cycle 25 - 120 sec
Backwash volume per unity, per backwash cycle 148 - 800 gal Backwash flow rate per unit, instantaneous 180 - 740 gpm

UF
Manufacturer Toray
Model Number HFU-2020N
Membrane nominal pore size 0.01 µm
Membrane area 775 ft2
System rated capacity (filtrate flow) 19.1 mgd
Feed flow 20.5 mgd
UF Recovery (assumed) 93 %
Number of total racks 10
Number of membrane modules per rack, installed 86
Number of membrane modules per rack, total
available 96
Design flux, maximum instantaneous (N-2) 38.4 gfd
Backwash water supply UF filtrate
Backwash type Reverse flow with air scour
Backwash interval 24 min
Design NaOCl Maintenance Cleaning (MC)
frequency 2x/week
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System Component Design Value Unit
Design Citric Acid (C6H8O7) (MC) frequency 1/month
Design Cleaning In Place (CIP) frequency 1/month
Direct Integrity Testing (DIT) method Daily PDTs
Indirect integrity testing method
Continuous filtrate turbidity
monitoring

UF Backwash Pumps
Pump type Horizontal Centrifugal
Number of duty pumps 1
Number of standby pumps 1
Flow rate, each pump 2,800 gpm
Total Dynamic Head (TDH) 100 ft

UF Backwash Flow Rates
Cycle length between backwashes (duration of
permeate production) 24 min
Total backwash cycle duration 3.17 min
Backwash flux 54.8 gfd
Backwash flow rate per module 29.5 gpm
Modules per rack, total 96
Backwash f low rate, per rack (maximum
instantaneous) 2,830 gpm

UF Backwash Residuals Estimates
Backwash cycles per day (system) 424
Backwash waste volume per cycle per rack 8,884 gal
Daily average residuals 1.4 mgd

UF Air Scour Blowers
Blower Type
Positive-displacement lobe,
or hybrid rotary lobe
Number of sets 2
Number of blowers on duty 1
Number of blowers on standby 1
Blower capacity, each 665 cfm
Blower pressure 15 psi
Blower motor power, each 60 hp

UF CIP/MC Cleaning procedures
Typical duration, each rack, each clean 27-90 min
Design Frequency
NaOCl: 2x/week
C6H8O7: 1/month
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System Component Design Value Unit
Make-up water UF filtrate
Solution temperature, typical 100 ˚F

CIP/MC System
CIP/MC systems, total 2
CIP fill pumps on duty 1
CIP fill pumps on standby 1
CIP fill pump flow rate, each 500 gpm
CIP fill pump TDH
38 ft
CIP fill pump motor power, each 7.5 hp
MC fill pumps on duty 1
MC fill pumps on standby 1
MC fill pump flow rate, each 500 gpm
MC fill pump TDH 20 ft
MC fill pump motor power, each 5 hp
CIP tanks per system 2
CIP tank volume, each 6,000 gal
CIP pumps on duty 1
CIP pumps on standby 1
CIP pump flow rate, each 1,235 gpm
CIP pump TDH 97 ft
CIP pump motor power, each 50 hp

Neutralization System
Neutralization systems 2
Neutralization tanks per system 1
Neutralization tank volume, each 15,000 gal
Pumps on duty 1
Pumps on stand-by 1
Neutralization/drain pump TDH 43 ft
Neutralization/drain pump flow rate, each pump 500 gpm Neutralization/drain p ump motor power, each
pump 10 hp
Time to drain neutralization tank 30 min

UF CIP/MC Residuals Estimates
Average CIP waste flow 6,300 gpd
CIP duration, total 4 to 6 hr
CIP chemical solutions, per CIP

1. Chlorine

2. C6H8O7
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System Component Design Value Unit
CIP waste volume per CIP chemical solution 11,100 gal
CIP waste volume per CIP total 22,200 gal
Average MC waste flow 35,500 gpd
MC duration, total Up to 90 min
MC waste volume per MC, total 11,100 gal
CIP/MC waste flow from neutralization tanks to
drain, total 1,000 gpm
Average MC waste flow 35,500 gpd

UF compressed air system (for pneumatic valves and the integrity testing system) Compressors duty 1
Compressors standby 1
Compressor type Rotary screw compressor
Compressor size, each 15 kW
Air receivers duty 1
Air receivers standby 1
Air receiver pressure rating 200 psi
Air receiver operating pressure 100-150 psi

Table 3-8: RO System Design Parameters
System Component Design Value Unit
RO Feed Tank
Number of tanks 1
Available volume for operational equalization 8,000 gal Residence time, minimum 15 min
Volume required for minimum residence time 198,600 gal

Cartridge Filters
On duty 3
On standby 1
Flow per vessel 4,413 gpm
Vessel configuration Horizontal
Vessel pressure rating 150 psi
Cartridges per vessel 32
Cartridge rating 5 um
Cartridge material Polypropylene
Cartridge diameter 6 in
Cartridge length 40 in

RO System Flow Stream pH and Chemical Doses
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System Component Design Value Unit
pH Ranges
UF filtrate 6.7 - 7.7
RO feed (dosed) 6.2 - 6.7
RO permeate (typical) 4.8 - 5.7
RO concentrate 7.0 - 7.5
Chemical Dosing
Antiscalant 1.0 - 5.0 mg/L
H2SO4 10 - 100 mg/L
RO Trains
RO Feed 19.1 mgd
RO Permeate 16.2 mgd
Duty 7
Standby 1
RO feed pump flow 1890 gpm
RO feed pressure 100-225 psi
RO recovery (assumed) 85%
RO Stages 3
1st Stage Pressure Vessels 46 Pressure Vessels
Elements Per Vessel 6
2nd Stage Pressure Vessels 23 Pressure Vessels
Elements Per Vessel 6
3rd Stage Pressure Vessels 11 Pressure Vessels
Elements Per Vessel 6
Elements per train 480
Total Elements 3,360
Membrane Hydranautics ESPA2-LD

RO CIP System
CIP tanks on duty 1
CIP tanks on standby 1
CIP tank volume 7,000 gal
CIP tank diameter 12 ft
CIP tank total height 10 ft
Heaters per CIP tank 2
CIP heat power 200 kW
Target CIP solution temperature 45 °C
CIP solution heating time 2 hr
Target CIP solution pH 2 or 11.5
Recirculation rate: Stage 1 1,060 gpm (two halves)
Recirculation rate: Stage 2 1,060 gpm
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System Component Design Value Unit
CIP pumps on duty 1
CIP pumps on standby 0
CIP pump flow rate 1,060 gpm
CIP pump pressure 60 psi

Table 3-9: UV/AOP Design Parameters
System Component Design Value Unit
UV/AOP TrojanUV
Reactors on duty 3
Reactors on standby 1
Oxidant type HOCl
Flow, design 15.7 mgd
Flow capacity per duty train 5.2 mgd
Minimum electrical energy delivered (EED) 0.2 kWh/kgal
Design EED 0.2 kWh/kgal
Minimum UV dose 920 mJ/cm2
Maximum operating pressure 30 psi
Head loss at full flow 4 in
Minimum UVT 96 %

Oxidant Dosing
Oxidant Dosing Free chlorine (HOCl)
Oxidant dose, design 2 mg/L as Cl2
Oxidant dosing system, minimum 2 mg/L as Cl2
Oxidant dosing system, maximum 5 mg/L as Cl2
Chemical Addition NaOCl
Strength of solution 12.5 %

Product Water Tank HRT Volume (gal)
HRT at Full
Capacity (min)
CO2 injection box 40,000 3.6
Lime injection box: 2 boxes on line 22,000 2.0
Lime injection ox: 1 box off line 11,000 1.0
Pump wet well 35,000 3.1

CO2 Storage
Storage time: worst-case conditions 4 days
Tanks 2
CO2 transfer efficiency 95 %
CO2 dose: max 90 mg/L
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System Component Design Value Unit
CO2 feed rate: max (actual) 26,886 lb/d
Net capacity: max conditions, per tank 24 metric ton

Lime Silo
Diameter 12 ft
Height 30 ft
Storage capacity per tank 3,393 ft3
Design total storage capacity 6,786 ft3

FAT AWTF Footprint
The total footprint of the proposed AWTF is approximately 226,300 ft2 (5.2 acres). The total area is based on the footprint provided by the equipment manufacturers and includes the area for the administration building, electrical room, electrical building, roadway, and parking (Table 3-10). Figure 3-2 shows the tentative location of the AWTF on EWA’s South Parcel.

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Table 3-10: FAT AWTF Footprint.

Figure 3-2: Representative Layout of the FAT AWTF on EWA’s South Parcel.

Process Footprint (ft2)2
UF Trains 16,000
RO Trains 18,000
CIP System 2,000
UV System 3,600
Electrical Rooms 5,000
Electrical Building 9,000
Chemical Feed System /Storage 11,300
CO2 Dosing System 2,000
Lime Dosing System 3,000
Product Water Tank 14,700
Pump Station 8,100
Administration Building1 14,000
Parking 40,600
Roadway 79,000
Total Footprint 226,300
Footnotes:

1. The administration building area includes offices, conference rooms, exhibit space, maintenance shops/ storage, control room, water quality laboratory, lunchroom, restrooms, showers, and miscellaneous storage space.

2. Rounded to the nearest 100.

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3.5.2 AWTF for Raw Water Augmentation
The assumed preliminary design parameters used for the conceptual design of the AWTF including O₃/BAF + FAT are shown in Table 3-11. The O₃/BAF provides favorable conditions to design the UF with a higher flux. For the UV/AOP process, the design uses sodium hypochlorite (NaOCl).

Table 3-11. Ozone Design Parameters.

System Component Design Value Unit
Liquid Oxygen (LOX) System
LOX Tanks 2
Tank volume (each) 10,000 gal
Vaporizers 3
Vaporizer capacity (each) 27,500 scfh
Number of Gaseous Oxygen (GOX) Particulate Filters 1
Number of Stand-by GOX Particulate Filters 1
Minimum GOX Filter Capacity 400 scfm

Ozone Generators
Ozone dose, design 14 mg/L
Ozone dose, minimum 5 mg/L
Flow, design 20.5 mgd
Number of duty ozone generators 2
Number of standby ozone generators 1
Minimum generator capacity (each) 1,200 lb/d
O₃ Gas Concentration range at design dose 7 - 12 %
Oxygen supply LOX System
Power Requirements 4.5 kWh/lb O₃
Maximum feed gas dew point -65 °C

Cooling Water System
Open-Loop cooling water pumps, duty 2
Open-Loop cooling water pumps, Standby 1
Closed-Loop Cooling Water Pumps, Duty 2
Closed-Loop Cooling Water Pumps, Standby 1
Number of duty heat exchangers 1
Number of standby heat exchangers 1
Source of open-loop cooling water UF filtrate
Open-loop flow per pump 250 gpm
Motor horsepower per open-loop pump 20 hp
Source of closed-loop makeup water Stabilized RO
product water

Max temperature of open-loop supply 86 F
Max temperature rise across open loop 7.5 F
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System Component Design Value Unit
Minimum heat transfer efficiency 90 %
Pressure differential between loops 5 psi

Ozone Side Stream Injection System
Injection Type Side stream
Number of duty skids 4
Number of standby skids 2
Number of injectors per skid 1
Number of pumps per skid 1
Pump capacity 1,200 gpm
Pump Pressure 80 psi
Number of injection nozzles per flash reactor 6
Minimum 3 transfer efficiency 90%

Ozone Contactors
Type of ozone contactor Serpentine, vertically stacked
Number of ozone contactors 2
Flow, design 20.5 mgd
Flow, design (per contactor) 10.25 mgd
Design HRT 9.65 min
T12/HRT 0.79
Effective HRT (T10) 7.6 min
Design CT (@ 20°C) 3.8 mg-min/L

Sodium Bisulfite Quenching System
Injection Point Ozone Contactors
Design HRT for quenching ozone residual in ozone
contactors 1.2 min
Concentration 25 % by weight
Maximum dose, design 3 mg/L

Ozone Off-Gas Destruct System
Number of duty destruct units 2
Number of standby destruct units 1
Type of destruct units Thermal Catalytic
Maximum ozone concentration in destruct 0.1 ppm
Minimum pressure at basin headspace -4 inches

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Table 3-12: BAC Design Parameters
System Component Design Value Unit
Number of duty filters 5
Number of standby filters 1
Media depth 10 ft
Feed flow, design 20.5 mgd
Filtrate flow, design 20.2 mgd
Filtrate flow, design (per filter) 4.0 mgd
Water Recovery 98.5%
Filter surface area (per filter) 750 ft2
Backwash frequency per filter 2 per week
Backwash water supply source UF feed tank
Backwash flux 10 - 25 gpm/ft2
Backwash flow rate 12.4 - 24.8 mgd
Backwash time 10 min
Backwash volume per filter 173,000 gal
EBCT 14 min
Air scour rate 4 cfm/ft2
Air scour flow rate 3,000 scfm
Air scour duration 6 min
Hydraulic pause duration 5 min

Filter Media Bed Design Criteria
Media Product 8 x 16 mesh granulated activated carbon
Media Type Virgin bituminous coal-based GAC
Effective size 1.3 to 1.5 mm
Uniformity coefficient, maximum 1.4
Media bed length-to-diameter ratio 2,177
Predicted clean bed head loss 1.8 to 2.1 ft

BAC System Backwash Equipment
Number of backwash pumps, duty 2
Number of backwash pumps, standby 1
Backwash pump flow, each 9,375 gpm
Backwash pump pressure 37 psi
Backwash pump power 125 hp
Backwash pump type Horizontal split case
Number of air scour blowers, duty 1
Number of air scour blowers, standby 1
Air scour blower flow, each 3,000 scfm
Air scour blower backpressure 9.1 psi
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System Component Design Value Unit
Air scour blower power 200 hp
Air scour blower type Positive displacement

Table 3-13: UF Design Parameters
System Component Design Value Unit
UF Feed Tank
Number of tanks 1
Available volume for operational
equalization, minimum 130,000 gal
Total residence time, minimum 11.5 min
Total water volume (including
submergence) 163,000 gal

UF Feed Pump
Pump type Vertical Turbine
Number of duty pumps 4
Number of standby pumps 1
Capacity per pump 5.0 mgd
Drive type VFD

Automatic Strainer
Manufacturer/model
Amiad Omega, SP Kinney: AF, Eaton 2596, Fluid Engineering Model 723, or equal
Type Auto-backwash strainer
Design flow 20.2 mgd
Clean head loss, minimum <1 psi
Duty units 4
Standby units 1
Excess capacity required 25 %
Capacity per strainer 6.31 mgd
Screen pore size, minimum 3 m
Strainer recovery 99.93 %

Automatic strainer backwash residuals estimates
Backwash average waste flow 3,000 - 33,000 gpd
Backwash duration per unit, per cycle 25-120 sec
Backwash volume per unity, per backwash
cycle 148-800 gal
Backwash flow rate per unit, instantaneous 180 - 740 gpm

UF
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System Component Design Value Unit
Manufacturer Toray
Model Number HFU-2020N
Membrane nominal pore size 0.01 m
Membrane area 775 ft2
System rated capacity (filtrate flow) 18.8 mgd
Feed flow 20.2 mgd
Assumed Recovery 93 %
Number of total racks 8
Number of membrane modules per rack,
installed 86
Number of membrane modules per rack,
total available 96
Design flux, instantaneous (N-2) 50.5 gfd
Backwash water supply UF filtrate
Backwash type Reverse flow with air scour
Backwash interval 24 min
Design NaOCl EFM frequency 2x/week
Design C6H8O7 EFM frequency 1/month
Design CIP frequency 1/month
DIT method Daily PDTs
Indirect integrity testing method Continuous filtrate turbidity monitoring

UF Backwash Pumps
Pump type Horizontal Centrifugal
Number of duty pumps 1
Number of standby pumps 1
Flow rate, each pump 2,800 gpm
TDH 100 ft

UF Backwash Flow Rates Toray
Cycle length between backwashes
(duration of permeate production) 24 min
Total backwash cycle duration 3.2 min
Backwash flux 54.8 gfd
Backwash flow rate per module 29.5 gpm
Modules per rack, total 95
Backwash flow rate, per rack (maximum
instantaneous) 2,800 gpm

UF Backwash Residuals Estimates
Backwash cycles per day 424
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System Component Design Value Unit
Backwash waste volume per cycle per
rack 8,884 gal
Average backwash waste flow 1.4 mgd

UF Air Scour Blowers
Blower Type Positive-displacement lobe, or hybrid rotary lobe Number of sets 2
Number of blowers on duty 1
Number of blowers on standby 1
Blower capacity, each 665 cfm
Blower pressure 15 psi
Blower motor power, each 60 hp

UF CIP/EFM Cleaning procedures MC
Typical duration, each rack, each clean 27-90 min
Design Frequency NaOCl: 2x/week, C6H8O7: 1/month
Make-up water UF filtrate
Solution temperature, typical 100°F

CIP/EFM System
CIP/EFM systems, total 2
CIP fill pumps on duty 1
CIP fill pumps on standby 1
CIP fill pump flow rate, each 500 gpm
CIP fill pump TDH 38 ft
CIP fill pump motor power, each 7.5 hp
EFM fill pumps on duty 1
EFM fill pumps on standby 1
EFM fill pump flow rate, each 500 gpm
EFM fill pump TDH 20 ft
EFM fill pump motor power, each 5 hp
CIP tanks per system 2
CIP tank volume, each 6,000 gal
CIP pumps on duty 1
CIP pumps on standby 1
CIP pump flow rate, each 1,235 gpm
CIP pump TDH 97 ft
CIP pump motor power, each 50 hp

Neutralization System
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System Component Design Value Unit
Neutralization systems 2
Neutralization tanks per system 1
Neutralization tank volume, each 15,000 gal
Pumps on duty 1
Pumps on standby 1
Neutralization/drain pump TDH 43 ft
Neutralization/drain pump flow rate, each
pump 500 gpm
Neutralization/drain pump motor power,
each pump 10 hp
Time to drain neutralization tank 30 min

UF CIP/EFM Residuals Estimates
Average CIP waste flow 6,300 gpd
CIP duration, total 4 to 6 hr
CIP chemical solutions, per CIP 1. Chlorine 2. Citric Acid (C6H8O7) CIP waste volume per CIP chemical
solution 11,100 gal
CIP waste volume per CIP total 22,200 gal
Average MC waste flow 35,500 gpd
MC duration, total Up to 90 min
MC waste volume per clean, total 11,100 gal
CIP/MC waste flow from neutralization
tanks to drain, total 1,000 gpm

UF compressed air system
Compressors duty 1
Compressors standby 1
Compressor type Rotary screw compressor
Compressor size, each 15 kW
Air receivers duty 1
Air receivers standby 1
Air receiver pressure rating 200 psi
Air receiver operating pressure 100 - 150 psi

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Table 3-14: RO Design Parameters.

System Component Design Value Unit
RO Feed Tank
Number of tanks 1
Available volume for operational
equalization, minimum 8,000 gal
Residence time, minimum 15 min
Available volume required for
minimum residence time 220,000 gal
Total water volume (including
submergence) 235,000 gal
Total residence time 18.4 min

Cartridge Filters Main
On duty 3
On standby 1
Flow per vessel 4,246 gpm
Vessel configuration Horizontal
Vessel pressure rating 150 psi
Cartridges per vessel 32
Cartridge rating 5 m
Cartridge material Polypropylene
Cartridge diameter 6 in
Cartridge length 40 in

RO System Flow Stream pH and
Chemical Doses
pH Ranges
UF filtrate 6.7 - 7.7
RO feed (dosed) 6.2 - 6.7
RO permeate (typical) 4.8 - 5.7
RO concentrate 7.0 - 7.5
Chemical Dosing
Antiscalant 1.0 - 5.0 mg/L
H2SO4 10 - 100 mg/L

RO Trains
RO Feed 18.3 mgd
RO Permeate 15.6 mgd
On duty 7
On standby 1
RO feed pump flow 1,820 gpm
RO feed pressure 100 - 225 psi
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System Component Design Value Unit
RO recovery 85%

RO CIP System
CIP tanks on duty 1
CIP tanks on standby 1
CIP tank volume 7,000 gal
CIP tank diameter 12 ft
CIP tank total height 10 ft
Heaters per CIP tank 2
CIP heat power 200 kW
Target CIP solution temperature 45 °C
CIP solution heating time 2 hr
Target CIP solution pH 2 or 11.5
Recirculation rate: Stage 1 3,600 gpm
Recirculation rate: Stage 2 1,800 gpm
CIP pumps on duty 2
CIP pumps on standby 1
CIP pump flow rate 900 gpm
CIP pump pressure 60 psi

Table 3-15: UV/AOP Design Parameters
System Component Design Value Unit
Reactors on duty 3
Reactors on standby 1
Oxidant type HOCl
Flow, design 15.6 mgd
Flow capacity per duty train 5.20 mgd
Minimum EED 0.2 kWh/kgal
Design EED 0.22 kWh/kgal
Minimum UV dose 850 mJ/cm2
Maximum operating pressure 30 psi
Head loss at full flow 4 in
Minimum UVT 96 %

Oxidant Dosing
Oxidant Dosing Free chlorine (HOCl)
Oxidant dose, design 2 mg/L as Cl2
Oxidant dosing system, minimum 2 mg/L as Cl2
Oxidant dosing system, maximum 5 mg/L as Cl2
Chemical Addition NaOCl
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System Component Design Value Unit
Strength of solution 6.9 %

Product Water Tank HRT Volume (gal) HRT at Full
Capacity (min)
CO2 injection box 40,000 3.7
Lime injection box: 2 boxes on line 22,000 2.0
Lime injection ox: 1 box off line 11,000 1.0
Pump wet well 35,000 3.2

CO2 Storage
Storage time: worst-case conditions 4 days
Tanks 2
CO2 transfer efficiency 95 %
CO2 dose: max 90 mg/L
CO2 feed rate: max (actual) 26,886 lb/d
Net capacity: max conditions, per
tank 24 metric ton

Lime Silo
Diameter 12 ft
Height 30 ft
Storage capacity per tank 3,393 ft3
Design total storage capacity 6,786 ft3

FAT+O3/BAF AWTF Footprint
The assumed AWTF for this option will require a total area of approximately 286,100 ft2 (6.6 acres). Table 3-16 summarizes the individual footprint for the equipment requirement for each process and administration and electrical building, roadway, and parki ng. Figure 3-3 shows the tentative location of the AWTF on EWA’s South Parcel.

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Table 3-16: Footprint of FAT + O3/BAF AWTF
Process Footprint (ft2)
LOX System 2,000
Ozone System 6,400
BAC Filters 15,000
UF Trains 16,000
RO Trains 18,000
CIP System 2,000
UV System 3,600
Electrical Rooms 5,000
Electrical Building 9,000
Product Water Tank 14,700
CO2 Dosing System 2,000
Lime Dosing System 3,000
Chemical Storage 11,300
Pump Station 12,100
Admin. / Maint. Building1 14,000
Parking 27,000
Roadway/ 125,000
Total 286,100
Footnotes:

1. The administration building area includes offices, conference rooms, exhibit space, maintenance shops and storage, control room, water quality laboratory, lunch room, restrooms, showers, and of miscellaneous storage space.

2. Rounded to the nearest 100.

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Figure 3-3: Representative Layout of the O₃/BAF + FAT AWTF on EWA’s South Parcel (Far View).

3.5.3 WTP for Treated Drinking Water Augmentation
The purified water from the O₃/BAF + FAT treatment facility would be sent to an ESB + Cl2. The assumed residence time is thirty minutes before being treated b y UF syst em. Due to the highly-treated feed water quality, the UF would be able to operate at a higher flux (120 gfd). Table 3 -17 provides a summary of the design criteria for the ESB and the UF system.

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Table 3-17. Design Criteria for ESB-Cl2 + UF System
System Component Design Value Unit
Oxidant Dose
Oxidant dose, design 2 mg/L as Cl2
Oxidant dosing system, minimum 2 mg/L as Cl2
Oxidant dosing system, maximum 6 mg/L as Cl2
Effluent Chlorine Residual 3 mg/L as Cl2
Chemical Addition NaOCl
Strength of solution 12.5 %

Engineered Storage Buffer
Retention Time 2 hours
Volume per tank 173,708 ft3
Tank Water Height 40 ft
Diameter of tank 74 ft
Number of tanks 3 (fill, hold, draw)
Length of ESB area 253 ft
Width of ESB area 94 ft

Ammonia Dosing System
Ratio NH3-N:Cl2 1:5
Dose 1 mg/L
Loading 130 lb/day
Aqua Ammonia Concentration 19 %

UF
Membrane area / module 775 ft2
System rated capacity (filtrate flow) 15.44 mgd
Feed flow 15.59 mgd
Assumed Recovery 99 %
Number of racks 6
Number of membrane modules per rack, installed 28
Number of membrane modules per rack, total available 37 Design flux, instantaneous 120 gfd

FAT+O3/BAF AWTF plus WTP Footprint
The assumed AWTF for this option will require a total area of approximately 324,400 ft2 (7.4 acres). Table 3-18 summarizes the individual footprint for the equipment requirement for each process and administration and electrical building, roadway, and parki ng. Figure 3-4 shows the tentative location of the AWTF on EWA’s South Parcel.

Table 3-18: O₃/BAF + FAT + WTP for Treated Drinking Water Augmentation Footprint Sept. 27, 2022
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Process Footprint (ft2)
LOX System 2,000
Ozone System 6,400
BAC Filters 15,000
UF Trains 16,000
RO Trains 18,000
CIP System 2,000
UV System 3,600
Engineered Storage Buffer 15,600
High-Flux UF 800
Electrical Rooms 5,000
Electrical Building 9,000
CO2 Dosing System 2,000
Lime Dosing System 3,000
Chemical Storage 11,300
Product Water Tank 14,700
Pump Station 14,000
Admin. / Maint. Building1 14,000
Parking 27,000
Roadway 145,000
Total 324,400
Footnotes:

1. The administration building area includes offices, conference rooms, exhibit space, maintenance shops and storage, control room, water quality laboratory, lunch room, restrooms, showers, and of miscellaneous storage space.

2. Rounded to the nearest 100.

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Figure 3-4: Representative Layout of the O₃/BAF + FAT + WTP on EWA’s South Parcel (Far View).

3.5.4 Future AWTF Expansion Footprint
A future expansion of the FAT+O3/BAF AWTF from 16 mgd to 25 mgd was evaluated for space planning purposes. This option will require a total area of approximately 389,600 ft2 (8.9 acres). Table 3-19 summarizes the individual footprint for the equipment requirement for each process and administration and electrical building, roadway, and parking. Figure 3-5 shows the tentative location of the AWTF on EWA’s South Parcel.

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Table 3-19. Footprint of FAT + O3/BAF AWTF at 25 mgd
Process Footprint (ft2)
LOX System 3,100
Ozone System 7,200
BAC Filters 17,000
UF Trains 19,000
RO Trains 28,200
CIP System 3,600
UV System 5,600
Electrical Rooms 5,000
Product Water Tank 22,900
CO2 Dosing System 2,000
Lime Dosing System 3,000
Chemical Feed System/Storage 11,300
Electrical Building 9,000
Pump Station 21,000
Admin./ Maint. Building1 23,000
Parking 68,200
Roadway 140,500
Total 389,600
Footnotes:

1. The administration building area includes offices, conference rooms, exhibit space, maintenance shops and storage, control room, water quality laboratory, lunch room, restrooms, showers, and of miscellaneous storage space.

2. Rounded to the nearest 100.

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Figure 3-5: Representative Layout of the O₃/BAF + FAT AWTF Expansion (25 mgd) on EWA’s South Parcel.

Conceptual Costs for Advanced Treatment

3.6.1 Capital Costs
Based on the conceptual design assumptions listed above, a Class 4 Budget Estimate was performed. This conceptual cost estimate includes all the components of the advanced water treatment plant (i.e., UF, RO, AOP, and additional e quipment including pumps, administrative building, brine disposal, engineering, taxes, shipping, and site work. This estimate does not include the estimated costs and any footprint needed for finished water conveyance or integration with the potable reuse receptor, which is discussed in Sections 4 and 5 below. The cost estimate also does not include potential brine treatment; however, it does include a pressurized brine pipeline from the AWTF to the Encina Ocean Outfall (connection assumed to be made immediately upstream of the final secondary effluent sampling station).

The AWTF cost estimates are provided in Appendix A and are summarized as follows:
• FAT AWTF: capital cost of $164,000,000.
• FAT with O₃/BAF: capital cost of $235,000,000.
• FAT with O₃/BAF and WTP: capital cost of $284,000,000.

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3.6.2 O&M Costs
Operation an d maintenance (O&M) costs include power cost (at $0.1 5 per kWh), chemical costs, and replacements of consumables (membranes, filter media, UV lamps and ballasts, RO cartridge filters, and RO membrane elements). Maintenance costs are included for each of th e systems in the treatment train, product water conditioning, chemical system and electrical equipment. Annual labor costs were based on four full-time employees (FTEs) operating the facility working 2080 hours per employee per year for the FAT AWTF, six FTEs for the FAT with O ₃/BAF AWTF, and seven FTEs for the FAT with O ₃/BAF and WTP AWTF.

The O&M costs are provided in Appendix A and are summarized as follows:
• FAT AWTF: O&M cost of $7,000,000.
• FAT with O₃/BAF: O&M cost of $8,600,000.
• FAT with O₃/BAF and WTP: O&M cost of $9,900,000.

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4 Conveyance Concepts
Introduction
The purpose of this section is to develop the concepts for conveyance within the three proposed options to be further evaluated as part of this report:
• Option F - Carlsbad Desalination Plant product water pump station (North) • Option G - San Dieguito Reservoir, Groundwater Basin and SDCWA Second Aqueduct Augmentation (South)
• Option H - San Marcos Groundwater Basin and SDCWA Second Aqueduct Augmentation (East) For each option, a preliminary hydraulic evaluation was conducted to determine approximate pipe size, pressure requirements, pumping requirements, and a preliminary opinion of construction costs. A summary of each Option’s hydraulics is provided in Figure 4-1.

4.1.1 Pipeline Alignment Assumptions
Conveyance alignments were selected with input from stakeholders and are based on the shortest right-of- way corridors from the proposed Encina Advanced Water Treatment Facility (AWTF) to the San Diego County Water Authority (SDCWA) aqueduct and did n ot consider utilities and other constructability constraints nor environmental impacts. Pipeline routes within existing easements, such as ov erhead electrical transmission easements, were not considered. A detailed alignment evaluation should be conducted if the project moves forward as part of a preliminary design phase.

4.1.2 Hydraulic Requirement Assumptions
Due to changes in elevation and the high pressure requirements, multiple pump stations are assumed for this analysis to avoid pressures greater than 400 psi throughout miles of pipeline. It is assumed that for each SDCWA turnout, a smaller booster station can be constructed to adequately meet the pressure requirements.

A spreadsheet model and calculations were used to select pipe diameter, determine pumping requirements, and pressure requirements. Flow velocity and pumping horsepower requirements were calc ulated for each option and its segments.
• Nominal pipe diameter is used as the interior pipe diameter in the hydraulic calculations. Variance in internal diameter based on pipe material were not considered. • Elevation of the proposed conveyance pump station at the AWTF is estimated to be 55 feet above mean sea level (MSL). Elevation and requirements of intermediate booster stations and discharge elevations are noted below by Option.
• Headloss calculations are based on Hazen-Williams equation with a friction factor (C-value) of 130 for new pipe.
• Pumping efficiency is estimated to be 80%.

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Figure 4-1: Pumping Requirements Summary

Option F Carlsbad Desalination Plant Effluent Augmentation EWA AWT - Pump Station Segment 1 Desal Plant Wet Well Desal Plant Pump Station Flow: 15.8 mgd Length: 2.5 miles Flow: 15.8 mgd Flow: 15.8 mgd Pump Sta: 1,000 hp Pipe Size: 30 inch Elevation: 70 feet Pump Sta: 8,000 hp Pressure: 61 psi Velocity: 5.0 ft/s Pressure: 40 psi Pressure: 40 psi Option G San Dieguito Reservoir + Groundwater Basin and SDCWA Aqueduct Augmentation EWA AWT - Pump Station Segment 2 - future phase Booster Pump to SDCWA Segment 4 - future phase Turnout at Badger WTP Flow: 15.96 mgd Length: 6.3 miles Flow: 15.96 mgd Length: 2.1 miles Flow: 15.96 mgd Pump Sta: 1,200 hp Pipe Size: 20 inch Pump Sta: 4,800 hp Pipe Size: 30 inch Elevation: 460 feet Pressure: 73 psi Velocity: 4.2 ft/s Pressure: 314 psi Velocity: 5.0 ft/s Pressure: 209 psi Segment 1 Segment 3 - exist pipe SD Reservoir Turnout
Length: 8.3 miles Length: 5.2 miles Flow: 10 mgd
Pipe Size: 30 inch Pipe Size: 24 inch Elevation: 240 feet Velocity: 5.0 ft/s Velocity: 4.9 ft/s Pressure: 46 psi
SEJPA WRF - Pump Station Segment 5 SD GWR Turnout
Flow: 15.96 mgd Length: 2.3 miles Flow: 2 mgd
Pump Sta: 3,200 hp Pipe Size: 12 inch High Point: 250 feet Pressure: 184 psi Velocity: 3.9 ft/s Pressure: 46 psi
Option H San Marcos Groundwater Basin and SDCWA Aqueduct Augmentation EWA AWT - Pump Station Segment 1 Segment 2 San Marcos GWR Turnout Flow: 15.96 mgd Length: 7.5 miles Length: 2.7 miles Flow: 2 mgd Pump Sta: 5,600 hp Pipe Size: 30 inch Pipe Size: 12 inch Elevation: 580 feet Pressure: 345 psi Velocity: 5.0 ft/s Velocity: 3.9 ft/s Pressure: 40 psi SDCWA Turnout Booster Pump to SDCWA
Flow: 13.96 mgd Flow: 13.96 mgd
Elevation: 570 feet Pump Sta: 2,000 hp
Pressure: 78 psi Pressure: 214 psi
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Option F – North
Option F will provide a maximum flow of 15.8 mgd from the proposed AWTF to the Carlsbad Desalination Plant clearwell immediately upstream of the existing booster station for treated drinking water augmentation. Pressure required at the clearwell air-gap is assumed to be 40 psi. The existing Desalination Plant Pump Station will boost pressure to 533 psi to meet SDCWA requirements . The e levation of the Desalination Plant is approximately 70 feet above MSL.

The clearwell at t he Desalination Plant may be undersized and may be unable to accept additional flow.

Therefore, Option F include s additional costs for clearwell construction/e xpansion to allow for blending and addition of baffling to provide mixing of the AWTF effluent with the desalinated product water.

Phasing Options:
• Option F1: full 15.8 mgd to a new clearwell at the Carlsbad Desalination Plant for integration with the des alinated product water and distribution to the SDCWA potable water system via the desalinated water pipeline. Project will include a new clearwell sized to provide 30 minutes of storage capacity along with a new pump station to booster pressure to 533 psi to match existing system pressure.
• Option F2: first phase of 5.1 mgd conveyed to the south for surface water augmentation at the San Dieguito Reservoir (3.1 mgd) and groundwater augmentation in the San Dieguito Basin (2 mgd).

As a second phase, the remaining 10.7 mgd would be integrated with the desalinated product water for treated drinking water augmentation as in Option F1 above. The pump station at the desalination plant could be scaled down to match the 10.7 mgd flow, or could be kept at 15.8 mgd as in Option F1 to allow flexibility of operations in determining which receptor to send the AWTF product water to.

For the purposes of this section, Option F is assumed to consist only of Option F1 , as the first phase of Option F2 is discussed under Section 4.3 below. See Table 4-1 for this Option’s hydraulics summary. See Table 4-2 for this Option’s pumping requirements.

Table 4-1: Pipeline Velocity and Headloss – Option F
Pipe Segment Flow Length Pipe
Diameter
Flow
Velocity
Pipe
Headloss
Option F – Carlsbad Desalination Plant Augmentation
1-Backbone to Desal Plant turnout 15.8 mgd 2.6 miles 30 in. 4.98 ft/s 34 ft

Table 4-2: Pumping Requirements – Option F
Option HGL Static
Head
TDH Hydraulic
Horsepower 1
Est. Total Station
Horsepower 2
Option F – Carlsbad Desalination Plant Augmentation
Pump at EWA AWTF 196 ft 15 ft 141 ft 500 hp 1,000 hp
Pump at Desal Plant
Wet Well 1300 ft 15 ft 1245 ft 4,000 hp 8,000 hp
Footnotes:
1) Hydraulic horsepower is the minimum actual motor horsepower for a single pump required to move the water rounded up to the nearest 100 hp to meet the pumping requirements. 2) Total station horsepower is total motor horsepower and will depend on the number of pumps installed. A reasonable estimate of total station horsepower considering standard motor sizes and standby pumps is twice the hydraulic horsepower. For cost estimating purposes, two (2) duty pumps are assumed and one (1) standby pump.

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Length of pipeline from the proposed AWTF to the connection point to the Desalination Plant c learwell is estimated to be 2.5 miles. This will provide approximately 45 minutes of travel time from the AWTF to the Desalination Plant clearwell. Alignment crosses the I-5 Freeway via trenchless construction, then follows Paseo del Norte to Cannon Road before crossing back across the I-5 Freeway via trenchless construction to Avenida Encinas into the Desalination Plant property.

See Figure 4-2 for Option F proposed alignment. See Figure 4-3 for Option F proposed HGL.

Figure 4-2: Option F - Carlsbad Desalination Plant Augmentation Alignment Sept. 27, 2022
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Figure 4-3: Option F - Carlsbad Desalination Plant Augmentation HGL

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Option G – South
Option G will provide a maximum flow of 15.96 mgd from EWA AWTF to San Elijo Joint Power Authority (SEJPA). A new pump station will be constru cted at SEJPA to convey flows: 3.1 mgd will be discharged to San Dieguito Reservoir for surface water augmentation, 2 mgd to San Dieguito Groundwater Basin fo r groundwater injection, and 10.86 mgd to SDCWA Second Aqueduct for raw water augmentation.

An additional Pump Station will boost pressure from San Dieguito Reservoir turnout to the SDCWA turnout to 208 psi to meet SDCWA requirements. Elevation of the SDCWA Second Aqueduct at the connection location is approximately 670 feet above MSL. Elevation of the proposed discharge facility at San Dieguito Reservoir is approximately 250 feet above MSL. Elevation of the proposed discharge facility at GWR is approximately 100 feet above MSL.

Phasing Options:
• Option G1: First phase of 5.1 mgd conveyed to the south for surface water augmentation at the San Dieguito Reservoir (3.1 mgd) and groundwater augmentation in the San Dieguito Basin (2 mgd). • Option G2: Second phase of up to 15.96 mgd to the Second Aqueduct for raw water augmentation.

This would then form part of the supply for the Badger WFP, so surface water augmentation at the San Dieguito Reservoir would no longer be required as in the first phase. Note that groundwater augmentation in the San Dieg uito Basin would continue at approximately 2 mgd; however, since the water would be conveyed via the same pipeline, it would need to be at a quality suitable for raw water augmentation.

See Table 4-3 for pipeline Option G hydraulic s summary. See Table 4-4 for Option G Pumping Requirements.

Table 4-3: Pipeline Velocity and Headloss – Option G
Pipe Segment Flow Length Pipe
Diameter 1
Flow
Velocity
Pipe
Headloss
Option G – San Dieguito Reservoir, Groundwater Basin & SDCWA Augmentation 1-Backbone to SEJPA WRF 15.96 mgd 8.3 mi. 30 in. 5.0 ft/s 110 ft 2-New Pipe to SD Reservoir 5.96 mgd 6.3 mi. 20 in. 4.2/ft/s 97 ft 3-Existing pipe to SD Reservoir 10.0 mgd 5.2 mi. 24 in. 4.9 ft/s 100 ft 4-Backbone to Badger WTP 15.96 mgd 2.1mi. 30 in. 5.0 ft/s 33 ft 5-Lateral to GWR at Via de la Valle 2.0 mgd 2.3 mi. 12 in. 3.9 ft/s 57 ft

Table 4-4: Pumping Requirements – Option G
Option HGL Static
Head
TDH Hydraulic
Horsepower 1
Est. Total Station
Horsepower 2
Option G – San Dieguito Reservoir, Groundwater Basin & SDCWA Augmentation Pump at EWA AWTF 223 ft -35 ft 168 ft 600 hp 1,200 hp
Pump at SEJPA WRF 444 ft 220 ft 424 ft 1,600 hp 3,200 hp Pump at SD Reservoir 928 ft 210 ft 679 ft 2,400 hp 4,800 hp Footnotes:
1) Hydraulic horsepower is the minimum actual motor horsepower for a single pump required to move the water rounded up to the nearest 100 hp to meet the pumping requirements. 2) Total station horsepower is total motor horsepower and will depend on the number of pumps installed. A reasonable estimate of total station horsepower considering standard motor sizes and standby pumps is twice the hydraulic horsepower. For cost estimating purposes, two (2) duty pumps are assumed and one (1) standby pump.

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Segment 1 Pipeline alignment is 8.3 miles traveling south from EWA AWTF along Avenida Encinas to San Batiquitos Lagoon which will be crossed via trenchless methods to La Costa Avenue. Alignment will continue south along Vulcan Avenue, San Elijo Avenue, and Manchester Avenue to SEJPA WRF.

Segment 2 Pipeline alignment is 6.3 miles traveling east from SEJPA WRF along Manchester Avenue to Encinitas Boulevard to El Mirlo to Via de Fortuna to El Montevideo ending at San Dieguito Reservoir.

Segment 3 Pipeline al ignment is 5.2 miles utilizing the existing abandoned 30 -inch San Dieguito Water District pipeline from SEJPA WRF ending at San Dieguito Reservoir. Segment 4 Pipeline alignment is 2.1 miles traveling east from San Dieguito Reservoir along El Camino del Norte to Aliso Canyon Road ending at Badger WTP.

Segment 4 Pipeline alignment is 2.3 miles traveling south from San Dieguito Reservoir along El Montevideo to Paseo Delic ias to Via de la Valle ending at proposed injection wells in the San Dieguito Groundwater Basin.

See Figure 4-4 for Option G proposed alignment. See Figure 4-5 for Option G proposed HGL.

Figure 4-4: Option G Alignment Analysis

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Figure 4-5: Option G - San Dieguito Reservoir, Groundwater Basin & SDCWA Second Aqueduct Augmentation HGLs

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Option H - East
Option H will provide a maximum flow of 15. 96 mgd from the AWTF to SDCWA Second Aqueduct for raw water augmentation. There is potential for up to 2 mgd to be diverted via a branch off the main proposed pipeline to the San Marcos Groundwater Basin for groundwater i njection. Thus, all water produced at the proposed AWTF would need to be at a quality suitable for raw water augmentation.

An additional Pump Station will boo st pressure at SDCWA turnout to 208 psi to meet SDCWA requirements. Elevation of the discharge at SDCWA is approximately 570 feet above MSL. Elevation of the discharge at GWR turnout is approximately 580 feet above MSL.

See Table 4-5 for pipeline Option H hydraulics summary . See Table 4-6 for Option H Pumping Requirements.

Table 4-5: Pipeline Velocity and Headloss – Option H
Pipe Segment Flow Length Pipe
Diameter 1
Flow
Velocity
Pipe
Headloss
Option H – San Marcos Groundwater Basin & SDCWA Augmentation 1-Backbone to SDCWA 15.96 mgd 7.5 mi. 30 in. 5.0 ft/s 101 ft 2-Existing Pipe to GWR 2.0 mgd 2.7 mi. 12 in. 3.9/ft/s 78 ft

Table 4-6: Pumping Requirements – Option H
Option HGL Static
Head
TDH Hydraulic
Horsepower 1
Est. Total Station
Horsepower 2
Option H – San Marcos Groundwater Basin & SDCWA Augmentation Pump at EWA AWTF 848 ft 515 ft 796 ft 2,800 hp 5,600 hp Pump at Turnout 883 ft 10 ft 493 ft 1,000 hp 2,000 hp
Footnotes:
1) Hydraulic horsepower is the minimum actual motor horsepower for a single pump required to move the water rounded up to the nearest 100 hp to meet the pumping requirements. 2) Total station horsepower is total motor horsepower and will depend on the number of pumps installed. A reasonable estimate of total station horsepower considering standard motor sizes and standby pumps is twice the hydraulic horsepower. For cost estimating purposes, two (2) duty pumps are assumed and one (1) standby pump.

Length of pipeline from EWA AWTF to the connection point to the SDCWA turnout is estimated to be 7.5 miles. Alignment crosses the I -5 Freeway via trenchless construction, then follows Paseo del Norte to Palomar Airport Road to S an Marcos Boulevard ending at Rancho S anta Fe Road with a new SDCWA turnout with booster station.

Segment 2 Pipeline alignment is 2.7 miles utilizing existing abandoned 12 -inch Vallecitos Water District pipeline along San Marcos Boulevard to Twin Oaks Val ley Road ending at new proposed inject ion wells in the San Marcos Groundwater Basin.

See Figure 4-6 for Option H proposed alignment. See Figure 4-7 for Option H proposed HGL.

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Figure 4-6: Option H Alignment.

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Figure 4-7: Option H - San Marcos Groundwater Basin & SDCWA Aqueduct #2 Augmentation HGL

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Conceptual Costs for Conveyance
An opinion of probable const ruction cost was developed based on the concept presented in this TM. The cost estimate is a Class IV estimate. Table 4-7 provides a summary of the preliminary capital and O&M cost estimate s for the conveyance syst em for each Option at the full product water flows. Detailed conveyance construction cost estimates are provided Appendix A.

Table 4-7: Conveyance & Receptor Integration Costs by Option

Option
Capital Cost
O&M
Costs Conveyance
(Pipe + Pump)
Receptor
Integration
F - Carlsbad Desalination Plant Effluent
Augmentation $39,000,000 $104,000,000 $17,100,000
G - San Dieguito Reservoir + Groundwater Basin
and SDCWA Augmentation $254,000,000 $33,000,000 $18,800,000 H - San Marcos Groundwater Basin and SDCWA
Augmentation $159,000,000 $21,000,000 $15,200,000

4.5.1 Capital Costs
Each potable water reuse option will require receptor integration according to the form of potable reuse:

Treated Drinking Water Augmentation (TDWA), Groundwater Augmentation (GWA), and Surface Water Augmentation (SWA). The following summarizes the key capital cost assumptions for receptor integration for each project concept in addition to conveyance pipelines and pumping:
• Option F – Carlsbad Desalination Plant Effluent:
o Project includes construction of a 350,000 -gallon clearwell at the Desalination Plant to allow for blending and addition of baffling to provide mixing of the AWTF effluent with the desalinated product water. Assumes 30 minutes of clearwell storage. Includes 8,000 hp pump station to match desalination plant effluent pressure requirements. • Option G – San Dieguito Reservoir + Groundwater Basin and SDCWA Augmentation:
o For surface water augmentation, project includes turnout with dechlorination to Reservoir; costs for surface water treatment are not included.
o For groundwater augmentation, project includes construction of two groundwater injection wells, two extraction wells, and expansion cost s for pre -treatment and RO treatment.

Expansion costs for brine disposal and product water conveyance are assumed to be included in the planned groundwater desalination plant. o For raw water augmentation, project includes pumping to meet turnout requirement s; treatment costs are not included.
• Option H – San Marcos Groundwater Basin and SDCWA Augmentation:
o For groundwater augmentation, project includes construction of two groundwater injection wells and two groundwater extraction wells with wellhead treatment . Assumes RO treatment is not required as TDS levels in basin are less than 750 ppm. o For raw water augmentation, project incl udes pumping to meet turnout requirements; treatment costs at downstream water plants are not included.

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4.5.2 O&M Costs
O&M costs assumes $0.15/kWh for pumping costs and 1% of pipeline construction costs for conveyance infrastructure maintenance. Pumping power is based on total motor horsepower for the pump station. • Option F – Carlsbad Desalination Plant Effluent:
o Project includes 1,000 hp pump station at the AWTF, and a new 8,000 hp pump station at the desalination plant.
o Project includes 2.5 miles of piping to be maintained. • Option G – San Dieguito Reservoir + Groundwater Basin and SDCWA Augmentation:
o Project includes 800 hp pump station at the AWTF, 3,200 hp pump station at SEJPA, and a 4,800 hp pump station at the Badger WTP.
o Expansion of the groundwater desalination facility from 1 to 3 mgd, 2 injection wells, and 2 additional extraction wells.
o Project includes 29.1 miles of piping to be maintained. • Option H – San Marcos Groundwater Basin and SDCWA Augmentation:
o Project includes 5,600 hp pump station at the AWTF and a 2,000 hp pump station at the SDCWA turnout.
o 2 groundwater injection wells and 2 extraction wells. o Project includes 10.3 miles of piping to be maintained.

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5 Purified Water Receptor Integration Concepts
Groundwater Augmentation

5.1.1 San Dieguito Basin Recharge (Option G) and San Marcos Basin Recharge (Option H)
Reliability in potable reuse can be achieved in a number of ways. At one extreme, strategies can rely heavily on the prevention of failures, namely, through the provision of redundancy in treatment. Alternatively, reliability can be achieved by creating sy stems that are capable of consistently responding to failures, i.e., halting the distribution of off -spec water before it reaches consumers. In both cases, public health is maintained by protecting consumers from contaminants. Most potable reuse systems utilize a combination of these two strategies —failure prevention and fail ure response. Groundwater recharge, for example, requires both (1) treatment and (2) the retention and passage of water through the environment. The retention in the aquifer provides some additional treatment—e.g., 1-log of virus reduction credit per month in the ground (see TM 1)—but also a significant period of time during which a project sponsor could detect and respond to any upstream treatment excursion or failure. The degree to which these two components are used—treatment and retention time —can be ba lanced in different ways. For this reason, the d egree of treatment is integral in determining the requirements for the aquifer.

Analyzing the groundwater recharge portions of Options G and H, the FAT treatment train provides sufficient treatment to meet th e 10-log protozoa requirements, but alone cannot fully achieve the 12 -log requirement for viruses (refer to Table 3-2). Accordingly, the groundwater recharge system will need to rely on additional treatment in the aquifer to complete the 12-log requirement. This treatment train provides the opportunity to engage in both groundwater spreading and injection. While spreading is allowable from the standpoint of regulations, it is likely infeasible due to the large footprint necessary for spreading basins and the density of developme nt in the areas of the San Dieguito and the San Marcos Basins. For the groundwater augmentation option, it is assumed that groundwater injection will be pursued. Furthermore, because the treatment train alone cannot achieve the pathogen reduction credits, it is assumed that the water will have a minimum 6-month residence time in the groundwater basin. This assumption allows the project to comply with the 12-log virus requirement and is in line with the retention times provided by the majority of the existing, permitted groundwater recharge projects. Hydraulic modeling is necessa ry to ensure that a 6-month residence time is reasonable for the 2 mgd intended for injection in both the San Dieguito and San Marcos Basins.

Assuming there will be no phasing of the AWTF treatment train, the FAT treatment train will not be sufficient as all three remaining options include either raw or treated drinking water augmentation and these DPR elements will require more stringent treatment than the FAT treatment train provides. For thi s scenario, we will assume the FAT treatment train with O ₃/BAF addition w ill be implemented for the purposes of analysis. Most of the same requirements discussed above will still apply, however the residence time in the aquifer will no longer be needed for the purposes of achieving sufficient virus LRC. Referring to Table 3-4, LRC of 15.9, 16.8, and 14.2 are expected for virus, Cryptosporidium, and Giardia, respectively, for the FAT treatment train with O₃/BAF addition, irrespective of retention time in the aquifer (excluding the addition of a WTP after the AWTF). To permit this portion of the project as an IPR project, a 2-month residence time in the aquifer will still be necessary. Again, hydraulic model ing is necessary to determine if a 2-month residence time is reasonable for the 2 mgd intended for injection.

Assuming that the water will be injected into the aquifer, the following facilities/equipment are necessary:
• Pipeline from AWTF to groundwater basin (as described in Section 4 - Conveyance Concepts) • Pump stations
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• Injection wells and associated buildings
• Extraction wells
• Treatment facilities, which are expected to include RO treatment, as necessary, and disinfection • Monitoring wells
Surface Water Augmentation

5.2.1 San Dieguito Reservoir Discharge and Blending (Options F + G) To assess surface water augmentation (SWA) projects, the most important components of the draft regulations pertain to (1) the retention time of the advanced treated water in the reservoir and (2) the dilution and mixing therein. The retention time in the reservoir is calculated as the theoretical hydraulic residence time on a monthly basis as follows:

𝑉𝑒𝑛𝑑
𝑄 ≥ 6 𝑚𝑜𝑛𝑡ℎ𝑠
Where:

𝑉𝑒𝑛𝑑= volume in the reservoir at the end of the month
Q = total outflow (withdrawals + overflow)
Assuming a 6 -month V/Q, the San Dieguito Reservoir can only accomm odate ~1 mgd of flow from the AWTF2. However, while 6 months is the curr ent minimum theoretical residence time in the reservoir for SWA projects in draft regulations, it is likely that projects with residence times as low as 2 months will be permitted, giv en additional treatment and redundancy. If 2 -month residence time is use d as the lower bookend, the reservoir can accommodate ~3.1 mgd of advanced treated water 1. This analysis assumes that the advanced treated water is the only input to the reservoir, which is not currently the case.

In addition, th e SWA project must meet dil ution and mixing requirements. Currently, there are two pathways to meet the mixing and dilution requirements based on the degree of treatment provided: 100:1 dilution in the reservoir and LRC of 12/10/10 for virus, Giardia, and Cryptosporidium, or 10:1 dilution and provision of an additional 1-log removal of all three regulated pathogens (thus, final LRC of 13/11/11). For this analysis, we will assume that a minimum dilution of 10:1 will be achieved, thus requiring the additional 1-log removal credit. Rese rvoir characterization, modeling, and tracer tests will be essential to determine the extent of mixing and dilution in the reservoir. Numerous data inputs will be necessary for the modeling team, including meteorological, water q uality, and flow data. The most recent bathymetry evaluation was completed 7 years ago and demonstrated the presence of significant solids build -up within the reservoir (Anderson 2010). Updated bathymetry may be necessary given the high solids deposition r ate (0.5 inches per year). This would also be necessary following any future dredging and removal of solids from the reservoir. The modeling results will provide important information to understand the mixing an d dilution in the reservoir, and the need for any engineered solutions to improve these characteristics. Tracer studies to validate the model will also be necessary, per the draft requirements.

The log removal credits for a 2-month residence time project with 10:1 dilution will be at least 13/11/11, if not significantly higher . LRC gained at the drinking water treatment plant downstream of the reservoir count toward this 13/11/11 goal. Assuming the drinking water treatment plant provides the typical 4/3/2 log reductions, the AWTF would only be required to achieve LRC of 9/8/9 for an overall LRC of 13/11/11.

2 Capacity calculated using the following storage volume equation derived in (Anderson, 2010): Volume (acre-ft) = -

54.2 + 10.807*H – 0.7045*H2 + 0.01498*H3
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It is important to note that the only current project pursuing a 2 -month retention time (the City of San Diego’s Miramar Lake SWA project) is providing A WTF LRC of >20/>20/16, i.e., values in great excess of 13/11/11.

For these reasons, it is likely that FAT treatment alone will not be sufficient for a 2 -month project, even if the project provides more than 9 -logs (9.4-logs) of removal for virus (refer to Table 3-2). The pr oposed train for a 2-month SWA project is therefore assumed to be equivalent to the one used by the City of San Diego, namely, FAT treatment train with O₃/BAF pre-treatment. Referring to Table 3-4, LRC of 15.9, 16.8, and 14.2 are expected for virus, Cryptosporidium, and Giardia, respectively, for the FAT treatment train with O₃/BAF addition (without an additional WTP after the AWT F). This treatment train provides a high degree of redundancy beyond 13/11/11.

As mentioned above, additional reservoir characterization is necessary to determine whether these V/Q and dilution values are feasible in the San Dieguito Reservoir. The operati on of the reservoir will also need to be modified in a variety of ways to maxim ize its potable reuse capacity and to comply with regulations.

One significant assumption made in the V/Q calculations was that the only influent to the reservoir will be advanced treated water; all other existing inflows, including flows from Lake Hodges, filter backwash water from the Badger Water Filtration Plant, storm water runoff, and urban runoff, will need to be redirected. In addition, it is likely that the reservoir will need to be specifically engineered to meet the dilution requirement of 10:1. Engineering solutions likely to be relevant in the San Dieguito reservoir include optimizing placement of the influent site relative to the extraction site, as well the implemen tation of equipment that increases mixing in the reservoir to maximize dilution. The reservoir is currently operated using a diffused aeration system, which facilitates a well -mixed, oxic state in the bulk water. Additional equipment necessary for the implementation of a SWA project in San Dieguito reservoir could include the following:
• Diffusers
• Additional aeration equipment
• Floating baffles
Raw Water and Treated Drinking Water Augmentation
There are select examples of blending purified water with raw or finished water (e.g., Big Spring TX DPR blending with raw surface water, CDP blending of purifi ed water with other finished water). A recent project funded by Water Research Foundation (WRF 4536) provides recommendations and guidance for the appropriate use of blending as part of a DPR project, including evaluations of treatment, impact of different water qualities, and corrosion control issues, impact on engineered storage, blending location, and blending percentages (WRRF-13-15). There are key issues that should be addressed including (i) aesthetics; (ii) regulated and emerging contaminants; (iii) microbiology; (iv) corrosion; and (v) location of blending (WRRF- 13-15).

Aesthetics
Aesthetics challenges arises when blending water from multiple sources. Ble nding water fro m multiple sources might cause changes in taste, odor color, turbidity, formati on of scum, lack of lathering with soap if hardness changes, etc. (Peet et al., 2001). Taste issues may be particularly important in RO -treated recycled waters th at lack hardnes s, alkalinity, and minerals. Bench or pilot -scale testing must be used to evaluate the effects of blending because most of these parameters cannot be evaluated by the law of mixtures or chemical theory. Maintaining the aesthetic quality of t he water is a k ey issue when blending water, because some consumers will relate the aesthetics of the water to its safety. With that said, stabilized purified water (after chemical addition of minerals and pH adjustment) is consistently served to tour visitors at the Orange County Water District, with high marks for flavor. The Big Spring TX DPR facility has been Sept. 27, 2022
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blending ~50% purified water (similar treatment to OCWD) with other surface waters, followed by a water treatment plant, and has not experienced aesthetic challenges.

Regulated and Emerging Contaminants
Recycled water may contain more chemi cals than conventional water supplies, depending upon the level of recycled water treatment and the origin of existing raw water supplies. Of critical importance are those pollutants that may present health risks, including regulated inorganic, radiologic, industrial, and pesticide contaminants (Tchobanoglous et al., 2011). NWRI (2013) lists a number of chemicals of potential health concerns that may be present in wastewater, inc luding non -regulated contaminants, such as pharmaceuticals, hormones, and consumer chemicals. Trussell et al. (2013) has determined the level of both pathogen reduction and pollutant reduction needed for safe implementation of both IPR and DPR treatment, and the use of UF/RO/UV AOP was proven to provide more than sufficient treatment . Other health and risk evaluations have shown that such levels of purification provide a water quality that is equal or greater in quality compared to conventional water supplies in the United States (NRC, 2012).

Disinfection byproducts remain an important item of water quality focus. NDMA and tri-halomethanes are formed and destroyed in the purification process and can be properly managed to maintain concentrati ons below regulated values. At the point of blending, the formation of these and other DBPs should be examined through bench-scale studies to best understand the impact of disinfectant residuals, blending concentrations, and TOC impacts (WRRF - 13-15).

Microbiology
Microorganisms that may remain in treated recycled water represent a threat to water quality. NRC (2006) identified the high risks associated with regrowth in premise plumbing and the Centers for Disease Control has acknowledged that opportunisti c pathogens (OP s), such as Legionella, Pseudomonas, and Mycobacterium, proliferating in buildi ng plumbing systems are now the primary source of waterborne disease outbreaks (and a majority of associated deaths) in the U.S. (CDC, 2011; Brunkard et al., 2011 ).

Concerns are also emerging regarding the potential to spread antibiotic resistance genes (A RGs) via microbial re-growth in water reuse systems, a topic that is of concern to policy makers in the U.S. and world-wide (Fahrenfeld et al., 2013; Pruden, 2013 ; Wellington et al., 2013). Addressing knowledge gaps related to opportunistic pathogens and antibiotic resistance will help to advance water reuse system design, including water treatment and distribution, in order to minimize potential risks of emerging microbiological constituents of concern. Regrowth of OPs, bacteria with ARGs, microbes influencing corrosion (MIC) and indicator organisms such as heterotrophic plate counts (HPCs) is a function of many parameters including disinfectant residual, type of disinfectant, temperature, nutrient concentrations, turbidity, pH, and alkalinity.

As it perta ins to this evaluation, WRF 4536 is documenting the relative improvement in blended water quality as a result of the use of purified water for blending (Salveson et al., in prog ress). Results clearly document that higher percentages of purified water reduc e the levels of microorganisms in the blended water within the simulated distribution systems; a clear improvement in water quality.

Corrosion
Increased corrosiveness or aggress iveness of water following blending is another concerning issue. This corrosion can be directly linked to corrosive water quality (e.g., RO permeate), or can be the result of microbiologically induced corrosion. Microbial activity during sta gnation has been linked to rapid loss of disinfectant (Zhang and Edwards, 2009; Nguyen et al., 2012), contamination of potable water with high levels of copper, lead and iron (McNeill and Edwards, 2001; Edwards et al., 2000; Zhang et al., 2009), microbial corrosion failures (Videla, 1996) and aesthetic problems (taste and odor) of potable water (NRC, 2006). The corrosion influencing parameters that are most relevant to recycled waters are temperature, pH, alkalinity, dissolved inorganic carbon, oxidants, total dissolved solids, calcium hardness, chloride, sulfate, hydrogen sulfide, and natural organic carbon (Vik et al., 1996).

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As it pertains to this evaluation, the purified water will be stabilized and a chloramine residual will be maintained prior to blending with other raw or finished water, minimizing the corrosion impacts.

Location of Blending
Another important aspect of blending water of different quality pertains to the location of blending.

Blending water of different quality may locally disrupt the natural “ecology” of the receiving environment.

Because of this, blending in a storage reservo ir or within a treatment plant will have a different impact compared to blending in the distribution system, as measured by biofilm detachment, or disruption of passive protective scale layers. Depending on water quality, blending recycled water upstream o f a WTP may result in positive or negative impacts on the existing treatment processes. The State of California Division of Drinking Water has expressed this very concern related to DPR integration. In other cases, blending upstream of a water treatment pl ant can be expected to improve treated water quality, as in the case of blending purified water, resulting in decreased total organic carbon, potentially leading to more stable disinfectant residuals and reduced microbial growth feeding into a water treatment plant.

Pertaining to this project, the primary concern is the blending of purified water with other finished water, which could result in a localized change to pipeline biofilms.

5.3.1 Second Aqueduct Raw Water Augmentation (Options G-H) As part of another effort, the San Diego County Water Authority (SDCWA) considered the effects on water quality of delivering water directly from the Carlsbad Desalination Plant (CDP) to the south and into the SDCWA's aqueduct. A chemical injection facility was proposed at the San Marcos connection point to assure water quality. It should be noted that this is not a normal operation mode and water from the desalination plant is typica lly routed to t he Twin Oaks Valley Water Treatment Plant (TOVWTP). The chemical injection facility would inject sodium hypochlorite (11% - 14% solution) at a rate of 700 gal/day and aqueous ammonia (17% - 20% solution) at a rate of 350 gal/day (SDCWA, 2006 ). In the fourt h addendum of the environmental impact report, additional modifications were made to ensure the desalinated product water can be safely and reliably integrated into the distribution system.

The proposed Encina AWT facilities, as described pr eviously, will use sodium hypochlorite as part of the UV/AOP, leaving a free chlorine residual of 2 to 3 mg/L. The aqueous ammonia dosing station would likely be installed at the new AWTF to combine with the free chlorine to create a stable chloramine residual. The AWTF also will stabilize the purified water with a lime solution and neutralize the pH, making the new water less aggressive. Overall, it is unlikely that any further chemical addition facilities will be needed at the SDCWA blending location.

5.3.2 Carlsbad Desalination Plant Treated Drkinking Water Augmentation (Option F)
SDCWA has experience blending water from the CDP with their other supplies. The desalinated water must meet primary and secondary drinking water standards and does not differ sig nificantly from the water quality of the other sources of product water in the distribution. However, certain measures are taken to prevent any possible effects on the water quality, aesthetics, and distribution system. The desalinated water is chemically conditioned prior to delivery. The post -treatment stabilization for the RO product water includes a combination of lime with carbon dioxide. Additionally, the desalinated water is then disinfected using chloramines and blended with potable water, also disi nfected with chloramines, from the Metropolitan Water District. The blending of the desalinated water and the potable water does not result in any measurable impacts related to water quality. Finally, the effects on the distribution system were considered, because the existing water su pply is delivered via gravity flow and delivering water from the desalination plant will require continuous pumping to reach delivery points. This issue was addressed by Sept. 27, 2022
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modeling the potential effects and providing design feat ures to minimize this effect b y including surge control facilities to avoid damage to water delivery facilities (SDCWA, 2014).

Pertaining to this project, blending of purified water (that has also been chemically stabilized) with other water supplies in the region, such as with the CDP finished water, is not expected to have negative effects on the combined finished water.

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6 Permitting Considerations and Brine Disposal
Permitting Overview
Although a variety of permits and approvals would be required for a potable reuse project (includin g demonstration of CEQA compliance, construction -related permits, land use and/or coastal permits, air quality permits, etc.), this TM focuses on the Regional Water Quality Control Board (RWQCB) and State Water Resources Cont rol Bo ard (SWRCB) Division of D rinking Water (DDW) permitting issues that warrant early feasibility evaluation.

The RWQCB regulates the treatment, reclamation, and discharge of wastewater or recycled water through federal NPDES (National Pollutant Dischar ge Elimination System) permits and State of California Waste Discharge Requirements (WDRs). NPDES permits regulate discharges to federal surface waters 3 pursuant to requirements established within the federal Clean Water Act. In California, NPDES permits are iss ued by the RWQCB under au thority delegated by the U.S. Environmental Protection Agency (EPA). NPDES permits are valid for up to five years, after which renewal of the permit is required. WDRs are issued by the RWQCB to regulate discharges to state waters4 pursuant to provisions of the State of California Porter- Cologne Water Quality Act.5 WDRs do not have an expiration date, but may be replaced or updated by the RWQCB at any time.

NPDES permits and WDRs for proposed facilities would implement applicable fe deral and state water quality plans and policies, including:
• The Water Quality Plan for the San Diego Basin (Basin Plan), which is applicable to all discharges to ground and surface waters.6
• The Water Quality Control Plan, Ocean Waters of California (Ocean Plan), which is applicable to all discharges to marine waters.7

3 Federal surface waters include inland surface waters and wetlands, estuaries, bays, and the Pacific Ocean.

NPDES permits regulate discharges to federal surface waters or tributaries to such surface waters. 4 State waters include both federal surface waters and groundwaters. NPDES permits issued by the RWQCB for discharges to federal surface waters also double as WDRs, as the NPDES permits combine both federal and state requirements into a single permit. Individual WDRs are issued for discharges to groundwater, as groundwater discharges are regulated under state law but not federal law. 5 The Porter-Cologne Water Quality Act (as amended in 2017) preceded implementation of the federal Clean Water Act, and includes the following portions of the California Water Code: Division 1, Sections 100-540; Division 2, Sections 1000-5976, and Division 7, Sections 13000-16104. 6 The Basin Plan designates beneficial uses of ground and surface waters within the San Diego Region, and establishes water quality objectives to protect the beneficial uses on a watershed-by-watershed basis. The Basin Plan also establishes implementation policies for protecting beneficial uses and achieving the water quality objectives.
7 The Ocean Plan establishes effluent and receiving water standards applicable for all discharges to State- regulated waters of the Pacific Ocean (i.e., waters within three nautical miles of the shore). The Ocean Plan also establishes requirements and implementation policies applicable to ocean discharges.

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• The California Toxics Rule (CTR), which is applicable to all discharges to fede ral inland surface waters, enclosed bays, and estuaries.8
DDW acts as a consulting agency to the RWQCB, and t he RWQCB incorporates all applicable DDW recycled water, source water, discharge, and receiving water requirements within the NPDES permits or WDRs that are issued by the RWQCB to discharging agencies. In addition, DDW also implements drinking water standards and potable reuse req uirements in the water supply permits issued by DDW to potable water supply agencies.

6.1.1 RWQCB Permit Application Process
Dischargers must submit a Report of Waste Discharge (RWD) to the RWQCB in application for NPDES permits or WDRs . The RWD consists of app licable permit applications forms; descriptions of proposed facilities (including descriptive text, tables and figures); demonstrations of compliance with applicable water quality plans and policies; and demonstrations of complianc e with applicable environ mental regulations. The RWQCB is empowered to request any information, data, or studies needed to support RWQCB assessment potential discharge compliance or impacts of the discharge. The RWQCB endeavors to notify dischargers within 30 days of submission of the RWD as to whether the RWD is complete or if supplemental information is required.

RWDs must be received by the RWQCB no later than 180 days in advance of the proposed discharge, but RWQCB action on the submitted application may be delayed by RWQCB staff priorities and workloads. It is advantageous to submit the RWD as soon as CEQA compliance is certified in order to el iminate uncertainty on final RWQCB effluent concentration limits.9 In recent years, RWQCB workloads have been such that processing of NPDES permits typically takes the entire 180 -day period (or more). Processing of WDRs, on the other hand, is often completed in significantly less time.

6.1.2 Required Permits for Reuse Options
Table 6-1 summarizes required RWQCB and DD W permits that would be required for reuse options considered within TM3. As shown in Table 6-1, RWQCB permits required to implement the TM3 options may include:
• WDRs to regulate the treatment and use of recycled water to recharg e the San Dieguito Valley Groundwater Basin (Option F and G) or the San Marcos Basin (Option H), • a NPDES permit to regulate the discharge of purified water to San Dieguito Reservoir (Options F and G).

In addition, modification of the existing Encina Ocean Outfall (EOO) NPDES permit would be required to allow the discharge of AWTF waste brine to the EOO 10. Modification of the EOO NPDES permit would also be required to address any significant changes to Encina Water Pollution Control F acility (EWPCF) onsite facilities that support implementation of any of the regional reuse options.

8 The California Toxics Rule (CTR) is established by EPA within Title 40, Section 131.38 of the Code of Federal Regulations (CFR). The CTR establishes state-wide water quality standards for all discharges to inland surface waters, enclosed bays, and estuaries.
9 The RWD can be submitted to the RWQCB prior to completing CEQA (and, if applicable, National Environmental Protection Act) certification, but the RWQCB typically does not process the application until after completion of the CEQA process. Regardless of the sequence of completion, information presented in the RWD must be consistent with information presented within the CEQA documents. 10 Note that the EOO is used to discharge RO waste brine from the Carlsbad Water Reclamation Facility when the RO system is in operation (e.g., to reduce salinity of the recycled water produced).

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Finally, modification of existing DDW water supply permits would be required for any water agency that makes use of source water derived from EWA recycled water sources (e.g. , groundwater augmentation, surface water augmentation).

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Table 6-1: Anticipated RWQCB and DDW Permits for TM3 Reuse Options.

Option Activity
Type of Required Permit
RWQCB
NPDES
Permit11
RWQCB
WDRs12
DDW Water
Supply Permit
F
Groundwater augmentation (up to 2 mgd) in
San Dieguito Valley Groundwater Basin ●
●13, 15
Surface water augmentation (up to 3.1 mgd)
in San Dieguito Reservoir ●14
Treated drinking water augmentation (10.7 to

15.8 mgd) with Desalination Plant finished
water
See note15 See note12
Brine discharge to Encina Ocean Outfall ●16
G
Groundwater augmentation (up to 2 mgd) in
San Dieguito Valley Groundwater Basin ●
●13, 15 Surface water augmentation (up to 3.1 mgd)
in San Dieguito Reservoir ●14
Raw water augmentation (10.9 to 14 mgd) in
the Second Aqueduct Pipeline No. 5 See note12 See note12 Brine discharge to Encina Ocean Outfall ●13
H
Groundwater augmentation (up to 2 mgd) in
San Marcos Basin ●
●12, 15 Raw water augmentation (14 to 16 mgd) in
Second Aqueduct Pipeline No. 5 See note12 See note12
Brine discharge to Encina Ocean Outfall ●16

11 The RWQCB would adopt the NPDES permit pursuant to authority delegated by EPA. The NPDES permit would implement applicable state and federal water quality plans, policies, and standards. The treating/discharging agency would be the NPDES permittee. 12 WDRs would be adopted by the RWQCB pursuant to the State of California Porter-Cologne Water Quality Act.

The WDRs would implement applicable state water quality plans, policies, and standards. The treating/discharging agency would be the NPDES permittee. 13 Modification of existing DDW water supply permits would be required for any agency issued to the Santa Fe Irrigation District (operator of San Dieguito Reservoir) would be required. 14 NPDES permit would address the treatment and discharge of purified water to San Dieguito Reservoir, and would implement applicable Basin Plan water quality standards for the reservoir as well as statewide water quality standards established by the EPA California Toxics Rule. 15 Regulations governing direct potable reuse (DPR) have not been developed, but Senate Bill 918 directs the SWRCB to convene an expert panel and investigate the feasibility of developing uniform water recycling criteria for DPR projects. As documented in TM1, the SWRCB in a draft report released in 2016 determined that “it is technically feasible to develop uniform water recycling criteria for DPR in California, and that those criteria could incorporate a level of public health protection as good as or better than what is currently provided by conventional drinking water supplies and IPR.”
16 Modification of the existing Encina Wastewater Authority NPDES permit (NPDES CA0107395) would be required to address the discharge of brine to the EOO. The brine discharge NPDES modifications would implement applicable Ocean Plan water quality standards.

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6.1.3 DPR Permitting Issues
As noted in Table 6-1, DPR regulations are not currently in place that would allow the use of purified water to augment either (1) treated supplies in the CDP product water pipeline, or (2) raw water supplies in t he SDCWA Second Aqueduct Pipeline No. 5. As a result, it is uncertain how these treated or raw water augmentation discharges would be regulated. Because directing purified recycled water to the Carlsbad Desalination Proj ect product water pipeline would not involve a discharge to federal surface waters, however, it is probable that the RWQCB and DDW would regulate purified water treatment operations through the following:
• RWQCB issuance of WDRs to recycled water agencies that incorporate applicable DDW-mandated DPR requirements, and
• requirements established by DDW within water supply permits issued to water purveying agencies.

Because raw water augmentation would allow for discharge to imported water storage rese rvoirs, i t is probable that raw water augment ation to the SDCWA Second Aqueduct would be regulated through the following:
• RWQCB issuance of a NPDES permit to the recycled water (discharging) agency that incorporates applicable DDW-mandated DPR requirements, and
• requirements established by DDW within the water supply permits issued to water purveying agencies.

Groundwater Augmentation
As shown in Table 6-1, groundwater recharge within the San Dieguito Valley Groundwater Basin (Options F and G) or San Marcos Basin (Option H) would be regulated by RWQCB issuance of WDRs that implement applicable DDW groundwater recharge regulations and RWQCB groundwater quality objectives established within the Basin Plan. DDW regulations governing th e use of recycled water for recharging potable groundwater basins are established in Title 22, Division 4, Chapter 3 of the California Code of Regulations (CCR). As detailed within TM1, DDW groundwater recharge regulations establish requirements governing, in part:
• source control,
• level of treatment, recharge methods, and pathogen removal, • diluent (dilution) water and recycled water contribution, • recycled water (underground) retention times,
• restrictions on the construction of new groundwater wells within the restricted zone, • tracer and treatment performance studies, and
• monitoring.

DDW acts as a consulting agency within the RWQCB permitting process, and the RWQCB will implement DDW-mandated requirements 17 directly into the WDRs governing the recycled wate r treatme nt and groundwater recharge operations. As noted, DDW will also implement the groundwater recharge regulations within the Water Supply Permits issued to each applicable water agency that would derive potable supply from the affected groundwater basin.

In addition to implementing the DDW recycled water groundwater recharge requirements established within Title 22, WDRs issued by the RWQCB would implement applicable prohibitions, requirements, and

17 See TM1 for a summary of DDW groundwater recharge regulations and requirements.

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water quality objectives established within the Basin Plan. Table 6-2 summarizes Basin Plan groundwater quality objectives for mineral constituents for the San Dieguito Vall ey Groundwater Basin (Option F and G) and the San Marcos Basin (Option H). Purified recycled water that compl ies with DDW treatment requirements should readily comply with applicable Basin Plan groundwater quality objectives.

In addition to the objectives for mineral constituents listed in Table 6-2, the Basin Plan also applies DDW primary drink ing water Maximum Contaminant Levels (MCLs) directly to groundwaters of the San Dieguito Valley and San Marcos Basin. As a result, WDRs issued by the RWQCB will likely prohibit recycled water used for groundwater recharge from exceeding the potabl e water MCLs. The DDW water supply permit, on the other hand, will apply the MCLs to the finished blended potable water supply.

Table 6-2: Basin Plan Groundwater Quality Objectives.

Constituent
Basin Plan Groundwater Quality Objective
(mg/L)18
San Dieguito Valley
Groundwater Basin San Marcos Basin
Total dissolved solids, TDS 1500 1000
Chloride 500 400
Sulfate 500 500
Nitrate (as NO3) 45 45
Iron 0.85 0.3
Manganese 0.15 0.05
Boron 0.75 0.75
Fluoride 1.0 1.0

Surface Water Augmentation
The use of recycled water for surface water augmentation of San Dieguito Reservoir (Options F and G) would be regulated by RWQCB issuance of a NPDES permit to the recycled water treatment and discharging agency. The NPDES permit would implement applicable DDW potable reuse regulations as well as applicable state and regional surface water quality objectives.

As discussed in TM1, DDW has issued uniform regulations governing the use of recycled water for augmenting supplies within surface water reservoirs that serve as a source of raw water supply to potable water treatment plants. Initial draft surface water augmentation regulations were distributed by DDW for public comment in mid-2017.19 As summarized in TM1, the draft DDW potable reuse regulations address requirements for:
• source control,
• advanced treatment and pathogen removal,

18 Basin Plan groundwater quality objective not to be exceeded more than 10 percent of the time. It is probable that the RWQCB will establish effluent concentration limits for groundwater recharge projects at the listed objective.
19 Draft proposed regulations released by DDW in 2017 (dated October 12, 2016) include revisions to the following sections of Title 22, Division 4 of the California Code of Regulations: Chapter 3, Article 1 (Section 60301); Chapter 3, Article 5.3 (Section 60320); and Article 9 (Section 64668).

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• reservoir dilution,
• reservoir retention,
• reservoir modeling and tracer studies,
• emergency and operations plans to ensure reliability, and • ongoing performance monitoring.

DDW potable reuse regulations will be incorporated in the NPDES permit issued by the RWQCB to the recycled water treatment agency as well as the water supply permit issued by DDW to the reservoir operator.

Additionally, the NPDES permit that regulates the discharge of purified water to San Dieguito Reservoir would establish purified water concentration standards that implement:
• state and federal water quality standards 20 for San Dieguito Reservoir t hat are established by the RWQCB within the Basin Plan, and
• state-wide standards for inland surface waters that have been imposed by EPA within the California Toxics Rule (CTR).21
The Basin Plan establishes surface water quality standards within the San D iego Region on a watershed- by-watershed basis. Basin Plan water quality standards for San Dieguito Reservoir watershed are established for:
• mineral constituents such as total dissolved solids, chloride, sulfate, manganese, iron, boron, and fluoride,
• nutrient constituents (total nitrogen and total phosphorus), and • toxic constituents for which state and federal primary drinking water standards have been established.

6.3.1 Basin Plan Standards
Table 6-3 summarizes Basin Plan surface water quality objectives for mineral constituents for San Dieguito Reservoir. Because the purified water used for surface water augmentation would be required (p er DDW regulations) to undergo full reverse osmosis treatment, compliance with the Basin Plan mineral standards is not projected to represent a compliance concern.

The Basin Plan establishes a narrative objective that concentrations of nitrogen and phospho rus, by themselves or in combination with any other nutrient, shall be maintained a t levels below those that stimulate algae and emergent plant growth. As shown in Table 6-3, the Basin Plan also establishes numerical concentration objectives for total phosphorus. While Basin Plan concentration objectives for total phosphorus are stringent, phosphorus is readily removed through advanced treatment and compliance with the Basin Plan standard for total phosphorus should not represent a compliance concern for the level of treatment mandated under proposed DDW surface water augmentation regulations.

20 Basin Plan water quality objectives for surface waters have been adopted by EPA as federal water quality standards that are subject to requirements and enforcement provisions of the federal Clean Water Act. 21 CTR regulations were promulgated by EPA within 40 CFR 131.38. (EPA, 2000).

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Table 6-3: Basin Plan Surface Water Quality Objectives for San Dieguito Reservoir Constituent
Basin Plan Surface Water
Quality Objective (mg/L)22
San Dieguito Reservoir
Total dissolved solids, TDS 500
Chloride 250
Sulfate 250
Iron 0.3
Manganese 0.05
Boron 0.75
Fluoride 1.0
Total Phosphorus 0.02523
Total Nitrogen See Note24,25

Total nitrogen, on the other hand, is not completely removed through advanced t reatment and would represents a significant compliance concern for a surface water augmentation project at San Dieguito Reservoir. The Basin Plan requires that “natural” N:P ratios are to be identified and upheld, and that in the absence of data, a N:P ratio of 10:1 is to be used. Applying a 10:1 N:P ratio to the 0.025 mg/ L Basin Plan standard for total phosphorus would result in a total nitrogen concentration limit of 0.25 mg/ L – a value that cannot readily be achieved even with 100 percent reverse osmosis treatment.

To address this issue, after initial review of two local surface water augmentation projects26, the RWQCB has tentatively agreed to a surface water augmentation regulatory concept under which purified water discharges to imported water reservoirs could be regulated through:

22 Basin Plan groundwater surface water quality objective not to be exceeded more than 10 percent of the time. It is probable that the RWQCB will establish NPDES effluent concentration limits for surface water augmentation discharges at the listed objective.
23 Threshold total phosphorus (P) shall not exceed 0.05 mg/L in any stream at the point where it enters any standing body of water, nor 0.025 mg/L in any standing body of water. 24 The Basin Plan does not establish analogous concentration values for total nitrogen, but requires that natural ratios of nitrogen to phosphorus (N:P) are to be identified through monitoring and upheld. In the absence of data, the Basin Plan specifies that a N:P ratio of 10:1 is to be used. If applied to San Dieguito Reservoir, such a 10:1 N:P ratio would translate to a total nitrogen standard of 0.5 mg/L in discharges to standing bodies of water, and a nitrogen standard of 0.25 mg/L within the ambient reservoir water. 25 In indirect potable reuse (IPR) projects proposed by the City of San Diego for Miramar Reservoir and by the Padre Dam Municipal Water District and Helix Water District for Lake Jennings, the RWQCB has indicated a willingness to consider imposing total nitrogen standards on the order of 2 mg/L for purified recycled water discharges to these reservoirs. The basis for this consideration is that “natural” N:P ratios do not exist in reservoirs that are dominated by imported water or by IPR water. Instead, N:P ratios are dependent on the source and quality of the imported water supply. Consequently, operators of such reservoirs can manage and maintain N:P ratios at sufficiently high values to ensure that phosphorus remains the limiting nutrient and the limited phosphorus concentrations prevent adverse biostimulation effects. 26 The City of San Diego has proposed the use of purified recycled water for supplying Miramar Reservoir, and the Padre Dam Municipal Water District and Helix Water District have proposed the use of purified recycled

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• recycled water treatment to ensure compliance with the Basin Plan 0.025 mg/L total phosphorus objective, and
• ensuring that phosp horus-limited conditions (e.g. maintaining a high N:P ratio) are maintained within the reservoir to prevent biostimulation.

Additional study will be required to determine if the tentative nutrient compliance proposed for Miramar Reservoir and Lake Jennings is workable at San Dieguito Reservoir. It is probable that this approach will only be feasible if purified water completely replaces Lake Hodges water as the source of supply within San Dieguito Reservoir.27

6.3.2 Application of Drinking Water Standards
In addi tion to establishing standards for mineral constituents, the Basin Plan imposes state and federa l primary drinking water standards on raw waters stored in San Dieguito Reservoir. As a result, while DDW applies the drinking water standards to the final pota ble supply, the RWQCB applies the state and federal primary drinking water concentration standards to the untreated source water waters within the watershed.

6.3.3 California Toxics Rule
EPA in 2000 promulgated the California Toxics Rule (CTR) which established state-wide water quality standards for inland surface waters of California.28 CTR standards have been established for toxic inorganic and toxic organic constituents for the protection of aquatic habitat and for the protection of public health.

The CTR standards also incorporate national standards for toxic chemicals established by EPA within the National Toxics Rule (NTR).29
Table 6-4 presents CTR standards for the protection of aquatic habitat that would be applicable to San Dieguito Reservoir. Table 6-5 presents CTR standards for the protection of public health. Since San Dieguito Reservoir is closed to public access and fishing, only the CTR standards for the consump tion of water would apply to the reservoir.

As shown in Table 6-4 and Table 6-5, CTR standards for some tox ic constituents are more stringent than corresponding drinking water standards. As a result, the CTR concentration limits (rather than drinking water limits) would govern purified water treatment and production for these constituents.

water for supplying Lake Jennings. The RWQCB has tentatively provided verbal agreement with a phosphorus- limited approach for the Miramar Reservoir and Lake Jennings surface water augmentation projects that would allow for total nitrogen effluent standards on the order of 2 mg/L. The RWQCB to date, however, has not formally committed in writing to any particular tentative NPDES permit limits for these projects. 27 Lake Hodges receives significant nutrient contributions from its watershed, and it may not be possible to manage or properly control nutrient concentrations in San Dieguito Reservoir if Lake Hodges supply continues to be introduced in San Dieguito Reservoir. On the other hand, if the Lake Hodges supply is 100 percent replaced by purified recycled water (e.g. no Lake Hodges water to San Dieguito), management of nutrient conditions within San Dieguito Reservoir will be greatly simplified and it is probable that the RWQCB would entertain total nitrogen standards on the order of 2 mg/L – standards that would be consistent with those being considered by the RWQCB for proposed potable reuse projects at Miramar Reservoir and Lake Jennings. 28 Title 40, Section 131.38 of the Code of Federal Regulations (40 CFR 131.38). (EPA, 2000) 29 NTR standards are promulgated by EPA within 40 CFR 131.36. (EPA, 1993)

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It should be noted t hat CTR s tandards apply to ambient receiving waters, and SWRCB implementation policies allow the RWQCB to apply the CTR standards outside designated mixing zones. 30 As a result, where appropriate dilution and mixing documentation is provided, the RWQCB may consider dilution credits in establishing CTR-based NPDES effluent concentration standards.

Table 6-4: California Toxic Rule Standards for the Protection of Aquatic Habitat Constituent
Concentration (µg/l)
Standard for Protection
of Aquatic Habitat31
Constituent
Concentration (µg/l)
Standard for Protection
of Aquatic Habitat28
CMC32 CCC33 CMC29 CCC30

TOXIC INORGANIC CONSTITUENTS CHLORINATED PESTICIDES
Antimony NS NS Aldrin 3.0 NS
Arsenic 340 150 gamma BHC
(Lindane) 0.95 NS
Cadmium 4.334 2.231 Chlordane 2.4 0.0043
Chromium III 55031 18031 4,4'-DDT 1.1 0.001
Chromium VI 16 11 4,4'-DDD NS NS
Copper 1331 931 4,4'-DDE NS NS
Lead 6531 2.531 Dieldrin 0.24 0.056
Mercury 1.4 0.77 alpha Endosulfan 0.22 0.056
Nickel 470 52 beta Endosulfan 0.22 0.056
Selenium NS 5.0 Endosulfan Sulfate NS NS
Silver 3.431 NS Endrin 0.086 0.036
Thallium NS NS Endrin Aldehyde NS NS
Zinc 12031 12031 Heptachlor 0.52 0.0038
Cyanide 22 5.2 Heptachlor Epoxide 0.52 0.0038
ACID EXTRACTABLE COMPOUNDS PCBs NS 0.014
Pentachlorophenol 19 15 Toxaphene 0.73 0.0002
Footnotes:

1. NS indicates that no standard has been established for the listed constituent.

30 The SWRCB established CTR implementation policies within Policy for Implementation of Toxics Standards for Inland Surface Waters, Enclosed Bays, and Estuaries of California. (SWRCB, 2005) 31 California Toxics Rule (40 CFR 131.38) per EPA (2000). CTR numeric criteria for protection of aquatic habitat.

Standards are applicable to all freshwater surface waters of the San Diego Region. All values rounded to two significant figures. Discharge concentration standards established in the NPDES permit adopted by the RWQCB may take into account potential mixing zone dilution credits allowed by the RWQCB. 32 CMC is the criteria maximum concentration, the highest concentration to which aquatic life can be exposed for a short period of time without deleterious effect
33 CCC is the criteria continuous concentration, the highest concentration to which aquatic life can be exposed for 4 days without deleterious effect.
34 CMC and CCC water quality criteria for cadmium, chromium III, copper, lead, silver, and zinc are dependent on receiving water hardness. (CTR limits become more stringent with lower hardness, and less stringent with higher hardness concentrations.) The above values are based on a receiving water hardness of 100 mg/L.

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Table 6-5: California Toxics Rule Standards for the Protection of Human Health Constituent
Concentration (µg/l)
Standard Protection of
Human Health
(Monthly Average)35
Constituent
Concentration (µg/l)
Standard Protection of
Human Health
(Monthly Average)32
Consumption
of Water36

Consumption
of Water plus
Organisms37
Consumption
of Water33

Consumption
of Water plus
Organisms34

TOXIC INORGANIC CONSTITUENTS ACID EXTRACTABLE COMPOUNDS Antimony 4300 14 2-chlorophenol 400 120
Mercury 1300 NS 2,4-dichlorophenol 790 93
Copper 0.051 0.05 2,4-dimethylphenol 2300 540
Nickel 4600 610 2-methyl 4,6
dinitrophenol 765 13.4
Thallium 6.3 1.7 2,4-dinitrophenol 14,000 70
Cyanide 220,000 700 Pentachlorophenol 8.2 0.28
VOLATILE ORGANIC COMPOUNDS Phenol 4,600,000 21,000
Acrolein 780 320 2,4,6-trichlorophenol 6.5 2.1
Acrylonitrile 0.66 0.059 BASE NEUTRAL COMPOUNDS
Benzene 71 1.2 Acenaphthene 2700 1200
Bromoform 360 4.3 Anthracene 110,000 9600
Carbon
tetrachloride 4.4 0.25 Benzidene 0.00054 0.00012
Chlorobenzene 21,000 680 Benzo (a) anthracene 0.049 0.0044 Chlorodibromom
ethane 34 0.41 Benzo (a) pyrene 0.049 0.0044
Dichlorobromom
ethane 46 0.56 Benzo (b)
fluoranthene 0.049 0.0044
1,2-
dichloroethane 99 0.38 Benzo (k)
fluoranthene 0.049 0.0044
1,1-
dichloroethylene 3.2 0.057 Bis (2-chloroethoxy)
ether 1.4 0.031
1,2-
dichloropropane 39 0.52 Bis (2-
chloroisopropyl) ether 170,000 1400
1,3-
dichloropropene 1700 10 Bis (2-ethylhexyl)
phthalate 5.9 1.8

California Toxics Rule (40 CFR 131.38) per EPA (2000). All values rounded to two significant figures.

Standards are applicable to all freshwater surface waters of the San Diego Region. 35 California Toxics Rule (40 CFR 131.38) per EPA (2000). All values rounded to two significant figures. The above standards are for ambient surface waters. Actual discharge concentration standards will be established in the NPDES permit adopted by the RWQCB, and may take into account potential mixing zone dilution credits allowed by the RWQCB.
36 CTR criteria for the consumption of water. Standard applicable to San Dieguito Reservoir. 37 CTR criteria for the consumption of water plus organisms. Standards applicable to potable water reservoirs that allow fishing.

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Constituent
Concentration (µg/l)
Standard Protection of
Human Health
(Monthly Average)35
Constituent
Concentration (µg/l)
Standard Protection of
Human Health
(Monthly Average)32
Consumption
of Water36

Consumption
of Water plus
Organisms37
Consumption
of Water33

Consumption
of Water plus
Organisms34
Ethylbenzene 29,000 3100 Butyl benzyl
phthalate 5200 3000
Methyl bromide 4000 48 2-chloronaphthalene 4300 1700
Methylene
chloride 1600 4.7 Chrysene 0.049 0.0044
1,1,2,2-
tetrachloroethan
e
11 0.17 Dibenzo (a,h)
anthracene 0.049 0.0044
Tetrachloroethyl
ene 8.85 0.8 1,2-dichlorobenzene 17,000 2700
Toluene 200,000 6,800 1,3-dichlorobenzene 2600 400
1,2 trans-
dichloroethylene 140,000 700 1,4-dichlorobenzene 2600 400 1,1,2-
trichloroethane 42 0.60 3,3-
dichlorobenzidene 0.077 0.04
Trichloroethylen
e 81 2.7 Diethyl phthalate 120,000 23,000
Vinyl chloride 525 2.0 Dimethyl phthalate 2,900,000 313,000 CHLORINATED PESTICIDES Di-n-octyl phthalate 12,000 2700 Aldrin 0.00014 0.00013 2,4-dinitrotoluene 9.1 0.11
alpha BHC 0.013 0.0039 1,2-
diphenylhydrazine 0.54 0.04
beta BHC 0.046 0.014 Fluoranthene 370 300
gamma BHC
(Lindane) 0.063 0.019 Fluorene 14,000 1300
Chlordane 0.00059 0.00057 Hexachlorobenzene 0.00077 0.00075 4,4'-DDT 0.00059 0.00059 Hexachlorobutadiene 50 0.44
4,4'-DDD 0.00059 0.00059 Hexachlorocyclopent
adiene 17,000 240
4,4'-DDE 0.00084 0.00083 Hexachloroethane 8.9 1.9
Dieldrin 0.00014 0.00014 Ideno 1,2,3-cd
Pyrene 0.049 0.0044
alpha
Endosulfan 240 110 Isophorone 600 8.4
beta Endosulfan 240 110 Nitrobenzene 1900 17
Endosulfan
Sulfate 240 110 N-
nitrosodimethylamine 8.1 0.00069
Endrin 0.81 0.76 N-nitrosodi-n-
propylamine 1.4 0.005
Endrin Aldehyde 0.81 0.76 N-
nitrosodiphenylamine 16 5.0
Heptachlor 0.00021 0.00021 Pyrene 11,000 960
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Constituent
Concentration (µg/l)
Standard Protection of
Human Health
(Monthly Average)35
Constituent
Concentration (µg/l)
Standard Protection of
Human Health
(Monthly Average)32
Consumption
of Water36

Consumption
of Water plus
Organisms37
Consumption
of Water33

Consumption
of Water plus
Organisms34
Heptachlor
Epoxide 0.00011 0.00010 1,2,4-
trichlorobenzene 940 260
PCBs 0.00017 0.00017 DIOXANS AND DIFURANS
Toxaphene 0.00075 0.00073 2,3,7,8-TCDD 1.4E-08 1.3E-08
Footnotes:

1. NS indicates that no standard has been promulgated for the listed constituent and category.

6.3.4 Chlorine Policy
The CTR does not establish a standard for chlorine residual, but EPA has established national criteria for chlorine residual concentrations to protect freshwater aquatic life.38 The SWRCB in 2006 proposed that the EPA criteria be established as a statewide standard, but to date the draft chlorine residual standards have not been implemented.39 The draft statewide chlorine standards currently being considered by the SWRCB would require that dischargers reduce chlorine residual in discharges to receiving waters to as close to zero as practicable. Pending approval of statewide standards for chlorine residual, the SWRCB has implemented the EPA criteria maximum concentration (CMC) water quality criteria (see Table 6-6 below) in the current statewide NPDES permit governing discharges to surface waters from drinking water systems. 40 It is anticipated that such a standard would also be applied to any surface water augmentation discharge to San Dieguito Reservoir.

38 National water quality criteria for total chlorine published by EPA. (EPA, 2017) 39 See Policy for Implementation of Toxics Standards for Inland Surface Waters, Enclosed Bays, and Estuaries of California. (SWRCB, 2006)
40 SWRCB General Order No. WQ 2014-0194-DWQ. (SWRCB, 2014)

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Table 6-6: Recommended Criteria for Chlorine for the Protection of Freshwater Aquatic Life Parameter
National Recommended Water Quality Criteria41
(concentration in µg/L)
CMC42 CCC43
Chlorine Residual 1944 11
Raw Water Augmentation
Options G and H involve the potential use of purified recycled water for augmenting untreated water supplies in Pipeline No. 5 of the SDCWA Second Aque duct. Pipeline No. 5 provides supply to potable water treatment plants and reservoirs operat ed by the Olivenhain Municipal Water District, Santa Fe Irrigation District/San Dieguito Water District, City of San Diego, and Sweetwater Authority.

6.4.1 DDW Regulation
As noted in TM1, DDW has not developed uniform regulations governing the use of purified recycled water for augmenting aqueduct supplies. It is probable, however, that such regulations (when developed) would include additional treatment and monitoring re quirements that would ensure the aqueduct discharge scenario provides a degree of public hea lth protection that is at least as protective as current water supply operations and proposed DDW indirect potable reuse regulations.45

6.4.2 Probable RWQCB Regulation
Because aqueduct water from Pipeline No. 5 may be discharged to and stored in reservoirs, the RWQCB would likely regulate the discharge of purified recycled water to the Second Aqueduct through issuance of a NPDES permit that implements (1) applicable DDW re quirements, and (2) surface water standards for applicable terminal reservoirs. The same Basin Plan standards that are applicable to San Dieguito Reservoir (see Table 6 -3) are also applicable to each of the terminal reservoirs for Pipeline No. 5 (e.g. , Olivenhain Reservoir, Miramar Reservoir, San Vicente Reservoir, Sweetwater Reservoir).

Fishing is allowed in City of San Diego and Sweetwater Authority reservoirs that receive supply from Pipeline No. 5. As a result, CTR human health standards for the consumption of water plus organisms (see Table 6-5) would be applicable for any purified recycled water flow discharged to the Second Aqueduct.

In addition to Basin Plan and CTR standards, any NPDES permit governing aqueduct augmentation would, of course, incorporate all applicable DDW regulations or requirements governing augmentation of Second Aqueduct flows.

41 National recommended water quality criteria per EPA (2017) for the protection of aquatic freshwater life. 42 CMC is the criteria maximum concentration, the highest concentration to which aquatic life can be exposed for a short period of time without deleterious effect.
43 CCC is the criteria continuous concentration, the highest concentration to which aquatic life can be exposed for 4 days without deleterious effect.
44 This 19 µg/l criterion has been established as a NPDES effluent concentration limit in the SWRCB general NPDES permit (Order WQ 2014-0194-DWQ) that regulates discharges of potable water to surface waters. (SWRCB, 2014)
45 See TM1 for a summary of issues and probable regulatory approaches associated with direct potable reuse.

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Brine Disposal
Each of the reuse options considered herein involve discharging waste brine to the EOO. Modification of the EOO NPDES permit would be required to:
• address changes in facilities descriptions within the findings and Fact Sheet of the existing EMWPF NPDES permit,46
• establish requirements for the discharge of waste brine to the EEO, and • address changes in initial dilution created by the brine discharge.

NPDES permit effluent limitations in the EOO NPDES permit implement receiving water standards and technology-based effluent standards that are established in the Ocean Plan, including receiving water standards (Ocean Plan Table 1 standards) and technology-based standards (Ocean Plan Table 2 standards).47

6.5.1 Ocean Plan Technology-Based Standards
In part, Table 2 of the Ocean Plan includes technology-based standards for:
• Grease and oil (30-day average limit of 25 mg/L; daily maximum limit of 75 mg/L), • Settleable solids (30-day average of 1.0 milliliters per liter; daily maximum of 1.5 ml/l), • Turbidity (30-day average limit of 75 NTU; daily maximum limit of 225 NTU), and • pH (pH to be maintained between 6.0 and 9.0 units at all time) Ocean Plan Table 2 effluent standards apply to each individual discharge stream to the EOO, and the Ocean Plan Table 2 standards would be imposed as NPDES effluent concentration standards for any brine discharge to the EEO.

6.5.2 Ocean Plan Receiving Water Standards and Initial Dilution Implications
Ocean Plan Table 1 receiving water standards apply to the combined discharge from the EOO. Ocean Plan Table 1 standards apply to receiving waters beyond designated zones of initial dilution, and the Table 1 standards are to be achieved after completion of the initial dilution process. The Ocean Plan specifies that NPDES effluent limits for regulated constituents within Table 1 be established on the basis of the following equation: 𝐶𝑒 = 𝐶𝑜 + 𝐷𝑚 ∙ (𝐶𝑜 − 𝐶𝑠)
Where Ce = NPDES effluent concentration standard for the Ocean Plan Table 1 constituent, Co = Ocean Plan Table 1 receiving water concentration standard, Dm = minimum probable initial dilution assigned by the RWQCB, and Cs = ambient ocean water concentration.

The RWQCB currently assigns an initial dilution of 144:1 to the EOO on the basis of plume buoyancy and dilution modeling completed by the SWRCB.48 Implementation of the reuse options considered herein will increase the salinity of the EEO discharge, as EWPCF wastewater discharges to the EOO will be reduced

46 The EEO discharge (including discharges from the EWPCF, the Meadowlark Water Reclamation Plant, the Shadowridge Water Reclamation Plant, and the Carlsbad Water Recycling Facility) is currently regulated by RWQCB Order No. R9-2011-0009 (NPDES CA0107395). NPDES CA0107395 was set to expire on June 1, 2016, but the permit has been administratively continued by the RWQCB, and RWQCB action on the Encina Wastewater Authority application for renewal of the NPDES permit is pending. 47 See Tables 1 and 2 of the Water Quality Control Plan, Ocean Waters of California (SWRCB, 2015). 48 See Section II.B of the Fact Sheet (Attachment F) to Order No. R9-2011-0019 (NPDES CA0107395).

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while the waste brine flows to the EOO will be increased. Dilution modeling will be required to assess how the increased brine flows to the EOO will affect the assigned initial dilution, but it is possible that increased brine contributions within the EOO would reduce the discharge plume buoyancy to the point where the assigned initial may be significantly reduced.

Such a reduction in the assigned initial dilution should not affect EOO compliance with most constituents, as the EOO currently complies with Ocean Plan -based NPDES requirements for individual toxic organic and inorganic constituents by a comfortable margin. A reduction in the assigned initial dilution, however, may potentially affect compliance with the Ocean Plan Table 1 receiving water standard for chronic toxicity. Additional analysis will be required to (1) assess the impact of increa sed brine on EOO initial dilution, and (2) evaluate how this reduction in initial dilution may affect compliance with the Ocean Plan receiving water standard for chronic toxicity.

A brine discharge to the EOO under Options F, G or H would contain salinity concentrations well below ambient ocean salinity levels. Such a brine discharge would not be subject to 2016 Ocean Plan Amendments that address brine discharges from seawater desalination facilities.

An engineering report describing the proposed facilities and potable reuse operations will be required.

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7 Conceptual Cost Analysis
Cost Opinion Methodology

7.1.1 Cost Classification
An opinion of probable construction cost (OPCC) for each option was developed as a Class 4 opinion, which is expected to be within a +50% to -30% accuracy range under a competitive bidding environment.49 Cost opinions were developed relying heavily on histo rical bid-based and cost-based methods to develop raw construction costs. From the raw construction costs, several construction cost factors were applied to develop opinions of total construction costs, followed by implementation factors to develop opinions of total capital costs.

7.1.2 Construction Cost Allowances
From the raw construction cost subtotal, the construction cost factors listed below are applied to develop an opinion of total construction costs.
• Construction contingency of 25% – The construction contingency is defined as unknown costs due to lack of detailed engineering during the preliminary design phase that are estimated as a percentage of defined project costs (i.e. , raw construction cost subtotal). As the level of project definition and understa nding increases and the level of unknown decreases, the construction contingency typically decreases. For this Study, a construction contingency of 25% was applied to the raw construction co st estimates. This is also intended to include O wner’s reserve for change orders, which may be a result of the Owner’s direction to implement additional work, differing field conditions that require additional work, or an error in the project contract documents. • Tax on Materials = 8%, applied to 50% of construction subtotal – A Class 4 estimate uses installed unit cost metrics that include both raw materials and installation (i.e., labor and equipment) costs. Therefore, tax on materials was estimated as 8. 0% (local tax) and applied to 50% of the construction cost subtotal.
• Shipping rate = 15% applied to 40% of the construction cost subtotal – A Class 4 estimate uses installed unit cost metrics that include both raw materials and installation (i.e., labor and equipment) costs. Therefore, shipping costs for equipment delivery were estimated as 15% and applied to 40% of the construction cost subtotal.
• Overhead and Profit = 15% – Overhead and profit (O&P) represents the general contractor’s operating costs and estimated profit levels. The O&P factor typically varies between 10% and 25%, depending on the size of the project and market conditions, with larger projects typically having lower O&P factors. An O&P factor of 15% was applied to the construction cost subtotal.

At this conceptual feasibility study stage, costs not considered include but are not limited to additional planning, administration, legal, and property acquisition.

7.1.3 Implementation Cost Allowances
To generate the opinions of total capital costs for the project, implementation costs such as design, environmental review, construction management, engineering services during construction, and other administrative costs associated with the project are included. Implementation costs are typically estimated

49 As defined by the Association for the Advancement of Cost Engineering International (AACE International).

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as a percentage of total construction cost, inclu ding all allowances described in Section 7.1.2 above. The implementation allowances used are summarized below.
• Environmental Documentation and Permits = 5% – Environmental documentation and permits involves producing environmental studies and acquiring any permits necessary to construct a project. A factor of 5% was applied to the total construction cost for environmental documentation and permits.
• Engineering Services = 10 % – Engineering services include field investigations (e.g. , surveys, geotechnical reports, hazard materials investigations), preliminary and final design, contract document development (i.e. plans and specifications), preparation of detail ed cost estimates, a nd project scheduling. An engineering services factor of 1 0% was applied to the total construction cost.
• Construction Management = 5% – Costs for construction management, including inspection, can vary greatly with project size and com plexity and whether the Owner performs this work with in - house staff or through a consultant. A construction management factor of 5% was applied to the total construction cost.
• Engineering Services During Construction = 5% – Engineering services during co nstruction (ESDC) ty pically include submittal and request for information (RFI) reviews, design clarifications, and startup support services. An ESDC factor of 5% was applied to the total construction cost.

7.1.4 Capital Financing Assumptions
Financing assumptions used to annualize capital costs are:
• Capital costs would be 100% financed
• Annual interest rate: 2.0%
• Term of Financing: 30 years
• Discount Rate: 0%
Over the last 10 years, the General Obligation (GO) Bond interest rate has varied from 1.7% to 3.0% and may increase. Actual p roject financing will vary based o n the current market conditions and the type of loan secured. For the purposes of the analysis in this TM, no consideration was given to any grants or special loans that may be awarded to EWA for this Project.

7.1.5 Operations and Maintenance (O&M) Costs
Operations and maintenance (O&M) requirements were derived from experience on similar projects and standard engineering methods. The three components used to develop annual O&M costs were:
• Labor – Labor costs associated with new treatment and conveyance facilities O&M are calculated on an hourly basis, with 2080 hours per year assumed to be one full -time equivalent (FTE) . The required labor hours are estimated based on experience with prior projects and othe r c urrent systems in op eration. The average hourly cost of an O&M personnel, including overhead , is estimated to be $75.
• Power – The unit cost of electricity used is $0.15/kWh. Any offsets available from power produced at the EWPCF were not considered.
• Equipment Rehabilitation/R eplacement and Consumables - Consumables are major component of operation expenditures and include resources that are intended and expected to be used up relatively quickly. Example of consumables include chemicals, gaskets, and potable water.

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Where specific consumable line items could not be quantified, consumable costs were estimated as 1% of the raw construction cost.

Costs by Option
This section presents the cost opinions for each of the three main Options evaluated. The capital costs are summarized under three categories:
• EWPCF Secondary Improvements
• AWTF
• Conveyance
The annual O&M costs are summarized under the following categories:
• Power for treatment (including both the incremental power requirements at the EWPCF and the requirements for the AWTF)
• Power for conveyance (pumping)
• Other O&M costs: this includes equipment rehabilitation/replacement and consumables (across all improved and new facilities) , and l abor for the AWTF and the conveyance system (pipeline maintenance)
The total capital costs are annualized using the financing assumptions presented in Section 7.1.4 above and combined with the O&M costs to develop a cost of water per acre -foot produced. An overview of the OPCCs and costs of water for the three Options are provided in Figures 7 -1 and 7-2; cost summary tables are provided in Tables 7-1 through 7-5. Detailed cost tables for the components of each option are provided in Appendix A.

Figure 7-1: Capital Cost Summary for Options F, G, and H.

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Figure 7-2: Cost of Water Summary for Options F, G, and H.

Table 7-1: Cost Summary for Option F.

Option F: Carlsbad Desalination Plant Cost Notes
EWPCF Secondary Improvements $89,000,000 at 31 mgd flow rate Advanced Water Treatment Facility
(FAT+O3/BAF+WTP) $283,900,000 at 20.5 mgd influent rate Conveyance - North $142,800,000 at 20.5 mgd influent rate Total Capital Cost $515,700,000
Annual O&M Costs
Power - Treatment (EWPCF + AWTF) $5,671,000 24/7/365 operations Power - Conveyance $15,853,000 24/7/365 operations
Equipment Rehabilitation/Replace, Consumables $6,309,000 All new facilities (incl. EWCPF) Labor $1,270,000 AWTF + Conveyance
Total Annual O&M Cost $29,110,000
Cost of Water
Annualized Capital Cost $23,026,000 2.0% rate, 30-yr term Total Annual Cost $52,136,000 for first 30 years
Annual Yield 17,700 acre-feet
Unit Cost - Capital $1,310 per acre-foot
Unit Cost - O&M $1,650 per acre-foot
Unit Cost of Water $2,960 per acre-foot

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Table 7-2: Cost Summary for Option G.

Option G: San Dieguito Groundwater Basin and
SDCWA Second Aqueduct (All Phases) Cost Notes
EWPCF Secondary Improvements $89,000,000 at 31 mgd flow rate Advanced Treatment (FAT + O3/BAF) $234,400,000 at 20.5 mgd influent rate Conveyance - South $287,400,000 at 20.5 mgd influent rate Total Capital Cost $610,800,000
Annual O&M Costs
Power - Treatment (EWPCF + AWTF) $5,403,000 24/7/365 operations Power - Conveyance $15,501,000 24/7/365 operations
Equipment Rehabilitation/Replace, Consumables $6,580,000 All new facilities (incl. EWCPF) Labor $1,221,000 AWTF + Conveyance
Total Annual O&M Cost $28,705,000
Cost of Water
Annualized Capital Cost $27,273,000 2.0% rate, 30-yr term Total Annual Cost $55,978,000 for first 30 years
Annual Yield 17,800 acre-feet
Unit Cost - Capital $1,540 per acre-foot
Unit Cost - O&M $1,620 per acre-foot
Unit Cost of Water $3,160 per acre-foot
Table 7-3: Cost Summary for Option H.

Option H1: SDCWA Second Aqueduct and San
Marcos Groundwater Basin Cost Notes
EWPCF Secondary Improvements $89,000,000 at 31 mgd flow rate Advanced Treatment (FAT + O3/BAF) $234,400,000 at 20.5 mgd influent rate Conveyance - East $180,400,000 at 20.5 mgd influent rate Total Capital Cost $503,800,000
Annual O&M Costs
Power - Treatment (EWPCF + AWTF) $5,403,000 24/7/365 operations Power - Conveyance $13,387,000 24/7/365 operations
Equipment Rehabilitation/Replace, Consumables $5,724,000 All new facilities (incl. EWCPF) Labor $1,144,000 AWTF + Conveyance
Total Annual O&M Cost $25,658,000
Cost of Water
Annualized Capital Cost $22,495,000 2.0% rate, 30-yr term Total Annual Cost $48,153,000 for first 30 years
Annual Yield 17,800 acre-feet
Unit Cost - Capital $1,270 per acre-foot
Unit Cost - O&M $1,450 per acre-foot
Unit Cost of Water $2,720 per acre-foot
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7.2.1 Comparison to Projected Cost of Water for Other Water Sources To provide context for the co st of water developed for this Study’s Options, information on the costs of other sources of water available in the region and in the State of Calif ornia is provided below (California Public Utilities Commission [CPUC] 2016):
• SDCWA treated water costs are expected to reach $3,880/af by 2040. • Conservation programs can provide substantial incentives for water savings, such as t he CPUC unaccounted for water (UFW) incentive mechanism that provides $2,019/af. • Planning for other recent potable reuse projects in California, such as San Diego Pure Water and Monterey Pure Water, have projected costs in the $2,000 to $5,000 per af range. • Desalinated product water provided to SDCWA member agencies cost up to $2,367/af in 2016.

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8 Conclusions
In evaluating the relative merits of the three options presented in this TM, the following criteria were used:
• Cost of water
• Likely timeframe for regulatory acceptance and project implementation • Complexity of operations and compliance
• Expected demand and stakeholder support
Key information for each of these criteria is presented in Table 8-1, based on each option at the full projected 2040 flows for the EWPCF (i.e., 20.5 mgd influent to the AWTF).

Table 8-1: Summary of Key Considerations for EWA’s Potable Reuse Options.

Option F
Carlsbad Desal. Plant
Option G
San Dieguito + 2nd Aqueduct
Option H
2nd Aqueduct + San Marcos
Cost of Water
(at 20.5 mgd
influent)
$2,960/af $3,160/af $2,720/af
Time to
Implement 15-20+ years 10-15 years 10-15 years
Regulatory
Considerations Timeframe uncertain Legislation pending Legislation pending Complexity of
Operations &
Compliance
AWTF “c”
Blending & Pumping at
CDP
AWTF “b”
Up to three forms of potable
reuse (reservoir +
groundwater + raw water)
AWTF “b”
Up to two forms of potable
reuse (raw water +
groundwater)
Key
Stakeholders
SDCWA
Poseidon

SEJPA, SDWD, SFID,

OMWD, SDCWA
SDCWA
Vallecitos WD

Based on these criteria, it is recommended that Option H be carried forward for further phasing analysis under TM4 and funding analysis under TM5. A potential imp lementation schedule for the variou s components of Option H (i.e., E WPCF improvements, AWTF, and conveyance/receptor integration infrastructure) will also be provided under TM4.

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Date: 1/25/2018
Project Number: 0305-059
Prepared By: Trussell Technologies, Inc.

Reviewed by: RMC / Woodard & Curran
Cost Opinion Type: Planning (Class IV)
Item Description Size Units Quantity Unit Unit Cost Total Cost Primary Effluent Flow Equalization 7,900,000$
Flow EQ Basin 2 EA $2,700,000 5,400,000$
Primary Effluent Pipe 1 LS $1,500,000 1,500,000$
Pump Station/ Modulating Valve 1 LS $1,000,000 1,000,000$ Item Description Size Units Quantity Unit Unit Cost Total Cost Aeration Basins (4) 8,620,000$
Baffling 12 EA $50,000 600,000$
Blower Upgrades 1 LS $2,800,000 2,800,000$
Anoxic Zone Mixers 1 LS $960,000 960,000$
Fine Bubble Aeration Equipment 1 LS $2,000,000 2,000,000$ Internal Mixed Liquor Pumps 1 LS $460,000 460,000$
Piping/Basin Modifications for IMLR 1 LS $100,000 100,000$ Scum and Foam Control 1 LS $500,000 500,000$
Demo of Existing Aeration Equipment 1 LS $100,000 100,000$ Air Piping/Valves/ DO Control 1 LS $1,100,000 1,100,000$ Item Description Size Units Quantity Unit Unit Cost Total Cost 7,000,000$
Circular Clarifier, New 2 EA $1,500,000 3,000,000$
Retaining Wall 1 LS $1,000,000 1,000,000$
Equipping Existing Clarifier No. 7 1 LS $500,000 500,000$ Secondary Effluent Pump Station 1 LS $1,500,000 1,500,000$ Piping/Valving 1 LS $1,000,000 1,000,000$
Item Description Size Units Quantity Unit Unit Cost Total Cost Tertiary Filters 19,300,000$
Gravity Filter Housing and Underdrain 6 EA $1,333,333 8,000,000$ Piping/Valving 1 LS $5,000,000 5,000,000$
Filter Media 1 LS $1,200,000 1,200,000$
Backwash Pump Station 1 LS $2,000,000 2,000,000$
Air Scour Wash 1 LS $2,800,000 2,800,000$
Waste Wash Water Equalization Tank 1 LS $300,000 300,000$ Project: Encina Water Reuse Feasibility Study
Element: EWPCF Improvements
Secondary Clarifiers