Attachment 1 - Water Supply Alternatives Plan — Santa Rosa City Council, October 24, 2023 (part 1 of 2)

DRAFT | SEPTEMBER 2023

WATER SUPPLY

ALTERNATIVES PLAN
for the City of Santa Rosa
Attachm ent 1

City of Santa Rosa Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

ACKNOWLEDGEMENTS
Santa Rosa Water would like to acknowledge the hundreds of hours that community stakeholders and Water staff have given to the Water Supply Alternatives Plan and its development. The valuable input and thoughtful discussions have meaningfully contributed to this document and to Santa Rosa’s water future. Many thanks to:

Water Team
Jennifer Burke, Director of Santa Rosa
Water
Peter Martin, Deputy Director of Water
Resources
Sean McNeil, Deputy Director of
Environmental Services
Mike Prinz, Deputy Director of Regional
Operations
Joe Schiavone, Deputy Director of Water
and Sewer Operations
Lori Urbanek, Deputy Director of
Engineering Services
Colin Close, Senior Water Resources
Planner & Project Manager
Heather Johnson, Environmental
Compliance Officer
Ron Marincic, Utilities System
Superintendent
Claire Nordlie, Water Use Efficiency
Supervisor
Jason Tibbals, Utilities System
Superintendent
Stakeholder Group (with alternates)
Berreta Family Diary (Doug Berreta)
Calpine (Chris Schofield)
City of Rohnert Park (Mary Grace
Pawson)
Community Action Partnership (Johnny
Nolen, Nathan Smith)
Los Cien Sonoma County (Herman G.

Hernandez)
NAACP Santa Rosa-Sonoma (Kirstyne
Lange)
North Bay Black Chamber of Commerce
(Nancy Rogers)
North Coast Builders Exchange (Lisa
Wittke Schaffner)
RED Housing (Michelle Whitman)
Regional Climate Protection Authority
(Suzanne Smith)

City of Santa Rosa Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Russian River Watershed Association
(Indigo Bannister, Sandi Potter)
Russian River Watershed Protection
Comm (Brenda Adelman)
Santa Rosa Metro Chamber of
Commerce (Peter Rumble)
Santa Rosa Plain Groundwater
Sustainability Agency (Andy Rodgers)
Santa Rosa Subregional Tech Adv
Committee (Craig Scott)

Sonoma Clean Power (Geof Syphers)
Sonoma County Alliance (Dick Dowd,
Marlene Soiland)
Sonoma Resource Conservation District
(Valerie Minton Quinto, Jessica Pollitz)

Sonoma Water (Don Seymour, Stephen
Maples, Todd Schram)

Members of the Public
Santa Rosa Water would like to thank all of the members of the public who attended community meetings, asked great questions, offered suggestions, and expressed interest in this endeavor.

City of Santa Rosa i Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

TABLE OF CONTENTS
Executive Summary ....................................................................................................................................................................... ES-1

1. Introduction ................................................................................................................................................................................... 1

1.1 Background ............................................................................................................................................................................ 1

1.2 Purpose of the Water Supply Alternatives Plan ....................................................................................................... 4

1.2.1 Coordination with Regional Efforts ...................................................................................................................... 5

1.3 Water Supply Alternatives Plan Organization .......................................................................................................... 6

2. Approach to Developing the Water Supply Alternatives Plan .................................................................................. 7

2.1 Water Supply Goals ............................................................................................................................................................ 7

2.2 Water Supply Options ........................................................................................................................................................ 8

2.3 Analysis Methodology ....................................................................................................................................................... 9

2.3.1 Pre-Screening ............................................................................................................................................................. 10

2.3.2 Screening Analysis ................................................................................................................................................... 10

2.3.3 Detailed Feasibility Analysis ................................................................................................................................. 10

2.4 Collaboration and Stakeholder Involvement ......................................................................................................... 12

3. Water Supply Options ............................................................................................................................................................ 14

3.1.1 Groundwater .............................................................................................................................................................. 14

3.1.2 Purified Recycled Water ......................................................................................................................................... 16

3.1.3 Recycled Water .......................................................................................................................................................... 17

3.1.4 Desalination ................................................................................................................................................................ 18

3.1.5 Stormwater.................................................................................................................................................................. 18

3.1.6 Efficiency Programs ................................................................................................................................................. 19

4. Analysis of Water Supply Options ..................................................................................................................................... 20

4.1 Pre-Screening Outcome ................................................................................................................................................. 20

4.2 Screening Analysis Result .............................................................................................................................................. 21

4.3 Feasibility Analysis Results ............................................................................................................................................ 28

4.3.1 Groundwater Options ............................................................................................................................................. 31

4.3.2 Purified Recycled Water Options ....................................................................................................................... 34

4.3.3 Stormwater Capture ................................................................................................................................................ 36

4.3.4 Efficiency Programs ................................................................................................................................................. 37

4.3.5 Cost Sensitivity Analysis ......................................................................................................................................... 38

City of Santa Rosa ii Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

4.4 Analysis Summary ............................................................................................................................................................. 39

5. Portfolios ..................................................................................................................................................................................... 40

5.1 Overview of Portfolios .................................................................................................................................................... 40

5.2 Portfolio 1: Most Economical ....................................................................................................................................... 41

5.3 Portfolio 2: Fastest ............................................................................................................................................................ 45

5.5 Portfolio 3: Most Water .................................................................................................................................................. 48

5.7 Portfolio 4: Most Adaptive ............................................................................................................................................ 52

5.8 Summary of Portfolios .................................................................................................................................................... 62

6. Next Steps ................................................................................................................................................................................... 68

7. References ................................................................................................................................................................................... 72

LIST OF FIGURES
Figure ES-1: Analysis Methodology Flowchart .................................................................................................................. ES-2 Figure 1-1: Santa Rosa Water Use by End Use and Supply Type (2020) ........................................................................ 1 Figure 1-2: Water Use in Santa Rosa (1990 – 2022) ............................................................................................................... 3 Figure 1-3: Lake Sonoma Water Supply Storage ..................................................................................................................... 4 Figure 2-1: Analysis Methodology Flowchart ............................................................................................................................ 9 Figure 4-1: Cost-Effectiveness vs Max Yield (with Weighted Score) ............................................................................. 30 Figure 4-2: Supply Option Cost Performance with Varying Hydrology ($/AF) ......................................................... 38 Figure 4-3: Supply Option Cost Performance with Varying Sonoma Water Cutbacks ($M/yr) ......................... 39 Figure 5-1: Portfolio 1 Cost and Yield Performance ............................................................................................................ 43 Figure 5-2: Portfolio 1 Implementation Concept .................................................................................................................. 44 Figure 5-3: Portfolio 2 Cost and Yield Performance ............................................................................................................ 46 Figure 5-4: Portfolio 2 Implementation Concept .................................................................................................................. 47 Figure 5-5: Portfolio 3 Cost and Yield Performance ............................................................................................................ 50 Figure 5-6: Portfolio 3 Implementation Concept .................................................................................................................. 51 Figure 5-7: Portfolio 4 Cost and Yield Performance (Baseline Scenario) .................................................................... 55 Figure 5-8: Portfolio 4 Implementation Concept (Baseline Scenario) .......................................................................... 56 Figure 5-9: Portfolio 4 Cost and Yield Performance (Alternative Scenario) ............................................................... 58 Figure 5-10: Portfolio 4 Implementation Concept (Alternative Scenario) .................................................................. 59 Figure 5-11: Portfolio 4 Implementation Concept (Alternative Scenario, 1st Variant) ........................................... 60 Figure 5-12: Portfolio 4 Implementation Concept (Alternative Scenario, 2nd Variant) .......................................... 61 Figure 5-13: Cumulative Estimated Water Yield (AFY) ........................................................................................................ 64 Figure 5-14: Capital Funding Needs by Year ($M/Year) .................................................................................................... 65 Figure 5-15: Cumulative Capital Investment ($M/Year) ..................................................................................................... 66 Figure 5-16: Net Operating Burden ($M/Year) ...................................................................................................................... 67

City of Santa Rosa iii Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

LIST OF TABLES
Table ES-1: Water Supply Targets for Santa Rosa’s Water Future Goal .................................................................. ES-2 Table ES-2: Initial List of Water Supply Options ................................................................................................................ ES-4 Table ES-3: Supply Options Removed During Pre-Screening ..................................................................................... ES-5 Table ES-4: Supply Options Removed During the Screening Analysis .................................................................... ES-6 Table ES-5: Summary of Supply Option Scores................................................................................................................. ES-8 Table ES-6: Draft Portfolio Compositions ............................................................................................................................ ES-9 Table ES-7: Portfolio 1 Composition .................................................................................................................................... ES-10 Table ES-8: Portfolio 2 Composition .................................................................................................................................... ES-11 Table ES-9: Portfolio 3 Composition .................................................................................................................................... ES-12 Table ES-10: Portfolio 4 Composition ................................................................................................................................. ES-14 Table 2-1: Water Supply Goals for the Water Supply Alternatives Plan ......................................................................... 8 Table 2-2: Initial List of Water Supply Options ......................................................................................................................... 9 Table 2-3: Evaluation Criteria Scoring Rubric ......................................................................................................................... 11 Table 2-4: Stakeholder and Community Outreach Meeting Summary........................................................................ 12 Table 3-1: Summary of Water Supply Options ...................................................................................................................... 14 Table 4-1: Supply Options Removed During Pre-Screening ............................................................................................ 20 Table 4-2: Screened List of Water Supply Options .............................................................................................................. 21 Table 4-3: Supply Options Removed During the Screening Analysis ........................................................................... 22 Table 4-4: Screening Analysis Results Summary ................................................................................................................... 24 Table 4-5: Summary of Supply Option Scores ....................................................................................................................... 29 Table 4-6: Detailed Scoring for Option GW-1 ....................................................................................................................... 31 Table 4-7: Detailed Scoring for Option GW-2 ....................................................................................................................... 32 Table 4-8: Detailed Scoring for Option GW-3 ....................................................................................................................... 33 Table 4-9: Detailed Scoring for Option PR-2 .......................................................................................................................... 34 Table 4-10: Detailed Scoring for Option PR-4 ....................................................................................................................... 35 Table 4-11: Detailed Scoring for Option SW-1 ...................................................................................................................... 36 Table 4-12: Detailed Scoring for Option E-1 .......................................................................................................................... 37 Table 4-13: Distribution of Water Year Types in Hydrologic Scenarios ....................................................................... 38 Table 5-1: Draft Portfolio Compositions .................................................................................................................................. 41 Table 5-2: Portfolio 1 Composition ............................................................................................................................................ 42 Table 5-3: Portfolio 2 Composition ............................................................................................................................................ 45 Table 5-4: Portfolio 3 Composition ............................................................................................................................................ 48 Table 5-5: Portfolio 4 Composition ............................................................................................................................................ 53

City of Santa Rosa iv Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

ACRONYMS AND ABBREVIATIONS
AF acre-foot
AFY acre-feet per year
AOP advanced oxidation process
ASR Aquifer Storage and Recovery
AWPF Advanced Water Purification Facility
BAF biological activated filtration
BPU Board of Public Utilities
City City of Santa Rosa
CII Commercial, industrial, and institutional
DPR direct potable reuse
FAT full advanced treatment
gpf gallons per flush
gpm gallons per minute
GSP Groundwater Sustainability Plan
IPR Indirect Potable Reuse
LTP Laguna Treatment Plant
MF microfiltration
MGD million gallons per day
O&M Operations and Maintenance
SFR Single family residential
State Board State Water Resources Control Board
SWA surface water augmentation
UWMP Urban Water Management Plan
WSAP Water Supply Alternatives Plan

APPENDICES
Appendix A: Feasibility Analysis Technical Memorandum
Appendix B: Links to Recorded Meetings
Appendix C: Portfolio 1 Example Schedule
Appendix D: Portfolio 2 Example Schedule
Appendix E: Portfolio 3 Example Schedule
Appendix F: Portfolio 4 Example Schedule (Baseline Scenario) Appendix G: Portfolio 4 Example Schedule (Alternative Scenario) Appendix H: Santa Rosa Water’s Recent Budgets for Operations and Capital Projects Appendix I: Memorandum on Desalination Supply Options in the Water Supply Feasibility Analysis

City of Santa Rosa ES-1 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

EXECUTIVE SUMMARY

1. INTRODUCTION

1.1 Our Water Future: Purpose of the Water Supply Alternatives Plan The City of Santa Rosa (City) wishes to expand and diversify its potable water supply portfolio to enhance its resiliency to mitigate the potential impacts of future water supply shortages caused by severe and/or prolonged droughts or catastrophic service interruptions. Currently, the City’s Water Department (Santa Rosa Water) meets approximately 5-7 percent of its annual urban potable water demand from municipal wells and relies on Sonoma Water supplies for the remaining 93-95 percent. As a result of this dependency, if Sonoma Water were to experience a supply shortage or an interruption in service, the City’s public water system will have a water supply shortage.

The City is particularly concerned about the impacts of drought. Over the past 20 years, the Sonoma County region has experienced three multi-year droughts: 2007-2009, 2013-2016, and 2020-2022. In response, Sonoma Water called for water use reductions, triggering the City to require its customers to reduce potable water use by 20 percent. Regional climate change assessments project that local droughts will likely become more severe and more frequent. Likewise, local water use analysis shows demand hardening (permanent reductions in water use by customers). Given these realities, Santa Rosa Water wishes to increase water supply resiliency and reliability by increasing the diversity and production capacity of its water supply portfolio.

As a result, Santa Rosa Water launched the Our Water Future project in May of 2022 a nd undertook development of this Water Supply Alternatives Plan (WSAP) in September 2022 to identify an adaptive approach to diversifying Santa Rosa’s water supply portfolio and production capacity over time. The WSAP provides a variety of water supply portfolios for Santa Rosa Water to consider when planning future strategic investments and projects for increasing water supply resiliency and reliability. The WSAP is not intended to be a prescriptive document, but rather an adaptive guide for Santa Rosa Water to use as it embarks on water supply and infrastructure planning for Santa Rosa’s future.

2. APPROACH TO DEVELOPING THE WATER SUPPLY ALTERNATIVES PLAN

2.1 Goal
The first objective of the Our Water Future project was establishing a water supply resiliency and reliability goal for Santa Rosa’s future. Discussions with Santa Rosa Water staff (referred to as the Water Team), an external group of community leaders (referred to as the Stakeholder Group), the community at large, and the Board of Public Utilities (BPU) yielded the following framework outlining what the goal should accomplish:

1. Guide Decision Making: The goal should provide essential guidance to make informed decisions concerning the scale and scope of the resiliency portfolio.

2. Improve Water Resiliency: The goal should reduce the City’s reliance on Sonoma Water supplies and enhance the City's potable water supply resiliency.

City of Santa Rosa ES-2 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

3. Mitigate Shortages: The goal should help mitigate potential shortages in Sonoma Water supply and minimize service interruptions during dry periods.

4. Meet Peak Day Demand Locally: The goal should help the City meet a portion of peak day demand using local supply.

5. Allow for Flexibility and Adaptability: The goal should be percentage based, thereby making it easier to adjust if future conditions change the amount of supply needed.

Thus, the water supply goal is to diversify and increase Santa Rosa Water’s potable water supplies to reduce dependence on Sonoma Water, particularly to mitigate the impacts of future supply shortages or disruptions in service. New supplies would augment existing City groundwater production capacity (approximately 1,300 AFY, with an average of 2 million gallons per day (MGD) over approximately 6.5 months per year) to achieve the following targets outlined in Table ES-1 below.

Table ES-1: Water Supply Targets for Santa Rosa’s Water Future Goal Mitigating Droughts Mitigating Natural Disasters &
Catastrophic Events Mitigating Peak Day Demand
Meet 30% of City’s water demand
with municipal supplies to mitigate
impacts of Russian River supply
shortages (e.g., due to prolonged
and/or severe drought).

Based on current City demand
projections, the volume of water
required to meet this is 7,500 acre-
feet per year (AFY) by 2045.

Provide 50% of normal
domestic/indoor demand for
potable water with municipal
supplies during Russian River supply
disruption.

Based on current City demand
projections, the volume of water
required to meet this is 9 MGD by
2045.

Meet 30 percent of peak month
average day demand for potable
water with municipal supplies.

Based on current City demand
projections, the volume of water
required to meet this is 9 MGD by
2045.

2.2 Analysis Methodology
The analysis methodology described briefly below was developed with input from the Water Team, Stakeholder Group, community, and BPU. After compiling a list of supply options with stakeholder input, Santa Rosa Water implemented pre-screening, screening, and feasibility analyses to identify the best candidates for achieving its water supply goal. Figure ES-1 shows the overall steps in the analysis process.

Figure ES-1: Analysis Methodology Flowchart

City of Santa Rosa ES-3 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
• Pre-screening: Prior to in-depth analysis, all supply options were subjected to a high-level pre- screening to identify and remove options deemed infeasible or substantially similar to existing and anticipated reginal efforts or other supply options considered in the analysis. • Screening Analysis: After pre-screening, all viable water supply options were screened for high- level assessments of cost-effectiveness and scalability.1, 2 The screening tool helped determine the conceptual performance of each supply option in areas such as water yield and capital cost and removed options that were not cost-effective. Furthermore, the screening tool analyzed supply options in two hypothetical scenarios: baseline and maximum production. The baseline scenario assumed each water supply option would be operated in a realistic capacity (more in dry years, less in normal supply years) that aimed to minimize operational costs, in contrast to the maximum production scenario that assumed water supply options would be operated to maximize wa ter production via nonstop (24/7) operation.
• Detailed Feasibility Analysis: Following the screening analysis, the short-listed supply options underwent a detailed feasibility analysis that involved developing eight evaluation criteria, assigning numerical weights reflecting community priorities to each criterion, and using a detailed rubric to issue each option a score between 0 to 2, with 2 being most favorable. A score of 0 signals that the option is not as responsive to a criterion or does not perform as well as the other options, while a score of 2 indicates that the option performs very well. A full description of the feasibility analysis and its findings are included in Appendix A.

3. WATER SUPPLY OPTIONS
To prepare for the feasibility analysis, Santa Rosa Water compiled an initial list of water supply options gathered from the Water Team, Stakeholder Group, community, and BPU. The final list of supply options includes a broad range of water supply sources such as groundwater, purified recycled water, recycled water, desalinated water, stormwater, and aggressive water efficiency programs. Each supply type has nested supply options that differ in project description, water capacity, and geography.

Table ES-2 lists the water supply options that were considered in the feasibility analysis. Chapter 3 includes descriptions of each water supply option.

1 Water supply options assessed in the feasibility analysis were developed at a conceptual level to estimate potential water supply costs. The cost estimates are considered Class 5 per the Association for the Advancement of Cost Engineering International guidelines as they are rough order of magnitude. Actual project costs would be expected to fall within +50 percent to -15 percent of the cost estimate.

2 Scalability refers to how much water Santa Rosa Water could produce from the option now and how much water it could possibly produce in the future. An option with low scalability would yield similar amounts of water now and in the future.

City of Santa Rosa ES-4 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table ES-2: Initial List of Water Supply Options
Supply Type Supply Option Name
Groundwater
GW-1: Additional Groundwater Extraction Wells
GW-2: Convert Emergency Wells to Production Wells
GW-3: Aquifer Storage and Recovery (ASR) Wells
GW-4: Regional Groundwater Extraction Wells
GW-5: Regional ASR Wells
Purified Recycled
Water
PR-1: Direct Potable Reuse (DPR) Advanced Water Purification Facility (AWPF) at Laguna Treatment Plant (LTP)
PR-2: Satellite DPR AWPF
PR-3a: Indirect Potable Reuse (IPR) AWPF at LTP into Groundwater Basin PR-3b: IPR AWPF at LTP into Lake Ralphine
PR-3c: IPR AWPF at LTP into Lake Sonoma
PR-4: Regional DPR AWPF at LTP
Recycled Water RW-1: Expand City’s Urban Non-Potable Recycled Water System Desalination
DE-1: Regional Brackish Desalination
DE-2: Ocean Desalination
Stormwater
SW-1: Stormwater Storage in Aquifer
SW-2: Stormwater Storage in Lake Ralphine
SW-3: Regional Stormwater
Efficiency Programs E-1: Efficiency Programs

4. ANALYSIS OF WATER SUPPLY OPTIONS

4.1 Pre-Screening Results:

The 18 initial supply options were subjected to pre-screening to remove infeasible options or those that overlap with existing or planned efforts in the region. Five supply options, GW-4, GW-5, PR-3b, SW-2, and SW-3, were identified in this process and not advanced for further study.

Two options (PR-3b and SW-2) would rely on Lake Ralphine for storage. However, Lake Ralphine lacks sufficient capacity for storage, and expansion would require raising the existing dam, displacing adjacent recreational areas, and encroaching upon residential neighborhoods and unfavorable topography.

Therefore, PR-3b and SW-2 were deemed infeasible and did not continue to the screening process.

Santa Rosa expects options GW-4, GW-5, and SW-3 will be moving forward regionally under the leadership of Sonoma Water, the Santa Rosa Plain Groundwater Sustainability Agency (GSA), and the

City of Santa Rosa ES-5 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Russian River Water Forum. Santa Rosa is deeply involved in regional efforts as a primary water contractor to Sonoma Water, as an active member of the GSA Board and the GSA Board’s Advisory Committee, and as an active member of the Planning Group for the Russian River Water Forum. The City is committed to continue working with these and other partners on regional efforts to enhance regional water suppl y resiliency and groundwater basin sustainability as opportunities arise. Table ES-3 summarizes the reasons for removal during pre-screening.

Table ES-3: Supply Options Removed During Pre-Screening Category Supply
Option Reason for Removal
Groundwater
GW-4:

Regional
groundwater
extraction
wells
Regional groundwater projects are likely to move forward as Sonoma Water continues to increase its water supply reliability efforts and the City is committed to participate as a water contractor. However, GW-4, in its current form, would likely require a recharge element to comply with the Santa Rosa Plain Groundwater Sustainability Agency (GSA) sustainability efforts. Therefore, GW-4 overlaps substantially with local and regional ASR supply options. Additionally, this supply option does not reduce reliance on the Sonoma Water distribution system. Thus, this option was not carried forward to the screening analysis.

GW-5:

Regional ASR
wells
Regional ASR projects are likely to move forward as Sonoma Water continues to increase its water supply reliability efforts and as the GSA pursues long-term groundwater basin sustainability. The City is committed to working with its partners on these future regional ASR projects. However, GW-5, in its current form, does not reduce reliance on the Sonoma Water distribution system. Therefore, this supply option did not advance to the screening analysis.

Purified
Recycled
Water
PR-3b:

IPR AWPF at
LTP via Lake
Ralphine
Lake Ralphine lacks sufficient capacity to store purified water for the minimum required 2-month retention period. Expansion would require raising the existing dam, displacing adjacent recreational areas, and encroaching upon residential neighborhoods and unfavorable topography. Therefore, this supply option was deemed infeasible and did not continue to the screening process.

Stormwater
SW-2: Capture
stormwater
and store in
Lake Ralphine
(or alternate
site)
Lake Ralphine lacks sufficient capacity to store captured stormwater. Expansion would require raising the existing dam, displacing adjacent recreational areas, and encroaching upon residential neighborhoods and unfavorable topography. Likewise, prior City review of planning, water systems, and topography has failed to identify a suitable alternative surface water site. Therefore, this supply option was deemed infeasible and did not continue to the screening process.

SW-3:

Regional
stormwater
SW-3 would have substantial overlap with regional stormwater projects for water supply resiliency, flood control, and groundwater sustainability. As a water contractor with Sonoma Water and as an engaged participant in the GSA, the City will participate in future regional stormwater projects implemented by Sonoma Water and/or the GSA. Due to these factors, this supply option was not advanced to the screening analysis.

City of Santa Rosa ES-6 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

4.2 Screening Analysis Results:

Following pre-screening, the 13 remaining supply options were input into a screening tool that analyzed the conceptual performance of the supply options in two hypothetical scenarios: baseline and maximum production. This process produced technical data regarding each supply option, removing an additional six supply options deemed to be not cost-effective. These options included PR-1, PR-3a, PR-3c, RW-1, DE- 1, and DE-2. Table ES-4 presents the supply options removed during the screening process with a brief rationale for why they were removed.

Table ES-4: Supply Options Removed During the Screening Analysis Category Supply Option Reason for Removal
Purified
Recycled
Water
PR-1: DPR AWPF at
LTP
This supply option was removed because it is not cost-effective based on Santa Rosa’s current and projected water supply needs.
1 PR3a: IPR AWPF at
LTP via Delta Pond
This supply option was removed because it is not cost-effective based on Santa Rosa’s current and projected water supply needs.

PR-3c: IPR AWPF at
LTP via Lake
Sonoma
This supply option was removed because it is not cost-effective based on Santa Rosa’s current and projected water supply needs. Additionally, it does not reduce Santa Rosa’s reliance on Sonoma Water.

Non-potable
Recycled
Water
RW-1: Expand City’s
non-potable
recycled water
system
This supply option was removed because it does not provide the City with potable water and is not cost-effective based on the City’s current and projected water supply needs.

Desalination2
DE-1: Regional
brackish
desalination
This supply option was removed because it is not cost-effective based on the City’s current and projected water supply needs. While future circumstances could improve its performance, it does not reduce the City’s reliance on regional partner involvement (i.e., Marin Municipal Water District) and the Sonoma Water system). Additionally, it currently faces significant permitting and regulatory challenges and uncertainties.

DE-2: Ocean
desalination
This supply option was removed because its high operational and energy costs are not currently cost-effective based on the City’s current and projected water supply needs. Additionally, it currently faces significant permitting and regulatory challenges and uncertainties; However future circumstances could improve its performance.

Notes:
(1) Despite PR-1 being marginally more cost-effective than PR-2, the latter was chosen to advance because it more closely aligns with the City’s goals to be less reliant on the Sonoma Water system and would require less siting constraint than if the AWPF was collocated at LTP. Additionally, it is important to note that less cost-effective supply options were carried forward to provide a broader suite of options and greater diversity of potential supplies.
(2) Appendix I discusses the reason for removing desalination as a supply option and outlines how changes to future circumstances could improve desalination’s viability and trigger the City to reassess its potential as a supply option.

Desalination presents substantial challenges that are not fully captured in the brief summary of the screening process for cost effectiveness and scalability. The WSAP presents an ideal opportunity to document in greater detail what was learned about desalination in the process of conducting the study,

City of Santa Rosa ES-7 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
why DE-1 and DE-2 did not advance, and which changing circumstances in the future could trigger reassessing one or both desalination options to determine if they have become more viable. Therefore, additional discussion and analysis of the desalination options DE-1 and DE-2 have been compiled and included as Appendix I.

Appendix I also provides an assessment of how DE-1 and DE-2 would have scored in the feasibility analysis, more detailed information about the reasons these options did not advance at this time, and the primary triggers (or changing circumstances) that could help the City determine whether and when it might be advantageous to reconsider desalination in the future. In addition, Portfolio 4 includes reminders to reassess whether to trigger a reassessment of desalination at key decision points.

4.3 Detailed Feasibility Analysis Results
Upon completion of the screening analysis, the remaining seven water supply options advanced to the detailed feasibility study. During this process, supply options were graded using eight evaluation criteria and assigned a numerical score of 0 through 2, with 2 being most favorable. A score of 0 indicates that an option is not as responsive to a criterion or does not perform as well as the other options, while a score of 2 indicates that the option performs very well. The production potential of each option was considered individually and not limited to the targets in the goal, to assess a wide range of capacity. Table ES-5 displays the result of the feasibility analysis and the scores of each supply option.

City of Santa Rosa ES-8 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table ES-5: Summary of Supply Option Scores
Criterion
Groundwater Purified Recycled Water Stormwater
E-1:

Efficiency
Programs
GW-1: Add
Extraction
Wells
GW-2:

Convert
Emergency
Wells
GW-3: City
ASR Wells
PR-2:

Satellite DPR
PR-4:

Regional
DPR
SW-1:

Stormwater
Storage in
Aquifer
Cost
effectiveness
[$/AF]
2 [$840/AF]
2 [$540/AF]
2 [$2,600/AF]
0 [$3,900/AF]
0 [$3,200/AF]
0 [$3,500/AF]
1 [$2,800/AF]
Scalability
[Yield in
AFY]
2 [6,734 –
10,080 AFY]
0 [1,744 –
2,462 AFY]
1 [3,634 –
5,130 AFY]
2 [3,019 –
10,065 AFY]
2 [3,019 –
10,065 AFY]
1 [2,600 –
10,080 AFY]
1 [2,145 AFY]
Resiliency 1 1 2 2 2 1 1
Equity 1 1 1 1 1 1 2
Environment
al
performance
1 2 1 0 1 1 2
Legal,
permitting,
& regulatory
1 2 0 0 0 1 2
City control
&
interagency
coordination
2 2 1 2 0 2 2
Multi-
benefit 0 0 1 0 0 2 1
Total
Unweighted 10 10 9 7 6 9 12
Total
Weighted 32 26 29 21 22 19 30

City of Santa Rosa ES-9 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

5. PORTFOLIOS
For the WSAP, Santa Rosa Water elected to use portfolios instead of individual supply options because they offer the dual benefits of diversification and flexibility. This enables Santa Rosa to diversify the risk of each water supply option, periodically assess the performance of each portfolio, and, if necessary, pivot between supply options to adequately address water supply needs. The WSAP includes four portfolios for the City to consider for its water future, to achieve its targets by augmenting existing City groundwater production capacity (approximately 1,300 AFY, with an average of 2 MGD for about 6.5 months per year) with new supplies. Each portfolio is comprised of water supply options that underwent the detailed feasibility analysis described above and in greater detail in Chapter 4. Scoring was influential in the formation of portfolios but was not the only determining factor. Generally speaking, supply options that scored well are included or considered in multiple portfolios; however, some supply options that did not score as highly are included in portfolios to further diversify the range of supply options. Table ES-6 provides an overview of the supply options included in each portfolio.

Table ES-6: Draft Portfolio Compositions
Option Description
Portfolio 1
Most
Economical
Portfolio
2 Fastest
Portfolio
3 Most
Water
Portfolio
4 Most
Adaptive
GW-1 Add Extraction Wells (Up to
12)   
GW-2 Convert Emergency Wells to
Production Wells
   
GW-3 Aquifer Storage & Recovery
Wells
Consider
PR-2 Satellite Direct Potable Reuse  Consider
PR-4 Regional Direct Potable Reuse
at Laguna Treatment Plant Consider
SW-1 Stormwater Storage in Aquifer Consider Consider
E-1 Efficiency Programs    

5.1 Portfolio 1: Most Economical
The first portfolio’s theme focuses on meeting the City’s water supply goals in the most economical way.

Portfolio 1 integrates two options: enhanced efficiency measures (E-1) and conversion of existing emergency groundwater wells to production wells (GW-2). While this portfolio could meet the 7,500 AFY water supply goal based on water capacity, it is estimated to realistically provide about 4,600 AFY.

Because E-1 has no capital costs, this portfolio’s total capital costs are equivalent to the costs for GW-2.

Annual Operations and Management (O&M) costs are equal to the costs needed to run the efficiency

City of Santa Rosa ES-10 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
program (E-1) and the incremental cost to operate and maintain the former emergency wells as new production wells. Table ES-7 presents estimated cost, yield, and scalability information for the portfolio components.

Table ES-7: Portfolio 1 Composition
Portfolio 1 Water
Capacity1 (AFY)
Estimated
Yield (AFY)2
Total Capital
Costs
Annual O&M
Costs
Scalability3
E-1 1,500 – 4,500 2,145 $0 $6,000,000 1
GW-2 1,500 – 3,000 2,462 $12,000,000 $530,000 0
TOTAL 3,000 – 7,500 4,607 $12,000,000 $6,530,000
Notes:
(1) Water capacity refers to the range of water supply that could be achieved if the water supply option were implemented.
(2) Estimated yield is an estimate of the amount of water that would be supplied by the option based on certain operating and/or implementation assumptions. More information on these assumptions is included in Appendix A.
(3) Scalability for each of the portfolio components refers to the degree to which an option could provide a different amount of water now and in the future. Scalability was assigned a numerical score of 0 through 2, with 0 indicating an option is not as responsive to a criterion or does not perform as well as the other options and 2 indicating that the option performs very well.

In this portfolio’s conceptual timeline, both projects would be implemented at the same time. E-1 would begin with developing new programs, increasing the uptake of existing water efficiency programs, and hiring the additional staff needed to implement those programs. GW-2 would begin with technical studies to determine the conversion design for the emergency wells and environmental documentation to cover the work under the California Environmental Quality Act (CEQA). A key aspect of the technical studies would be focused on sustainable yield, to ensure that conversion of the standby wells to production wells would not adversely affect groundwater basin sustainability.

5.2 Portfolio 2: Fastest
The second portfolio focuses on achieving fast implementation of the portfolio’s projects to quickly meet the City’s water supply goal. Portfolio 2 is comprised of enhanced efficiency measures (E -1), converting emergency groundwater wells to production wells (GW-2), and constructing 12 new production wells (GW-1), all of which can begin relatively quickly and proceed simultaneously. When compared to Portfolio 1, this portfolio offers more water supply and would reduce the risk of the City falling short of its water supply goals. The City recognizes that establishing 12 new wells (GW-1) could result in exceeding the cumulative production targets of 7,500 AFY and 9 MGD by 2045. By carefully monitoring aggregated production capacity before considering each new well, Santa Rosa Water would avoid developing more groundwater facilities than needed to achieve its targets. Table ES-8 presents estimated cost, yield, and scalability information for the portfolio components.

City of Santa Rosa ES-11 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table ES-8: Portfolio 2 Composition
Portfolio 2 Water
Capacity1 (AFY)
Estimated
Yield (AFY)2
Total Capital
Costs
Annual O&M
Costs
Scalability3
E-1 1,500 – 4,500 2,145 $0 $6,000,000 1
GW-2 1,500 – 3,000 2,462 $12,000,000 $530,000 0
GW-1 5,040 – 10,080 10,080 $96,500,000 $3,900,000 2
TOTAL 8,040 – 17,580 14,687 $108,500,000 $10,430,000
Notes:
(1) Water capacity refers to the range of water supply that could be achieved if the water supply option were implemented.
(2) Estimated yield is an estimate of the amount of water that would be supplied by the option based on certain operating and/or implementation assumptions. More information on these assumptions is included in Appendix A. By carefully monitoring actual aggregated production capacity before considering new projects, the City would avoid developing more supply facilities than needed to achieve the targets. (3) Scalability for each of the portfolio components refers to the degree to which an option could provide a different amount of water now and in the future. Scalability was assigned a numerical score of 0 through 2, with 0 indicating low scalability compared to other options and 2 indicating a high degree of scalability.

Implementation of Portfolio 2 is very similar to that of Portfolio 1 in that E-1 and GW-2 are implemented right away. Portfolio 2 differs in that GW-1 will also start immediately with siting studies aimed at identifying the best locations for new groundwater wells. However, one potential drawback of this portfolio and its guiding theme is that Santa Rosa Water may risk overbuilding by drilling new production wells before the benefits of GW-2 and E-1 are realized.

5.3 Portfolio 3: Most Water
The third portfolio focuses on maximizing water supply reliability by including a diverse array of supply options. Portfolio 3 incorporates the three supply options included in Portfolio 2 (E -1, GW-2, GW-1), and adds PR-2 (satellite direct potable reuse) and SW-1 (stormwater capture and reuse). Since this portfolio aims to maximize water production from a varied selection of supply options, even the lower bound of Portfolio 3’s capacity far exceeds the City’s cumulative production targets of 7,500 AFY and 9 MGD.

However, the City recognizes that a full buildout would likely surpass its target and, therefore, Portfolio 3 is unlikely to be fully executed. By carefully monitoring aggregated production capacity before considering each new source, Santa Rosa Water would avoid developing more facilities than needed to achieve its water supply targets. Table ES-9 presents estimated cost, yield, and scalability information for the portfolio components.

City of Santa Rosa ES-12 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table ES-9: Portfolio 3 Composition
Portfolio 3 Water Capacity1
(AFY)
Estimated
Yield (AFY)2
Total Capital
Costs
Annual O&M
Costs
Scalability3
E-1 1,500 – 4,500 2,145 $0 $6,000,000 1
GW-2 1,500 – 3,000 2,462 $12,000,000 $530,000 0
GW-1 5,040 – 10,080 10,080 $96,500,000 $3,900,000 2
PR-2 8,000 – 10,065 10,065 $314,000,000 $12,030,000 2
SW-1 5,000 – 10,080 10,080 $222,500,000 $8,390,000 1
TOTAL 21,040 – 37,725 34,832 $645,000,000 $30,850,000
Notes:
(1) Water capacity refers to the range of water supply that could be achieved if the water supply option were implemented.
(2) Estimated yield is an estimate of the amount of water that would be supplied by the option based on certain operating and/or implementation assumptions. More information on these assumptions is included in Appendix A. By carefully monitoring actual aggregated production capacity before considering new projects, the City would avoid developing more supply facilities than needed to achieve the targets. (3) Scalability for each of the portfolio components refers to the degree to which an option could provide a different amount of water now and in the future. Scalability was assigned a numerical score of 0 through 2, with 0 indicating low scalability compared to other options and 2 indicating a high degree of scalability.

The conceptual timeline for Portfolio 3 begins similarly to Portfolio 2, with options E -1, GW-2, and GW-1 implemented right away. To maximize the amount of water available, PR-2 also begins immediately with planning studies, followed by CEQA and other permitting/regulatory processes which are anticipated to be extensive for a direct potable reuse project. Design and construction of the satellite direct potable reuse facility would begin directly following regulatory and environmental approvals.

In contrast to the prior two portfolios, Portfolio 3 introduces a degree of flexibility with the phasing of SW-1, which is why it is noted as “consider” in the portfolio. Planning studies and stormwater modeling for SW-1 would begin immediately, in line with the timing of the other elements of this portfolio.

However, further work on SW-1 would pause until the yield performance of E-1, GW-2, and GW-1 is established. Depending on the need for additional water at that time, Santa Rosa Water may decide to move into design and construction of SW-1. This timeline enables staff to plan for some level of flexibility as this portfolio also works to maximize water availability.

5.4 Portfolio 4: Most Adaptive
The fourth portfolio focuses on adaptability, building upon the flexibility introduced in Portfolio 3, by providing the most flexible path forward of all the portfolios. This portfolio incorporates interactions among the various supply options to afford Santa Rosa Water additional opportunities to reassess and adjust its needs when pursuing new water supply sources in the future. Portfolio 4 includes largely the same elements as Portfolio 3: enhanced efficiency measures (E-1), converting emergency groundwater wells to production wells (GW-2), constructing new production wells (GW-1), satellite direct potable reuse (PR-2), and stormwater capture and reuse (SW-1). There are several defining features of Portfolio 4 that distinguish it from Portfolio 3. One crucial difference is the addition of ASR elements (GW-3) to GW-1 (referred to as GW-1+ in the table below). Furthermore, Portfolio 4 allows for the consideration of LTP as a

City of Santa Rosa ES-13 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
location for a direct potable reuse facility (PR-1) and considers a regional direct potable reuse option (PR- 4) when studying PR-2 (referred to as PR-2+ in the table below). Most critically, Portfolio 4 incorporates “adaptive pathways” for its implementation to maximize flexibility. As such, the City would carefully monitor aggregated production capacity before considering new projects to avoid developing more supply facilities than needed to achieve the targets outlined in the goal.

In alignment with the portfolio’s theme of adaptability, Portfolio 4 offers flexibility via adaptive implementation pathways. One potential implementation pathway (a baseline scenario) would begin as the other WSAP portfolios do, with E-1, GW-2, and GW-1+ beginning right away. Siting studies for GW- 1+ would identify and prioritize locations that could be suitable for both extraction and injection wells.

SW-1 studies would also begin since stormwater could potentially be used for an ASR well within GW -1+.

Once siting studies are complete for GW-1+, this component would pause while E-1 and GW-2 advance.

Work on GW-1+ would continue when Santa Rosa Water had developed a better understanding of the actual yield of E-1 and GW-2. This would allow staff to right-size GW-1+ by only constructing what is required to meet the remaining need for water. Depending on the need for water provided by GW -1+, SW-1 would continue with design and construction to provide any stormwater required for injection as part of GW-1+.

The start time for PR-2+ coincides with the anticipated release of final guidelines on direct potable reuse from the State Water Resources Control Board (State Board), potentially by spring 2024 but likely several years later to adopt amendments or adjustments based on the experiences of early implementers. This portfolio advises that Santa Rosa Water may wish to wait to begin planning studies on PR-2+ until these regulations are a bit more established, in order to provide the most realistic planning and design criteria.

Once planning studies for PR-2+ are complete, work on this component would pause until the actual yield for GW-1+ is established and the need for PR-2+ is better understood. This would allow Santa Rosa Water to scale PR-2+ to meet any remaining water needs. Another benefit of pausing the further planning of PR - 2+ is to allow time for staff to study the best location and to assess and develop any regional partnerships that may support the scalability of this component. There may also be opportunities to use water available under SW-1 to supply PR-2+, if there is additional SW-1 water available after its potential use in GW-1+.

Furthermore, the phasing of PR-2+ enables the City to reassess the viability of alternative supply options at various key decision points, allowing for the reconsideration of supply options like desalination if changing future circumstances would improve potential performance.

Table ES-10 presents cost, yield, and scalability information for Portfolio 4. Because this portfolio is structured around adaptability, the estimated cost and capacity figures would only be reached if the entire portfolio were built. Due to flexibility offered by this portfolio, these figures are likely to be much lower.

City of Santa Rosa ES-14 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table ES-10: Portfolio 4 Composition
Portfolio 4 Water Capacity1
(AFY)
Estimated
Yield (AFY)2
Total Capital
Costs
Annual O&M
Costs
Scalability3
E-1 1,500 – 4,500 2,145 $0 $6,000,000 1
GW-2 1,500 – 3,000 2,462 $12,000,000 $530,000 0
GW-1+4 5,040 – 10,080 10,080 $96,500,000 $3,900,000 2
PR-2+5 8,000 – 10,065 10,065 $314,000,000 $12,030,000 2 SW-1 5,000 – 10,080 10,080 $222,500,000 $8,390,000 1
TOTAL 21,040 – 37,725 34,832 $645,000,000 $30,850,000
Notes:
(1) Water capacity refers to the range of water supply that could be achieved if the water supply option were implemented.
(2) Estimated yield is an estimate of the amount of water that would be supplied by the option based on certain operating and/or implementation assumptions. More information on these assumptions is included in Appendix A. By carefully monitoring actual aggregated production capacity before considering new projects, the City would avoid developing more supply facilities than needed to achieve the targets. (3) Scalability for each of the portfolio components refers to the degree to which an option could provide a different amount of water now and in the future. Scalability was assigned a numerical score of 0 through 2, with 0 indicating low scalability compared to other options and 2 indicating a high degree of scalability. (4) GW-1+ indicates that the component includes aquifer storage and recovery elements. The information presented for GW-1+ is consistent with GW-1, though Santa Rosa Water acknowledges that if ASR wells were incorporated into this supply component, capacity, yield, and costs would very likely change. (5) PR-2+ indicates that the component could incorporate studying and potentially developing a regional approach to direct potable reuse (PR-4). Santa Rosa Water acknowledges that capacity, yield, and costs would very likely change should a regional project move forward. Additionally, PR-2+ allows for reassessment at key decision points if changing circumstances have improved the viability of alternative supply option, such as desalination.

A more detailed version of the baseline conceptual implementation timeline for Portfolio 4 is included in Appendix F.

City of Santa Rosa ES-15 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

6. NEXT STEPS
The WSAP presents a variety of potential pathways that Santa Rosa Water may follow as it plans for its water future. Based on discussions with stakeholders, Portfolio 4 appears to offer the most benefits, primarily because it is most responsive to the City’s initial goals and provides the most flexibility to adapt to changing conditions in the future. If Santa Rosa Water decided to adopt Portfolio 4, staff could begin by following several key steps.
• Identify funding sources to support early project work and establish scoping to better understand costs and determine which work will be completed by Santa Rosa Water staff and which work will be opened for bidding. Also, Santa Rosa Water could begin planning for the initial capital expenditures that will come as GW-1+ and GW-2 advance.
• Begin implementing the early stages of E-1, GW-2, and GW-1+. For E-1, Santa Rosa Water staff can rely on extensive staff experience in efficiency programs to begin internal implementation plans and identify internal and external funding opportunities. Because Santa Rosa Water has already acquired some funding for emergency well conversion, it may be able to begin hydrogeologic studies and confirm the CEQA coverage required for GW-2. Once hydrogeologic studies are completed, they will support the environmental documentation process and enable the State Board and interagency coordination (including Public Trust Review) to begin regulatory approvals. Furthermore, staff could prepare its siting study for GW-1+ by identifying potential sites that could be eligible for extraction only and ASR wells and begin conducting field investigations of promising sites. During this step, results from the modeling and siting study work for SW-1 can be folded into the process so staff can determine if ASR wells with stormwater is a viable path forward.
• Begin discussions with the GSA to coordinate strategies that align GW-2 and GW-1+ with the mandate for groundwater sustainability detailed in the Groundwater Sustainability Plan (GSP). As both a member of the GSA Board and the Board’s Advisory Committee, Santa Rosa is deeply committed to ensuring groundwater basin sustainability. • Begin work on PR-2 by tracking the draft guidelines from the State Board before beginning a treatment study to identify the processes needed to produce and use water through direct potable reuse. Additionally, begin initial planning studies for SW-1 including stormwater modeling, a siting study, and a treatment study.

Regardless of the path forward, staff must consider the following four areas that are subject to dynamic change as Santa Rosa Water continues to plan for its water future: funding, technology, regulations, and regional efforts. Monitoring advancements and opportunities in these areas will help staff remain agile and able to quickly adapt its water supply planning efforts.

1. Implementing any of portfolios outlined in the WSAP would require varying levels of funding and funding strategies. Santa Rosa Water typically funds capital projects through some combination of grants, bonds, connection fees, and water rates. State and federal agencies often award grants or low-interest loans and this funding source will likely be instrumental if Santa Rosa Water considers implementing direct potable reuse. Likewise, Santa Rosa Water may opt to issue bonds to raise capital, as it has previously done for large projects. Finally, Santa Rosa Water could review

City of Santa Rosa ES-16 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
connection fees and water rates to develop a new fee and/or rate schedule to support continued investment in its water infrastructure and operations and maintenance. However, the WSAP only provides a snapshot in time. Factors such as advances in technology, regulatory changes, worsening drought severity and/or frequency, and increases in wholesale water rates all contribute to the cost-effectiveness of water supply options. Thus, Santa Rosa Water should continuously re-analyze the cost-effectiveness of projects and make adjustments that enable the best options to move forward.

2. Technological advances continue to influence the way in which water suppliers select and implement water supply projects. Both direct and indirect advancements in areas including wastewater treatment, energy efficiency, and artificial intelligence may substantially impact the feasibility and cost-effectiveness of water supply options. Staying informed about technological developments will help Santa Rosa Water remain agile and adjust its water supply planning to more effectively manage its water resources and continue to improve resiliency.

3. Regulations at the local, state, and federal levels continue to greatly impact water resources planning. Emerging water quality concerns, such as microplastics and per- and polyfluoroalkyl substances (PFAS), are nascent areas for regulation that will likely impact how Santa Rosa Water implements water supply projects. Staff should continue to monitor regulatory developments that would have the potential to alter the course of water supply components in the WSAP.

4. As a primary water contractor to Sonoma Water and a member of the GSA Board, the GSA’s Advisory Committee, and the Russian River Water Forum, Santa Rosa is actively involved in a number of regional efforts and is committed to continue working with regional partners to enhance regional water sustainability and resiliency. With thoughtful planning, the City has positioned itself to stay informed about and seek opportunities to work with partners on mutually beneficial water supply projects.

City of Santa Rosa 1 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

1. INTRODUCTION

1.1 Background
The City of Santa Rosa’s Water Department (Santa Rosa Water) is responsible for delivering high -quality, reliable water to roughly 54,000 metered connections. Utilizing an extensive network of 600 miles of pipes, Santa Rosa Water supplies drinking water to 176,000 residents and thousands of local businesses and institutions. Santa Rosa Water also manages a comprehensive wastewater system with 600 miles of pipelines leading to the Laguna Treatment Plant (LTP). The LTP not only treats wastewater from Santa Rosa, but also processes wastewater from neighboring areas including Sebastopol, Cotati, Rohnert Park, and South Park Sanitation District. The LTP produces about seven billion gallons of high-quality recycled water annually, used for agricultural, urban irrigation, and delivered to Calpine to generate clean energy through steam production.

The City’s 2020 Urban Water Management Plan (UWMP) includes details about Santa Rosa ’s planned water supplies and projected demands through 2045 during an average water year, a single dry year, and dry five-year periods. As documented in the UWMP, Santa Rosa Water has three existing and planned sources of water: entitlement limit of 29,100 acre-feet per year (AFY) from Sonoma County Water Agency (Sonoma Water), 2,300 AFY of local groundwater supply from City wells, and 140 AFY of recy cled water supply from the City’s Regional Water Reuse System. Sonoma Water is the primary source, accounting for approximately 93 percent of the City’s total supply. This water originates primarily from the Russian River which benefits from natural filtration through the riverbed to meet or exceed water quality standards.

The UWMP concludes that the City’s three supply sources would be sufficient to meet projected water demands through 2045 in average rainfall years and even below average rainfall years. However, in severely dry years, water supplies would not be sufficient to meet projected ordinary water demands of Santa Rosa Water’s customers. If the City were to experience a water shortage of 30 percent or more, water customers would be required to adhere to strict, site-specific water allocations (water rationing) and new development would be required to offset new demand for water to achieve a net zero impact.

Figure 1-1
below shows 2020 water use in Santa Rosa and the water supply sources.

Figure 1-1: Santa Rosa Water Use by End Use and Supply Type (2020)

City of Santa Rosa 2 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Over two-thirds (68 percent) of the water used in Santa Rosa is for residential purposes. About 24 percent is used by businesses and other institutions, with the remaining eight percent of water use categorized as non-revenue water for firefighting and system maintenance.

Santa Rosa Water has a long-standing strong commitment to water supply planning and efficiency. The City gradually began to develop its municipal water supply system in 1896 to serve residents within the corporate city limits. In 1947, the City acquired a privately owned water company that had served portions of Santa Rosa under a franchise agreement for nearly 75 years. At that time, the City ensured that all water service connections throughout its jurisdiction had meters. The City’s water supply sources at that time included Lake Ralphine, natural springs, and wells. Over the next 10 years, the City saw rapid population growth and projections that growth would continue. This spurred Santa Rosa to contract with Sonoma Water and connect to its new water supply system in 1959, to secure a reliable and clean water supply from the Russian River.

The City first implemented water conservation efforts during the severe drought experienced in 1976 to 1978. In 1991, Santa Rosa Water hired its first professional water conservation manager and began to offer ongoing water use efficiency rebates and assistance. Since that time, Santa Rosa Water has fully staffed and funded water use efficiency programs to help the community use water wisely during wet years and dry years. In addition, Santa Rosa Water has a long history of charging water customers based on their water usage, which also encourages careful water consumption. Since the State adopted the Urban Water Management Planning Act in 1983, Santa Rosa has been developing and updating long - term water supply plans with a 25-year planning horizon every five years; the City also adopted its first Water Shortage Contingency Plan in 1992, which is updated with the Urban Water Management Plan every five years. Furthermore, the City has been an early implementer of State water efficient development standards, including adopting the first Water Efficient Landscape Ordinance in 1993 and early “Cal Green” building and plumbing codes in 1995. The City also adopted a Water Waste Ordinance in 1999 to prohibit waste of water due to customer plumbing leaks and runoff from landscape irrigation. The City actively enforces the ordinance and also closely monitors its own water distribution system for leaks and makes repairs quickly to prevent waste.

Over the last 30 years, water use in Santa Rosa has seen a remarkable decline despite significant population growth. Figure 1-2
below shows total water use (sales to customers and nonrevenue water use) in Santa Rosa from 1990 to 2022. Comparing water use in 2020 (orange bar) to drought years like 1990 and peak use in 2004 (blue bars), Santa Rosa has seen a reduction in water use of 14 percent and 20 percent, respectively. During this same period, the population in Santa Rosa increased 57 percent.

City of Santa Rosa 3 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Figure 1-2: Water Use in Santa Rosa (1990 – 2022)

This reduction in water use can be attributed to Santa Rosa Water’s successful expansion of its conservation initiatives, including staffing its water use efficiency team and providing customer assistance, rebates, and incentives to promote water-saving practices. These efforts along with early adoption of State building and plumbing codes have resulted in a decrease in the number of gallons used per person per day (gallons per capita per day, or GPCD) from 177 GPCD in 1990 to 97 GPCD in 2020, marking a significant 45 percent reduction in use per person. The residential sector has contributed to this, with a 45 percent decrease in average daily use from 120 GPCD in 1990 to 65 GPCD in 2020. Santa Rosa ’s community has become more water-efficient, resulting in a significant reduction in water use despite considerable population growth in the last 30 years.

In typical years with average rainfall, Santa Rosa’s current water supply meets the needs of its customers through 2045 and beyond, due to the significant water efficiency improvements and the City’s adoption of water efficient building and plumbing codes, as highlighted above. Future projections indicate that even with a potential 48 percent increase in residents compared to 2005, water demand is estimated to be only 9 percent higher by 2045, reflecting the continued effectiveness of water use efficiency measures and water efficiency building and plumbing codes. While Santa Rosa’s water supply is very reliable during average and slightly below-average rainfall years, its heavy dependence on Sonoma Water and the Russian River system poses risks during prolonged or very severe droughts as well as catastrophic events that could interrupt supply delivery from Sonoma Water.

California’s most recent drought (2020-2022) is the second most severe on record in the Sonoma County region and resulted in critically low water storage in Lake Sonoma. Figure 1-3 shows water supply levels in Lake Sonoma. The green line represents the average monthly water storage over a thirty -year period, while the dotted black line shows the lowest month of any year from 1992 to 2020. Most of the lowest months occurred in the last decade, indicating increased water scarcity. The red dashed line indicates a critical threshold of 100,000 acre-feet. If storage falls below this level, Sonoma Water may be required by

City of Santa Rosa 4 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
the State to reduce water diversions by 30 percent or more. This would necessitate the City implementing its Water Shortage Contingency Plan (WSCP) with mandated reductions in water use, which could include water rationing. In this most recent drought beginning in 2020, Lake Sonoma water supply storage levels remained consistently below the 30-year average (the green line) for nearly three years, below the lowest months (the dotted black line) for nearly two years and drew dangerously close to the critical threshold (the red line) at the end of water years 2021 and 2022, before winter precipitation replenished supply reserves.

While Santa Rosa is well-prepared for normal and slightly below-average rainfall years, the most recent drought highlights the importance of addressing water supply planning and resiliency to ensure sustainable water management for the future.

Figure 1-3: Lake Sonoma Water Supply Storage

1.2 Our Water Future: Purpose of the Water Supply Alternatives Plan The City wishes to diversify and increase its potable urban water supply portfolio to enhance its resiliency to mitigate the impacts of future water supply shortages due to severe and/or prolonged droughts or service interruptions that could occur in catastrophic events. Currently Santa Rosa Water can meet about 6-7 percent of its annual urban demand for potable water using municipal wells and relies on Sonoma Water to provide the remaining 93-94 percent of potable supply for urban customers (non-potable recycled water for urban irrigation within a small section of Santa Rosa’s municipal jurisdiction accounts for less than one percent of demand). As a result of this dependency, if Sonoma Water experiences a supply shortage or an interruption in service, Santa Rosa’s public water system will have a water supply shortage.

City of Santa Rosa 5 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Santa Rosa is particularly concerned about drought impacts. In the past 20 years the Sonoma County region has experienced three multi-year droughts: 2007-2009, 2013-2016, and 2020-2022. In response, Sonoma Water worked with its water contractors to establish was use reduction targets , triggering Santa Rosa to declare water shortage conditions that required its customers to reduce potable water use by 20 percent each time. Santa Rosa’s customers successfully reduced water use during each drought . When water supply conditions returned to normal, the Santa Rosa community did not return to pre -drought rates of use, resulting in a significant decrease in per capita water use of approximately 38 percent (compared to 2006). Regional climate change assessments warn that local droughts will likely become more severe (hotter, drier, longer) and more frequent, and local water use analysis shows demand hardening (permanent decreases in per capita use). Given these realities, Santa Rosa Water wishes to increase water supply resiliency and reliability by increasing the diversity and production capacity of its water supply portfolio.

To determine the best path forward, Santa Rosa Water launched the Our Water Future Project in May of 2022 and undertook development of this Water Supply Alternatives Plan in September of 2022 to identify an adaptive approach to diversifying Santa Rosa’s water supply portfolio and production capacity over time. The project scope of work has included soliciting input from an interdisciplinary team of Water staff, a group of external Stakeholder Group consisting of leaders from wide range of organizations and interests, the community at large, and the Board of Public Utilities.

The primary objectives of this Plan and the work supporting the Plan are to:
• Determine the appropriate amount of new water supply required to minimize the risk of water shortages in Santa Rosa,
• Explore various water supply options that warrant further study, • Establish criteria for assessing the suitability of these supply options for the Santa Rosa community, and
• Outline various portfolios or mixes of the most suitable supply options Santa Rosa Water could consider in its future planning efforts.

The Water Supply Alternatives Plan (WSAP) provides a menu of water supply options and portfolios for Santa Rosa Water to consider when planning future strategic investments and projects for increasing water supply resiliency and reliability. The Plan is not intended to be a prescriptive document, but rather an adaptive guide for Santa Rosa to use as it embarks on water supply and infrastructure planning for Santa Rosa’s water future.

1.2.1 Coordination with Regional Efforts
As described above, the WSAP is designed to outline options that Santa Rosa Water can take to increase its resiliency and mitigate the impacts of water shortages due to droughts or interruptions in service from Sonoma Water. While the WSAP does consider regional options, Santa Rosa Water acknowledges that a number of regional efforts are currently underway or being considered which may contribute to meeting Santa Rosa’s water supply goals. Examples include Sonoma Water’s Regional Water Supply Resiliency Study, the GSA’s future groundwater sustainability projects outlined in its GSP, and multi-agency water- supply resiliency solutions that respond to PG&E’s planned decommissioning of the Potter Valley Project and the associated Eel River diversion into the upper Russian River. These options are not included in the WSAP because they are moving forward under the leadership of Sonoma Water, the Santa Rosa Plain

City of Santa Rosa 6 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Groundwater Sustainability Agency (GSA), and the Russian River Water Forum, all of which already include Santa Rosa’s involvement as a primary water contractor to Sonoma Water, as a member of the GSA Board and the Board’s Advisory Committee, and as a member of the Planning Group for the Russian River Water Forum. The City is committed to continue working with these and other partners to enhance regional sustainability as future opportunities arise.

1.3 Water Supply Alternatives Plan Organization
The Acknowledgements page provides a list of the participants who generously committed their time and energy to contribute to this effort over nearly a year, from October 2022 through September 2023.

Chapter 2 describes the processes used to engage these participants and integrate their input.

From October through December 2022, the project team worked with the Water Team, Stakeholder Group, community, and Board of Public Utilities to gather their input on the water supply resiliency goal, list of potential water supply options to be studied, evaluation criteria for analyzing the feasibility of each supply option, and the study methodology. Chapter 2 also provides additional details about the development of these study parameters and presents the final goal statement, list of supply options, a nd criteria for the study.

With the study parameters finalized, the feasibility study was conducted to assess a wide range of water supply sources, described in Chapter 3, and then develop alternative portfolios (mixes) of the most feasible options for achieving Santa Rosa Water’s long-term urban water supply goal. The study results were discussed in detail with the Water Team, Stakeholder Group, community, and Board of Public Utilities to gather their input and refine the study as needed. The study and findings are discussed in Chapter 4 and the full feasibility study report is attached as Appendix A. The supply portfolio alternatives are described in detail in Chapter 5.

To move forward, Santa Rosa Water will need to determine the best portfolio to be gin pursuing, while tracking and adjusting to changes in funding sources, technology, regulations, as well as regional efforts and opportunities. Chapter 6 discusses next steps that Santa Rosa Water may wish to undertake as it moves forward toward achieving its water supply resiliency and reliability goals.

City of Santa Rosa 7 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

2. APPROACH TO DEVELOPING THE WATER SUPPLY ALTERNATIVES PLAN Santa Rosa’s Our Water Future effort began by establishing water supply goals, an extensive list of water supply options, and evaluation criteria, collectively referred to as the “study parameters.” The se study parameters were established through a collaborative process with four groups of participants: Santa Rosa Water staff (referred to as the Water Team), an external group of community leaders (referred to as the Stakeholder Group), the community at large, and the Board of Public Utilities (BPU). Once the study parameters were established, Santa Rosa Water further developed the supply options to prepare them for analysis. Work then involved the use of pre-screening and screening tools and evaluation criteria designed to slate a short-list of supply options. The following subsections describe the study parameters, analysis methodology, and stakeholder involvement.

2.1 Water Supply Goals
The first task of the WSAP focused on setting goals to understand how much and under what conditions water is needed in the future to mitigate drought and catastrophic Sonoma Water service interruptions.

Discussions during the goal development process with the Water Team, Stakeholder Group, community, and BPU yielded the following insights about what the water supply goal should do:

1. Guide Decision Making: The goal should provide essential guidance to make informed decisions concerning the scale and scope of the resiliency portfolio, thereby supporting effective water management.

2. Improve Water Resiliency: The goal should result in reduced reliance on Sonoma Water supplies, thereby enhancing Santa Rosa’s potable water supply resiliency and supporting a more stable and dependable water system for the Santa Rosa community.

3. Mitigate Shortages: The goal should help mitigate potential shortages in Sonoma Water supply and minimize interruptions in service during dry periods.

4. Meet Peak Day Demand Locally: The goal should help meet a portion of Santa Rosa’s projected peak day demand using local supply.

5. Allow for Flexibility and Adaptability: The goal should be percentage based, thereby making it easier to adjust if future conditions change the amount of supply needed.

Based on this input, the water supply goal for the WSAP effort is to diversify and increase Santa Rosa’s potable water supplies to reduce dependence on Sonoma Water, particularly during Sonoma Water supply shortages or disruption in delivery. New supplies would augment existing City groundwater production capacity (approximately 1,300 AFY, with an average of 2 million gallons per day (MGD) over 7 to 9 months per year) to achieve three targets included in this goal, as outlined in Table 2-1 below.

For the purposes of the WSAP, Santa Rosa Water assumes that potential water supply options would need to provide an aggregated total of 7,500 AFY and 9 MGD of supply by 2045, either individually or collectively in conjunction with Santa Rosa’s existing groundwater well capacity (approximately 1,300 AFY, with an average of 2 MGD over approximately 6.5 months per year). The water supplies would generally be used in response to droughts or disruptive events since Santa Rosa’s existing water supplies (Sonoma Water, groundwater wells, and recycled water) are more than sufficient to meet demand in normal years.

As noted above, these goals allow for flexibility in the future; should projected future demands change, the percentage-based goals can be adjusted to arrive at new volumetric goals.

City of Santa Rosa 8 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table 2-1: Water Supply Goals for the Water Supply Alternatives Plan Mitigating Droughts Mitigating Natural Disasters &
Catastrophic Events Mitigating Peak Day Demand
Meet 30% of City’s water
demand with municipal supplies
to mitigate impacts of Russian
River supply shortages (e.g., due
to prolonged and/or severe
drought).

Based on current City demand
projections, the volume of water
required to meet this is 7,500
AFY by 2045.

Provide 50% of normal
domestic/indoor demand for
potable water with municipal
supplies during Russian River
supply disruption.

Based on current City demand
projections, the volume of water
required to meet this is 9 MGD
by 2045.

Meet 30 percent of peak month
average day demand for potable
water with municipal supplies.

Based on current City demand
projections, the volume of water
required to meet this is 9 MGD
by 2045.

2.2 Water Supply Options
Water supply options that are included in this effort were compiled from a number of sources, including discussions with the Water Team, Stakeholder Group, community, and BPU. The final list of supply options includes a broad diversity of options from the type of water supply to their scale (in AFY and geography).

Table 2-2 lists the water supply options that are part of the WSAP. More information about each of the supply options is presented in Chapter 3.

City of Santa Rosa 9 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table 2-2: Initial List of Water Supply Options
Supply Type Supply Option Name
Groundwater
GW-1: Additional Groundwater Extraction Wells
GW-2: Convert Emergency Wells to Production Wells
GW-3: Aquifer Storage and Recovery (ASR) Wells
GW-4: Regional Groundwater Extraction Wells
GW-5: Regional ASR Wells
Purified Recycled
Water
PR-1: Direct Potable Reuse (DPR) with Advanced Water Purification Facility (AWPF) at Laguna Treatment Plant (LTP)
PR-2: Satellite DPR with AWPF
PR-3a: Indirect Potable Reuse (IPR) with AWPF LTP into Groundwater Basin PR-3b: IPR with AWPF LTP into Lake Ralphine
PR-3c: IPR with AWPF at LTP into Lake Sonoma
PR-4: Regional DPR with AWPF at LTP
Recycled Water RW-1: Expand City’s Urban Non-Potable Recycled Water System Desalination
DE-1: Regional Brackish Desalination
DE-2: Ocean Desalination
Stormwater
SW-1: Stormwater Treatment and Storage in Aquifer
SW-2: Stormwater Storage in Lake Ralphine with Treatment SW-3: Regional Stormwater
Efficiency Programs E-1: Efficiency Programs

2.3 Analysis Methodology
After compiling a final list of supply options with stakeholder input, Santa Rosa Water implemented three processes: pre-screening, screening, and feasibility analysis. Each step is described briefly in the following sections and analysis results are presented in Chapter 4. As shown below, Figure 2-1 illustrates the overall steps in the analysis process.

Figure 2-1: Analysis Methodology Flowchart

City of Santa Rosa 10 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

2.3.1 Pre-Screening
Prior to the screening and detailed feasibility analyses, all supply options were subjected to a high-level pre-screening to identify and remove options deemed infeasible or substantially similar to existing or proposed supply options. The options passing the pre-screening were advanced to the screening analysis.

2.3.2 Screening Analysis
The purpose of the screening analysis was to gather preliminary data on feasible supply options to focus the scope of the subsequent detailed feasibility analysis. All potential water supply options were screened using two key criteria: high-level assessments of cost-effectiveness and scalability.1, 2 A screening tool was developed and used in the analysis to help determine the conceptual performance of each supply option in areas such as water yield and capital cost. A critical component of the screening analysis and a key input in the tool included cost estimates for each supply option. The screening tool analyzed two scenarios: baseline and maximum production. The baseline scenario assumed realistic operation (more in dry years, less in normal supply years) to minimize operational costs. Conversely, the maximum production scenario assumed the goal of maximizing water production via 24/7 operation. More information on the screening tool and the methodology for determining capital cost estimates is included in the feasibility study report, attached as Appendix A.

2.3.3 Detailed Feasibility Analysis
Following the screening analysis, the remaining supply options underwent a detailed feasibility analysis.

This step involved developing evaluation criteria, adding numerical weights to each criterion, and scoring the projects against each criterion. In consultation with stakeholders, eight evaluation criteria were used to score the supply options. Each criterion was assigned a weight that corresponds to a score multiplier so the analysis could reflect community priorities about the relative importance of each criterion .

Once evaluation criteria and weights were established, Santa Rosa Water developed a detailed rubric so water supply options could be scored against the qualitative criteria. The numerical system provides a score of 0 through 2, with 2 being most favorable. A score of 0 indicates that an option is not as responsive to a criterion or does not perform as well as the other options, while a score of 2 indicates that the option performs very well. The evaluation criteria scoring rubric used for the evaluation of the short- listed supplemental supply options is summarized in Table 2-3. More information on the development of the evaluation criteria and the weights is included in Appendix A.

Actual project costs would be expected to fall within +50 percent to -15 percent of the cost estimate. 2 Scalability refers to how much water Santa Rosa Water could produce from the option now and how much water it could possibly produce in the future. An option with low scalability would yield similar amounts of water now and in the future.

City of Santa Rosa 11 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table 2-3: Evaluation Criteria Scoring Rubric
Criterion Evaluation Metric Quantitative Score Qualitative Score: 0 Qualitative Score: 1 Qualitative Score: 2 Weight Score Multiplier
Cost
effectiveness
Quantitative calculation of life-cycle costs, based on the baseline scenario per the project goals (e.g., five-year drought occurring on average every 10 years).
$/AF >$3,000/AF under baseline scenario

Between $2,000/AF and $3,000/AF
under baseline scenario < $2,000/AF under baseline scenario High
+ Screening
Criterion
5 Scalability
Qualitative assessment of ability to provide sufficient supply to satisfy goals, i.e., achieve desired level of service for each scenario; secondarily, ability to scale further to address future uncertainty.

Yield (AFY)
Low flexibility: No ability, or
minimal ability, to scale down
production when supply is not
needed.

Moderate flexibility: Some ability to
scale production up or down
depending on need for supply but
would require significant effort or
construction of new facility phases.

High flexibility: Production can be
easily scaled up or down depending
on need without significant
investment.

High
+ Screening
Criterion
5 Resiliency
Qualitative assessment of performance in the face of future uncertainty; for example, future regulations, energy costs, hydrology.

The best options will suffer only modest degradation of performance if future conditions are worse than anticipated while inferior options will show marked degradation if planning assumptions aren’t met.

Change in costs due
to energy prices and
hydrology scenarios
can be accounted for
quantitatively. These
would feed into the
qualitative scores.

Substantial change in cost-
effectiveness under changing
energy and hydrology conditions.

Moderate change in cost-effectiveness
under changing energy and hydrology
conditions.

Little or no change in cost-
effectiveness under changing
energy and hydrology conditions.

High 3
Equity Qualitative assessment of any disproportionate impacts on vulnerable communities. N/A
Would have the potential for a
disproportionate impact (such as
providing different water supply
sources to certain parts of City).

Would have no impact on vulnerable
communities.

Would have a benefit to vulnerable
communities. High 3
Environmental
performance
Qualitative assessment of potential environmental impacts not already included in permitting/regulatory compliance (e.g., level of GHG emissions).

N/A
Unknown or high potential for
environmental impacts (e.g., large
project footprint, high energy use,
or location in undeveloped area).

Moderate potential for environmental
impacts (e.g., medium or unknown
project footprint, moderate energy use,
unknown project location).

Limited potential for environmental
impacts (e.g., small project footprint,
low energy use, location in existing
developed area).

High 3
Legal,
permitting, and
regulatory
Qualitative assessment of complexity/effort to address legal issues (e.g., water rights), obtain necessary permits, and comply with regulations
N/A
High complexity/effort: Requires
major permitting/ regulatory effort,
with little or no established
precedent to follow.

Moderate complexity/effort: May have
major permitting/ regulatory effort
permits, etc., but there is an
established process to follow.

Low complexity/effort: Permitting/
regulatory steps are known, and
projects of this type are routinely
implemented.

Med 1
City control and
interagency
coordination
Qualitative assessment of level of City control and coordination with potential partner agencies, if any (e.g., agreements needed for regional projects).

N/A
Coordination required with partner
agencies that City does not already
work with.

Coordination required with partner
agencies that City already works with.

No need for coordination with other
parties. Med 1
Multi-benefit Qualitative assessment of benefits provided in addition to water supply. N/A No other benefits provided. One additional benefit would be provided by the project.

Two or more additional benefits
would be provided by the project. Med 1

City of Santa Rosa 12 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

2.4 Collaboration and Stakeholder Involvement
Table 2-4 summarizes the series of meetings held with four distinct groups to gather input on the study parameters. The first group, referred to as the Water Team, was composed of Santa Rosa Water staff from five Division (Engineering Services, Environmental Services, Local Operations, Regional Operations, and Water Resources) covering a range of disciplines and subject matter expertise (e.g., water resources planning, asset management and planning, wastewater treatment, water recycling, stormwater and environmental compliance, water use efficiency, and water and sewer operations). The second group, referred to as the Stakeholder Group, included leaders of local interest organizations (e.g., resource agencies, business and economic interests, environmental and climate action organizations, community service and social justice nonprofits, and local resources agencies). The third group is referred to as “the community.” Interactive community meetings, open to all and held virtually, were advertised via social media, email, bill inserts, and postings on the City website. Lastly, the study parameters were reviewed by the BPU, which provides oversight of and direction for the management and operation of the Santa Rosa Water’s water and wastewater facilities. The Acknowledgements page provides a list of the participants who generously committed their time and energy to contribute to this effort over nearly a year, from October 2022 through September 2023. Appendix B includes links to all of the recorded public meetings.

Feedback from the Water Team, Stakeholder Group, community, and BPU was incorporated into the study parameters, resulting in the final water supply goal, water supply options, and evaluation criteria and methodology.

Table 2-4: Stakeholder and Community Outreach Meeting Summary Meeting Date Topics
Water Team Meeting #1 October 17, 2022 Project overview; introduction of study parameters (water supply goals, water supply options, evaluation criteria, and methodology); input on study parameters.

Community Meeting #1 October 26, 2022 Overview of Santa Rosa water supplies; project background and overview; introduction of water supply goals, supply options, and evaluation criteria; polling questions, input on study parameters, and question and answer time.

Stakeholder Group
Meeting #1
November 16, 2022 Overview of Santa Rosa water supplies; project background and overview; high-level group discussion of study parameters, and input on study parameters.

Stakeholder Group
Meeting #2
December 14, 2022 Project update; group discussion of proposed study parameters, and input on the refined study parameters.

Water Team Meeting #2 December 15, 2022 Proposed study parameters; input on final refinements of study parameters, and input on the refined study parameters.

Board of Public Utilities
Meeting #1
January 19, 2023 BPU direction on proposed study parameters.

Community Meeting #2 January 25, 2023 Project update; review of proposed study parameters; question and answer time.

City of Santa Rosa 13 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Meeting Date Topics
Water Team Meeting #3 May 17, 2023 Project update on options development and refinement, screening analysis; input on draft study results and portfolio approach.

Stakeholder Group
Meeting #3
May 24, 2023 Project update on options development and screening analysis; input on draft study results and portfolio approach.

Community Meeting #3 June 26, 2023 Project update; review of water supply option analysis and introduction to portfolios; question and answer time.

Water Team Meeting #4 July 6, 2023 Project update on portfolio development; input on draft portfolios and implementation pathways.

Stakeholder Group
Meeting #4
July 18, 2023 Project update on portfolio development; input on draft portfolios.

Water Team Meeting #5 August 14, 2023 Review of Draft Water Supply Alternatives Plan.

Board of Public Utilities
Meeting #2
August 17, 2023 Project update on options development and screening analysis; BPU direction on portfolios.

Community Meeting #4 August 28, 2023 Project update; review of Draft Water Supply Alternatives Plan; question and answer time.

City Council Meeting #1 September 26, 2023 Project update on options development and screening analysis; Council direction on portfolios.

Board of Public Utilities
Meeting #3
October 5, 2023 Draft Water Supply Alternatives Plan presented to BPU.

Board of Public Utilities
Meeting #4
October 19, 2023 Final Water Supply Alternatives Plan presented to BPU.

City Council Meeting #2 October 24, 2023 Final Water Supply Alternatives Plan presented to City Council.

City of Santa Rosa 14 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

3. WATER SUPPLY OPTIONS
To prepare for the feasibility analysis, Santa Rosa Water compiled an initial list of water supply options which was refined with input from the Water Team, Stakeholder Group, community, and BPU. This section summarizes each of the evaluated water supply options, listed in Table 3-1. More detailed information about each option is included in Appendix A.

Table 3-1: Summary of Water Supply Options
Supply Type Supply Option Name
Groundwater
GW-1: Additional Groundwater Extraction Wells
GW-2: Convert Emergency Wells to Production Wells
GW-3: Aquifer Storage and Recovery (ASR) Wells
GW-4: Regional Groundwater Extraction Wells
GW-5: Regional ASR Wells
Purified Recycled Water
PR-1: DPR AWPF at LTP
PR-2: Satellite DPR AWPF
PR-3a: IPR AWPF at LTP into Groundwater Basin
PR-3b: IPR AWPF at LTP into Lake Ralphine
PR-3c: IPR AWPF at LTP into Lake Sonoma
PR-4: Regional DPR AWPF at LTP
Recycled Water RW-1: Expand City’s Urban Non-Potable Recycled Water System Desalination
DE-1: Regional Brackish Desalination
DE-2: Ocean Desalination
Stormwater
SW-1: Stormwater Storage in Aquifer
SW-2: Stormwater Storage in Lake Ralphine
SW-3: Regional Stormwater
Efficiency Programs E-1: Efficiency Programs

3.1.1 Groundwater
The feasibility analysis considered five groundwater supply options, summarized below. More detailed information on each option is included in Appendix A. All groundwater supply options will be closely coordinated with the GSA to support groundwater basin sustainability as outlined in the GSP.

GW-1 Additional Groundwater Extraction Wells
This supply option would construct up to 12 additional production wells, wellhead disinfection, and iron and manganese treatment (if necessary) to connect to Santa Rosa’s existing potable water distribution system. For the sake of estimating costs, the study assumes a general location for the extraction wells and associated infrastructure (within the City’s Southeast Greenway Area, north of Hoen Avenue).

Approximately 3,000 linear feet (LF) of 20-inch pipe and a 240 horsepower (hp) pump station would be required to convey the extracted groundwater to the Sonoma Water aqueduct for distribution .

City of Santa Rosa 15 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
GW-2: Convert Existing Emergency Wells into Production Wells This supply option would rehabilitate Santa Rosa’s three existing emergency wells into production wells:
the Leete Well, Carley Well, and Peter Springs Well. The Leete Well is currently out of service due to concerns over a possible casing separation and rehabilitation is currently in design. The Carley and Peter Springs wells have the capacity to provide Santa Rosa with approximately 1 MGD of groundwater capacity on a stand-by-emergency basis.

GW-3: Local Aquifer and Storage Recovery (ASR) Wells
This supply option involves constructing up to six aquifer storage and recovery (ASR) wells which inject water directly into the groundwater aquifer during wet periods for later recovery and use during dry periods and/or during peak demands when additional supplies are needed. Due to the underground storage nature of ASR projects, this supply is more resilient than other alternative storage methods such as surface recharge or storage, which experience water losses due to evaporation. A phased approach can be followed to develop a pilot ASR project to understand local conditions and ensure there are no “fatal flaws” before a full-scale ASR implementation. The number of wells to meet the demand would vary depending on well capacities; for the WSAP, a 500 gallons per minute (gpm) capacity and 500 feet well depth was assumed.

GW-4: Regional Groundwater Extraction Wells
This supply option involves constructing new production wells outside City limits (in neighboring jurisdictions) where the geology may allow for greater well yields than within the City’s jurisdiction. This option assumes that the potential partner is a Sonoma Water contractor who receives sufficient Sonoma Water contract supplies to make them open to a partial trade with the City. Provided this, a paper exchange could be completed where Santa Rosa takes a portion of the partner’s Sonoma Water allocation, and the pumped groundwater is used directly by the partner. The paper exchange option would not reduce regional reliance on the Sonoma Water system overall. Based on historical Sonoma Water deliveries, potential candidates could be Petaluma, North Marin Water District, Rohnert Park, and possibly City of Sonoma or Valley of the Moon Water District. This option also assumes that Santa Rosa would find a partner for whom well yields of 1,000 gpm or more could be achieved, in order to provide a benefit over existing pumping rates of City wells.

GW-5: Regional Aquifer Storage and Recovery
This supply option proposes the development of a regional ASR project in collaboration with one or more agencies in the region to use Sonoma Water and ASR water supplies conjunctively. As a regional effort, ASR wells could be installed in the most feasible and promising aquifers in the region. Logistically, Santa Rosa Water could either connect directly to the ASR wells or engage in a paper exchange to utilize participating agencies’ surface water supplies from Sonoma Water while partnering agencies pump th e same amount from the ASR wells. Implementation would require identifying feasible ASR well locations, connections to existing distribution systems, regional coordination and agreements, and the possible need for additional water rights.

City of Santa Rosa 16 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

3.1.2 Purified Recycled Water
The WSAP includes six purified recycled water supply options, summarized below. More detailed information on each option is included in Appendix A.

PR-1: DPR AWPF at LTP
This supply option would purify the tertiary effluent at a proposed AWPF co-located at LTP for direct distribution to Santa Rosa’s potable water system. Operationally, the City would convey its tertiary effluent via a proposed 24-inch pipeline to a newly constructed AWPF at LTP sized to meet the projected 9 MGD peak monthly supply needs. The AWPF would be capable of meeting anticipated DPR regulations and would be equipped with a 1.8 million gallon equalization basin, conventional full advanced treatment (FAT) plus ozone/biological activated filtration (BAF), a microfiltration (MF) station, a reverse osmosis (RO) system, ultraviolet (UV) /advanced oxidation process (AOP), an RO brine disposal system, and ancillary facilities. The AWPF waste streams would return to LTP headworks while purified water would be conveyed to a newly constructed 20-inch product water pipeline and pump station for distribution to Santa Rosa’s potable water system, potentially using existing Sonoma Water infrastructure.

PR-2: Satellite DPR AWPF
This supply option would purify tertiary effluent at a proposed satellite AWPF located at Stone Farm, City owned agricultural leased land, for direct distribution to the Santa Rosa’s potable water system.

Operationally, the City would convey its tertiary effluent via a proposed 24-inch pipeline to a newly constructed satellite AWPF sized to meet the projected 9 MGD peak monthly supply need. The AWPF would be capable of meeting anticipated DPR regulations and would be equipped with a 1.8- million- gallon equalization basin, conventional FAT plus ozone/BAF, an MF station, an RO system, UV/AOP, an RO brine disposal system, and ancillary facilities. The AWPF waste streams would return to the nearest sewer via a proposed 10-inch pipeline while purified water would be conveyed to a newly constructed 20-inch product water pipeline and pump station for distribution to the Santa Rosa’s potable water system , potentially using existing Sonoma Water infrastructure.

PR-3a: IPR AWPF at LTP into Groundwater Basin
This supply option would purify the City’s tertiary effluent at a proposed AWPF co -located at LTP for indirect distribution to Santa Rosa’s potable water system after groundwater augmentation at Delta Pond.

Operationally, the City would convey its tertiary effluent via a proposed 24-inch pipeline to a newly constructed AWPF at LTP sized to meet the projected 9 MGD peak monthly supply needs. The AWPF would be capable of meeting anticipated GWA IPR regulations and would be equipped with a 1.8 million gallon equalization basin, conventional FAT, a MF station, an RO system, UV/AOP, an RO brine disposal system, and ancillary facilities. The AWPF waste streams would return to LTP headworks while purified water would be conveyed via a proposed 22-inch pipeline to Delta Pond where it will be injected into the aquifer via ASR wells for a minimum retention time of 2-months and later extraction for potable use.

PR-3b: IPR AWPF at LTP via Lake Ralphine
This supply option would purify the City’s tertiary effluent at a proposed AWPF co -located at LTP for indirect distribution to Santa Rosa’s potable water system after surface water augmentation (SWA) via Lake Ralphine. Operationally, the City would convey its tertiary effluent via a proposed 24 -inch pipeline to

City of Santa Rosa 17 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
a newly constructed AWPF at LTP sized to meet the projected 9 MGD peak monthly supply needs. The AWPF would be capable of meeting anticipated SWA IPR regulations and would be equipped with a 1.8 million gallon equalization basin, conventional FAT, an MF station, an RO system, UV/AOP, an RO brine disposal system, and ancillary facilities. The AWPF waste streams would return to LTP headworks while purified water would be conveyed via a proposed pipeline to Lake Ralphine where it would remain for a minimum retention time of 2-months.

PR-3c: IPR AWPF at LTP via Lake Sonoma
This supply option would purify the City’s tertiary effluent at a proposed AWPF co -located at LTP for indirect distribution to Santa Rosa’s potable water system after SWA via Lake Sonoma. Operationally, the City would convey its tertiary effluent via a proposed 24-inch pipeline to a newly constructed AWPF at LTP sized to meet the projected 9 MGD peak monthly supply needs. The AWPF would be capable of meeting anticipated SWA IPR regulations and would be equipped with a 1.8 million gallon equalization basin, conventional FAT, an MF station, an RO system, UV/AOP, an RO brine disposal system, and ancillary facilities. The AWPF waste streams would return to LTP headworks while purified water would be conveyed to Lake Sonoma via a proposed 22-inch pipeline within the existing Geysers pipeline corridor/easement. Once at Lake Sonoma, the purified water would become part of Sonoma Water’s system.

PR-4: Regional DPR AWPF at LTP
This supply option would purify the City’s tertiary effluent at a proposed AWPF co -located at LTP for direct distribution to regional partners within the Sonoma Water system. Operationally, the City would convey its tertiary effluent via a proposed 24-inch pipeline to a newly constructed AWPF at LTP sized to meet the projected 9 MGD peak monthly supply needs. The AWPF would be capable of meeting anticipated DPR regulations and would be equipped with a 1.8 million gallon equalization basin, conventional FAT plus ozone/BAF, an MF station, an RO system, UV/AOP, an RO brine disposal system, and ancillary facilities. The AWPF waste streams would return to LTP headworks while purified water would be conveyed via Sonoma Water’s 48-inch Cotati Pipeline for delivery to another regional partner in a paper exchange for the partnering agency’s Sonoma Water allocation.

3.1.3 Recycled Water
The WSAP includes one recycled water supply option, summarized below. More detailed information on this option is included in Appendix A.

RW-1: Expand City’s Urban Non-Potable Recycled Water System This supply option would increase the amount of Santa Rosa urban water reuse generated via recycled water from Santa Rosa, Cotati, and Rohnert Park. The Santa Rosa Urban Reuse Project Feasibility Study identified 4 phases of expansion: 1) Phase 1 West, including pipelines located in northwest Santa Rosa extending from either the west transmission main or the West College Facility; 2) Phase 1 South, including pipelines generally located in southeast Santa Rosa extending from the south transmission main; 3) Phase 2 South, including pipelines extending from Phase 1 South system into southwest Santa Rosa to connect south and west systems; 4) Phase 2 West, including pipelines extending from Phase 1 West to interconnect with the south system. However, RW-1 would not provide a new source of potable drinking water required for severe water shortages to emergencies.

City of Santa Rosa 18 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

3.1.4 Desalination
The WSAP includes two water desalination supply options, summarized below. More detailed information on each option is included in Appendix A.

DE-1: Regional Brackish Water Desalination
This supply option would see Santa Rosa Water partner with Marin Water in the construction of a brackish water desalination facility at Marin Water’s Pelican Way Site to augment both Marin Water’s local supply and the City’s Sonoma Water supply via water transfers. The proposed desalination facility would have an initial capacity of 5 to 10 MGD that could eventually be expandable to 15 MGD. Operationally, the facility would perform screened intake in the North San Francisco Bay and an onshore pump station would convey raw water to the treatment facility via an HDPE pipeline on or under the bay floor. Following treatment, desalinated water would be conveyed to Marin Water’s distribution system. Under this scheme, Marin Water and Santa Rosa Water would enter into a paper exchange that would see Santa Rosa receive 9 MGD of Marin Water’s Sonoma Water allocation and the desalinated water would be used directly by Marin Water.

DE-2: Ocean Desalination
This supply option would construct a seawater desalination facility sized to produce 9 MGD required to meet Santa Rosa’s projected 9 MGD peak month demands. For costing purposes, a general location for ocean desalination was estimated, however, a full sitting study would be required to determine the most feasible and optimal location for the facility. The screened intake would be offshore with an onshore pump station near the desalination site. Following treatment, desalinated water would be conveyed to Santa Rosa via a newly constructed 24-inch pipeline.

3.1.5 Stormwater
The WSAP includes three stormwater supply options, summarized below. More detailed information on each option is included in Appendix A.

SW-1: Stormwater Storage in Aquifer
This supply option proposes the construction of a diversion structure within Santa Rosa Creek to divert excess winter stormwater flows to new spreading basins for storage within the Santa Rosa aquifer. The diversion location would be within Santa Rosa Creek near existing USGS stream gage 11466320 due to its proximity to Delta Pond for potential storage prior to aquifer recharge via spreading basins and ASR wells.

A preliminary stream gage determined the allowable diversion volume from Santa Rosa Creek during the months of December through March would be all flows above the 90 th percentile of stormwater volume
within the creek unless the diversion amount is 20 percent of the day’s flow. This supply option assumes maximum annual usage of 7,500 AFY to allow for sufficient aquifer recharge. Captured stormwater would be treated at a 9 MGD conventional treatment plant before injection via ASR wells.

City of Santa Rosa 19 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
SW-2: Stormwater Storage in Lake Ralphine or Alternate Site This supply option would capture excess winter stormwater flows for surface storage. Lake Ralphine was suggested as a potential storage option; however, it currently holds only 500 AF. Therefore, it would require substantial augmentation including raising the existing dam and displacing adjacent recreational areas. Furthermore, surrounding topography and residential neighborhoods make expanding Lake Ralphine infeasible. A review of City planning work did not yield alterative surface storage sites.

SW-3: Regional Stormwater
This supply option proposes developing a regional stormwater project in collaboration with one or more agencies in the region. Several regional projects are underway and could be bolstered with City partnership. Potential regional partners include Marin Municipal Water District, North Marin Water District, the City of Petaluma, Sonoma Water, and the San Francisco Estuary Institute.

3.1.6 Efficiency Programs
The WSAP includes one efficiency program that aims to decrease water demand rather than increase water supply. More detailed information on this option is included in Appendix A.

E-1: Efficiency Programs
While water use efficiency measures do not provide a new source of drinking water supply to mitigate the impacts of drought and emergencies, efficiency programs can reduce water demand over time. This option proposes a series of citywide efficiency measures designed to reduce customer water demands and supplement existing efficiency programs. These programs include: 1) enhanced rebates for commercial, industrial, and institutional (CII) turf removals, 2) enhanced rebates for single-family residential (SFR) turf removals, and 3) a new City-funded toilet direct install program that includes installation of high efficiency faucet aerators and showerheads. If full participation is achieved, the CII turf enhanced rebate program could remove up to 400,000 square feet of turf per year for a potential total of up to 16.3 million square feet of turf removed over the project lifespan of 41 years. Additionally, the SFR turf enhanced rebate program could remove up to 1 million square feet per year for a potential total of up to 42.7 million square feet of turf removed over the project lifespan of 43 years. Furthermore, Santa Rosa Water estimates that it could replace up to 45,600 1.6 gallons per flush (gpf) toilets in City residences with more efficient 0.8 gpf toilets over 15 years. Moreover, this program could directly install up to 3,000 sets of high efficiency water fixtures per year for 15 years. However, full voluntary participation is unlikely and therefore more conservative estimates were calculated.

City of Santa Rosa 20 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

4. ANALYSIS OF WATER SUPPLY OPTIONS

4.1 Pre-Screening Outcome
Before beginning in-depth analysis, an initial pre-screening process was performed to identify and remove supply options deemed infeasible or substantially similar to other options. Five supply options displayed in Table 4-1 were identified and not subjected to further study.

Table 4-1: Supply Options Removed During Pre-Screening
Category Supply
Option Reason for Removal
Groundwater
GW-4:

GW-5:

Purified
Recycled
Water
PR-3b:

Likewise, prior City review of planning, water systems, and topography has failed to identify a suitable alternative surface water site. Therefore, this supply option was deemed infeasible and did not continue to the screening process.

SW-3:

City of Santa Rosa 21 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

4.2 Screening Analysis Result
Following initial pre-screening, 13 supply options were input into a screening tool that analyzed the conceptual performance of the supply options in two hypothetical scenarios: baseline and maximum production. The list of supply options submitted for screening is included in Table 4-2 and includes both City and regional projects aiming to increase supply as well as efficiency programs designed to reduce demand over time.

Table 4-2: Screened List of Water Supply Options
Supply Type Supply Option Name
Groundwater
GW-1: Additional Groundwater Extraction Wells
GW-2: Convert Emergency Wells to Production Wells
GW-3: Aquifer Storage and Recovery (ASR) Wells
Purified Recycled
Water
PR-1: DPR AWPF at LTP
PR-2: Satellite DPR AWPF
PR-3a: IPR AWPF at LTP into Groundwater Basin
PR-3c: IPR AWPF at LTP into Lake Sonoma
PR-4: Regional DPR AWPF at LTP
Recycled Water RW-1: Expand City’s Urban Non-Potable Recycled Water System Desalination
DE-1: Regional Brackish Desalination
DE-2: Ocean Desalination
Stormwater SW-1: Stormwater Storage in Aquifer
Efficiency Programs E-1: Efficiency Programs
The screening process produced technical data regarding each supply option, removing an additional six supply options. These options included PR-1, PR-3a, PR-3c, RW-1, DE-1, and DE-2. Table 4-3 presents the supply options removed during the screening process with a brief rationale for why they were removed.

City of Santa Rosa 22 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table 4-3: Supply Options Removed During the Screening Analysis Category Supply Option Reason for Removal
Purified
Recycled
Water
PR-1: DPR AWPF at
LTP
This supply option was removed because it is not cost-effective based on Santa Rosa’s current and projected water supply needs.
1 PR3a: IPR AWPF at
LTP via Delta Pond
This supply option was removed because it is not cost-effective based on Santa Rosa’s current and projected water supply needs.

PR-3c: IPR AWPF at
LTP via Lake Sonoma
This supply option was removed because it is not cost-effective based on Santa Rosa’s current and projected water supply needs. Additionally, it does not reduce Santa Rosa’s reliance on Sonoma Water.

Non-potable
Recycled
Water
RW-1: Expand City’s
non-potable recycled
water system
This supply option was removed because it does not provide the City with potable water and is not cost-effective based on the City’s current and projected water supply needs.

Desalination2
DE-1: Regional
brackish desalination
This supply option was removed because it is not cost-effective based on the City’s current and projected water supply needs. While future circumstances could improve its performance, it does not reduce the City’s reliance on regional partner involvement (i.e., Marin Municipal Water District) and the Sonoma Water system). Additionally, it currently faces significant permitting and regulatory challenges and uncertainties.

DE-2: Ocean
desalination
This supply option was removed because its high operational and energy costs are not currently cost-effective based on the City’s current and projected water supply needs. Additionally, it currently faces significant permitting and regulatory challenges and uncertainties. However, future circumstances could improve its performance.

Notes:
(1) Despite PR-1 being marginally more cost-effective than PR-2, the latter was chosen to advance because it more closely aligns with the City’s goals to be less reliant on the Sonoma Water system and would require less siting constraint than if the AWPF was collocated at LTP. (2) Appendix I discusses the reason for removing desalination as a supply option and outlines how changes to future circumstances could improve desalination’s viability and trigger the City to reassess its potential as a supply option.

Desalination presents substantial challenges that are not fully captured in the brief summary of the screening process. The WSAP presents an ideal opportunity to document in greater detail what was learned about desalination during the process of conducting the study, why DE-1 and DE-2 did not advance, and which changing circumstances in the future could trigger reassessing the viability of one or both desalination supply options at key decision points. Therefore, additional discussion and analysis of the desalination options DE-1 and DE-2 have been compiled and included as Appendix I.

Appendix I provides an assessment of how DE-1 and DE-2 would have scored in the feasibility analysis, more detailed information about the reasons these options did not advance at this time, and the primary triggers (or changing circumstances) that could help the City determine under what future circumstances it might be advantageous to reconsider desalination. In addition, Portfolio 4 includes reminders to periodically reassess the viability of desalination at key decision points.

Table 4-4 summarizes the results of the screening analysis for all 13 supply options assessed. The table depicts technical information about each supply option considered during screening, whethe r the option

City of Santa Rosa 23 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
advanced to the feasibility study, and reasoning as to why certain options were advanced or removed. A total of seven water supply options were selected to move forward to the detailed feasibility analysis.

City of Santa Rosa 24 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table 4-4: Screening Analysis Results Summary
Category
Supply
Option Technical Information
Moving
Forward?
Reasoning for Screening Out or
Advancing
Groundwater
GW-1: Local
groundwater
extraction
wells
Yield 10,080 AFY
Yes
This supply option proceeded to the feasibility
analysis because it offers a proven and
effective method of water production that
Santa Rosa Water staff is familiar with and
equipped to manage.

Total Capital Cost $96,400,000
Annualized Capital Cost $3,400,000
Annual O&M $3,165,000
Unit Cost of Water $700/AF
GW-2:

Convert
emergency
wells to
production
wells
Yield 2,462 AFY
Yes
This supply option moved forward because it is
the most cost-effective, fastest to implement,
and Santa Rosa Water staff is already familiar
with the wells that would be converted.

Total Capital Cost $11,590,000
Annualized Capital Cost $409,000
Annual O&M $705,000
Cost of Water $452/AF
GW-3: Local
ASR wells
Yield 5,130 AFY
Yes
This supply option advanced because it
provides Santa Rosa with a reliable water
supply and also promotes the health and
sustainability of the Santa Rosa Plain Subbasin
by avoiding overdraft.

Total Capital Cost $81,050,000
Annualized Capital Cost $2,860,000
Annual O&M $9,420,000
Cost of Water $2,400/AF

City of Santa Rosa 25 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Category
Supply
Option Technical Information
Moving
Forward?
Reasoning for Screening Out or
Advancing
Purified
Recycled
Water
PR-1: DPR
AWPF at LTP
Yield 10,065 AFY
No
This supply option was removed because it is
not cost-effective based on Santa Rosa’s
current and projected water supply needs.

Total Capital Cost $289,400,000
Annualized Capital Cost $10,200,000
Annual O&M $3,670,000
Cost of Water $2,050/AF
PR-2: Satellite

DPR AWPF
Yield 10,065 AFY Yes

This supply option was advanced because
purified recycled water offers greater diversity
of potential supplies and enhances Santa
Rosa’s water resilience.

Total Capital Cost $314,060,000
Annualized Capital Cost $11,070,000
Annual O&M $10,440,000
Cost of Water $2,150/AF
PR3a: IPR
AWPF at LTP
via Delta
Pond

Yield 10,065 AFY No This supply option was removed because it is not cost-effective based on Santa Rosa’s
current and projected water supply needs.

Total Capital Cost $419,330,000
Annualized Capital Cost $14,785,000
Annual O&M $12,700,000
Cost of Water $2,730/AF
PR-3c: IPR
AWPF at LTP
via Lake
Sonoma

Yield 10,065 AFY No This supply option was removed because it is not cost-effective based on Santa Rosa’s
current and projected water supply needs.

Additionally, it does not reduce Santa Rosa’s
reliance on Sonoma Water.

Total Capital Cost $562,130,000
Annualized Capital Cost $19,800,000
Annual O&M $6,320,000
Cost of Water $3,350/AF

City of Santa Rosa 26 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Category
Supply
Option Technical Information
Moving
Forward?
Reasoning for Screening Out or
Advancing
PR-4:

Regional DPR
AWPF at LTP
Yield 10,065 AFY Yes This supply option was advanced because it would incorporate regional partners and could
be appropriately scaled to adapt to changing
technology, water demands, and partnerships.

Total Capital Cost $246,960,000
Annualized Capital Cost $8,700,000
Annual O&M $9,620,000
Cost of Water $1,850/AF
Non-potable
Recycled
Water
RW-1: Expand
City’s existing
urban non-
potable
recycled
water system
Yield 3,000 AFY No
This supply option was removed because it
does not provide Santa Rosa with potable
water and is not cost-effective based on Santa
Rosa’s current and projected water supply
needs.

Total Capital Cost $214,000,000
Annualized Capital Cost $4,390,000
Annual O&M $1,300,000
Cost of Water $8,800/AF
Desalination
DE-1:

Regional
brackish
desalination
Yield 10,080 AFY No This supply option was removed because it is not cost-effective based on Santa Rosa’s
current and projected water supply needs.

Additionally, it does not reduce Santa Rosa’s
reliance on Sonoma Water.

Total Capital Cost $180,770,000
Annualized Capital Cost $6,370,000
Annual O&M $2,000,000
Cost of Water $1,200/AF
DE-2: Ocean
desalination
Yield 10,080 AFY No This supply option was removed because it is not cost-effective based on Santa Rosa’s
current and projected water supply needs.

Total Capital Cost $378,070,000
Annualized Capital Cost $13,330,000
Annual O&M $5,520,000
Cost of Water $2,700/AF

City of Santa Rosa 27 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Category
Supply
Option Technical Information
Moving
Forward?
Reasoning for Screening Out or
Advancing
Stormwater
SW-1:

Capture
stormwater
and store in
aquifer for
later potable
use
Yield 10,080 AFY Yes

This supply option advanced to further analysis
because it would provide Santa Rosa with a
sustainable water supply via stormwater that
would otherwise be discharged into non-
potable bodies of water.

Total Capital Cost $222,500,000
Annualized Capital Cost $4,740,000
Annual O&M $3,600,000
Unit Cost of Water $1,135/AF
Efficiency
Programs
E-1: Add
aggressive
efficiency
programs to
reduce
demand
Yield 2,145 AFY Yes The enhanced efficiency programs are highly symbiotic with any supply option because they
focus on reducing water demand and reinforce
existing City water efficiency programs.

Annual O&M $6,000,000

City of Santa Rosa 28 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

4.3 Detailed Feasibility Analysis Results
Upon completion of the screening analysis, seven water supply options advanced to the detailed feasibility analysis which included evaluating and scoring the short-listed water supply options. A numerical system was used for rating (scoring) each short-listed option against each criterion and against each other. The numerical system provides a score of 0 through 2, with 2 being most favorable. A score of 0 signals that an option is not as responsive to a criterion or does not perform as well as the other options, while a score of 2 indicates that the option performs very well. The score is based on knowledge of the project area, engineering judgment, and experience on past projects. The evaluation criteria scoring rubric used for the evaluation of the short-listed supplemental supply options is summarized in Table 2-3, a summary of the shortlist supply scores is shown in Table 4-5. Detailed scoring descriptions are found in the following subsections.

City of Santa Rosa 29 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table 4-5: Summary of Supply Option Scores
Criterion
Groundwater Purified Recycled Water Stormwater
E-1:

Efficiency
Programs
GW-1: Add
Extraction
Wells
GW-2:

Convert
Emergency
Wells
GW-3: City
ASR Wells
PR-2:

Satellite
DPR
PR-4: Regional
DPR
SW-1:

Stormwater
Storage in
Aquifer
Cost effectiveness *
[$/AF]
2 [$840/AF]
2 [$540/AF]
2 [$2,600/AF]
0 [$3,900/AF]
0 [$3,200/AF]
0 [$3,500/AF]
1 [$2,800/AF]
Scalability
[Yield in AFY]
2 [6,734 - 10,080
AFY]
0 [1,744 - 2,462
AFY]
1 [3,634 - 5,130
AFY]
2 [3,019 -
10,065 AFY]
2 [3,019 - 10,065 AFY]
1 [2,600 - 10,080
AFY]
1 [2,145 AFY]
Resiliency 1 1 2 2 2 1 1
Equity 1 1 1 1 1 1 2
Environmental
performance 1 2 1 0 1 1 2
Legal, permitting, and
regulatory 1 2 0 0 0 1 2
City control and
interagency
coordination
2 2 1 2 0 2 2
Multi-benefit 0 0 1 0 0 2 1
Total Unweighted 10 10 9 7 6 9 12
Total Weighted 32 26 29 21 22 19 30
* Costs shown reflect a realistic baseline usage scenario and include both capital and operating costs.

City of Santa Rosa 30 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Figure 4-1 shows cost-effectiveness under baseline operations1 along with maximum yield and incorporates the weighted scores of each supply option in the bubble sizes (as summarized Table 4-5).

Figure 4-1: Cost-Effectiveness vs Max Yield (with Weighted Score)

Notes:

Water Supply options:
• GW-1: Additional Groundwater Extraction Wells
• GW-2: Convert Emergency Wells to Production Wells
• GW-3: Aquifer Storage and Recovery (ASR) Wells
• PR-2: Satellite Direct Potable Reuse (DPR) with Advanced Water Purification Facility (AWPF) • PR-4: Regional DPR with AWPF at Laguna Treatment Plant • SW-1: Stormwater Storage in Aquifer
• E-1: Efficiency Programs

1 The baseline scenario used by the screening tool assumed each water supply option would be operated in a realistic capacity that aimed to minimize operational costs, in contrast to the maximum production scenario that assumed water supply options would be operated to maximize water production via nonstop (24/7) operation.

City of Santa Rosa 31 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

4.3.1 Groundwater Options
The detailed scoring and rationale for the groundwater options are provided in Table 4-6, Table 4-7, and Table 4-8 on the following pages below.

Table 4-6: Detailed Scoring for Option GW-1
Criterion Description Score
Cost effectiveness
Under the baseline scenario, actual costs are estimated at $843/AF, making this option one of the least expensive studied, and less expensive than the current Sonoma Water supply which is $1,200/AF.
2 Scalability
As evaluated, this option includes construction of 12 wells to meet Santa Rosa’s supply goals. However, Santa Rosa Water need not construct all 12 wells initially, and could potentially build fewer even in the long run if well yield is higher than estimated. Generally, this option could be scaled or phased to best fit City needs. 2 Resiliency
Moderate resiliency. Pumping costs would increase with rising power costs. Cost- effectiveness could decrease under certain hydrologic conditions, but groundwater availability may not be severely impacted unless there is a long- term change in hydrology.
1 Equity
The additional groundwater supply would have no impact on vulnerable communities. The additional groundwater supply would be available to Santa Rosa to offset purchased water from Sonoma Water.
1 Environmental
performance
The new extraction wells would be located in Santa Rosa within the Southeast Greenway area. Construction of 12 wells would have moderate potential for environmental impacts.
1 Legal, permitting, and
regulatory
Well construction would likely require some permitting and regulatory compliance but would not require unusual efforts. 1
City control and
interagency
coordination
While coordination with Sonoma Water and the other GSAs in Santa Rosa Plain would be required, the scope and timing of the work would be generally at Santa Rosa Water’s discretion.
2 Multi-benefit No other benefits provided. 0

City of Santa Rosa 32 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table 4-7: Detailed Scoring for Option GW-2
Criterion Description Score
Cost effectiveness
Based on conceptual analyses, the rehabilitation of the three existing emergency wells would provide up to 2,462 AFY of additional groundwater supply. The baseline scenario average cost of water is approximately $541/AF, the least expensive of all options studied.
2 Scalability
This option lends itself to phasing since well rehabilitation could occur one well at a time. However, the overall scale of the project would fall far short of Santa Rosa’s projected 7,500 AFY need.
0 Resiliency
Moderate resiliency. Pumping costs would increase with rising power costs.

Cost-effectiveness could decrease under certain hydrologic conditions, but groundwater availability may not be severely impacted unless there is a long- term change in hydrology.
1 Equity
The additional groundwater supply would have no impact on vulnerable communities. The additional groundwater supply would be available to Santa Rosa to offset purchased water from Sonoma Water.
1 Environmental
performance
The rehabilitation of the existing wells would have minimal potential for environmental impacts. 2
Legal, permitting, and
regulatory
Santa Rosa Water has previously completed similar permitting/ regulatory efforts required for approval to convert from emergency use to active supply (i.e., 2005 Farmer's Lane well).
2 City control and
interagency
coordination
No interagency coordination would be required. 2
Multi-benefit No other benefits provided. 0

City of Santa Rosa 33 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table 4-8: Detailed Scoring for Option GW-3
Criterion Description Score
Cost effectiveness
Based on conceptual level cost estimates, construction of six ASR wells would provide up to 5,130 AFY of additional groundwater supply. The baseline scenario average cost of water is approximately $2,632/AF which includes purchase of water ASR.
2 Scalability
The extraction wells included in this option could be constructed in phases to best fit City needs. At buildout, the option could provide most of Santa Rosa’s supplemental needs.
1 Resiliency
Moderate resiliency. Pumping and injection costs would increase with rising power costs. Cost-effectiveness could decrease under certain hydrologic conditions, but the ability to inject water into the aquifer would improve resiliency relative to extraction-only options.
2 Equity
The additional groundwater supply would have no impact on vulnerable communities. The additional groundwater supply would be available to Santa Rosa to offset purchased water from Sonoma Water.
1 Environmental
performance
The new ASR wells would be located in a less developed area west of the City.

Construction of six wells would have moderate potential for environmental impacts.
1 Legal, permitting, and
regulatory
While ASR projects are increasingly common, they pose more significant permitting and regulatory requirements. 0
City control and
interagency
coordination
Coordination would be required with GSAs in Santa Rosa Plain and with Sonoma Water to coordinate with other ASR programs underway. 1 Multi-benefit
This option would enable conjunctive management of surface water and groundwater, which allows for greater flexibility in optimizing surface water and groundwater use (which represents an additional benefit beyond strict water supply).
1 City of Santa Rosa 34 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

4.3.2 Purified Recycled Water Options
The detailed scoring and rationale for the purified recycled water options are listed in Table 4-9 and Table 4-10.

Table 4-9: Detailed Scoring for Option PR-2
Criterion Description Score
Cost effectiveness
Under the baseline scenario the average cost of water is approximately $3,854/AF, making it the most expensive option. Additionally, the option involves a financial upfront commitment for capital so even if future circumstances changed the obligation to pay for the project would continue unabated.
0 Scalability
The AWPF included in this option could be constructed in phases to best fit City needs. The AWPF could be scaled down 30% in low demand periods.
2 Resiliency
High resiliency. The ability to purify tertiary treated water into potable supply would improve resiliency, even in times of drought or future hydrologic uncertainty.
2 Equity
The additional purified water supply would have no impact on the City’s vulnerable communities as it will meet or exceed drinking water standards.
1 Environmental
performance
The satellite DPR AWPF would be located in a less developed area within City limits. Construction of the AWPF and extensive conveyance facilities may have moderate to high potential for environmental impacts.
0 Legal, permitting,
and regulatory
High permitting/regulatory effort would be required as discussed in Appendix A. The main challenges in pursuing DPR include the lack of regulatory certainty and the lack of permitting precedents. 0 City control and
interagency
coordination
No significant interagency coordination would be required. 2 Multi-benefit
This option would provide a potable supply benefit but would reduce tertiary water availability for the Geysers and for the non-potable customers.
0 City of Santa Rosa 35 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table 4-10: Detailed Scoring for Option PR-4
Criterion Description Score
Cost effectiveness
Under the baseline scenario the average cost of water is approximately $3,166/AF, making it among the most expensive options. Additionally, the option involves a financial upfront commitment for capital so even if future circumstances changed the obligation to pay for the project would continue unabated.
0 Scalability
The AWPF included in this option could be constructed in phases to best fit City needs. The AWPF could be scaled down 30% in low demand periods.
2 Resiliency
High resiliency. The ability to purify tertiary treated water into potable supply would improve resiliency, even in times of drought or future hydrologic uncertainty.
2 Equity The additional purified water supply would have no impact on the City’s vulnerable communities. 1
Environmental
performance
The DPR AWPF would be located on the City-owned LTP property.

Construction of the AWPF and purified water conveyance facilities would have low to moderate potential for environmental impacts. 1 Legal, permitting,
and regulatory
High permitting/regulatory effort would be required as discussed in Appendix A. The main challenges in pursuing DPR include the lack of regulatory certainty and the lack of permitting precedents. 0 City control and
interagency
coordination
Coordination with a regional partner for the paper exchange would be required in addition to continuing coordination with Sonoma Water if its aqueduct were used for distribution.
0 Multi-benefit
This option would provide a potable supply benefit but would reduce tertiary water availability for the Geysers and for the non-potable customers.
0 City of Santa Rosa 36 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

4.3.3 Stormwater Capture
The detailed scoring and rationale for SW-1 is listed in Table 4-11.

Table 4-11: Detailed Scoring for Option SW-1
Criterion Description Score
Cost Effectiveness The baseline scenario average cost of water is approximately $3,500/AF, making it among the most expensive options. 0
Scalability
While the diversion structure, spreading basins (or injection wells) and extraction wells included in this option could be constructed in phases, the treatment plant, if needed, would require significant cost up-front that could not be recovered even if changes in future conditions reduced the need for the project.
1 Resiliency
Moderate resiliency. While the ability to store water in the aquifer would improve resiliency, there are significant uncertainties in the project’s performance, specifically its yield in drought years.
1 Equity
The additional groundwater supply would have no impact on vulnerable communities. The recharge areas for the project may tend to focus construction impacts on less-developed, less affluent areas, which could reduce flooding in those areas.
1 Environmental
performance
The new diversion structure, spreading basins and extraction wells would be located in a less developed area within City limits. Construction of the twelve wells would have moderate potential for environmental impacts. 1 Legal, permitting,
and regulatory
Some permitting/regulatory effort would be required, but stormwater diversion projects are increasingly common and would not require outsize legal, permitting, or regulatory effort to implement.
1 City control and
interagency
coordination
No interagency coordination would be required. 2
Multi-benefit
This option would enable conjunctive management of surface water and groundwater, which allows for greater flexibility in optimizing surface water and groundwater use (which represents an additional benefit beyond strict water supply).
2 City of Santa Rosa 37 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

4.3.4 Efficiency Programs
The detailed scoring and rationale for the Efficiency Programs option is provided in Table 4-12.

Table 4-12: Detailed Scoring for Option E-1
Criterion Description Score
Cost effectiveness
As summarized above, based on cost estimates provided by Santa Rosa Water, efficiency program would provide water savings at a cost of approximately $2,780/AF under the Baseline Scenario. This makes it less expensive than the options involving major costs for water treatment (e.g., PR-2, PR-4, SW-1) but more expensive than the groundwater options.
1 Scalability
Water savings could be increased depending on the scale of the program and number of customers that could be reached. Once water savings are achieved, they are considered to be relatively secure because they are built into the landscapes/fixtures, which have typically become more efficient with time due to plumbing codes and price signals.
1 Resiliency
Performance of efficiency measures would not degrade with changes in future regulations, energy costs or hydrology. However, the option does not provide “new water” that would help mitigate catastrophic loss of the Sonoma Water supply.
1 Equity
Direct installation programs reduce barriers to participation by low-income residents and organizations and agencies managing low-income and subsidized housing that have not been able to participate in rebate programs in the past due to upfront costs.
2 Environmental
performance
The program would have little to no adverse environmental impact and would provide a potential environmental benefit by reducing water consumption. 2 Legal, permitting,
and regulatory
Large-scale construction would not be needed. Physical changes as a result of the project would include toilet and fixture replacements, and relandscaping in existing developed areas. Work would need to be completed by qualified contractors, but additional permitting and regulatory requirements would not be anticipated for this option.
2 City control and
interagency
coordination
No interagency coordination would be required. 2
Multi-benefit In addition to providing water savings, the program would provide a cost savings to customers by helping them to reduce their water use. 1

City of Santa Rosa 38 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

4.3.5 Cost Sensitivity Analysis
The screening tool allows the supply option costs to be estimated under a variety of scenarios. The baseline scenario was modified to assess supply option performance under multiple hydrologic scenarios (Figure 4-2), and multiple Sonoma Water dry-year reduction levels (Figure 4-3). In that figure, scenarios SW-35 and SW-40 represent dry-year reductions of 35 percent and 40 percent respectively, versus a base scenario of 30 percent.

In general, most supply options would be more cost-effective in a drier hydrologic scenario because more water would be produced to meet normal demand during Sonoma Water supply shortages. The wetter hydrologic scenario contains more wet years than the baseline, but also contains more dry years (as summarized in Table 4-13). Therefore, for some options, the wetter scenario is also more cost-effective than the baseline scenario. All supply options become more cost-effective if greater dry-year Sonoma Water reductions are assumed.

Figure 4-2: Supply Option Cost Performance with Varying Hydrology ($/AF)

Table 4-13: Distribution of Water Year Types in Hydrologic Scenarios Hydrologic Scenario
Year Types by Percent
Wet Normal Dry
Wet 37% 29% 34%
Historic 33% 37% 30%
Dry 23% 30% 47%

City of Santa Rosa 39 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Figure 4-3: Supply Option Cost Performance with Varying Sonoma Water Cutbacks ($M/yr)

SW35: Scenario in which dry-year Sonoma Water supply reduction is 35% of baseline usage rather than the Base assumption of 30% reduction.

SW40: Scenario in which dry-year Sonoma Water supply reduction is 40% of baseline usage.

Although this analysis focused on hydrologic scenarios and Sonoma Water cutbacks , reflecting Santa Rosa’s goals of addressing climate change and Sonoma Water reliance, future work could use other variables to test cost-sensitivity (such as price of power, interest rate, and demand reduction percent).

4.4 Analysis Summary
There are several key takeaways from the analysis of supply options that Santa Rosa Water should consider as it continues to embark on planning for Santa Rosa’s water future. • Future conditions: Certain assumptions were made during the development of the WSAP about future hydrology, Sonoma Water supply reductions, cost of Sonoma Water supplies, and customer demand/conservation. Actual future conditions may be different which may change conclusions about the potential best fit water supplies. Options that could be implemented in phases may help provide resiliency against uncertainty while minimizing capital outlay. • Operational assumptions: This analysis incorporated reasonable operational assumptions into the baseline scenario. The cost per AF of water is sensitive to those assumptions. Generally, the cost per AF for a supplemental supply will be reduced as usage increases. However, many of the options cost more than the existing Sonoma Water supply, which may vary in the future. • Sensitivity: This analysis considered the impact of changing hydrology and reduced Sonoma Water dry-year allocations under the baseline scenario. The supply options generally become more cost-effective under more pessimistic scenarios (drier hydrology and higher Sonoma Water cutbacks) because more water is produced via the new options. However, the relative rankings of the supply options do not vary substantially with these changes to the baseline condition.

City of Santa Rosa 40 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

5. PORTFOLIOS

5.1 Overview of Portfolios
For the WSAP, Santa Rosa Water elected to use portfolios instead of individual supply options because they offer the dual benefits of diversification and flexibility. This enables Santa Rosa to diversify the risk of each water supply option, periodically assess the performance of each portfolio, and , if necessary, pivot between supply options to adequately address water supply needs. This WSAP presents four portfolios that Santa Rosa Water can consider as it plans for its water future, to achieve its targets by augmenting existing City groundwater production capacity (approximately 1,300 AFY, with an average of 2 MGD when operated about 6.5 months per year) with new supplies. The following sections summarize the portfolios, including estimated cost and yield information and how that portfolio might be implemented. Each portfolio is built around a theme that represents the portfolio’s primary focus: economics, implementation speed, water maximization, and adaptability, respectively.

The four portfolios were compiled by weighing a variety of factors including prescreening, screening, and feasibility analyses that applied evaluation criteria to specific options. While the scoring was not the final determining factor of a supply option’s inclusion in a portfolio, scores did help inform the composition of portfolios. Supply options that scored well are included or considered in multiple portfolios, however some supply options that did not score as highly are included in portfolios to further diversify the range of supply options. Water efficiency (E-1) is included in all portfolios, reflecting Santa Rosa’s goals of water use efficiency and environmental protection. While E-1 would reduce overall demand thereby reducing the volume of new water needed to achieve Santa Rosa’s goals. However, efficiency cannot address another key aspect of Santa Rosa’s goal which is resilience against a catastrophic interruption of Sono ma Water supply. Therefore, all portfolios contain new water supply source options in addition to efficiency programs (E-1). The City also recognizes that developing all supply options included in Portfolios 2, 3, or 4 would result in exceeding the cumulative production targets outlined in the water supply resiliency goal.

By carefully monitoring aggregated production capacity before considering each new source, Santa Rosa Water can avoid developing more facilities than needed to achieve the City’s goal.

Table 5-1 provides an overview of which supply options are included in each portfolio.

City of Santa Rosa 41 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table 5-1: Draft Portfolio Compositions
Option Description
Portfolio 1
Most
Economical
Portfolio 2
Fastest
Portfolio 3
Most Water
Portfolio 4
Most
Adaptive
GW-1 Add Extraction Wells (Up to 12)   
GW-2 Convert Emergency Wells to
Production Wells    
GW-3 Aquifer Storage & Recovery Wells Consider
PR-2 Satellite Direct Potable Reuse  Consider
PR-4 Regional Direct Potable Reuse at
Laguna Treatment Plant
Consider
SW-1 Stormwater Storage in Aquifer Consider Consider
E-1 Efficiency Programs    

5.2 Portfolio 1: Most Economical
The first portfolio focuses on meeting Santa Rosa’s water supply goals in the most economical way.

Portfolio 1 integrates two options: enhanced efficiency measures (E-1) and conversion of existing emergency groundwater wells to production wells (GW-2).

Table 5-2 presents estimated cost, yield, and scalability information for the portfolio components. Water capacity refers to the range of potential water supply that could be achieved if the option were implemented. Estimated yield is an estimate of the amount of water that would be supplied by the option based on certain implementation and operating assumptions. While this portfolio could meet the 7,500 AFY water supply goal based on water capacity, it is estimated to more realistically provide about 4,600 AFY. Because E-1 has no capital costs, this portfolio’s total capital costs are equivalent to the costs for GW-2. Annual O&M costs are equal to the costs needed to run the efficiency program (E -1) and the incremental cost to operate and maintain the former emergency wells as new production wells.

Figure 5-1 presents the cost and yield performance for this portfolio.

City of Santa Rosa 42 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table 5-2: Portfolio 1 Composition
Portfolio 1 Water
Capacity1
(AFY)
Estimated
Yield (AFY)2
Total Capital
Costs
Annual O&M
Costs Scalability3
E-1 1,500 – 4,500 2,145 $0 $6,000,000 1
GW-2 1,500 – 3,000 2,462 $12,000,000 $530,000 0
TOTAL 3,000 – 7,500 4,607 $12,000,000 $6,530,000
Notes:
(1) Water capacity refers to the range of water supply that could be achieved if the water supply option were implemented.
(2) Estimated yield is an estimate of the amount of water that would be supplied by the option based on certain operating and/or implementation assumptions. More information on these assumptions is included in Appendix A.
(3) Scalability for each of the portfolio components refers to the degree to which an option could provide a different amount of water now and in the future. Scalability was assigned a numerical score of 0 through 2, with 0 indicating low scalability compared to other options and 2 indicating a high degree of scalability.

A conceptual implementation timeline for this portfolio is presented in Figure 5-2. In this conceptual timeline, both projects included in Portfolio 1 would be implemented at the same time. E-1 would begin with developing the water efficiency programs and hiring the staff needed to implement those programs. GW-2 would begin with technical studies to determine the conversion design for the emergency wells and environmental documentation to cover the work under the California Environmental Quality Act (CEQA). A key aspect of the technical studies would be focused on sustainable yield, to ensure that conversion of the standby wells to production wells did not adversely affect the aquifer. The various decision points along the implementation timelines for each supply option repre sent various points at which Santa Rosa Water adjust the project scope. A more detailed version of the conceptual implementation timeline is included in Appendix C.

City of Santa Rosa 43 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

Figure 5-1: Portfolio 1 Cost and Yield Performance

City of Santa Rosa 44 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

Figure 5-2: Portfolio 1 Implementation Concept

City of Santa Rosa 45 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

5.3 Portfolio 2: Fastest
Portfolio 2 focuses on implementation speed. It includes enhanced efficiency measures (E-1), converting emergency groundwater wells to production wells (GW-2), and constructing new production wells (GW-1).

Of the supply options considered, these three options in combination can begin relatively quickly and proceed simultaneously. When compared to Portfolio 1, this portfolio offers more water supply and would reduce the risk of Santa Rosa falling short of its water supply goals.

Table 5-3 presents estimated cost, yield, and scalability information for the portfolio components. Water capacity for this portfolio ranges from roughly 8,000 to 17,500 AFY; estimated total yield is approximately 14,700 AFY, more than three times that of Portfolio 1. The capital costs ($108.5 million) are nearly five times that of Portfolio 1, due to the addition of GW-1 to this portfolio. Annual O&M costs are approximately $10.5 million, roughly 60% higher than those in Portfolio 1.

Figure 5-3 presents the cost and yield performance for this portfolio.

Table 5-3: Portfolio 2 Composition
Portfolio 2 Water
Capacity1
(AFY)
Estimated
Yield (AFY)2
Total Capital
Costs
Annual O&M
Costs
Scalability3
E-1 1,500 – 4,500 2,145 $0 $6,000,000 1
GW-2 1,500 – 3,000 2,462 $12,000,000 $530,000 0
GW-1 5,040 – 10,080 10,080 $96,500,000 $3,900,000 2
TOTAL 8,040 – 17,580 14,687 $108,500,000 $10,430,000
Notes:
(1) Water capacity refers to the range of water supply that could be achieved if the water supply option were implemented.
(2) Estimated yield is an estimate of the amount of water that would be supplied by the option based on certain operating and/or implementation assumptions. More information on these assumptions is included in Appendix A.
(3) Scalability for each of the portfolio components refers to the degree to which an option could provide a different amount of water now and in the future. Scalability was assigned a numerical score of 0 through 2, with 0 indicating low scalability compared to other options and 2 indicating a high degree of scalability.

A conceptual implementation timeline for this portfolio is presented in Figure 5-4. Implementation of Portfolio 2 is very similar to that of Portfolio 1 in that E-1 and GW-2 are implemented right away. Given that the guiding theme for this portfolio is implementation speed, GW-1 is also shown starting immediately with siting studies focused aimed at identifying the best locations for new groundwater wells.

As for GW-2, sustainability would be a key focus of technical studies; however, GW-1 would have more options to explore to meet that goal, including various site selection and well screen intervals. One potential drawback of this portfolio and its guiding theme is that Santa Rosa Water would need to commit resources to GW-1 before the benefits of GW-2 and E-1 are realized. This may risk overbuilding GW-1 by drilling more wells than would be needed to meet the 7,500 AFY water supply goal. A more detailed version of the conceptual implementation timeline is included in Appendix D.

City of Santa Rosa 46 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

Figure 5-3: Portfolio 2 Cost and Yield Performance

City of Santa Rosa 47 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

Figure 5-4: Portfolio 2 Implementation Concept

City of Santa Rosa 48 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

5.5 Portfolio 3: Most Water
Portfolio 3 focuses on maximizing water supply reliability by including more diverse supply options than the prior two portfolios. It incorporates the three supply options included in Portfolio 2 (E -1, GW-2, GW- 1), and adds PR-2 (satellite direct potable reuse) and SW-1 (stormwater capture and reuse).

Table 5-4 presents estimated cost, yield, and scalability information for the portfolio components.

Estimated yield for this portfolio is approximately 34,800 AFY while water capacity ranges from about 21,000 to 38,700. Even the lower bound of this range is far more than Santa Rosa’s current estimate of need; the portfolio’s theme of maximizing supply is based on the fact that one or more supply options could encounter unforeseen delays or suffer less yield than even lower-bound estimates. Capital costs ($645 million) are significantly more than the prior two portfolios as a result of PR-2 and SW-1. Annual O&M costs are approximately $31 million, about three times higher than those in Portfolio 2.

Figure 5-5 presents the cost and yield performance for this portfolio.

Table 5-4: Portfolio 3 Composition
Portfolio 3 Water Capacity1
(AFY)
Estimated
Yield (AFY)2
Total Capital
Costs
Annual O&M
Costs
Scalability3
E-1 1,500 – 4,500 2,145 $0 $6,000,000 1
GW-2 1,500 – 3,000 2,462 $12,000,000 $530,000 0
GW-1 5,040 – 10,080 10,080 $96,500,000 $3,900,000 2
PR-2 8,000 – 10,065 10,065 $314,000,000 $12,030,000 2
SW-1 5,000 – 10,080 10,080 $222,500,000 $8,390,000 1
TOTAL 21,040 – 37,725 34,832 $645,000,000 $30,850,000
Notes:
(1) Water capacity refers to the range of water supply that could be achieved if the water supply option were implemented.
(2) Estimated yield is an estimate of the amount of water that would be supplied by the option based on certain operating and/or implementation assumptions. More information on these assumptions is included in Appendix A.
(3) Scalability for each of the portfolio components refers to the degree to which an option could provide a different amount of water now and in the future. Scalability was assigned a numerical score of 0 through 2, with 0 indicating low scalability compared to other options and 2 indicating a high degree of scalability.

City of Santa Rosa 49 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
A conceptual implementation timeline for this portfolio is presented in Figure 5-6. This concept shows Portfolio 3 beginning very similarly to Portfolio 2, with options E-1, GW-2, and GW-1 beginning right away. To maximize the amount of water available to Santa Rosa, PR-2 also begins immediately with planning studies, followed by CEQA and other permitting/regulatory processes which are anticipated to be extensive for a direct potable reuse project1. Design and construction of the satellite direct potable reuse facility would begin directly following regulatory and environmental approvals.

In contrast to the prior two portfolios, Portfolio 3 begins to introduce some degree of flexibility with the phasing of SW-1. Planning studies and stormwater modeling for SW-1 would begin immediately, in line with the timing of the other elements of this portfolio. However, further work on SW -1 would pause until the yield performance of E-1, GW-2, and GW-1 is established. Depending on the need for additional water at that time, Santa Rosa Water may decide to move into design and construction of SW-1. Given that the estimated yield of this portfolio without SW-1 (~24,700) is more than three times what Santa Rosa Water estimates is the amount of water needed to meet its projected supply goals (7,500), it’s very unlikely that Santa Rosa would need the water provided by SW-1. Regardless, the conceptual implementation timeline shows how Santa Rosa Water could begin to plan for some level of flexibility as this portfolio also works to maximize water availability. A more detailed version of the conceptual implementation timeline is included in Appendix E.

1 In July 2023, the State Water Resources Control Board released draft guidelines for direct potable reuse implementation. Final guidelines are anticipated in Spring 2024.

City of Santa Rosa 50 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

Figure 5-5: Portfolio 3 Cost and Yield Performance

City of Santa Rosa 51 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

Figure 5-6: Portfolio 3 Implementation Concept

City of Santa Rosa 52 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

5.7 Portfolio 4: Most Adaptive
Building on the flexibility introduced in Portfolio 3, Portfolio 4 provides the most flexible, or adaptive, path forward of the WSAP portfolios. This portfolio incorporates interactions among the various supply options to afford Santa Rosa Water additional opportunities to assess its water supply needs and adjust appropriately when pursuing new water supply sources in the future. Portfolio 4 includes largely the same elements as Portfolio 3: enhanced efficiency measures (E-1), converting emergency groundwater wells to production wells (GW-2), constructing new production wells (GW-1), satellite direct potable reuse (PR-2), and stormwater capture and reuse (SW-1). The defining features of Portfolio 4 that make it distinct from Portfolio 3 are the addition of aquifer storage and recovery (ASR) to GW-1 (adding elements of GW-3 and shown as GW-1+), and the consideration of LTP as a location (PR-1) for a direct potable reuse facility and consideration of a regional direct potable reuse option (PR-4) when studying PR-2 (shown as PR-2+).

Most critically, Portfolio 4 incorporates “adaptive pathways” for its implementation to maximize flexibility.

These adaptive pathways allow the City to periodically reassess portfolio performance at key decision points. If future circumstances have improved the feasibility of alternative supply options, such as desalination, then it is possible that the City may utilize the flexibility of Portfolio 4 and elect to pivot in pursuit these newly viable options.

Table 5-5 presents estimated cost, yield, and scalability information for Portfolio 4 components. Because the components of Portfolio 4 are similar to that of Portfolio 3, the yield and cost characteristics are largely the same as Portfolio 3. Estimated yield is approximately 34,800 AFY while water capacity ranges from about 21,000 to 38,700. Capital costs ($645 million) are significant and annual O&M costs are approximately $31 million. Because this portfolio is structured around adaptabilit y, these figures would only be reached if the entire portfolio were built (a baseline scenario); in practice and as a result of taking advantage of the flexibility offered by this portfolio, these figures are likely to be much lower.

Figure 5-7 presents the cost and yield performance for this portfolio in its baseline form.

City of Santa Rosa 53 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
Table 5-5: Portfolio 4 Composition
Portfolio 4

Water Capacity1
(AFY)
Estimated
Yield (AFY)2
Total Capital
Costs
Annual O&M
Costs
Scalability3
E-1 1,500 – 4,500 2,145 $0 $6,000,000 1
GW-2 1,500 – 3,000 2,462 $12,000,000 $530,000 0
GW-1+4 5,040 – 10,080 10,080 $96,500,000 $3,900,000 2
PR-2+5 8,000 – 10,065 10,065 $314,000,000 $12,030,000 2 SW-1 5,000 – 10,080 10,080 $222,500,000 $8,390,000 1
TOTAL 21,040 – 37,725 34,832 $645,000,000 $30,850,000
Notes:
(1) Water capacity refers to the range of water supply that could be achieved if the water supply option were implemented.
(2) Estimated yield is an estimate of the amount of water that would be supplied by the option based on certain operating and/or implementation assumptions. More information on these assumptions is included in Appendix A.
(3) Scalability for each of the portfolio components refers to the degree to which an option could provide a different amount of water now and in the future. Scalability was assigned a numerical score of 0 through 2, with 0 indicating the option had a low scalability compared to other options and 2 indicating it had a high degree of scalability.
(4) GW-1+ indicates that the component includes aquifer storage and recovery elements. The information presented for GW-1+ is consistent with GW-1, though Santa Rosa Water acknowledges that if ASR wells were incorporated into this supply component, capacity, yield, and costs would very likely change. (5) PR-2+ indicates that the component could incorporate studying LTP as the location (PR-1) and potentially developing a regional approach to direct potable reuse (PR-4). Santa Rosa Water acknowledges that capacity, yield, and costs would very likely change should a regional project move forward. Furthermore, the phasing of PR-2+ enables the City to reassess the viability of alternative supply options, such as desalination, at various key decision points if changing future circumstances would improve potential performance.

As mentioned, a key aspect of this portfolio’s theme of adaptability is flexibility of implement ation. One potential implementation pathway (a baseline scenario) for this portfolio is presented in Figure 5-8.

Portfolio 4 would begin as the other WSAP portfolios do, with E-1, GW-2, and GW-1+ beginning right away. Siting studies for GW-1+ would identify and prioritize locations that could be suitable for both extraction and injection wells. SW-1 studies would also begin since stormwater could potentially be used for an ASR well within GW-1+. Once siting studies are complete for GW-1+, this component would pause while E-1 and GW-2 advance. Work on GW-1+ would continue when Santa Rosa Water had developed a better understanding of the actual yield of E-1 and GW-2. This would allow staff to right-size GW-1+ by only constructing what is required to meet the remaining need for water. Depending on the need for water provided by GW-1+, SW-1 would continue with design and construction to provide any stormwater required for injection as part of GW-1+.

The start time for PR-2+ coincides with the anticipated release of final guidelines on direct potable reuse from the State Water Resources Control Board (State Board). While final guidelines are expected spring 2024, it is likely that it will take the State Board several more years to make any amendments or

City of Santa Rosa 54 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
adjustments based on the experiences of early implementers. This portfolio advises that Santa Rosa Water may wish to wait to begin planning studies on PR-2+ until these regulations are a bit more established, in order to provide the most realistic planning and design criteria for Santa Rosa’s purposes. Once planning studies for PR-2+ are complete, work on this component would pause until the actual yield for GW-1+ is established and the need for PR-2+ is better understood. This would allow Santa Rosa Water to scale PR- 2+ to meet any remaining water needs. Another benefit of pausing the further planning of PR -2+ is to allow time for staff to assess and develop any regional partnerships that may support the scalability of this component. There may also be opportunities to use water available under SW-1 to supply PR-2+, if there is additional SW-1 water available after its potential use in GW-1+.

A more detailed version of the baseline conceptual implementation timeline for Portfolio 4 is included in Appendix F.

City of Santa Rosa 55 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

Figure 5-7: Portfolio 4 Cost and Yield Performance (Baseline Scenario)

City of Santa Rosa 56 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

Figure 5-8: Portfolio 4 Implementation Concept (Baseline Scenario)

City of Santa Rosa 57 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
The baseline scenario for Portfolio 4 assumes that all components are implemented at their studied capacity and as outlined in Chapter 3. While this baseline is helpful to understand the logic behind the sequencing of various components and their interactions, it is not a realistic picture of how the portfolio would actually be implemented. As shown in Table 5-5 and Figure 5-7 above, the baseline scenario would result in significantly more water than is needed to meet Santa Rosa’s water supply goals. In practice, this would mean that Santa Rosa Water would have committed more financial resources to build infrastructure than was needed to meet its water supply goals.

As shown below, Figure 5-9 (cost and yield performance) and Figure 5-10 (implementation timeline) present a more realistic implementation scenario (an alternative scenario) for Portfolio 4. This scenario begins as the baseline does: E-1, GW-2, GW-1+, and SW-1 beginning immediately; planning studies for SW-1 inform the siting and planning for GW-1+; and planning studies for PR-2 begin when State Board regulations are a bit more established, then work would pause while E-1, GW-2, and GW-1 advance. This scenario begins to deviate from the baseline scenario if, after GW-2 and E-1 are established, the remaining need for water is able to be met with GW-1. In this scenario, PR-2 and SW-1 would not advance past the initial planning stages because GW-1 is able to meet the remaining water need with extraction wells alone. In the end, this scenario would look very similar to Portfolio 2, with both portfolios implementing E-1, GW-2, and GW-1. The added benefit of this Portfolio 4 scenario is that staff would also be equipped with planning studies for direct potable reuse and stormwater capture. Having these studies in hand positions Santa Rosa to quickly leverage potential opportunities for funding and/or regional partnerships, and also hedges risk in case the other portfolio elements are delayed. A more detailed version of the alternative conceptual implementation timeline for Portfolio 4 is included in Appendix G.

Two variants of the alternative scenario are presented in Figure 5-11 and Figure 5-12. In the first variant, SW-1 is able to provide water cost-effectively to GW-1+, and design and construction of those elements continues alongside the design and construction of GW-1+. PR-2+ does not move past initial planning studies. In the second variant, SW-1 does not move past the initial planning stage because there is not sufficient water to achieve cost-effectiveness. However, during the pause in PR-2+ after the initial planning studies, regional partners have come forward and GW-1 is found not to close the remaining supply gap. As a result, PR-2+ continues with design and construction. In this iteration, Santa Rosa’s involvement would be consistent with its specific need for water, even if PR-2+ is sized closer to as it is presented in the WSAP.

City of Santa Rosa 58 Woodard & Curran, Inc.

DRAFT Water Supply Alternatives Plan August 7, 2023

Figure 5-9: Portfolio 4 Cost and Yield Performance (Alternative Scenario)

City of Santa Rosa 59 Woodard & Curran, Inc.

DRAFT Water Supply Alternatives Plan August 7, 2023

Figure 5-10: Portfolio 4 Implementation Concept (Alternative Scenario)

City of Santa Rosa 60 Woodard & Curran, Inc.

DRAFT Water Supply Alternatives Plan August 7, 2023

Figure 5-11: Portfolio 4 Implementation Concept (Alternative Scenario, 1st Variant)

City of Santa Rosa 61 Woodard & Curran, Inc.

DRAFT Water Supply Alternatives Plan August 7, 2023

Figure 5-12: Portfolio 4 Implementation Concept (Alternative Scenario, 2 nd Variant)

City of Santa Rosa 62 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

5.8 Summary of Portfolios
The following three figures compare the five portfolios (the primary four portfolios and the Alternative Scenario of Portfolio 4) in the areas of yield and capital costs. Figure 5-13 shows the cumulative estimated water yield for each of the four portfolios through 2045 and is consistent with the blue dotted line in the cost and yield performance graphs for each of the portfolios presented in the prior sections.

Figure 5-14 shows the capital funding needs for each of the portfolios by year. Figure 5-15 presents the cumulative capital cost for each by year and is consistent with the red line on the prior cost and yield performance graphs. Figure 5-16 shows the net operating burden, or full annualized cost, for each portfolio by year; the full annualized cost includes operating cost and debt service. For the purpose of these graphs, Santa Rosa Water needed to make assumptions about the sequencing and timing of project implementation elements; these assumptions are estimates and would be adjusted if Santa Rosa Water moved forward with implementing any portfolio or portfolio components. These assumptions are included in Appendix C (Portfolio 1), Appendix D (Portfolio 2), Appendix E (Portfolio 3), Appendix F (Portfolio 4 Baseline), and Appendix G (Portfolio 4 Alternative).

As shown in Figure 5-13, each of the portfolios begin providing the same amount of yield until Portfolios 2 and 3 split off in 2031, representing an estimate of when GW-1 would begin providing water. Portfolio 3 begins to deviate from Portfolio 2 in 2036 when SW-1 would start providing water. In Portfolio 3, water from PR-2 would begin in 2039. Portfolios 1 and 4 (Baseline and Alternative) mimic each other until 2035 when GW-1+ begins to provide water, both from extraction only wells and from ASR wells using stormwater from SW-1. In Portfolio 4 Baseline, PR-2 comes online in 2043 and provides the final increase in water.

The financial information for the portfolios shown in Figure 5-14, Figure 5-15, and Figure 5-16, as noted above, is based on the assumptions made regarding the timing and sequencing of implementation steps.

Portfolios 1 and 2 are difficult to see in Figure 5-13 because they follow the same path as other portfolios (Portfolio 1 follows Portfolio 4 Baseline and Portfolio 2 follows Portfolio 3) from 2027 until capital investments are complete (in 2028 for Portfolio 1 and 2031 for Portfolio 2). Portfolio 3 sees a large spike in capital required around 2035 due to investments needed in PR-2. The 2022-23 operating budget for Santa Rosa Water was set at roughly $21 million; Figure 5-16 shows that any of the WSAP portfolios will require a significant increase in Santa Rosa Water’s annual operating budget. At the low end in 2040, Portfolio 1 would result in a roughly $7 million, or 33 percent, increase. At the high end in 2040, Portfolio 3 would result in an approximately $31 million (148 percent) increase.

Across the three financial figures, the Baseline scenario for Portfolio 4 has a more gradual level of investment than Portfolio 3 because of its more adaptive approach; Portfolio 4’s Alternative scenario shows more scaled back investments than either Portfolio 3 or Portfolio 4’s Baseline scenario because neither PR-2 nor SW-1 advance past the planning stages so this scenario operates similarly to Portfolio 2.

Adaptive planning as seen in Portfolio 4 offers Santa Rosa a number of important benefits:
• Each project is implemented with a well-defined understanding of its milestones. Milestones offer Santa Rosa Water an opportunity to refine the remaining aspects of the project to meet current needs. For example, the phased approach to E-1. Depending on the success of various conservation programs, staff can adjust its future efficiency work to meet shifting water use patterns or changing regulatory requirements around end use. Santa Rosa Water can also

City of Santa Rosa 63 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
leverage these milestones to complete activities that will inform future work; for example, reassessing water demands to confirm project size before investing in design. • Timing and scale of later projects are informed by the performance of earlier projects . In Portfolio 4, PR-2 only moves forward based on the remaining need for water. It may be that no additional water is needed by that time and PR-2 does not move forward (1st variant of Portfolio 4, Figure 5-11). In another case, additional water may be needed, but not nearly the amount scoped in the WSAP for PR-2. At that point, Santa Rosa Water may opt to move forward with direct potable reuse, but in a very scaled back manner (second variant of Portfolio 2, Figure 5-12). • Early, inexpensive tasks are completed off the critical path. In both Portfolios 3 and 4, planning studies for PR-2 are completed early, even though its timing and scale depends on the performance of other projects like GW-1+. The same approach is used for SW-1 planning studies and stormwater modeling. This allows Santa Rosa Water to take a more measured approach to addressing the supply gap, while simultaneously positioning itself to quicky leverage favorable regulatory environments or funding opportunities.

City of Santa Rosa 64 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

Figure 5-13: Cumulative Estimated Water Yield (AFY)

City of Santa Rosa 65 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

Figure 5-14: Capital Funding Needs by Year ($M/Year)

City of Santa Rosa 66 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

Figure 5-15: Cumulative Capital Investment ($M/Year)

City of Santa Rosa 67 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

Figure 5-16: Net Operating Burden ($M/Year)1

1 Portfolios 2, 3, and 4 Baseline all experience a negative net operating burden, or an operating savings, as a result of water supply projects that reduce the purchase of Sonoma Water (GW-1 and SW-1 in these cases).

City of Santa Rosa 68 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

6. NEXT STEPS
The WSAP presents a number of potential pathways that Santa Rosa Water could take as it continues to plan for its water future. Based on discussions with stakeholders, Portfolio 4 appears to offer the most benefits to Santa Rosa Water, including that its most responsive to its original goals and provides the most flexibility to adapt to changing conditions in the future. If Santa Rosa Water chooses to make progress on Portfolio 4, staff could begin with the following steps:
• Identify funding for initial activities and plan for CIP funding. Santa Rosa Water would first need to identify funding to support early work which is outlined in the bullet points below. This would include scoping the work to better understand costs and determining which work would be completed by staff and which work would be conducted by one or more consulting firms. Santa Rosa Water could also begin planning for the initial capital expenditures that will come as GW-1+ and GW-2 advance. This would likely mean adopting CIP funding for these elements, which would require some lead time.
• P lan for Phase 1 of E-1. Because Santa Rosa Water has extensive experience implementing efficiency programs, work to further E-1 will be familiar to staff. This would likely include preparing an internal implementation plan for programs under Phase 1 and the development and maintenance of internal and external funding opportunities that could be used to support implementation.
• B egin hydrogeologic studies for GW -2 and determine CEQA pathway. Santa Rosa Water has already identified some funding for converting emergency wells to full time production wells . As a result, staff could begin hydrogeologic studies earlier as a result. Simultaneously, staff could confirm the CEQA coverage needed for GW-2. Once completed, the hydrogeologic studies would support the environmental documentation needed for GW-2. Regulatory approvals with the State Board and interagency coordination (including Public Trust Review) could also begin once hydrogeologic studies were complete. Additionally, Santa Rosa Water would coordinate with the Santa Rosa Plain GSA to ensure groundwater basin sustainability. • P repare siting stud y for GW-1+. The siting study for GW-1 could begin with a desktop effort to identify all potential sites that could be eligible for extraction only and which could include ASR wells. Santa Rosa Water could apply a screening process to these sites to narrow down the list and conduct field investigations of top ranked sites. During this step, results from the modeling and siting study work for SW-1 could be folded into the process so staff could assess at that time if ASR wells with stormwater would be a viable path forward. This step would also include discussions with Santa Rosa Plain GSA to coordinate strategies for basin sustainability. • T
rack direct potable reuse regulations and initiate planning studies for PR-2+. Santa Rosa Water could begin work on PR-2 by tracking the draft guidelines from the State Board and consider the best location, explore potential regional partnerships, and begin engaging with likely early adopters. Once the State has finalized regulations, staff could begin a treatment study to identify the processes needed to produce and use water through direct potable reuse. Santa Rosa Water could consider engaging with the San Francisco Public Utilities Commission and the Los Angeles Department of Public Works to learn about the best approach, as both agencies that have conducted treatment pilots for direct potable reuse.

City of Santa Rosa 69 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
• Conduct modeling and siting study for SW-1. Initial planning studies for SW-1 include stormwater modeling, a siting study, and a treatment study. This work would help Santa Rosa Water determine the amount, location, and timing of stormwater and how it might be treated for use in GW-1+ or in some other project. Initial scope and cost development could occur at the completion of this work.

Some of these items, such as planning for Phase 1 of E-1 and the hydrogeologic and siting studies for GW-2 and GW-1+, would also apply to the other WSAP portfolios. If Santa Rosa Water decided to embark on a different portfolio or path, this work would still provide benefit and support that new pathway.

Regardless of the path forward, Santa Rosa Water will need to consider the following four areas that are subject to dynamic change, as it plans for its water future: funding, technology, regulations, and regional efforts. Monitoring advancements and opportunities in these areas will help Santa Rosa Water remain agile and able to quickly adapt its water supply planning efforts.

Funding
Implementing any of portfolios outlined in the WSAP would require varying levels of fundin g and funding strategies, both in initial capital cost and annual operation and maintenance. Santa Rosa Water typically funds its capital projects through some combination of connection fees (for infrastructure), water rates (and periodic rate increases), grants, and bonds. These mechanisms, in addition to state revolving fund loans, could also be used to fund the water supply options and/or portfolios presented in the WSAP.

Grants/Loans: State and federal agencies often provide grants or low-interest loans to fund water projects. Santa Rosa Water has a successful history of securing grants. This funding mechanism will likely be an important source, particularly if Santa Rosa Water considers implementing direct potable reuse. In July 2022, the State Board released draft regulations for DPR implementation . Given the State’s focus on enhancing water supply resiliency throughout California, funding may become available in the future to support implementation of these projects.

Bonds: Santa Rosa Water may opt to issue bonds to raise capital for water projects as it has for large projects such as the new UV system currently being installed for disinfecting recycled water. Bonds are a form of debt where bondholders provide money in exchange for periodic interest pay ments and the return of the principal amount at the end of the bond period. Because bonds are usually repaid using revenue from water rates over an extended period, bonds can be a useful tool to avoid large spikes in water rates for customers.

Connection F
ees and Water Rates: To support continued investment in its water infrastructure and operations and maintenance of existing infrastructure, Santa Rosa Water uses connection fees and water rates. Santa Rosa Water reviews connection fees and water rates periodically and develops new fee and/or rate schedules based on studies. Due to Proposition 218, the Right to Vote on Taxes Act (1996), public water systems must demonstrate that any proposed fee and/or rate increases are necessary to cover the costs of providing water services, including the capital investments required for new projects.

Santa Rosa Water is keenly aware that in a successfully implemented water project, benefits must be equal to or outweigh the costs. During development of water supply projects, staff would continually weigh the anticipated costs of each project (e.g., financial, environmental) against the estimated benefits (e.g.,

City of Santa Rosa 70 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
reduced impacts of water shortages, increased local control). Purposefully balancing the costs and benefits of any project helps Santa Rosa make informed decisions that align with the broader interests of the community, foster responsible water resource management, and ensure a resilient water supply system for the future.

The WSAP provides a snapshot in time of the cost effectiveness of the included water supply options.

Factors such as regulatory changes, advances in technology, worsening drought severity and/or frequency, and increases in Sonoma Water’s wholesale water rates all contribute to the cost -effectiveness of potential water supply projects. As part of the further development of any WSAP elements, Santa Rosa Water is committed to re-analyzing the cost-effectiveness of projects and making adjustments so that the best options continue to move towards implementation.

To provide funding context for capital and operations and management costs, Santa Rosa Water’s annual budget for fiscal year 2023-2024 is included as Appendix H.

Technology
Technological advances have and will continue to change the way in which water suppliers select and implement water supply projects. Such past examples include advancements in wastewater treatment that opened opportunities for purple pipe recycled water and paved the way for potable reuse. Another example is automated metering infrastructure (AMI), which the Santa Rosa Water began implementing in 2016 and has helped manage end user demand and quickly identify system leaks. While these are direct examples of how water-related technology has shaped project implementation, there are also other examples of more indirect technological advances that may impact how Santa Rosa Water continues to plan future water supply. One example is advancements in energy generation. As recently as 10 years ago, energy prices made desalination often prohibitively expensive and only cost-effective at very large scales.

With technological advancements in the energy industry, the prevailing concern with desalination has shifted from energy use to one around brine disposal.

Artificial intelligence (AI) is another area of technological advancement that will likely impact water supply planning. The industry has already seen some of this influence with smart irrigation systems that can process weather data and soil moisture information to optimize water use in agriculture and landscaping.

Advancements in AI may impact how water quality is monitored or support siting for stormwater infrastructure as these projects consider how climate change will alter the frequency and timing of stormwater runoff. Staying informed about technological developments will help Santa Rosa remain agile and adjust its water supply planning to effectively manage its water resources and continue to improve resiliency.

Regulations
A third area that will continue to greatly impact water resources planning is regulations at the local, state, and federal levels. Recent examples include Sonoma County’s amended Well Ordinance and the State Board’s draft direct potable reuse guidelines, both of which will shape how Santa Rosa Water implements any new groundwater or potable reuse projects.

A more nascent area for regulations is around emerging water quality concerns, particularly microplastics and per- and polyfluoroalkyl substances (PFAS). PFAS are referred to as “forever chemicals” because they do not break down in nature; since the beginning of their widespread use in the 1950’s, they have been

City of Santa Rosa 71 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023
used in thousands of products for non-stick or stain-resistant purposes. The U.S. Environmental Protection Agency released proposed maximum containment levels (MCLs) for six different PFAS in March 2023; the California Division of Drinking Water (DDW) has yet to set MCLs for PFAS. Final MCLs and other PFAS- related regulatory requirements may impact how Santa Rosa Water implements water supply projects.

One potential impact may be on the final siting or well-head treatment required for groundwater wells. If substantial well-head treatment is ultimately required, it may shift the cost-effectiveness of GW-1+ and GW-2. Staff should continue to monitor regulatory developments that would have the potential to alter the course of water supply components in the WSAP.

Regional Efforts
As discussed in Section 1.2.1, the City is involved in a number of regional water supply reliability efforts, including Sonoma Water’s regional water supply and resiliency efforts, the GSA’s development and implementation of a its groundwater sustainability plan, and the Russian River Water Forum’s efforts to secure water supply resiliency as PG&E moves forward with decommissioning the Potter Valley Project and potentially impacts the associated Eel River diversion. The City is committed to continue working with these and other partners to enhance regional sustainability in the future as opportunities arise. There are also a number of neighboring water suppliers which have individually invested in studying and planning for their own long-term water supply resiliency and reliability. As these efforts evolve and advance throughout the region, Santa Rosa Water is well positioned to stay informed about and seek opportunities to work with partners on mutually beneficial water supply projects. For example, there could be opportunities for Santa Rosa Water to adjust SW-1 to increase economies of scale or to form a partnership for PR-2 which could lead the development of a regional direct potable reuse facility (similar to PR-4).

This concludes the Water Supply Alternatives Plan. This document is not intended to be prescriptive, but rather an adaptive guide for Santa Rosa Water to use as it begins water supply and infrastructure planning for Santa Rosa’s future.

City of Santa Rosa 72 Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

7. REFERENCES
City of Santa Rosa. (2018, February). Regional Water Reuse System Master Plan.

City of Santa Rosa. (2021, June). 2020 Urban Water Management Plan.

State Water Resources Control Board. (2021, August 17). A Proposed Framework of Regulating Direct Potable Reuse in California Addendum, version 8-17-2021.

The Technical Memorandum included in Appendix A includes a more robust list of references used for that work.

City of Santa Rosa Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

APPENDIX A: FEASIBILITY ANALYSIS TECHNICAL MEMORANDUM

City of Santa Rosa Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

APPENDIX B: LINKS TO RECORDED MEETINGS

City of Santa Rosa Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

APPENDIX C: PORTFOLIO 1 EXAMPLE SCHEDULE

City of Santa Rosa Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

APPENDIX D: PORTFOLIO 2 EXAMPLE SCHEDULE

City of Santa Rosa Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

APPENDIX E: PORTFOLIO 3 EXAMPLE SCHEDULE

City of Santa Rosa Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

APPENDIX F: PORTFOLIO 4 EXAMPLE SCHEDULE (BASELINE SCENARIO)

City of Santa Rosa Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

APPENDIX G: PORTFOLIO 4 EXAMPLE SCHEDULE (ALTERNATIVE SCENARIO)

City of Santa Rosa Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

APPENDIX H: SANTA ROSA WATER’S RECENT BUDGETS FOR OPERATIONS AND

CAPITAL PROJECTS

City of Santa Rosa Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

APPENDIX I: MEMORANDUM ON DESALINATION SUPPLY OPTIONS IN THE

WATER SUPPLY FEASIBILITY ANALYSIS

City of Santa Rosa Woodard & Curran, Inc.

Water Supply Alternatives Plan September 8, 2023

APPENDIX A: FEASIBILITY ANALYSIS TECHNICAL MEMORANDUM

City of Santa Rosa (project #0012267.00) i Woodard & Curran, Inc.

Feasibility Analysis August 2023

TECHNICAL MEMORANDUM
TO: Colin Close
PREPARED BY: Jennifer Kidson, Martha de Maria y Campos
REVIEWED BY: Xavier Irias, Christy Kennedy, Katie Cole
DATE: August 31, 2023
RE: Santa Rosa Water Supply Alternatives Plan Feasibility Analysis Findings, Task 7

1. Purpose and Background ......................................................................................................................................................... 1

2. Study Parameters and Methods ............................................................................................................................................ 1

2.1 Collaborative Development of Study Parameters .................................................................................................. 1

2.2 Water Supply Goal .............................................................................................................................................................. 3

2.3 Water Supply Options ........................................................................................................................................................ 3

2.4 Evaluation Criteria and Metrics ...................................................................................................................................... 5

2.5 Screening Analysis ............................................................................................................................................................... 7

2.5.1 Screening Tool .............................................................................................................................................................. 8

2.5.2 Capital Cost Estimate Methodology ................................................................................................................. 10

2.5.3 Feasibility Scoring Methodology........................................................................................................................ 11

3. Findings ........................................................................................................................................................................................ 13

3.1 Water Supply Option Descriptions ............................................................................................................................ 13

3.1.1 Groundwater Supply Options .............................................................................................................................. 14

3.1.2 Purified Recycled Water Supply Options ........................................................................................................ 27

3.1.3 Non-Potable Recycled Water Option ............................................................................................................... 49

3.1.4 Desalinated Water Supply Options ................................................................................................................... 50

3.1.5 Stormwater Capture Options ............................................................................................................................... 57

3.1.6 Efficiency Programs ................................................................................................................................................. 62

3.2 Screening Analysis Results ............................................................................................................................................ 63

3.3 Feasibility Analysis Results ............................................................................................................................................ 66

3.3.1 Groundwater Options ............................................................................................................................................. 68

City of Santa Rosa (project #0012267.00) ii Woodard & Curran, Inc.

Feasibility Analysis August 2023

3.3.2 Purified Recycled Water Options ....................................................................................................................... 72

3.3.3 Stormwater Capture ................................................................................................................................................ 74

3.3.4 Efficiency Programs ................................................................................................................................................. 75

3.3.5 Cost Sensitivity Analysis ......................................................................................................................................... 76

4. Conclusions ................................................................................................................................................................................ 77

5. References ................................................................................................................................................................................... 79

LIST OF FIGURES
Figure ES-1-1: Cost-Effectiveness vs Max Yield (with Weighted Score) .................................................................. ES-6 Figure 2-1: Screening and Feasibility Analysis Process ......................................................................................................... 8 Figure 3-1: Existing City Wells ...................................................................................................................................................... 15 Figure 3-2: Supply Option GW-1 ................................................................................................................................................. 19 Figure 3-3: Supply Option GW-3 ................................................................................................................................................. 24 Figure 3-4: Regional System Facilities ....................................................................................................................................... 29 Figure 3-5: Average Recycled Water Use (2019-2022) ....................................................................................................... 30 Figure 3-6: Forms of Potable Reuse in California ................................................................................................................. 31 Figure 3-7: Supply Option PR-1 ................................................................................................................................................... 34 Figure 3-8: Supply Option PR-2 ................................................................................................................................................... 37 Figure 3-9: Supply Option PR-3a ................................................................................................................................................ 40 Figure 3-10: Supply Option PR-3c .............................................................................................................................................. 44 Figure 3-11: Supply Option PR-4 ................................................................................................................................................ 47 Figure 3-12: Supply Option DE-1 ................................................................................................................................................ 53 Figure 3-13: Supply Option DE-2 ................................................................................................................................................ 55 Figure 3-14: Supply Option SW-1 ............................................................................................................................................... 58 Figure 3-15: Cost-Effectiveness vs Max Yield (with Weighted Score) .......................................................................... 68 Figure 3-16: Supply Option Cost Performance with Varying Hydrology ($/AF) ....................................................... 76 Figure 3-17: Supply Option Cost Performance with Varying Sonoma Water Cutbacks ($M/yr) ....................... 77

City of Santa Rosa (project #0012267.00) iii Woodard & Curran, Inc.

Feasibility Analysis August 2023

LIST OF TABLES
Table ES-1: Water Supply Options.......................................................................................................................................... ES-2 Table ES-2: Screening Analysis Results Summary ............................................................................................................ ES-3 Table ES-3: Summary of Supply Option Scores................................................................................................................. ES-5 Table 2-1: Stakeholder and Community Outreach Meeting Summary........................................................................... 2 Table 2-2: Water Supply Options ................................................................................................................................................... 4 Table 2-3: Evaluation Criteria, Metrics, and Weights.............................................................................................................. 6 Table 2-4: Baseline Screening Analysis Parameters and Assumptions ........................................................................... 9 Table 2-5: Evaluation Criteria Scoring Rubric ......................................................................................................................... 12 Table 3-1: Summary of Water Supply Options ...................................................................................................................... 13 Table 3-2: Preliminary Capital Cost, Supply Option GW-1 ............................................................................................... 17 Table 3-3: Preliminary Annual O&M Cost, Supply Option GW-1 ................................................................................... 18 Table 3-4: Preliminary Capital Cost, Supply Option GW-2 ............................................................................................... 21 Table 3-5: Preliminary Annual O&M Cost, Supply Option GW-2 ................................................................................... 21 Table 3-6: Preliminary Capital Cost, Supply Option GW-3 ............................................................................................... 25 Table 3-7: Preliminary Annual O&M Cost, Supply Option GW-3 ................................................................................... 26 Table 3-8: Preliminary AWPF Flow Summaries ...................................................................................................................... 33 Table 3-9: Preliminary Capital Cost, Supply Option PR-1 .................................................................................................. 35 Table 3-10: Preliminary Annual O&M Cost, Supply Option PR-1 .................................................................................. 36 Table 3-11: Preliminary Capital Cost, Supply Option PR-2 ............................................................................................... 38 Table 3-12: Preliminary Annual O&M Cost, Supply Option PR-2 .................................................................................. 39 Table 3-13: Preliminary Capital Cost, Supply Option PR-3a ............................................................................................. 41 Table 3-14: Preliminary Annual O&M Cost, Supply Option PR-3a ................................................................................ 42 Table 3-15: Preliminary Capital Cost, Supply Option PR-3c ............................................................................................. 45 Table 3-16: Preliminary Annual O&M Cost, Supply Option PR-3c ................................................................................ 46 Table 3-17: Preliminary Capital Cost, Supply Option PR-4 ............................................................................................... 48 Table 3-18: Preliminary Annual O&M Cost, Supply Option PR-4 .................................................................................. 49 Table 3-19: Preliminary Capital Cost, Supply Option DE-1 ............................................................................................... 51 Table 3-20: Preliminary Annual O&M Cost, Supply Option DE-1 .................................................................................. 52 Table 3-21: Preliminary Capital Cost, Supply Option DE-2 ............................................................................................... 56 Table 3-22: Preliminary Annual O&M Cost, Supply Option DE-2 .................................................................................. 57 Table 3-23: Preliminary Capital Cost, Supply Option SW-1 .............................................................................................. 59 Table 3-24: Preliminary Annual O&M Cost, Supply Option SW-1 ................................................................................. 60 Table 3-25: Screening Analysis Results Summary ................................................................................................................ 64 Table 3-26: Summary of Supply Option Scores .................................................................................................................... 67 Table 3-27: Detailed Scoring for Option GW-1 ..................................................................................................................... 69 Table 3-28: Detailed Scoring for Option GW-2 ..................................................................................................................... 70 Table 3-29: Detailed Scoring for Option GW-3 ..................................................................................................................... 71 Table 3-30: Detailed Scoring for Option PR-2 ....................................................................................................................... 72 Table 3-31: Detailed Scoring for Option PR-4 ....................................................................................................................... 73 Table 3-32: Detailed Scoring for Option SW-1 ...................................................................................................................... 74 Table 3-33: Detailed Scoring for Option E-1 .......................................................................................................................... 75 Table 3-34: Distribution of Water Year Types in Hydrologic Scenarios ....................................................................... 76

City of Santa Rosa (project #0012267.00) iv Woodard & Curran, Inc.

Feasibility Analysis August 2023

ACRONYMS AND ABBREVIATIONS
AACEI Association for the Advancement of Cost Engineering International AF acre-foot
AFY acre-feet per year
AOP advanced oxidation process
ASR Aquifer Storage and Recovery
AWPF Advanced Water Purification Facility
BAF biological activated filtration
BPU Board of Public Utilities
City City of Santa Rosa
CII Commercial, industrial, institutional
DPR direct potable reuse
FAT full advanced treatment
gpf gallons per flush
gpm gallons per minute
GSP Groundwater Sustainability Plan
GWR groundwater recharge
IPR Indirect Potable Reuse
LTP Laguna Treatment Plant
MF microfiltration
MGD million gallons per day
O&M Operations and Maintenance
Regional System Santa Rosa Regional Water Reuse System
RO reverse osmosis
RWA raw water augmentation
SFR Single family residential
SWA surface water augmentation
TM Technical Memorandum
TWA treated water augmentation
UF Ultra filtration
UWMP Urban Water Management Plan
WSAP Water Supply Alternatives Plan

APPENDICES
Appendix A: Cost Details
Appendix B: Screening Tool Detail (Baseline Scenario)
Appendix C: Memorandum on Desalination Supply Options in the Water Supply Feasibility Analysis

City of Santa Rosa (project #0012267.00) ES-1 Woodard & Curran, Inc.

Feasibility Analysis August 2023

EXECUTIVE SUMMARY
Purpose and Background
The City of Santa Rosa (City) is in the process of preparing a Water Supply Alternatives Plan (WSAP).

Ultimately, the WSAP will provide a menu of water supply options and portfolios for the City to consider when planning future strategic investments and projects. The planning process for the WSAP includes engaging a broad base of stakeholders in establishing water supply goals, identifying potential conceptual-level water supply options, establishing evaluation criteria for these options, and conducting a feasibility analysis of the supply options. Participants include the Water Team (Deputy Directors and k ey staff), an external Stakeholder Group (leaders from a range of community organizations, resource agencies, environmental groups, and social service providers), the community at large through webinars and public meetings, and the Board of Public Utilities (BPU). This Technical Memorandum (TM) summarizes the results of the feasibility analysis.

Study Methods
The WSAP effort began by establishing water supply goals, supply options, and evaluation criteria, collectively referred to as the “study parameters.” City staff and other stakeholders participated directly in this process during late 2022 based on their input, and the study parameters were finalized in early 2023.

In brief, the study parameters include:
• Water Supply Goal: Diversify and increase city potable water supplies to reduce dependence on Sonoma Water, particularly during Russian River supply shortages during droughts or due to emergency disruption in delivery. Targets established in conjunction with the stakeholders were:
o Minimize impact of shortages due to droughts – be able to provide 30 percent of annual water demand with City supplies to mitigate droughts (about 7,500 acre-feet per year (AFY) capacity in 2045)
o Minimize impacts of disruption in Sonoma Water service – be able to provide 50 percent of normal indoor demand with City supplies for catastrophic events (about 9 million gallons per day (MGD) in 2045)
o Minimize impacts of peak demand – be able to provide 30 percent of peak month , average day demand from City supplies from late spring through early fall (about 9 MGD in 2045)
• Water Supply Options: Table ES-1, below, summarizes the 18 water supply options that were considered.
• The following evaluation criteria were selected and assigned relative weights:
o Cost-effectiveness and scalability (high weight). These two criteria were also used as screening criteria to determine which water supply options merited full feasibility analysis. This screening step was implemented as part of the study parameters in order to focus the feasibility analysis on the most promising water supply options. o Resiliency, equity, and environmental performance (high weight). o Legal, permitting, and regulatory; City control and interagency coordination; and multi- benefit (medium weight).

City of Santa Rosa (project #0012267.00) ES-2 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table ES-1: Water Supply Options
Supply Type Supply Option Name
Groundwater
GW-1: Construct Additional Groundwater Extraction Wells GW-2: Convert Emergency Wells to Production Wells
GW-3: Construct Aquifer Storage and Recovery (ASR) Wells GW-4: Construct Regional Groundwater Extraction Wells
GW-5: Construct Regional ASR Wells
Purified Recycled
Water
PR-1: Direct Potable Reuse (DPR) with Advanced Water Purification Facility (AWPF) at Laguna Treatment Plant (LTP)
PR-2: Satellite DPR with AWPF
PR-3a: Indirect Potable Reuse (IPR) with AWPF LTP into Groundwater Basin PR-3b: IPR with AWPF LTP into Lake Ralphine
PR-3c: IPR with AWPF at LTP into Lake Sonoma
PR-4: Regional DPR with AWPF at LTP
Recycled Water RW-1: Expand City’s Non-Potable Recycled Water System Desalination DE-1: Regional Brackish Desalination
DE-2: Ocean Desalination
Stormwater
SW-1: Stormwater Treatment and Storage in Aquifer
SW-2: Stormwater Storage in Lake Ralphine with Treatment SW-3: Regional Stormwater
Efficiency Programs E-1: Efficiency Programs
Acronyms:

AWPF – Advanced Water Purification Facility
ASR – Aquifer Storage and Recovery
DPR – Direct Potable Reuse
IPR – Indirect Potable Reuse
LTP – Laguna Treatment Plant
Screening Analysis
Following identification of the study parameters, a pre-screening analysis was conducted to narrow the list of 18 water supply options for screening. Five options were set aside, and 13 options were advanced to the screening step. Each of the water supply options was developed at a conceptual level to estimate potential water supply yield and costs. Cost estimates in this document are considered Class 5 per Association for the Advancement of Cost Engineering International (AACEI) guidelines, i.e., conceptual.

Actual project costs would be expected to fall within +50 percent to -15 percent of the cost estimate.

Based on the yield and costs, cost-effectiveness of each water supply option was evaluated under two general scenarios:
• Maximum production: This scenario assumed that each water supply option would be operated to maximize water supply and meet as much of the water supply goal as possible, regardless of whether shortages would be present requiring additional supply. • “Baseline” scenario: This scenario assumed that each water supply option would be operated in a way that minimized operational costs. This is a more realistic scenario than the “maximum production” scenario.

The results of the screening analysis are summarized in Table ES-2 below.

City of Santa Rosa (project #0012267.00) ES-3 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table ES-2: Screening Analysis Results Summary
Option
Maximum Yield Baseline Usage Carried forward
for full Feasibility
Analysis?
Acre-
Feet/Year
$/Acre-
Foot
Avg Acre-
Feet/Year
$/Acre-
Foot*
GW-1: Construct Additional Groundwater Extraction Wells 10,080 $700 6,734 $840 Yes GW-2: Convert Emergency Wells to Production Wells 2,462 $500 1,744 $540 Yes GW-3: Construct Aquifer Storage and Recovery (ASR) Wells 5,130 $900 3,634 $1,100 Yes PR-1: Direct Potable Reuse (DPR) with Advanced Water Purification Facility (AWPF) at Laguna Treatment Plant (LTP) 10,065 $2,000 4,131 $3,600 No PR-2: Satellite DPR with AWPF 10,065 $2,100 4,131 $3,900 Yes PR-3a: IPR with AWPF at LTP into Groundwater Basin 10,065 $2,500 4,131 $4,800 No PR-3c: IPR with AWPF at LTP into Lake Sonoma 10,065 $3,700 4,131 $6,400 No PR-4: Regional DPR with AWPF at LTP 10,065 $1,800 4,131 $3,200 Yes RW-1: Expand City’s Non-Potable Recycled Water System 3,000 $2,900 900 $9,800 No DE-1: Regional Brackish Desalination 10,080 $1,100 4,441 $2,000 No DE-2: Ocean Desalination 10,080 $2,600 4,441 $4,500 No
SW-1: Stormwater Storage in Aquifer 10,080 $1,400 2,618 $3,500 Yes E-1: Efficiency Programs 2,145 $2,800 2,145 $2,800 Yes
Notes:

The following options are not shown in the table as they were eliminated from further consideration prior to completing the detailed cost/yield analysis:

GW-4, GW-5, PR-3b, SW-2 and SW-3. All of the water supply options considered in this study are described in more detail in Section 3.1.

* Costs include capital and operating costs consistent with a realistic baseline usage scenario.

Acronyms:

AWPF - Advanced Water Purification Facility
ASR – Aquifer Storage and Recovery
DPR – Direct Potable Reuse
IPR – Indirect Potable Reuse
LTP – Laguna Treatment Plant

City of Santa Rosa (project #0012267.00) ES-4 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Feasibility Analysis
The water supply options that passed the screening analysis were then scored based on the evaluation criteria established with input from stakeholders, the BPU, the community, and City staff. A numeric score was assigned for each criterion using a 3-point scale from 0 to 2, with 2 being the most favorable. A score of zero implies that an option is not responsive to a criterion or performs relatively poorly compared to the other options, while a score of 2 implies that the option performs very well.

The raw scores were then weighted consistent with the relative importance of each criterion described earlier, e.g., cost and scalability were assigned very high weight, permitting ease medium weight, etc. The specific weights are as follows:
• Cost-effectiveness and scalability: 5x multiplier
• Resiliency, equity, and environmental performance: 3x multiplier • Legal, permitting, and regulatory; City control and interagency coordination; and multi -benefit: 1x multiplier
Table ES-3, below, table summarizes the results of the feasibility scoring:

City of Santa Rosa (project #0012267.00) ES-5 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table ES-3: Summary of Supply Option Scores
Criterion
Groundwater Purified Recycled Water Stormwater
E-1: Efficiency
Programs GW-1: Add
Extraction
Wells
GW-2: Convert
Emergency
Wells
GW-3: City
ASR Wells
PR-2: Satellite
DPR
PR-4:

Regional DPR
SW-1:

Stormwater
Storage in
Aquifer
Cost
effectiveness*
[$/AF]
2 [$840/AF]
2 [$540/AF]
2 [$1,100/AF]
0 [$3,900/AF]
0 [$3,200/AF]
0 [$3,500/AF]
1 [$2,800/AF]
Scalability
[Yield in AFY]
2 [5,880 - 10,080
AFY]
0 [1,436 - 2,462 AFY]
1 [2,993 - 5,130 AFY]
2 [3,019 - 10,065
AFY]
2 [3,019 - 10,065
AFY]
1 [1,008 - 10,080
AFY]
1 [2,145 AFY]
Resiliency 1 1 2 2 2 1 1
Equity 1 1 1 1 1 1 2
Environmental
performance 1 2 1 0 1 1 2
Legal, permitting,
and regulatory 1 2 0 0 0 1 2
City control and
interagency
coordination
2 2 1 2 0 2 2
Multi-benefit 0 0 1 0 0 2 1
Total Unweighted 10 10 9 7 6 9 12
Total Weighted 32 26 29 21 22 19 30
* Costs include capital and operating costs consistent with a realistic baseline usage scenario.

City of Santa Rosa (project #0012267.00) ES-6 Woodard & Curran, Inc.

Feasibility Analysis August 2023
As shown in Figure ES-1-1, most supply options did not score substantially differently from one another.

Figure ES-1-1: Cost-Effectiveness vs Max Yield (with Weighted Score)

Notes: Water Supply options:
• E-1: Efficiency Programs
• GW-1: Construct Additional Groundwater Extraction Wells • GW-2: Convert Emergency Wells to Production Wells
• GW-3: Construct Aquifer Storage and Recovery (ASR) Wells • PR-2: Satellite Direct Potable Reuse (DPR) with Advanced Water Purification Facility (AWPF) • PR-4: Regional DPR with AWPF at Laguna Treatment Plant • SW-1: Stormwater Storage in Aquifer
The feasibility analysis also assessed supply option performance under a range of future conditions beyond the baseline scenario. Performance of the options was examined under varying future hydrologic conditions, and varying Sonoma Water dry-year allocations were evaluated. In general, as future conditions become less favorable, a supplemental water supply is used more and becomes more cost - effective.

Conclusions
This Feasibility Analysis reveals several key considerations for the City as it conducts future water supply planning:

City of Santa Rosa (project #0012267.00) ES-7 Woodard & Curran, Inc.

Feasibility Analysis August 2023
This Feasibility Analysis reveals several key considerations for the City as it conducts future water supply planning:
• Future conditions: Depending on the City’s assumptions about future hydrology, Sonoma Water cutbacks, cost of Sonoma Water supplies, and customer demand/conservation, the City may reach different conclusions about the potential best fit water supplies. For example, if the C ity assumes a less conservative scenario (e.g., business as usual), the amount of new water needed may be relatively modest, in which case the City would be well served by bridging that gap with a small number of new wells, which could be added one by one as the need arises. On the other hand, if the City assumes a more conservative scenario in which existing water supplies decrease, a broader range of options could be considered, including options such as potable reuse that would be run continuously once implemented. Options that could be implemented in phases (e.g., rehabilitating one well at a time, rather than 3 at once) may help provide resiliency while minimizing capital outlay.
• Operational assumptions: Similar to future conditions, the City would need to consider its operational philosophy for a new supply source. If the City elects to operate a new supply on a 24/7 basis, this would reduce the cost per AF of water but could also increase total operational costs.
• Sensitivity: This analysis considered the impact of changing hydrology and reduced Sonoma Water dry-year allocations. The supply options generally become more cost-effective under more pessimistic scenarios (drier hydrology and higher Sonoma Water cutbacks) because more water is produced via the new options. However, the analysis indicates that the relative rankings of the supply options do not vary substantially with changes to the baseline condition.

The next step of the WSAP project will be to propose portfolio options (mixes of water supply options to achieve the goals) based on the findings in this TM. This will involve developing portfolio alternatives and analyzing them to further assess the water supply options that passed the screening analysis. The portfolio analysis may consider downscaled versions of some supply options and will consider potential groupings of supply options that would allow the City to optimize different areas such as resilie ncy, supply volume, cost, and consistency with the multiple goals.

City of Santa Rosa (project #0012267.00) 1 Woodard & Curran, Inc.

Feasibility Analysis August 2023

1. PURPOSE AND BACKGROUND
On August 10, 2022, the City of Santa Rosa (City) contracted with Woodard & Curran to prepare the City’s Water Supply Alternatives Plan (WSAP). Ultimately, the WSAP will provide a menu of water supply options and portfolios for the City to consider when planning future strategic investments and projects for increasing water supply resiliency and reliability.

The planning process for the WSAP includes establishing water supply goals, identifying potential conceptual-level water supply options, establishing evaluation criteria for these options, and conducting a feasibility analysis of the supply options. This Technical Memorandum (TM) summarizes the results of the feasibility analysis and supporting work.

To increase the City’s water supply resiliency and reliability during a drought year or interruption of the Russian River supply, supplemental water is needed. Water conservation and recycled water alone or combined would not generate sufﬁcient water to meet normal water needs through 2045 during a reasonable, worst-case drought event. This TM explores a number of supply options including expansion of existing groundwater supplies, groundwater banking/exchange projects, construction of new purified recycled water projects, construction of a new ocean desalination plant, participation in the development of a regional desalination plant, and stormwater capture along with additional efficiency programs. These options include both local and collaborative regional efforts that would require the City to partner with one or more local water agencies. Each supplemental supply component would provide different amounts of water. When combined with one another in various portfolios (mixes of water supplies) and various levels of water conservation and existing water supplies, new water supplies would help to meet projected normal water needs throughout the planning period.

2. STUDY PARAMETERS AND METHODS
The WSAP effort began by establishing water supply goals, supply options, and evaluation criteria, collectively referred to as the “study parameters.” The following subsections describe the development of the study parameters and list the final parameters which acted as the foundation for the feasibility study.

2.1 Collaborative Development of Study Parameters
The study parameters were established through a collaborative process with four groups of participants:
the City, stakeholders, the community, and BPU.

Table 2-1 summarizes the series of meetings held with four distinct groups to gather input on the study parameters. The first group, referred to as the Water Team, was composed of City staff from multiple divisions (e.g., water resources planning, wastewater treatment and water recycling, stormwater and environmental compliance, water efficiency, and water and sewer operations). The second group, referred to as the Stakeholder Group, included leaders of local interest organizations (e.g., environmental groups, community associations, social justice organizations, local business groups, agricultural interests , and resource agencies). The third group is referred to as “the community”. Community meetings were open to all and held virtually. Community meetings were advertised via social media, email, bill inserts, and postings on the City website. Lastly, the study parameters were reviewed by the City’s BPU, which provides oversight of and direction for the management and operation of the City’s water and wastewater facilities.

City of Santa Rosa (project #0012267.00) 2 Woodard & Curran, Inc.

Feasibility Analysis August 2023
The project team incorporated feedback from the Water Team, Stakeholder Group, the community, and the BPU into the study parameters, resulting in the final water supply goal, water supply options, and evaluation criteria and methodology. These study parameters guided the feasibility analysis.

Table 2-1: Stakeholder and Community Outreach Meeting Summary Meeting Date Topics
Water Team
Meeting #1
October
17, 2022
Project overview; introduction of study parameters (water supply goals, water supply options, evaluation criteria, and methodology); input on study parameters.

Community
Meeting #1
October
26, 2022
Overview of Santa Rosa water supplies; project background and overview; introduction of water supply goals, supply options, and evaluation criteria; polling questions, input on study parameters, and question and answer time.

Stakeholder Group
Meeting #1
November
16, 2022
Overview of Santa Rosa water supplies; project background and overview; high-level group discussion of study parameters, and input on study parameters.

Stakeholder Group
Meeting #2
December
14, 2022
Project update; group discussion of proposed study parameters, and input on the refined study parameters.

Water Team
Meeting #2
December
15, 2022
Proposed study parameters; input on final refinements of study parameters, and input on the refined study parameters.

Board of Public
Utilities study
session
January
19, 2023
BPU direction on proposed study parameters.

Community
Meeting #2
January
25, 2023
Project update; review of proposed study parameters; question and answer time.

Water Team
Meeting #3
May 17,
2023
Project update on options development and refinement, screening analysis; input on draft study results and portfolio approach.

Stakeholder Group
Meeting #3
May 24,
2023
Project update on options development and screening analysis; input on draft study results and portfolio approach.

Water Team
Meeting #4
July 6,
2023
Project update and input on feasibility analysis and draft portfolios.

Stakeholder Group
Meeting #4
July 18,
2023
Project update and input on feasibility analysis and draft portfolios.

Water Team
Meeting #5
August
14, 2023
Project update and input on early draft of plan.

Board of Public
Utilities study
session
August
17, 2023
BPU direction on feasibility analysis and draft portfolios.

City of Santa Rosa (project #0012267.00) 3 Woodard & Curran, Inc.

Feasibility Analysis August 2023

2.2 Water Supply Goal
The City’s water supply goal for the WSAP effort is as follows:

Diversify and increase city potable water supplies to reduce dependence on Sonoma Water, particularly during Sonoma Water supply shortages or disruption in delivery:
• Mitigating Droughts: Meet 30 percent of city’s water demand with city supplies to mitigate impacts of Russian River supply shortages (e.g., due to prolonged and/or severe drought).

This goal assumes strict limits on, or banning of, landscape irrigation in severe droughts. • Mitigating Natural Disasters and Catastrophic Events: Provide half of normal domestic/indoor demand for potable water with city supplies during Russian River supply disruption. Critical facilities would be prioritized for health and safety. Landscape irrigation would be prohibited.
• Mitigating Peak Day Demand: Meet 30 percent of peak month average day demand for potable water with city supplies.

Based on current City demand projections, the volume of water required to meet these goals in 2045 would be:
• 7,500 acre-feet per year (AFY) (30 percent of the City’s annual water demand) • 9 million gallons per day (MGD) (which equates to half of normal indoor demand, or 30 percent of peak month average day demand)
This TM assumes that potential water supply options would need to provide 7,500 AFY and 9 MGD of supply for the City, either individually or collectively. The water supply(ies) would generally be used in response to droughts or disruptive events, since in normal years the City’s supplies are adequate.

During the goal development process, the following rationale was cited for selecting the goal:
• Provides guidance to support decision making regarding magnitude of resiliency portfolio. • Increases city potable water supply resiliency and reduces demand on Sonoma Water supplies. • Mitigates shortages in Sonoma Water supply and interruptions in service. • Increases ability to meet a portion of peak day demand using local supply. • Could be achieved over time with a mix of supplies.
• Allows for adjustments to volume target if demands are lower/higher than anticipated (percentage-based goals).
• Integrates input from the Water Team, Stakeholder Group, and the community.

2.3 Water Supply Options
Based on review of existing information and discussions with the City’s Water Team, Stakeholder Group, community, and BPU, a list of water supply options was established, as summarized in Table 2-2.

Potential water supply options and facilities were identiﬁed based on the City’s exist ing facilities and planning efforts already underway. Sources of information included, but were not limited to, the following:
• City of Santa Rosa 2020 Urban Water Management Plan (UWMP) • City of Santa Rosa 2020 Water Master Plan Update
• City of Santa Rosa 2018 Regional Water Reuse System Master Plan

City of Santa Rosa (project #0012267.00) 4 Woodard & Curran, Inc.

Feasibility Analysis August 2023
• City of Santa Rosa Subregional Water Resources Recovery Facilities Master Plan • Groundwater Sustainability Plan (GSP) Santa Rosa Plain Groundwater Subbasin • City of Santa Rosa Groundwater Master Plan
• Recycled water agreements
• Desalination white papers
• Peer agency work from Sonoma Water, North Marin, and Marin Municipal on water supplies, as well as UWMPs
• Well test boring results
• City of Santa Rosa Water Use Efficiency water savings workbook • Recycled water pond storage capacities
• GIS Info: City parcels; stormwater, recycled water, wastewater, and water distribution facilities; well locations
The City’s rationale for the selected suite of water supply options is listed below. The list of options achieves the following:
• Retains a broad diversity of options.
• Includes City and Regional projects.
• Includes aggressive efficiency incentives to reduce demand over time. • Integrates input from Water Team, Stakeholder Group, and the Community.

Table 2-2: Water Supply Options
Supply Type Supply Option Name
Groundwater
GW-1: Construct Additional Groundwater Extraction Wells GW-2: Convert Emergency Wells to Production Wells
GW-3: Construct Aquifer Storage and Recovery (ASR) Wells GW-4: Construct Regional ASR Wells
GW-5: Construct Regional Groundwater Extraction Wells
Purified Recycled
Water
PR-1: Direct Potable Reuse (DPR) with Advanced Water Purification Facility (AWPF) at Laguna Treatment Plant (LTP)
PR-2: Satellite DPR with AWPF
PR-3a: Indirect Potable Reuse (IPR) with AWPF LTP into Groundwater Basin PR-3b: IPR with AWPF LTP into Lake Ralphine
PR-3c: IPR with AWPF at LTP into Lake Sonoma
PR-4: Regional DPR with AWPF at LTP
Recycled Water RW-1: Expand City’s Non-Potable Recycled Water System Desalination DE-1: Regional Brackish Desalination
DE-2: Ocean Desalination
Stormwater
SW-1: Stormwater Treatment and Storage in Aquifer
SW-2: Stormwater Storage in Lake Ralphine with Treatment SW-3: Regional Stormwater
Efficiency Programs E-1: Efficiency Programs
The water supply options then went through a screening analysis to focus the list of options to undergo detailed feasibility analysis. This process is described in Section 2.5. All of the supply options are described in further detail in Section 3.1.

City of Santa Rosa (project #0012267.00) 5 Woodard & Curran, Inc.

Feasibility Analysis August 2023

2.4 Evaluation Criteria and Metrics
To assess the feasibility of each water supply option, a list of evaluation criteria and associated metrics and weights were established. After beginning the WSAP process with a list of approximately 16 individual criteria, the list was consolidated and refined with stakeholder input to a focused list of evaluation criteria to be used in the feasibility analysis. The criteria and their descriptions are provided in Table 2-3.

City of Santa Rosa (project #0012267.00) 6 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 2-3: Evaluation Criteria, Metrics, and Weights
Criterion Description Proposed Metric Weight
Cost
effectiveness
Quantitative calculation of life-cycle costs,
based on future scenarios per the project
goals (e.g., five-year drought occurring on
average every 10 years).

Life cycle cost effectiveness
for key scenarios ($/acre-foot)
(quantitative)
High
Scalability
Qualitative assessment of ability to
provide sufficient supply to satisfy goals,
i.e., achieve desired level of service for
each scenario; secondarily, ability to scale
further to address future uncertainty.

Volume of water provided
(AFY/MGD) (quantitative)
Ability to meet goals, and
secondarily to increase
production later, without
undue effort/cost increase
(qualitative)
High
Resiliency
Qualitative assessment of performance in
the face of future uncertainty; for
example, future regulations, energy costs,
hydrology. The best options will suffer
only modest degradation of performance
if future conditions are worse than
anticipated while inferior options will
show marked degradation if planning
assumptions aren’t met.

Performance in the face of
uncertainty (qualitative) High
Equity
Qualitative assessment of any
disproportionate impacts on vulnerable
communities.

Level of disproportionate
impact on vulnerable
communities (qualitative)
High
Environmental
performance
Qualitative assessment of potential
environmental impacts not already
included in permitting/regulatory
compliance (e.g., level of GHG emissions).

Magnitude of potential impact
(qualitative) High
Legal,
permitting,
and regulatory
Qualitative assessment of
complexity/effort to address legal issues
(e.g., water rights), obtain necessary
permits, and comply with regulations
Level of complexity and effort
to address (qualitative) Medium
City control
and
interagency
coordination
Qualitative assessment of level of City
control and coordination with potential
partner agencies, if any (e.g., agreements
needed for regional projects).

Level of City control and
coordination with potential
partner agencies, if any
(qualitative)
Medium
Multi-benefit Qualitative assessment of benefits
provided in addition to water supply.

Benefits provided in addition
to water supply (qualitative) Medium

City of Santa Rosa (project #0012267.00) 7 Woodard & Curran, Inc.

Feasibility Analysis August 2023
The selected criteria achieve the following:
• Captures key considerations that differentiate projects. • Consolidates criteria where appropriate. (For example, individual criteria for construction and operations costs were consolidated into the overall cost-effectiveness metric.) • Removes criteria that would pose a fatal flaw if not met. (For example, water quality was removed from the list of criteria because a supply option that would not provide adequate water quality would not merit further analysis.)
• Removes criteria that did not need to stand alone. (For example, a criterion for “ability to integrate with existing distribution systems” was removed since facilities required to integrate into the existing system would be captured as part of a supply option and its costs.) • Integrates input from Water Team, Stakeholder Group, the community, and BPU.

Additionally, each criterion was assigned a metric and weight so the feasibility analysis could reflect City priorities about the relative importance of each criterion. Weights and metrics are summarized in Table 2-3. The evaluation metrics and weights achieve the following:
• Emphasizes key considerations such as cost, resiliency, and equity via weighting. • Enables comparisons based on qualitative factors such as permitting/regulatory considerations. • Provides enough detail for meaningful comparison, given level of available information. • Integrates input from Water Team, Stakeholder Group, BPU, and the community.

Based on Water Team, BPU, and Stakeholders Group input, all criteria included on the final list were weighted as “high” or “medium” because criteria of lower importance had been removed from the criteria list. The final list of evaluation criteria represents a focused list of key considerations.

As part of the detailed feasibility analysis, a detailed rubric was developed to allow water supply options to be scored against the qualitative criteria (described further in Section 2.5.3).

2.5 Screening Analysis
Prior to detailed analysis, all supply options were subjected to a high-level pre-screening to identify and remove options deemed infeasible or substantially similar to existing and anticipated reginal efforts or other supply options considered in the analysis to remove options deemed infeasible or substantially similar to existing or anticipated regional efforts. After pre-screening, a screening step was implemented to yield a focused and manageable “short list” of water supply options to undergo detailed analysis. Some options were removed from consideration prior to screening based on obvious flaws. The workflow is shown in Figure 2-1. Each water supply option listed in Table 2-2 was evaluated against two key criteria:
cost-effectiveness and scalability (yield). The screening analysis involved a high-level assessment of these two criteria in order to determine which supply options are most promising for the City and document the reasoning by which certain supply options should advance for further detailed analysis, or not. The screening process allowed the City to identify any non-starter options early on and focus the remaining analysis. The results of the screening analysis are described further in Section 3.2.

City of Santa Rosa (project #0012267.00) 8 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 2-1: Screening and Feasibility Analysis Process

2.5.1 Screening Tool
The screening analysis was accomplished with the aid of a spreadsheet model. The model was used to determine the conceptual performance of each supply option. Specifically, the model evaluated the volume of water that would be supplied under various hydrologic, regulatory, and operational scenarios, and determined the associated unit cost for each supply option based on its projected usage. The screening tool included a number of default assumptions and options, referred to as the baseline scenario, as summarized in Table 2-4. Each of these variables can be manipulated in the model to evaluate changing conditions (e.g., higher energy prices).

City of Santa Rosa (project #0012267.00) 9 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 2-4: Baseline Screening Analysis Parameters and Assumptions Parameter Default Value Source Notes
2045 demand 25,000 AFY Provided by City
Sonoma Water
nominal allotment 29,100 AFY
Provided by City. In dry years, allotment is subject to reduction based on a percent of baseline demand,
which is significantly lower than nominal allotment.

Current groundwater
firm capacity 1,300 AFY Provided by City
Discount rate 2.5%
Federal water resources planning discount rate for FY
2023. This rate is used to compute the present-day
equivalent cost of future cash flows.

Price of energy $200/megawatt
hour
Prevailing price in California (note that time of use
surcharges were not considered in this high-level
analysis)
First year of simulation 2045
Water supply goal. Assumes water supply is available
in 2045, at which point the model begins its 50-year
simulation.

Planning horizon 50 years Typical water infrastructure planning horizon Sonoma Water
reduction in dry years 30%
Provided by City. The dry-year Sonoma Water supply is
assumed to be 70% of baseline purchases, which in
turn are baseline demands less non-Sonoma supplies
including existing groundwater plus the water supply
option being modeled.

Demand reduction in
dry years 10% Provided by City
Hydrology Historical replay
(beginning in 1920)
United States Geological Survey Russian River
Historical Data
A final key model parameter was the assumed hydrologic scenario. The model uses hydrologic scenarios to determine the distribution of normal, dry, and wet years modeled, which in turn determine the volume of supplemental supply required over the planning horizon. The model included the following hydrological scenarios: historical hydrology with selectable starting year (total range from 1911 to 2013); a synthetic hydrology which assumes a greater proportion of dry years; and a synthetic hydrology which assumes a greater proportion of wet years. The synthetic hydrologies employ a blend of inter-year randomness and first-order autoregression to capture the tendency of dry years to appear in runs, and thus cause droughts. The goal of using synthetic hydrologies is not to predict future climate, but rather to evaluate the performance of various water supply options under a variety of potential futures.

City of Santa Rosa (project #0012267.00) 10 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Model inputs included the following for each water supply option (except for options that were screened out at the conceptual stage):
• Maximum and minimum supply option yields in normal, wet, and dry years in acre-feet per year (AFY).
• Marginal operation and maintenance cost in normal, wet, and dry years as dollars per acre-foot $/AF). These costs include energy costs as appropriate, and purchase cost of water for the ASR option (GW-3).
• Fixed operations and maintenance costs ($/year).
• Capital costs ($).
• Storage capacity included in the supply option as acre-feet (AF) • Leave-behind percentage (if applicable) (%).

The key model output is cost-effectiveness ($/AF) for a supply option under the chosen scenario. Cost- effectiveness is determined within a given model scenario and is based on actual volume used from the supply source. The cost-effectiveness accounts for the water year type, potential required water allocations (reductions from normal use during water shortages) from Sonoma Water, and demand reduction during dry years (whether imposed by the state, imposed by the City, or done voluntarily) , assumed demand, supply from existing wells, and any storage associated with the water supply option.

The cost tables in Section 3.1 include the cost-effectiveness of each water supply option under the baseline scenario.

In addition, by varying the model parameters such as hydrology and demand reduction percent, the cost- sensitivity of each supply option could be evaluated under a range of conditions.

2.5.2 Capital Cost Estimate Methodology
A key component of the screening analysis included compiling cost estimates for each supply option on the initial list. The high-level cost estimates presented in this TM were developed from bid tabulations, information obtained from previous studies, and experience on other projects. Life cycle costs presented in this TM include planning level construction costs and operations and maintenance (O&M) costs. The Association for the Advancement of Cost Engineering International (AACEI) developed metrics to classify estimating accuracy through project development. The cost estimates presented in this document are considered Class 5 for a planning-level feasibility study estimate. Based on AACEI guidelines, actual project costs are typically within +50 percent to -15 percent of the planning-level cost estimate. However, there could be additional uncertainty not modeled in the initial estimates. Project feasibility and funding should consider the inherent level of uncertainty associated with planning level cost estimates.

Each planning level cost estimate includes an estimating contingency of 50 percent. Implementation costs were estimated at 40 percent for legal and administration, engineering design, engineering services during construction and construction management. The annual O&M cost estimate includes electricity, labor and maintenance costs.

Project costs were calculated in 2023 dollars using the January 2023 Construction Cost Index for San Francisco, 15498.78. Annual Project costs are amortized using a 2.5 percent interest rate over a 50-year period.

City of Santa Rosa (project #0012267.00) 11 Woodard & Curran, Inc.

Feasibility Analysis August 2023

2.5.3 Feasibility Scoring Methodology
Upon completion of the screening analysis, Woodard & Curran completed the feasibility analysis by evaluating and scoring the short-listed water supply options. This step of the analysis built upon the evaluation criteria established during development of the study parameters (Table 2-3). The evaluation process included developing criteria for the projects, adding numerical weights to each criterion, and scoring the projects against each criterion. The numerical system provides a score of zero through 2, with 2 being most favorable. A score of zero implies that an option is not responsive to a criterion or performs relatively poorly compared to the other options, while a score of 2 implies that the option performs very well. Applying a weight allows the ranking to better reflect the priorities of the City and its stakeholders, showing the relative importance of each criterion. The evaluation criteria scoring rubric used for the evaluation of the short-listed supplemental supply options is summarized in Table 2-5.

City of Santa Rosa (project #0012267.00) 12 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 2-5: Evaluation Criteria Scoring Rubric
Criterion Proposed Evaluation Metric Quantitative Score Qualitative Score: 0 Qualitative Score: 1 Qualitative Score: 2 Weight Score Multiplier Cost
effectiveness
Quantitative calculation of life-cycle costs,
based on the baseline scenario per the
project goals (e.g., five-year drought
occurring on average every 10 years).
$/AF >$3,000/AF under baseline scenario
Between $2,000/AF and $3,000/AF
under baseline scenario < $2,000/AF under baseline scenario High + Screening Criterion 5 Scalability
Qualitative assessment of ability to provide
sufficient supply to satisfy goals, i.e., achieve
desired level of service for each scenario;
secondarily, ability to scale further to address
future uncertainty.

Yield (AFY)
Low flexibility: No ability, or
minimal ability, to scale down
production when supply is not
needed.

Moderate flexibility: Some ability to
scale production up or down
depending on need for supply but
would require significant effort or
construction of new facility phases.

High flexibility: Production can be
easily scaled up or down depending
on need without significant
investment.

High + Screening Criterion 5
Resiliency
Qualitative assessment of performance in the
face of future uncertainty; for example, future
regulations, energy costs, hydrology. The best
options will suffer only modest degradation
of performance if future conditions are worse
than anticipated while inferior options will
show marked degradation if planning
assumptions aren’t met.

Change in costs due
to energy prices and
hydrology scenarios
can be accounted for
quantitatively. These
would feed into the
qualitative scores.

Substantial change in cost-
effectiveness under changing
energy and hydrology conditions.

Moderate change in cost-effectiveness
under changing energy and hydrology
conditions.

Little or no change in cost-
effectiveness under changing
energy and hydrology conditions.

High 3
Equity
Qualitative assessment of any
disproportionate impacts on vulnerable
communities.

N/A
Would have the potential for a
disproportionate impact (such as
providing different water supply
sources to certain parts of City).

Would have no impact on vulnerable
communities.

Would have a benefit to vulnerable
communities. High 3
Environmental
performance
Qualitative assessment of potential
environmental impacts not already included
in permitting/regulatory compliance (e.g.,
level of GHG emissions).

N/A
Unknown or high potential for
environmental impacts (e.g., large
project footprint, high energy use,
or location in undeveloped area).

Moderate potential for environmental
impacts (e.g., medium or unknown
project footprint, moderate energy use,
unknown project location).

Limited potential for environmental
impacts (e.g., small project footprint,
low energy use, location in existing
developed area).

High 3
Legal,
permitting, and
regulatory
Qualitative assessment of complexity/effort
to address legal issues (e.g., water rights),
obtain necessary permits, and comply with
regulations
N/A
High complexity/effort: Requires
major permitting/ regulatory effort,
with little or no established
precedent to follow.

Moderate complexity/effort: May have
major permitting/ regulatory effort
permits, etc., but there is an
established process to follow.

Low complexity/effort: Permitting/
regulatory steps are known, and
projects of this type are routinely
implemented.

Med 1
City control and
interagency
coordination
Qualitative assessment of level of City control
and coordination with potential partner
agencies, if any (e.g., agreements needed for
regional projects).

N/A
Coordination required with partner
agencies that City does not already
work with.

Coordination required with partner
agencies that City already works with.

Two or more additional benefits
would be provided by the project. Med 1

City of Santa Rosa (project #0012267.00) 13 Woodard & Curran, Inc.

Feasibility Analysis August 2023

3. FINDINGS

3.1 Water Supply Option Descriptions
This section describes each of the evaluated supplemental supply options, listed in Table 3-1. The options remained substantially the same as those listed in Table 2-2, with a numbering system applied and some revisions to the option titles. The preliminary level concepts were developed closely with the Water Team, as well as with input from the Stakeholder Group, BPU, and the community. Preliminary-level cost estimates are also summarized in the following subsections, where applicable. Additionally, the results of the screening tool’s baseline scenario average cost of water are presented in the following subsections. A summary of the results is provided in Section 3-2 Screening Analysis Results (see Table 3-35).

Table 3-1: Summary of Water Supply Options
Supply Type Supply Option Name
Groundwater
GW-1: Construct Additional Groundwater Extraction Wells GW-2: Convert Emergency Wells to Production Wells
GW-3: Construct ASR Wells
GW-4: Construct Regional Groundwater Extraction Wells
GW-5: Construct Regional ASR Wells
Purified Recycled Water
PR-1: DPR Advanced Water Purification Facility (AWPF) at LTP PR-2: Satellite DPR AWPF
PR-3a: IPR AWPF at LTP into Groundwater Basin
PR-3b: IPR AWPF at LTP into Lake Ralphine
PR-3c: IPR AWPF at LTP into Lake Sonoma
PR-4: Regional DPR AWPF at LTP
Recycled Water RW-1: Expand City’s Non-Potable Recycled Water System Desalination
DE-1: Regional Brackish Desalination
DE-2: Ocean Desalination
Stormwater
SW-1: Stormwater Storage in Aquifer
SW-2: Stormwater Storage in Lake Ralphine
SW-3: Regional Stormwater
Efficiency Programs E-1: Efficiency Programs
Baseline No Project Option, Continue to Import from Sonoma Water

City of Santa Rosa (project #0012267.00) 14 Woodard & Curran, Inc.

Feasibility Analysis August 2023

3.1.1 Groundwater Supply Options
The City has a total of six municipal groundwater wells, all within the Santa Rosa Plain Subbasin.1 These wells are shown in Figure 3-1.

Two of the City’s municipal wells (Carley and Peter Springs Wells) are currently operated primarily to serve an adjacent park and school for landscape irrigation but are also available and approved by the California Division of Drinking Water for emergency potable use on standby status. Two of the wells (Farmers Lane Wells No. W4-1 and W4-2) are on active status. One well is operated to provide landscape irrigation water supply only (Farmers Lane Well No. W4-3), and one well is used for emergency potable purposes only (Leete Well). In addition, a new emergency water supply well facility is currently being built at A Place to Play Park, with anticipated completion in calendar year 2023.

For all groundwater supply options developed, it is assumed that groundwater pumping would occur seasonally in the spring and summer months. In dry years, it is assumed that pumping would occur for a greater portion of the year.

1 Note that the City has two other municipal wells that are either out of service or inactive: Freeway Well (W3) is out of service due to groundwater contamination caused by others; Sharon Park Well (W6) is inactive due to severe sanding.

City of Santa Rosa (project #0012267.00) 15 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-1: Existing City Wells

City of Santa Rosa (project #0012267.00) 16 Woodard & Curran, Inc.

Feasibility Analysis August 2023
GW-1: Local Groundwater Extraction Wells
Supply option GW-1 proposes to construct additional production wells, wellhead disinfection, and iron and manganese treatment (if necessary) to connect to the City’s existing potable water distribution system. Based on existing well data for the City, an estimated 9 wells would be required to provide 7,500 AFY (i.e., to meet the City’s water supply goal 30 percent of the annual water demand), and 12 wells would be required to meet 30 percent of the peak month average day demand (9 MGD), based on a per- well capacity of ~500 gpm.1
For this conceptual-level analysis, the following potential limiting factors for the GW-1 supply option were identified:
• Identification of appropriate locations for new we lls. For this preliminary analysis, City -owned property was assumed as the location of the new groundwater extraction wells . For this preliminary analysis a 500-foot well depth was assumed. The City has both deep and medium deep wells in the vicinity.
• Well pumping capacity. For this preliminary analysis, well capacity was assumed to be 500 gpm. • Potential well interference . The proposed wells are assumed to be constructed with even spacing to avoid potential well interference.
• Sustainability. The City's wells generally have very stable non-pumping groundwater levels, with artesian conditions reported for Farmers 1, 2 , and Leete wells. However, additional studies would be needed to verify sustainable yields.

The 12 proposed extraction wells are assumed to be located within the City’s Greenway Area, north of Hoen Avenue. Figure 3-2 shows the proposed extraction well location zone and conveyance pipelines connecting to the Sonoma Water Aqueduct for distribution throughout the City’s R6R1 pressure zone. The 12 extraction wells would be constructed to be evenly spaced within the Greenway Area. Approximately 3,000 linear feet (LF) of 20-inch pipe and a 240 horsepower (hp) pump station would be required to convey the extracted groundwater to the Sonoma Water aqueduct for distribution. This conceptual option assumes the 12 wells to be connected to each other and one 20-inch water main connecting from the well zone to the City’s distribution system via Sonoma Water’s aqueduct as shown. Based on discussions with City staff, pumping into the aqueduct would not currently be an option; this configuration would require engaging in negotiations with Sonoma Water in the future.

The proposed infrastructure as part of GW-1 supply option may include:
• Well equipment including well head, pump, well house building for 12 wells • Conveyance pipelines
• Electrical service for each well
• Treatment systems for disinfection, manganese and iron onsite, if needed • Backup generator for power outage

1 For simplicity, this analysis assumes construction of 12 new wells. Other possible approaches could include converting emergency wells to production, in combination with new wells, to meet the 9 MGD goal, if GW-2 is not pursued. The City also has Freeway Well and Sharon Park Well, but they don’t appear feasible at this time due to site and water quality constraints.

City of Santa Rosa (project #0012267.00) 17 Woodard & Curran, Inc.

Feasibility Analysis August 2023
• Backwashing treatment system (assumes disposal to nearby sanitary sewer) The total preliminary capital cost for option GW-1, including all infrastructure listed, is approximately $96 million. A summary of the GW-1 capital cost is shown in Table 3-2. Additional cost detail can be found in Appendix A.

Table 3-2: Preliminary Capital Cost, Supply Option GW-1 Component Description Cost, in 2023
Dollars
New Well Construction
12 extraction wells, ~500 gpm capacity, 500 feet
deep, includes well head, casing, well pump and
equipment, electrical service, disinfection, backup
generator, well housing ($3.5 million per well)
$42,000,000
Groundwater Conveyance
Line 20-inch diameter; 3,000 linear feet linear feet $2,225,000 Groundwater Pump Station 240 horsepower $1,560,000
Potable System Connection $100,000
Estimating Contingency 50% of raw construction costs $22,950,000 Implementation 40% of total construction costs $27,540,000 Total Capital Cost $96,380,000
Annualized Capital Cost Annualized over 50 years, 2.5% interest $3,398,000 The O&M cost of the project was estimated on a per AF basis for scalability. The GW -1 option has a fixed annual O&M cost of $500,000 and an annual marginal O&M cost of approximately $264/ AF. Annual O&M costs will vary depending on the production of the extraction wells. The estimated annual O&M costs for the maximum potential yield of 10,080 AFY is approximately $3 million. Table 3-3 summarizes the annual O&M costs for option GW-1. Under the Baseline Scenario, as modeled by the screening tool, actual production would be less, resulting in a somewhat higher cost per AF. Constructing fewer wells would reduce the cost per AF under the Baseline Scenario but would not necessarily meet the 9 MGD goal.

City of Santa Rosa (project #0012267.00) 18 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-3: Preliminary Annual O&M Cost, Supply Option GW-1 Component Description Cost, $2023
Marginal Cost Marginal costs include power consumption, labor, chemical addition, water/sewer fees $264/ AF
Fixed Cost
Fixed costs include routine maintenance practices, water quality testing, Santa Rosa Plain Groundwater
Sustainability Agency fees
$501,000
Average cost of water (Baseline Scenario)1 $843/ AF
Annual O&M (10,080 AFY)2 $3,165,000
Cost of water (10,080 AFY)2 $700/ AF
Notes:

1. See Section 2.5 for description of baseline scenario, in which 6,734 AFY are used. That baseline is based on operating wells at least from April through October in all years, i.e., at a minimum of 7/12 of full capacity, and more as needed in dry years. The cited costs include capital and operating costs for the baseline usage scenario.

2. The maximum supply yield of 10,080 AFY assumes 24/7 operation of all supply option infrastructure. While this scenario does not reflect realistic operations because it would produce more water than the City would use, and because it does not reflect downtime for maintenance. The baseline scenario is more informative as to likely unit costs.

City of Santa Rosa (project #0012267.00) 19 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-2: Supply Option GW-1

City of Santa Rosa (project #0012267.00) 20 Woodard & Curran, Inc.

Feasibility Analysis August 2023
GW-2: Convert Existing Emergency Wells into Production Wells Supply option GW-2 proposes to rehabilitate the City’s three existing emergency wells into production wells. The three emergency wells for the City include the Leete Well, Carley Well, and Peter Springs Well, as shown in Figure 3-1.1 The Leete Well is currently out of service due to concerns over a possible casing separation, rehabilitation is currently in design. The Carley and Peter Springs wells have the capacity to provide the City with approximately 1 MGD of groundwater capacity on a stand-by-emergency basis.

For this conceptual-level analysis, the following potential limiting factors for the GW-2 supply option were identified:
• Well pumping capacity: Leete, Peter Springs, and Carley standby/emergency supply wells have a pumping capacity of 240, 500 and 700 gpm, respectively. The GW-2 option will provide up to 2,462 AFY of additional supply.
• Technical studies to verify that long-term use of the wells would be sustainable. • Permitting considerations to allow for water supply from the Leete, Peter Springs , and Carley wells.

The proposed infrastructure rehabilitation and upgrades as part of GW-2 supply option may include:
• Rehabilitation of the three emergency wells, using mechanical and chemical methods • Redevelopment of the wells
• Well house improvements for the w ells, including a pump and motor, a pre -packaged disinfection system with eyewash, and a SCADA connection • Site improvements including electrical, plumbing, and mechanical • Instrumentation and control
The total preliminary capital cost for option GW-2, including the improvements listed, is approximately $11.6 million. A summary of the GW-2 capital cost is shown in Table 3-4. Additional cost details can be found in Appendix A.

1 For simplicity, this analysis assumes rehabilitation of the three existing emergency supply wells. Other possible approaches could include rehabilitating existing inactive wells to production status (such as Freeway Well and Sharon Park Well), in combination with rehabilitation of the existing emergency wells, to provide additional supply. However at this time, Freeway Well and Sharon Park Well do not appear feasible due to water quality concerns.

City of Santa Rosa (project #0012267.00) 21 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-4: Preliminary Capital Cost, Supply Option GW-2 Component Description Cost, $2023
Well Rehabilitation and
Upgrades
Rehabilitation and redevelopment of the three-
emergency stand-by wells, well house
improvements, instrumentation and control
$5,520,000
Estimating Contingency 50% of raw construction costs $2,760,000 Implementation 40% of total construction costs $3,310,000 Total Capital Cost $11,590,000
Annualized Capital Cost Annualized over 50 years, 2.5% interest $409,000 The O&M cost of the project was estimated on a per AF basis for scalability. The GW -2 option has a fixed annual O&M cost of $123,000 and an annual marginal O&M cost of approximately $236/ AF. Annual O&M costs will vary depending on the production of the converted wells. The estimated annual O&M costs for the maximum potential yield of 2,462 AFY is approximately $705,000. Table 3-5 summarizes the annual O&M costs for option GW-2. Under the Baseline Scenario, as modeled by the screening tool, actual production would be less than 2,462 AFY, resulting in a greater cost per AF.

Table 3-5: Preliminary Annual O&M Cost, Supply Option GW-2 Component Description Cost, $2023
Marginal Cost Marginal costs include power consumption, labor, chemical addition, water/sewer fees $236/ AF
Fixed Cost
Fixed costs include routine maintenance practices,
water quality testing, Santa Rosa Plain Groundwater
Sustainability Agency fees
$123,000
Average cost of water (Baseline Scenario)1 $540/ AF
Annual O&M (2,462 AFY)2 $705,000
Cost of water (2,462 AFY)2 $452/ AF
Notes:

1. See Section 2.5 for description of baseline scenario, under which 1,744 AFY are used. That baseline is based on operating wells at least from April through October in all years, i.e., at a minimum of 7/12 of full capacity, and more in dry years as needed. Costs for the baseline scenario include capital and operating costs.

2. The maximum supply yield of 2,462 AFY assumes 24/7 operation of all supply option infrastructure. This scenario may not reflect realistic operations.

GW-3: Local Aquifer Storage and Recovery (ASR) Wells
An additional groundwater supply option is GW-3, which proposes to inject water directly into the groundwater aquifer for later recovery and use. Water is typically injected during wet periods when there is supply available (e.g., potable water) and extracted during dry periods and/or during peak demands

City of Santa Rosa (project #0012267.00) 22 Woodard & Curran, Inc.

Feasibility Analysis August 2023
when additional supplies are needed. GW-3 could include injecting excess potable supplies when available into the groundwater basin.

ASR offers advantages as a method to increase water supply for drought mitigation. Due to the underground storage nature of ASR projects, this supply is more resilient than other alternative storage methods such as surface recharge or storage, which experience water losses due to evaporation. A phased approach can be followed to develop a pilot ASR project to understand local conditions and ensure there are no “fatal flaws” before a full-scale ASR implementation. The number of wells to meet the demand would vary depending on well capacities, for this conceptual-level analysis, a 500 gpm capacity and 500 feet well depth was assumed.

For this conceptual-level analysis, the following potential limiting factors for the GW-3 supply option were identified:
• Appropriate site selection for ASR wells; right-of-way issues. • Hydrogeologic constraints with aquifer potential for injection, storage, and extraction of water.
o Well capacities range 400-1,000 gpm or greater. Assumed 500 gpm for this level of analysis based on existing City well information.
o Well depths range from 300-1,000 feet. Assumed 500 feet for this level of analysis based on existing City well information. (Note that actual well depth could be deeper depending on hydrogeologic conditions; for reference, Sonoma Water wells range from about 800 to 1,000 feet deep (Sonoma Water, n.d.)). • Source of water for injection
• Chemical properties of source water versus native groundwater and potential reactions due to mixing
• Retention time or storage capacity of aquifer prior to injection • Regulatory constraints and compliance with environmental requirements with injection of water into groundwater
• Pre-treatment of water prior to injection for storage to meet regulatory requirements • Disinfection and potential treatment prior to distribution (high concentrations of iron and manganese were noted in this area)
• Extensive monitoring of water levels and quality and reporting Preliminary review of Airborne Electromagnetic survey data available from the Department of Water Resources (DWR) shows potential target areas along the western boundary of the subbasin that appear promising for ASR (California Department of Water Resources, 2022). Figure 3-3 below shows potential ASR well areas within the City’s boundary. Additional areas would be considered as well, if this option is chosen for further development.

In the Santa Rosa Plain Subbasin, groundwater generally flows westward from recharge areas in the mountains into the west side of the subbasin. The shallow aquifer generally extends from the water table to depths ranging from 150 feet to 200 feet below land surface (Santa Rosa Plain Groundwater Sustainability Agency, 2021). Elevations in the deeper zone aquifers are approximately 10 to 40 feet lower than groundwater elevations in the shallow aquifer system in the Subbasin (Santa Rosa Plain Groundwater Sustainability Agency, 2021). The shallow aquifer is present over the entire extent of the subbasin and generally present under unconfined or semiconfined conditions. Shallow wells in this area (with depths

City of Santa Rosa (project #0012267.00) 23 Woodard & Curran, Inc.

Feasibility Analysis August 2023
ranging from 90 to 167 ft below land surface) do not show enough injection capacity with groundwater levels being close to the land surface.

For the concept-level analysis for this feasibility analysis, the proposed six ASR wells were assumed to be constructed within the intermediate/deep aquifer (although the City could elect to include both shallow and deep ASR wells in order to minimize mounding of groundwater levels in areas with lower storage coefficients). The deep aquifer occurs under confined or semiconfined conditions with groundwater levels generally 20 feet lower in this area compared to the shallow aquifer system. The proposed well area is also home to existing dedicated shallow monitoring wells (three wells SRP0713, SRP0355, and SRP0357) and deep monitoring wells (SRP0347, SRP0359, and SRP0725) established as part of the Santa Rosa Plain GSP.

These existing wells can be used for future monitoring of local conditions in support of future ASR implementation for sustainable management of the basin. Wells in this area are generally completed in the Wilson Grove Formation (formerly known as the Merced Formation). The Wilson Grove Formation is a sand-dominated formation exposed in the western Santa Rosa Plain Subbasin. Further hydrogeologic investigations would be needed to confirm local conditions.

The potential ASR and conveyance infrastructure required for GW-3 would be:
• Well equipment including well head, pump, and well house building for six ASR wells • Conveyance pipelines
• Electrical service for each well
• Treatment systems for disinfection and if needed for manganese and iron • Backup generator for power outage
• Backwashing treatment system (assumes disposal to nearby sanitary sewer) • Dechlorination prior to injection

City of Santa Rosa (project #0012267.00) 24 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-3: Supply Option GW-3

City of Santa Rosa (project #0012267.00) 25 Woodard & Curran, Inc.

Feasibility Analysis August 2023
The total preliminary capital cost for option GW-3, including the improvements listed, is approximately $81 million. A summary of the GW-3 capital cost is shown in Table 3-6. Additional cost details can be found in Appendix A.

Table 3-6: Preliminary Capital Cost, Supply Option GW-3 Component Description Cost, $2023
ASR Well Construction
Six ASR (injection/extraction) wells, 500 feet
deep, well head, casing, well pump and
equipment ($5 million/ well)
$30,000,000
Groundwater Conveyance Line 16-inch diameter; 12,000 linear feet $7,120,000 Groundwater Pump Station 210 horsepower $1,365,000
Potable system connection $100,000
Estimating Contingency 50% of raw construction costs $19,300,000 Implementation 40% of total construction costs $23,160,000 Total Capital Cost $81,050,000
Annualized Capital Cost Annualized over 50 years, 2.5% interest $2,858,000

The O&M cost of the project was estimated on a per AF basis for scalability. The GW -3 option has a fixed annual O&M cost of $121,000 and an annual marginal O&M cost of approximately $1,813, which includes the cost to purchase water from Sonoma Water for injection. Annual O&M costs will vary depending on the production of the ASR wells. The estimated annual O&M costs for the maximum potential yield of 5,130 AFY is approximately $9.42 million. Table 3-7 summarizes the annual O&M costs for option GW-3.

Under the Baseline Scenario, as modeled by the screening tool, actual production would be less than 5,130 AFY, resulting in a greater cost per AF. Installing fewer ASR wells would reduce the cost per AF under the Baseline Scenario.

City of Santa Rosa (project #0012267.00) 26 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-7: Preliminary Annual O&M Cost, Supply Option GW-3 Component Description Cost, $2023
Marginal Cost
Marginal costs include power consumption, labor,
chemical addition, water/sewer fees, purchase of
water for injection.
$1,813/ AF
Fixed Cost
Fixed costs include routine maintenance practices,
water quality testing, Santa Rosa Plain Groundwater
Sustainability Agency fees
$121,000
Average cost of water (Baseline Scenario)1 $2,600/ AF
Annual O&M (5,130 AFY)2 $9,420,000
Cost of water (5,130 AFY)2 $2,400/ AF
Notes:

1. See Section 2.5 for description of baseline scenario, under which on average 3,634 AFY would be used. That baseline is based on operating wells at least from April through October in all years, i.e., at a minimum of 7/12 of full capacity, and more in dry years as needed. Cited costs include operating and capital.

2. The maximum supply yield of 5,130 AFY assumes 24/7 operation of all supply option infrastructure. This scenario may not reflect realistic operations. Cited costs include operating and capital.

GW-4: Regional Groundwater Extraction Wells
Option GW-4 consists of constructing new production wells outside the City limits (in neighboring jurisdictions) where the geology may allow for greater well yields than within the City. Provided that the wells are located in or near another Sonoma Water contractor agency’s jurisdiction, a paper exchange could be completed where the City takes a portion of the partner’s Sonoma Water allocation, and the pumped groundwater is used directly by the partner. The paper exchange option would not reduce regional reliance on the Sonoma Water system overall.

Implementation of option GW-4 would require identification of possible well locations, connections to existing distribution systems, regional coordination and agreements, and possible need for regulatory approvals. Components that would need to be constructed could include:
• Well equipping including well head, pump, well house building and equipment • Conveyance pipelines
• Electrical service for each well
• Treatment systems for manganese and iron onsite, if needed • Backup generator for power outage
• Backwashing treatment system (assumes disposal to nearby sanitary sewer) This option assumes that the potential partner would need to be a Sonoma Water contractor who receives sufficient Sonoma Water contract supplies to make them open to a partial trade with Santa Rosa. Based on historical Sonoma Water deliveries, potential candidates could be Petaluma, North Marin Water District, Rohnert Park, and possibly City of Sonoma or Valley of the Moon Water District. This option also assumes that the City would find a partner for whom well yields of 1,000 gpm or more could be achieved, in order to provide a benefit over existing pumping rates of City wells. Based on an initial review of

City of Santa Rosa (project #0012267.00) 27 Woodard & Curran, Inc.

Feasibility Analysis August 2023
information from Urban Water Management Plans of potential partners and DWR Bulletin 118, the Sonoma Valley Subbasin may provide enough yield to meet this threshold. The City of Sonoma and Valley of the Moon Water District are located within the Sonoma Valley Subbasin. Each of these agencies typically receives around 2,000 AFY or less from Sonoma Water. Based on these figures, it is assumed that 3,000 AFY at most would be available for trading, which would provide a portion of the City’s water supply goal of 7,500 AFY.

Were such a project to be implemented, it is assumed that in wet years with sufficient Sonoma Water allocations, no groundwater pumping would occur. In normal years, pumping would occur in summer months, and in dry years, pumping would occur for a greater portion of the year. According to the Sonoma Valley Basin GSP, groundwater levels in the subbasin are generally stable but have some persistent pumping depressions, and groundwater in storage declined by about 900 AFY during 2012- 2018. Therefore, it is assumed that any increase in groundwater extraction in Sonoma Valley would need to be offset by some form of recharge, and without recharge the project may not be compatible with groundwater management practices. Adding a recharge component to this supply option would likely yield a project similar to the Regional Aquifer Storage and Recovery option described in GW-5. Therefore, this supply option was not carried forward for detailed cost analysis or feasibility scoring.

GW-5: Regional Aquifer Storage and Recovery
Supply option GW-5 proposes developing a regional ASR project in collaboration with one or more agencies in the region and using Sonoma Water supplies and ASR water conjunctively. ASR wells can be constructed in the aquifer most feasible and promising in the region. Potential options would include: 1) the City connecting to ASR wells directly, and 2) the City utilizing participating agencies’ surface water supplies from Sonoma Water while partnering agencies pump from ASR wells by the same amount in lieu of taking Sonoma Water supply.

Implementation of this supply option would require identification of feasible ASR well locations, connections to existing distribution systems, regional coordination and agreements, and possible need for additional water rights.

Overall, a regional ASR project would include similar components as a local ASR project. In addition, the City would be part of future regional ASR projects implemented by Sonoma Water (and possibly by the GSA) by default. For example, Sonoma Water has been in the process of evaluating feasibility of ASR in the Sonoma Valley Subbasin, including a pilot test in 2018 (Santa Rosa Plain Groundwater Sustainability Agency, 2021). Because many project elements and implementation considerations for regional ASR would be similar to the local ASR option above (GW-3), and because the City would effectively be participating in possible future ASR projects implemented by Sonoma Water, this option did not undergo any further separate technical analysis.

3.1.2 Purified Recycled Water Supply Options
The City operates the LTP for the Santa Rosa Regional Water Reuse System (Regional System). Figure 3-4 depicts the location of the wastewater treatment facilities and the Regional System key facilities. LTP is a tertiary level treatment facility that has an overall average daily flow of 15.1 MGD and average dry weather flow of 13.6 MGD in 2020. LTP is permitted for 21.34 MGD average daily dry weather flow and takes wastewater from homes, businesses, and industry located within the Cities of Santa Rosa, Rohnert Park, Sebastopol, and Cotati, and the South Park Sanitation District. Over 500 miles of underground pipes bring

City of Santa Rosa (project #0012267.00) 28 Woodard & Curran, Inc.

Feasibility Analysis August 2023
wastewater to the LTP where water goes through three stages of treatment prior to disinfection, storage, and reuse. The water is treated to the highest non-potable level recognized in State water recycling regulations (Title 22 Tertiary).

The Regional System provides recycled water to the City of Rohnert Park for its urban reuse program for irrigation at many Rohnert Park schools, parks, and businesses, as well as Sonoma State University. In Santa Rosa, recycled water is used within the City’s urban growth boundary for landscape irrigation at City facilities (including the municipal services center, bus transfer station, Finley Park, and A Place to Play sports complex), as well as multi-family residential complexes, institutions, and business parks.

Depending upon the amount of rainfall in any given year, approximately 98 to 100 percent of the Regional System’s recycled water is reused for urban landscapes, rural agricultural irrigation, and the Geysers Recharge Project. The volume of Title 22 tertiary water produced by the City in recent years (2019 through 2022) is summarized in Figure 3-5; it should be noted that 2020-2022were historically dry years.

The purified recycled water options (also known as potable reuse) are limited by the reliable volume of tertiary effluent available given its existing use by current customers. For this level of study, it was assumed the City would size the AWPF to meet its 9 MGD peak month supply needs. This requires instantaneous flows as high as 11.4 MGD. That value is less than the average dry-weather flow available in 2020 of 13.6 MGD. However, should this option (or others involving purified water) move forward, an analysis of daily low flows would be needed to verify that the assumed amount of equalization storage was sufficient to allow the plant to run at full rate even during days and hours of low wastewater flows.

City of Santa Rosa (project #0012267.00) 29 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-4: Regional System Facilities

Source: Regional Water Reuse System Master Plan (City of Santa Rosa, 2018)

City of Santa Rosa (project #0012267.00) 30 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-5: Average Recycled Water Use (2019-2022)

Source: Recycled Water Flows - Volume and User Type by Month 2019-2022 (City of Santa Rosa, 2023) 0 100
200
300
400
500
600
700
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Million Gallons
City RW to Geysers Windsor to Geysers Urban
Landscape
Regional
Landscape
Agriculture Commercial Wholesale
To Rohnert Park

City of Santa Rosa (project #0012267.00) 31 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Potable Reuse Approaches
The spectrum of potable reuse approaches is commonly distinguished by the degree of separation between the treatment and ultimate consumption of purified water. This separation may be physical (e.g., when purified water travels through a groundwater aquifer), temporal (e.g., when water is retained in a tank or a reservoir), or both. IPR projects are characterized by the use of one of two environmental buffers—a groundwater aquifer or a surface water reservoir—that increase the separation between treatment and consumers. DPR projects are defined by the absence of a significant environmental buffer.

The State of California recognizes five forms of IPR and DPR that are depicted in Figure 3-6, all requiring a multitude of pathogen and chemical control requirements.

Figure 3-6: Forms of Potable Reuse in California

3.1.2.1.1 Indirect Potable Reuse
The first form of IPR distinguished by California regulations is groundwater recharge (GWR), which can be achieved by two different approaches: surface spreading and subsurface injection (Title 22, Chapter 3, Articles 5.1 and 5.2, respectively). The second form of IPR is surface water augmentation (SWA) which introduces purified water directly into a surface water reservoir that is used as a source of domestic drinking water supply.

City of Santa Rosa (project #0012267.00) 32 Woodard & Curran, Inc.

Feasibility Analysis August 2023
One of the benefits of pursuing IPR projects in California is the regulatory certainty associated with the existence of final, adopted regulations for both GWR and SWA. This streamlines the permitting process by providing clarity on the requirements for IPR implementation. In the case of GWR, there are also multiple precedents given that permitted California GWR projects have been producing water for nearly 60 years.

Based on this experience, the regulatory community has first-hand knowledge of the challenges with GWR allowing them to adapt the requirements to address these needs.

3.1.2.1.2 Direct Potable Reuse
The State Water Resources Control Board released draft criteria for DPR in March 2021 and revised criteria in August 2021 (State Water Resources Control Board, 2021). The draft criteria include stricter requirements than IPR to compensate for the protections that are lost from bypassing the environment al buffer. The criteria can be broken down into four major categories: 1) pathogen control, 2) chemical control, 3) monitoring and control, and 4) technical, managerial, and financial capacity.

Compared to IPR, DPR projects have stricter requirements for nearly all of these categories. One example of this difference is the level of treatment needed for IPR and DPR. Most categories of IPR require full advanced treatment (FAT), which is the treatment of the entire flow of water through both reverse osmosis (RO) and an advanced oxidation process (AOP). The draft DPR criteria specify higher levels of treatment, namely, pre-treatment with ozone and biological activated carbon (BAC) followed by FAT.

State regulations define two types of DPR—raw water augmentation (RWA) and treated water augmentation (TWA)—that are differentiated depending on whether the reuse project is providing a raw source water upstream of a surface water treatment plant, or a finished water directly into a public water system’s distribution system. RWA also encompasses projects that provide raw source water into an environmental buffer that cannot meet the IPR requirements. Despite the differences between RWA and TWA, the draft DPR criteria contain a single set of requirements to cover both forms. The State’s DPR Expert Panel—who is currently reviewing the public health protectiveness of the draft DPR criteria —has asked the State Board to provide separate criteria for these two forms. If the future regulations do not include separate requirements, then it is possible that projects designed for RWA may also have the flexibility to pursue TWA (and vice versa).

One benefit of DPR is that it does not restrict projects to areas with access to groundwater aquifers or reservoirs. Many agencies in California are considering the RWA form of DPR to continue leveraging investments they have made in existing treatment plant infrastructure. The main challenges in pursuing DPR include the lack of regulatory certainty (though draft criteria are on track to be finalized by the end of 2023) and the lack of permitting precedents.

Table 3-8 summarizes the flow requirements for the proposed DPR and IPR AWPFs assumed for this study.

City of Santa Rosa (project #0012267.00) 33 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-8: Preliminary AWPF Flow Summaries
Parameter Units
DPR Maximum
Treatment Flow
IPR Maximum
Treatment Flow
Production Capacity MGD 9.0 9.0
System Feed MGD 11.6 11.4
Ozone/Biological Activated Filtration (BAF)
Assumed Recovery % 98 --
Feed MGD 11.60 --
Brine MGD 0.23 --
Effluent MGD 11.37 --
Microfiltration System (MF)
Assumed Recovery % 93 93
Feed MGD 11.37 11.40
Backwash MGD 0.80 0.80
Effluent MGD 10.6 10.6
Reverse Osmosis (RO) System
Assumed Recovery % 85 85
Feed MGD 10.6 10.6
Brine MGD 1.59 1.59
Effluent MGD 9.0 9.0
Ultraviolet-Peroxide Disinfection (Ultraviolet/Advanced Oxidation Process -

UV/AOP)
Assumed Recovery % 100 100
Feed MGD 9.0 9.0
Effluent MGD 9.0 9.0
Free Chlorine Disinfection
Assumed Recovery % 100 --
Feed MGD 9.0 --
Effluent MGD 9.0 --
PR-1: DPR AWPF at LTP
Option PR-1 would convey the City’s tertiary effluent to an AWPF co-located at the City’s existing LTP and return AWPF waste streams to the LTP headworks. The concept 9 MGD AWPF would include treatment processes in compliance with future anticipated regulations for TWA. The purified water would be conveyed to Sonoma Water’s 36-inch Kawana Pipeline for distribution to the City’s potable water system.

PR-1 is limited by the reliable volume of tertiary effluent available. For this level of study, it was assumed the City would size the AWPF to meet its 9 MGD peak month supply needs. Figure 3-7 shows the PR-1 concept, including the AWPF and conveyance infrastructure to the proposed potable connection point along Occidental Road.

City of Santa Rosa (project #0012267.00) 34 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-7: Supply Option PR-1

City of Santa Rosa (project #0012267.00) 35 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Components that would need to be constructed as part of PR-1 include:
• 24-inch tertiary water pipeline from LTP to AWPF
• 1.8 million gallon equalization basin
• AWPF to meet anticipated DPR regulations, conventional FAT plus ozone/ BAF o Ozone/BAF
o Microfiltration system (MF)
o Reverse Osmosis (RO) system
o UV/AOP
o RO brine disposal system (Evaporator and Crystallizer) o Ancillary facilities
• 20-inch product water pipeline and pump station to potable connection point • Potable connection infrastructure
The total preliminary capital cost for option PR-1, including all infrastructure listed, is approximately $289 million. A summary of the PR-1 capital cost is shown in Table 3-9. Additional cost detail can be found in Appendix A.

Table 3-9: Preliminary Capital Cost, Supply Option PR-1 Component Description Cost, $2023
Equalization 1,820,000 gallon equalization basin prior to feeding AWPF $2,275,000
Tertiary Water Pipeline 24-inch diameter; assumed 500 linear feet $445,000 9 MGD DPR AWPF
Ozone, BAF, Ultra Filtration (UF)/Micro Filtration
(MF), RO, chemical storage and feed systems,
sitework, piping, structures, waste disposal to
headworks
$100,659,000
Brine Disposal Brine evaporator and crystallizer for zero liquid discharge $10,730,000
Purified Water Line 20-inch diameter; 26,330 linear feet $19,528,000 Purified Water Pump Station 625 horsepower $4,063,000
Potable system connection $100,000
Estimating Contingency 50% of raw construction costs $68,900,000 Implementation 40% of total construction costs $82,680,000 Total Capital Cost $289,380,000
Annualized Capital Cost Annualized over 50 years, 2.5% interest $10,203,000 The O&M cost of the project was estimated on a per AF basis for scalability. The PR-1 option has a fixed annual O&M cost of $873,000 and an annual marginal O&M cost of approximately $927/ AF. Annual O&M costs will vary depending on the production of the AWPF. It is assumed the AWPF could be turned down to a production capacity of 30 percent during low demand periods. The estimated annual O&M

City of Santa Rosa (project #0012267.00) 36 Woodard & Curran, Inc.

Feasibility Analysis August 2023
costs for the maximum potential yield of 10,065 AFY is approximately $10.2 million. Table 3-10 summarizes the annual O&M costs for option PR-1.

Table 3-10: Preliminary Annual O&M Cost, Supply Option PR-1 Component Description Cost, $2023
Marginal Cost Marginal costs include power consumption, labor, and chemical addition $927/ AF
Fixed Cost Fixed costs include routine maintenance practices, water quality testing $873,000
Average cost of water (Baseline Scenario)1 $3,600/AF
Annual O&M (10,065 AFY)2 $10,200,000
Cost of water (10,065 AFY)2 $2,050/ AF
Annual O&M (3,019 AFY)3 $3,671,000
Cost of water (3,019 AFY)3 $4,600/ AF
Notes:

1. See Section 2.5 for description of baseline scenario, under which on average 4,131 AFY are produced by PR-

1. Costs including operating and capital.

2. The maximum supply yield of 10,065 AFY assumes 24/7 operation of all supply option infrastructure. This scenario may not reflect realistic operations because it would produce more water than the City would use, which causes the unit cost of water to appear artificially low.

3. The minimal yield of 3,019 AFY assumes 30 percent turndown of the AWPF’s maximum yield to provide a range of supply available for the PR options.

PR-2: Satellite DPR AWPF
Option PR-2 would convey the City’s tertiary effluent to a satellite AWPF and return AWPF waste stream s to the nearest sewer. The AWPF would include treatment processes in compliance with future anticipated regulations for TWA. The purified water would be conveyed to Sonoma Water’s 36-inch diameter pipeline for distribution to the City’s potable water system. The satellite AWPF is assumed to be located on City- owned agricultural leased land, Stone Farm. Although siting the AWPF as a satellite facility allows the City to reduce the purified water conveyance facilities, the satellite AWPF requires more ancillary facilities to support operations staff than if the AWPF were sited within the existing LTP.

For this level of study, it was assumed the City would size the AWPF to meet its 9 MGD peak month supply needs. The tertiary effluent to feed the AWPF would be conveyed to the satellite AWPF through new conveyance infrastructure assuming the existing Geysers pipeline corridor/ easement. The purified water would be conveyed to Sonoma Water’s aqueduct for distribution to the City as shown in Figure 3-8.

City of Santa Rosa (project #0012267.00) 37 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-8: Supply Option PR-2

City of Santa Rosa (project #0012267.00) 38 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Components that would need to be constructed as part of PR-2 include:
• 24-inch tertiary water pipeline from LTP to AWPF
• 400 horsepower tertiary water pump station
• 1.8 million gallon equalization basin
• AWPF to meet anticipated DPR regulations, conventional FAT plus ozone/BA C o Ozone/BAC
o MF/Spell out (UF) System
o RO System
o UV/AOP
o RO brine disposal system (Evaporator and Crystallizer) o Ancillary facilities
o 10-inch AWPF waste disposal to nearest sewer with capacity • 20-inch purified water pipeline
• 250 horsepower pump station to potable connection point • Potable connection infrastructure
The total preliminary capital cost for option PR-2, including all infrastructure listed, is approximately $314 million. A summary of the PR-2 capital cost is shown in Table 3-11. Additional cost detail can be found in Appendix A.

Table 3-11: Preliminary Capital Cost, Supply Option PR-2 Component Description Cost, $2023
Equalization 1,820,000 gallon equalization basin $2,275,000 Tertiary Water Pipeline 24-inch diameter; 30,100 linear feet $26,789,000 9 MGD DPR AWPF
Ozone, BAC, MF, RO, chemical storage and feed
systems, sitework, piping, structures, waste disposal
to nearest sewer
$103,191,000
Brine Disposal Brine evaporator and crystallizer for zero liquid discharge $10,730,000
Purified Water Line 20-inch diameter; 26,330 linear feet $1,520,000 Purified Water Pump Station 250 horsepower $1,625,000
Potable system connection $100,000
Estimating Contingency 50% of raw construction costs $74,780,000 Implementation 40% of total construction costs $89,730,000 Total Capital Cost $314,060,000
Annualized Capital Cost Annualized over 50 years, 2.5% interest $11,073,000 The O&M cost of the project was estimated on a per AF basis for scalability. The PR -2 option has a fixed annual O&M cost of $954,000 and an annual marginal O&M cost of approximately $943/ AF. Annual O&M costs will vary depending on the production of the AWPF. It is assumed the AWPF could be turned

City of Santa Rosa (project #0012267.00) 39 Woodard & Curran, Inc.

Feasibility Analysis August 2023
down to a production capacity of 30 percent during low demand periods. The estimated annual O&M costs for the maximum potential yield of 10,065 AFY is approximately $10.4 million. Table 3-12 summarizes the annual O&M costs for option PR-2.

Table 3-12: Preliminary Annual O&M Cost, Supply Option PR-2 Component Description Cost, $2023
Marginal Cost Marginal costs include power consumption, labor, and chemical addition $943/ AF
Fixed Cost Fixed costs include routine maintenance practices, water quality testing $954,000
Average cost of water (Baseline Scenario)1 $3,900/ AF
Annual O&M (10,065 AFY)2 $10,443,000
Cost of water (10,065 AFY)2 $2,150/ AF
Annual O&M (3,019 AFY)3 $3,800,000
Cost of water (3,019 AFY)3 $5,000/ AF
Notes:

1. See Section 2.5 for description of baseline scenario, under which on average 4,131 AFY are produced. Costs include operating and capital.

3. The minimal yield of 3,019 AFY assumes 30 percent turndown of the AWPF’s maximum yield to provide a range of supply available for the PR options.

PR-3a: IPR AWPF at LTP, Ground Water Augmentation (GWA) via Delta Pond Option PR-3a would convey the City’s tertiary effluent to an AWPF at LTP and return AWPF waste stream to the headworks at LTP. The AWPF would include treatment processes in compliance with regulations for GWR. The purified water would be conveyed to the City-owned Delta Pond, after the minimum retention time of 2-months in the groundwater aquifer, the recharged groundwater could then be extracted. The purified water would be injected into and later extracted from the groundwater aquifer via new ASR wells.

The same capital cost assumptions for the GW-3 option were applied for the 12 new ASR wells. For this level of study, it was assumed the City would size the AWPF to meet its 9 MGD peak month supply needs .

As shown in Figure 3-9, the 9 MGD AWPF would be co-located at LTP and the purified water would be conveyed to the Delta Pond area through new conveyance infrastructure assuming use of the existing Geysers pipeline corridor/ easement.

City of Santa Rosa (project #0012267.00) 40 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-9: Supply Option PR-3a

City of Santa Rosa (project #0012267.00) 41 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Components that would need to be constructed as part of PR-3a include:
• 24-inch tertiary water pipeline from LTP to AWPF
• 1.8 million gallon equalization basin
• AWPF to meet IPR GWA regulations, conventional FAT
o MF System
o RO System
o UV/AOP
o RO brine disposal system (Evaporator and Crystallizer) o Ancillary facilities
o 8-inch AWPF waste disposal to LTP headworks
• 22-inch purified water pipeline
• 490 horsepower pump station to Delta Pond
• ASR wells
The total preliminary capital cost for option PR-3a, is approximately $419 million. A summary of the PR-3a capital cost is shown in Table 3-13. Additional cost detail can be found in Appendix A.

Table 3-13: Preliminary Capital Cost, Supply Option PR-3a Component Description Cost, $2023
Equalization 1,820,000 gallon equalization basin $2,275,000 Tertiary Water Pipeline 24-inch diameter; assumed 500 linear feet $445,000 9 MGD IPR AWPF
UF, RO, chemical storage and feed systems,
sitework, piping, structures, waste disposal to
headworks
$89,390,000
Brine Disposal Brine evaporator and crystallizer for zero liquid discharge $10,760,000
Purified Water Line to Delta Pond 22-inch diameter; 41,220 linear feet $33,628,700 Purified Water Pump Station 490 horsepower $3,185,000
New Well Construction
12 ASR wells (injection/ extraction) wells, 500
gpm capacity, 500 feet deep, well head,
casing, well pump and equipment
($5 million/ well)
$60,000,000
Estimating Contingency 50% of raw construction costs $99,840,000 Implementation 40% of total construction costs $119,810,000 Total Capital Cost $419,330,000
Annualized Capital Cost Annualized over 50 years, 2.5% interest $14,785,000

City of Santa Rosa (project #0012267.00) 42 Woodard & Curran, Inc.

Feasibility Analysis August 2023
The O&M cost of the project was estimated on a per AF basis for scalability. The PR -3a option has a fixed annual O&M cost of $1,069,000 and an annual marginal O&M cost of approximately $936/ AF. Annual O&M costs will vary depending on the production of the AWPF. It is assumed the AWPF could be turned down to a production capacity of 30 percent during low demand periods. The estimated annual O&M costs for the maximum potential yield of 10,065 AFY is approximately $12.7 million. Table 3-14 summarizes the annual O&M costs for option PR-3a.

Table 3-14: Preliminary Annual O&M Cost, Supply Option PR-3a Component Description Cost, $2023
Marginal Cost Marginal costs include power consumption, labor, and chemical addition $936/ AF
Fixed Cost Fixed costs include routine maintenance practices, water quality testing $1,069,000
Average cost of water (Baseline Scenario)1 $4,800/AF
Annual O&M (10,065 AFY)2 $12,700,000
Cost of water (10,065 AFY)2 $2,730/AF
Annual O&M (3,019 AFY)3 $4,558,000
Cost of water (3,019 AFY)3 $6,400/AF
Notes:

1. See Section 2.5 for description of baseline scenario, under which on average 4,131 AFY of water would be produced. Costs include capital and operating.

2. The maximum supply yield of 10,065 AFY assumes 24/7 operation of all supply option infrastructure. This scenario may not reflect realistic operations.

3. The minimal yield of 3,019 AFY assumes 30 percent turndown of the AWPF’s maximum yield to provide a range of supply available for the PR options.

PR-3b: IPR AWPF at LTP, SWA via Lake Ralphine
Option PR-3b would convey the City’s tertiary effluent to an AWPF at LTP and return AWPF waste stream to the headworks at LTP. The AWPF would include treatment processes in compliance with regulations for SWA. After preliminary retention calculations it was determined that Lake Ralphine would not provide the minimum required 2-month retention time to quality as IPR per California regulations. Therefore, option PR-3b would qualify as a DPR and would likely yield a project similar to the PR-1 option described above.

Therefore, this supply option was not carried forward for detailed cost analysis or feasibility scoring.

PR-3c: IPR AWPF at LTP, SWA via Lake Sonoma
Option PR-3c would convey the City’s tertiary effluent to an AWPF at LTP and return AWPF waste stream to the headworks at LTP. The AWPF would include treatment processes in compliance with regulations for SWA. The purified water would be conveyed to Lake Sonoma through a new purified water line assuming the existing Geysers pipeline corridor/ easement and extending to Lake Sonoma as shown in Figure 3-10.

For this level of study, it was assumed the City would size the AWPF to meet its 9 MGD peak month supply needs

City of Santa Rosa (project #0012267.00) 43 Woodard & Curran, Inc.

Feasibility Analysis August 2023
The AWPF would be located at LTP, and the purified water would be conveyed to Lake Sonoma through new conveyance infrastructure . Water would be withdrawn from Lake Sonoma using Sonoma Water’s existing infrastructure.

Components that would need to be constructed as part of option PR-3c include:
• 24-inch tertiary water pipeline from LTP to AWPF
• 1.8 million gallon equalization basin
• AWPF to meet IPR GWA regulations, conventional FAT
o MF system
o RO system
o UV/AOP
o RO brine disposal system (Evaporator and Crystallizer) o Ancillary facilities
o 8-inch AWPF waste disposal to LTP headworks
• 22-inch purified water pipeline
• 2,600 horsepower pump station to Lake Sonoma

This option incorporates some assumptions that would need to be vetted and refined if the option were implemented. Among them is an assumption that sufficient space exists in Lake Sonoma, and that withdrawing the water from Lake Sonoma could be done with existing infrastructure. Both of these issues would likely add cost and-or reduce yield to the option. However, given the very high cost of the option even without those burdens, the issues were not fully explored in the current study.

City of Santa Rosa (project #0012267.00) 44 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-10: Supply Option PR-3c

City of Santa Rosa (project #0012267.00) 45 Woodard & Curran, Inc.

Feasibility Analysis August 2023
The total preliminary capital cost for option PR-3c is approximately $650 million. A summary of the PR-3c capital cost is shown in Table 3-15. Additional cost detail can be found in Appendix A.

Table 3-15: Preliminary Capital Cost, Supply Option PR-3c Component Description Cost, $2023
Equalization 1,820,000 gallon equalization basin $2,275,000 Tertiary Water Pipeline 24-inch diameter; assumed 500 linear feet $445,000 9 MGD IPR AWPF
UF, RO, chemical storage and feed systems,
sitework, piping, structures, waste disposal to
headworks
$89,390,000
Brine Disposal Brine evaporator and crystallizer for zero liquid discharge $10,760,000
Purified Water Line to Lake
Sonoma 22-inch diameter; 181,300 linear feet $147,910,600 Purified Water Pump Station 2,600 horsepower $16,900,000 Estimating Contingency 50% of raw construction costs $133,840,000 Implementation 40% of total construction costs $160,610,000 Total Capital Cost $562,130,000
Annualized Capital Cost Annualized over 50 years, 2.5% interest $19,800,000 The O&M cost of the project was estimated on a per AF basis for scalability. The PR -3c option has a fixed annual O&M cost of $1,790,000 and an annual marginal O&M cost of approximately $1,200/ AF. Annual O&M costs will vary depending on the production of the AWPF. It is assumed the AWPF could be turned down to a production capacity of 30 percent during low demand periods. The estimated annual O&M costs for the maximum potential yield of 10,065 AFY is approximately $15.9 million. Table 3-16 summarizes the annual O&M costs for option PR-3c.

City of Santa Rosa (project #0012267.00) 46 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-16: Preliminary Annual O&M Cost, Supply Option PR-3c Component Description Cost, $2023
Marginal Cost Marginal costs include power consumption, labor, and chemical addition $1,200/ AF
Fixed Cost Fixed costs include routine maintenance practices, water quality testing $1,786,000
Average cost of water (Baseline Scenario)1 $6,430/AF
Annual O&M (10,065 AFY)2 $13,870,000
Cost of water (10,065 AFY)2 $3,350/ AF
Annual O&M (4,131 AFY)3 $6,319,000
Cost of water (4,131 AFY)3 $6,430/AF
Notes:

1. See Section 2.5 for description of baseline scenario, under which on average 4,131 AFY would be produced.

Operating and capital costs are included.

2. The maximum supply yield of 10,065 AFY assumes 24/7 operation of all supply option infrastructure. This scenario may not reflect realistic operations.

3. The minimal yield of 3,019 AFY assumes 30 percent turndown of the AWPF’s maximum yield to provide a range of supply available for the PR options.

PR-4: Regional DPR AWPF at LTP
Similar to Option PR-1, PR-4 would convey the City’s tertiary effluent to an AWPF located at the LTP and return AWPF waste stream to the LTP headworks. The AWPF would include treatment processes in compliance with future anticipated regulations for TWA. The purified water would be conveyed to Sonoma Water’s 48-inch diameter aqueduct for regional distribution, as shown in Figure 3-11.

Under the PR-4 project concept, the purified water could be delivered to another party rather than used directly by the City, and a paper exchange could be completed whereby the City receives water in return.

The paper exchange option would not reduce reliance on the Sonoma Water system overall.

City of Santa Rosa (project #0012267.00) 47 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-11: Supply Option PR-4

City of Santa Rosa (project #0012267.00) 48 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Components that would need to be constructed as part of PR-4 include:
• 24-inch tertiary water pipeline from LTP to AWPF
• 1.8 million gallon equalization basin
• AWPF to meet anticipated DPR regulations, conventional FAT plus ozone/ BAC o Ozone/BAC
o MF System
o RO System
o UV/AOP
o RO brine disposal system (Evaporator and Crystallizer) o Ancillary facilities
• 20-inch product water pipeline and pump station to potable connection point • Potable connection infrastructure
The total preliminary capital cost for option PR-4, including all infrastructure listed, is approximately $247 million. A summary of the PR-4 capital cost is shown in Table 3-17. Additional cost detail can be found in Appendix A.

Table 3-17: Preliminary Capital Cost, Supply Option PR-4 Component Description Cost, $2023
Equalization 1,820,000 gallon equalization basin prior to feeding AWPF $2,275,000
Tertiary Water Pipeline 24-inch diameter; assumed 500 linear feet $445,000 9 MGD DPR AWPF
Ozone, BAF, UF, RO, chemical storage and feed
systems, sitework, piping, structures, waste
disposal to headworks
$100,659,000
Brine Disposal Brine evaporator and crystallizer for zero liquid discharge $10,730,000
Purified Water Line 20-inch diameter; 2,200 linear feet $1,631,700 Purified Water Pump Station 270 horsepower $1,755,000
Potable system connection $100,000
Estimating Contingency 50% of raw construction costs $58,800,000 Implementation 40% of total construction costs $70,560,000 Total Capital Cost $246,960,000
Annualized Capital Cost Annualized over 50 years, 2.5% interest $8,707,000 The O&M cost of the project was estimated on a per AF basis for scalability. The PR-4 option has a fixed annual O&M cost of $714,000 and an annual marginal O&M cost of approximately $885/ AF. Annual O&M costs will vary depending on the production of the AWPF. It is assumed the AWPF could be turned down to a production capacity of 30 percent during low demand periods. The estimated annual O&M

City of Santa Rosa (project #0012267.00) 49 Woodard & Curran, Inc.

Feasibility Analysis August 2023
costs for the maximum potential yield of 10,065 AFY is approximately $9.6 million. Table 3-18 summarizes the annual O&M costs for option PR-4.

Table 3-18: Preliminary Annual O&M Cost, Supply Option PR-4 Component Description Cost, $2023
Marginal Cost Marginal costs include power consumption, labor, and chemical addition $885/ AF
Fixed Cost Fixed costs include routine maintenance practices, water quality testing $714,000
Average cost of water (Baseline Scenario)1 $3,200/AF
Annual O&M (10,065 AFY) $9,625,000
Cost of water (10,065 AFY) $1,850/ AF
Annual O&M (3,019 AFY) $3,387,000
Cost of water (3,019 AFY) $4,000/ AF
Notes:

1. See Section 2.5 for description of baseline scenario, under which an average of 4,131 AFY would be produced. Operating and capital costs are included.

3. The minimal yield of 3,019 AFY assumes 30 percent turndown of the AWPF’s maximum yield to provide a range of supply available for the PR options.

The costs presented for PR-4 would represent the total cost of the supply option. Were a regional partner to be identified, the costs would be distributed between the City and its partner(s), and the City presumably would not bear the entire project cost.

3.1.3 Non-Potable Recycled Water Option
As discussed in Section 3.1.2, the City is responsible for the operation and management of the Regional System. The Regional System operates the LTP, oversees the Industrial Pretreatment Program, and operates and maintains the recycled water system for more than 225,000 residents and 6,500 businesses for the Cities of Cotati, Rohnert Park, Santa Rosa, and Sebastopol, and the South Park Sanitation Dist rict and portions of unincorporated Sonoma County. As managing partner of the Regional System, the City is responsible for operating the system economically and safely and for planning for future regulatory changes and growth.

RW-1: Recycled Water System Expansion
Option RW-1 would increase the amount of urban reuse within Santa Rosa, Cotati, and Rohnert Park supplied by recycled water. The Santa Rosa Urban Reuse Project Feasibility Study identified the following phases, each with a capacity of 250 MGY (City of Santa Rosa, 2007). The total expansion would yield an additional 3,000 AFY for distribution. The four phases of the expansion are:

City of Santa Rosa (project #0012267.00) 50 Woodard & Curran, Inc.

Feasibility Analysis August 2023
• Phase 1 West: pipelines generally located in northwest Santa Rosa extending from either the west transmission main or the West College Facility. Diurnal storage may be included in Phase 1 West and would be located between elevation 300 and 400 feet in the Fountaingrove area. • Phase 1 South: pipelines generally located in southeast Santa Rosa extending from the south transmission main. Diurnal storage may be included in Phase 1 South and would be located between elevation 300 and 400 feet within the Santa Rosa U rban Growth Boundary or in the southeast of Santa Rosa area.
• Phase 2 South: pipelines extending from the Phase 1 South system into southwest Santa Rosa.

Connections between the south and west system may be made during this phase. Diurnal storage may be included in Phase 2 South and would be located between elevation 300 and 400 feet or at lower elevations in northwest Rohnert Park or west of Cotati. • Phase 2 West: pipelines extending from the Phase 1 West system to interconnect with the south system. Diurnal storage may be included in Phase 2 West and would be located between elevation 300 and 400 feet or at lower elevations near the Geysers pipeline o r east of Rohnert Park.

The total preliminary capital cost for option RW-1, escalated from the Santa Rosa Urban Reuse Project Feasibility Study in 2006 to 2023 dollars is approximately $214 million. The O&M cost of the project was estimated at $1.3M/year by prorating based on the City’s FY2020- 2021 Wastewater Resource Distribution Expenditure. The average cost of water for the Baseline Scenario (see Section 2.5) is approximately $8,800/ AF. Expanding use of recycled water would not provide a new source of potable drinking water for severe water shortages or emergencies (irrigation would be significantly restricted or banned).

3.1.4 Desalinated Water Supply Options
Marin Municipal Water District (Marin Water) is also considering alternatives for supplemental water supplies with the City of Petaluma, garnering potential for regional partnerships between Marin Water, Petaluma, and the City. The City’s service area is too far from saline water sources and the local groundwater supply does not require desalination. Alternative water supplies Marin Water is currently evaluating include a potential temporary or long-term seawater desalination facility (using brackish bay water) or a brackish groundwater desalination facility. This section evaluated a partnership between Marin Water and the City for a regional brackish bay water desalination facility and the concept of the City’s own ocean desalination facility.

DE-1: Regional Brackish Water Desalination
Option DE-1 would allow the City and Marin Water to partner in constructing a desalination facility to augment Marin Water’s local water supply and the City’s Sonoma Water supply via water transfers. A full- scale facility could have an initial capacity of 5 MGD or 10 MGD and be expandable up to 15 MGD. The full-scale facility could be located at the Marin Water Pelican Way Site in San Rafael as shown in Figure 3-12. The screened intake would be offshore with an on-shore pump station near the Marin Water Pelican Way Site. The bay water intake would include passive screens. The intake screens would be connected to an onshore wet well and pump station via an HDPE pipeline on and under the bay floor. The intake pump station would deliver raw water to the treatment facilities located at either or both the maintenance yard and parking lot sites. The 15 MGD long-term full-scale desalination facilities require approximately 6.5 acres of space. Treated water from the desalination facilities would be delivered to the Marin Water distribution system in San Rafael.

City of Santa Rosa (project #0012267.00) 51 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Provided that the desalination facility would be within the jurisdiction of Marin Water, a paper exchange could be completed where the City receives 9 MGD of Marin Water’s Sonoma Water allocation, and the desalinated water is used directly by Marin Water. Since the Sonoma Water aqueduct would be an integral component of operations, the paper exchange option would not reduce reliance on the Sonoma Water system overall, but it would reduce overall reliance on the Russian River.

The City’s total preliminary capital cost for option DE-1 is approximately $181 million. A summary of the DE-1 capital cost is shown in Table 3-19. Additional cost detail can be found in Appendix A.

Table 3-19: Preliminary Capital Cost, Supply Option DE-1 Component Description City Cost,
$2023
Brackish Water Intake Intake Screens, Pipeline and Pumps, Raw Water Pipe to facility $8,178,000
Desalination Plant
Rapid Mix Strainers, UF and Building, Filtrate and
Backwash Supply Tanks, RO Feed Pump Station, 1st
pass RO and Building, Permeate Tank, Chlorine Contact
Tank, Chemical Facilities, Backwash Equalization Basin, Gravity Thickener, Centrifuges, O&M Building,
Sitework/Piping, Electrical, Instrumentation and
Controls
$71,559,000
Brine Disposal Brine Pump Station, Brine Transmission Line $3,444,000 Distribution Distribution Booster Pumps, Treated Water Line $2,899,200 Estimating Contingency 50% of raw construction costs $43,040,000 Implementation 40% of total construction costs $51,650,000 Total Capital Cost $180,770,000
Annualized Capital Cost Annualized over 50 years, 2.5% interest $6,374,000 The O&M cost of the project was estimated on a per AF basis for scalability. The DE-1 option has a fixed annual O&M cost of $909,000 and an annual marginal O&M cost of approximately $401/ AF. Annual O&M costs will vary depending on the production of the desalination facility. It is assumed the desal facility could be turned down to a production capacity of 30 percent during low demand periods. The estimated annual O&M costs for the maximum potential yield of 10,080 AFY is approximately $5 million.

Table 3-20 summarizes the City’s portion of the estimated annual O&M costs for option DE -1.

City of Santa Rosa (project #0012267.00) 52 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-20: Preliminary Annual O&M Cost, Supply Option DE-1 Component Description Cost, $2023
Marginal Cost Marginal costs include power consumption, labor, and chemical addition $401/ AF
Fixed Cost Fixed costs include routine maintenance practices, water quality testing $909,000
Average cost of water (Baseline Scenario)1 $2,041/AF
Annual O&M (10,080 AFY)2 $4,954,000
Cost of water (10,080 AFY)2 $1,200/ AF
Annual O&M (3,360 AFY)3 $2,005,000
Cost of water (3,360 AFY)3 $2,500/ AF
Notes:

1. See Section 2.5 for description of baseline scenario, under which an average of 4,441 AFY would be produced. Capital and operating costs are included.

2. The maximum supply yield of 10,080 AFY assumes 24/7 operation of all supply option infrastructure. This scenario may not reflect realistic operations.

3. The minimal yield of 3,360 AFY assumes 30 percent turndown of the desalination plant’s maximum yield to provide a range of supply available for the DE options.

City of Santa Rosa (project #0012267.00) 53 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-12: Supply Option DE-1

Source: Marin Water Desalination Supply Study Draft Technical Memorandum (Marin Municipal Water District, 2021)

City of Santa Rosa (project #0012267.00) 54 Woodard & Curran, Inc.

Feasibility Analysis August 2023
DE-2: Ocean Desalination
Option DE-2 would construct a seawater desalination facility to increase the City’s local water supply. The desalination facility would be sized to produce 9 MGD to meet the City’s peak month demands. The screened intake would be offshore with an onshore pump station near the desalination site. For costing purposes only, a general location for ocean desalination option was estimated. For purposes of this study, the conceptual full-scale facility was assumed to be located offshore along Bodega Bay as shown in Figure 3-13. A full siting study would be required to determine the most feasible and optimal location for the seawater desalination facility if brought forward through the screening process.

Components that would need to be constructed for DE-2 include:
• The 9 MGD desalination facilities:
o Intake Screens, Pipeline and Pumps
o Raw Water Pipe to facility
o Rapid Mix Strainers
o UF System including Filtrate and Backwash Supply Tanks o RO Feed Pump Station
o RO System and permeate tank
o Chlorine Contact Tank
o Chemical Facilities
o Backwash Equalization Basin
o Gravity Thickener
o Centrifuges
o Ancillary facilities
• Brine disposal
o 290 horsepower pump station
o 24-inch Brine Transmission Line
• Potable Water Distribution
o 1,880 horsepower pump station
o 24-inch potable water pipeline

City of Santa Rosa (project #0012267.00) 55 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-13: Supply Option DE-2

City of Santa Rosa (project #0012267.00) 56 Woodard & Curran, Inc.

Feasibility Analysis August 2023
The capital cost estimate for option DE-2 is also based on a recent draft cost estimate from the 2021 Marin Water Desalination Supply Study (Marin Municipal Water District, 2021). The total preliminary capital cost for option DE-2 is approximately $378 million. A summary of the DE-2 capital cost is shown in Table 3-21. Additional cost details can be found in Appendix A.

Table 3-21: Preliminary Capital Cost, Supply Option DE-2 Component Description City Cost,
$2023
Seawater Intake
Intake Screens, Pipeline and Pumps
30-inch; 2,000 linear feet Raw Water Pipe to facility
$10,167,000
Desalination Plant
Rapid Mix Strainers, UF and Building, Filtrate and
Backwash Supply Tanks, RO Feed Pump Station, 1st pass
RO and Building, Permeate Tank, Chlorine Contact Tank,
Chemical Facilities, Backwash Equalization Basin, Gravity Thickener, Centrifuges, O&M Building, Sitework/Piping,
Electrical, Instrumentation and Controls
$71,560,000
Brine Disposal
290 horsepower Brine Pump Station
24-inch; 2,000 linear feet Brine Transmission Line
$3,665,000
Distribution
1,880 horsepower Distribution Pump Station
24-inch; 92,600 linear feet Treated Water Line
$94,634,000
Estimating Contingency 50% of raw construction costs $90,020,000 Implementation 40% of total construction costs $108,020,000 Total Capital Cost $378,070,000
Annualized Capital Cost Annualized over 50 years, 2.5% interest $13,330,000 The O&M cost of the project was estimated on a per AF basis for scalability. The DE-2 option has a fixed annual O&M cost of $1,604,000 and an annual marginal O&M cost of approximately $1,165/ AF. Annual O&M costs will vary depending on the production of the desalination facility. It is assumed the desal facility could be turned down to a production capacity of 30 percent during low demand periods. The estimated annual O&M costs for the maximum potential yield of 10,080 AFY is approximately $13.3 million. Table 3-22 summarizes the City’s portion of the estimated annual O&M costs for option DE-2.

City of Santa Rosa (project #0012267.00) 57 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-22: Preliminary Annual O&M Cost, Supply Option DE-2 Component Description Cost, $2023
Marginal Cost Marginal costs include power consumption, labor, and chemical addition $1,165/ AF
Fixed Cost Fixed costs include routine maintenance practices, water quality testing $1,604,000
Average cost of water (Baseline Scenario)1 $4,500/ AF
Annual O&M (10,080 AFY)2 $13,330,000
Cost of water (10,080 AFY)2 $2,700/ AF
Annual O&M (3,360 AFY)3 $5,520,000
Cost of water (3,360 AFY)3 $5,600/ AF
Notes:

1. See Section 2.5 for description of baseline scenario, under which an average of 4,441 AFY would be produced. Capital and operating costs are included.

2. The maximum supply yield of 10,080 AFY assumes 24/7 operation of all supply option infrastructure. This scenario may not reflect realistic operations.

3. The minimal yield of 3,360 AFY assumes 30 percent turndown of the desalination plant’s maximum yield to provide a range of supply available for the desalination options.

3.1.5 Stormwater Capture Options
SW-1: Capture Excess Winter Flows in Aquifer Storage
Option SW-1 proposes to construct a diversion structure within Santa Rosa Creek to divert excess winter flows to new spreading basins (it may be determined after future investigations that injection wells will be required for groundwater recharge) for storage within the Santa Rosa aquifer to increase the City’s local water supply. The diversion location for this study was assumed to be within Santa Rosa Creek near the existing USGS stream gage 11466320 due to its proximity to Delta Pond for potential storage prior to aquifer recharge via proposed spreading basins in the vicinity (see Figure 3-14). For the 9 MGD supply, 12 new extraction wells would be required. The same assumptions for the GW-1 option were applied for the proposed extraction wells.

A preliminary stream gage analysis was performed to determine the allowable diversion volume from Santa Rosa Creek. The allowable stream diversion period lies within the months of December through March. This level of analysis assumed that all flows above the 90th percentile of stormwater volume within the creek can be diverted unless the diversion amount is greater than 20 percent of the day’s flow (in which case, this analysis capped the diversion volume at 20 percent of that day’s flow). Based on dry year data from 1999 to 2023, the allowable diversion volume between the months of December through March can range from 1,200 to 212,640 AF. For purposes of the current study, it was assumed that adequate volumes are available on average to support the maximum annual usage of 7,500 AFY, accounting for the need to withdraw less than the amount recharged, and that sufficient aquifer storage exists to buffer intra-year and inter-year supply variations.

City of Santa Rosa (project #0012267.00) 58 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-14: Supply Option SW-1

City of Santa Rosa (project #0012267.00) 59 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Components that would need to be constructed as part of option SW-1 include:
• Stormwater diversion structure including pumps, pipes • Spreading basins in the Delta Pond vicinity
• 12 new extraction wells and conveyance
• Treatment plant providing conventional treatment (coagulation, flocculation, sedimentation, filtration); this is a conservative assumption and would need further exploration if the alternative were carried forward.

The total preliminary capital cost for option SW-1 is approximately $223million. A summary of the SW-1 capital cost is shown in Table 3-23. Additional cost details can be found in Appendix A.

Table 3-23: Preliminary Capital Cost, Supply Option SW-1 Component Description Cost, $2023
Santa Rosa Creek Diversion Diversion Structure, including pumps, spreading basins $18,144,000
New Well Construction 12 extraction wells, 500 gpm capacity, 500 feet deep, well head, casing, well pump and equipment $42,000,000 Treatment to Stormwater
Prior to Recharge 9 MGD conventional treatment plant $42,000,000 Groundwater Conveyance 20-inch; 3,000 linear feet $2,225,000 Groundwater Pump Station 240 horsepower $1,560,000
Potable Connection $100,000
Estimating Contingency 50% of raw construction costs $52,980,000 Implementation 40% of total construction costs $38,420,000 Total Capital Cost $222,500,000
Annualized Capital Cost Annualized over 50 years, 2.5% interest 4,741,000 The O&M cost of the project was estimated on a per AF basis for scalability. The SW-1 option has a fixed annual O&M cost of $542,000 and an annual marginal O&M cost of approximately $303/ AF. Annual O&M costs will vary depending on the amount of water diverted from Santa Rosa Creek during winter.

The estimated annual O&M costs for the maximum potential yield of 10,080 AFY is approximately $ 3.6 million. Table 3-24 summarizes the estimated annual O&M costs for option SW-1.

City of Santa Rosa (project #0012267.00) 60 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-24: Preliminary Annual O&M Cost, Supply Option SW-1 Component Description Cost, $2023
Marginal Cost Marginal costs include power consumption, labor, and chemical addition $303/ AF
Fixed Cost Fixed costs include routine maintenance practices, water quality testing $542,000
Average cost of water (Baseline Scenario)1 $3,500/ AF
Annual O&M (10,080 AFY)2 $3,600,000
Cost of water (10,080 AFY)2 $1,135/ AF
Notes:

1. See Section 2.5 for description of baseline scenario, under which on average 2,600 AFY are produced. Costs include capital and operating.

This baseline estimate of usage is uncertain as it would depend on adequate stormwater being captured and banked to support that level of usage. If this alternative were to be further developed, more detailed modeling would need to be performed.

2. The maximum supply yield of 10,080 AFY assumes 24/7 operation of all supply option infrastructure. This scenario may not reflect realistic operations. This is particularly true for this option, since its operation would be subject to a host of unknowns including hydrologic variations on the intra-seasonal and inter-seasonal timescales that would affect supply availability. Some of those variations, e.g., low stormwater availability, could be temporally correlated with Russian River droughts, thus limiting supplemental supply when it is most needed.

SW-2: Capture Excess Winter Flows in Surface Storage (Lake Ralphine or Alternate) This option explored the possibility of capturing excess winter stormwater flows for surface storage. The City does not currently have unused surface storage. Lake Ralphine holds slightly under 500 AF and served as a historical water supply source for the City (through the late 1950’s) and is currently used for recreation. A review of prior City planning work and City water systems and topography did not yield any alternative surface water sites for further exploration.

In order to store surface water in Lake Ralphine, the existing dam would need to be raised, which would displace the existing recreational areas (picnic areas, ball fields, etc.), which are highly valued by the community and City. The size of a potential reservoir would be limited due to surrounding topography and presence of residential neighborhoods surrounding the reservoir. Even an enlarged Lake Ralphine would likely fill naturally during wet periods, limiting its utility for providing additional stormwater storage in wet months. Furthermore, Lake Ralphine is not used for drinking water supply, meaning that a new water treatment plant would need to be constructed in order to use Lake Ralphine for drinking water supply. Given that enlarging Lake Ralphine would not provide a large water storage benefit and would have substantial financial and social costs (requiring a new treatment plant, impacting City recreational facilities), this supply option did not advance to undergo cost estimation.

City of Santa Rosa (project #0012267.00) 61 Woodard & Curran, Inc.

Feasibility Analysis August 2023
SW-3: Regional Stormwater
Supply option SW-3 proposes developing a regional stormwater project in collaboration with one or more agencies in the region. There are several regional stormwater programs underway that could be bolstered with City partnership and/or used to generate new ideas for a regional project. One such example is a project being explored by North Marin Water District which involves diverting stormwater into Stafford Lake. More information about regional efforts is included in the following plans:

Marin Municipal Water District
• Water Resiliency projects: https://www.marinwater.org/WaterSupplyResiliency North Marin Water District
• Local Water Supply Enhancement Study https://nmwd.com/save-water/new-water-supplies/ Petaluma
• Integrated Water Master Plan https://cityofpetaluma.org/iwmp/ Sonoma Water
• Drought Resiliency Project https://www.sonomawater.org/DroughtResiliency • Regional Water Supply Resiliency Study
• Presentation slides, May 1, 2023
https://www.sonomawater.org/media/PDF/About/WAC/2023_05/Item%207%20 - %202023%20Resiliency%20Update.pdf
• Presentation slides, May 2, 2023
https://www.sonomawater.org/media/PDF/About/WAC/2022_05/7.1.%20SonomaWater_R esiliencyStudy%20WAC%20Update_2022_0502.pdf
• Report: Accelerated 2021-2022 Drought Resiliency Analysis, April 27, 2022 https://www.sonomawater.org/media/PDF/About/WAC/2022_05/7.2.%20Sonoma%20Wat er%20Resiliency%20Study%20-%20Drought%20Analysis%20TM%20FINAL%20DRAFT.pdf • Presentation slides, Drought Options Update, Feb 7, 2023 https://www.sonomawater.org/media/PDF/About/WAC/2022_02/12.%20SonomaWater_R esiliencyStudy_WAC_Update_2022_0207_REDUCED.pdf
• Presentation slides, Nov 1, 2021
https://www.sonomawater.org/media/PDF/About/WAC/2021_11/Presentation- %20Sonoma%20Water%20Resiliency%20Study.pdf
• Memo, July 29, 2021
https://www.sonomawater.org/media/PDF/About/WAC/2021_08/9.%20SRP%20Drought% 20Resiliency%20Project%20WACTAC%20memo.pdf
San Francisco Estuary Institute
• Laguna de Santa Rosa restoration master plan

City of Santa Rosa (project #0012267.00) 62 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Implementation of this supply option would require identification of feasible detention storage and recharge locations, regional coordination and agreements, and possible need for additional water rights.

Because many project elements and implementation considerations for regional stormwater would be similar to the local stormwater option above (SW-1 and SW-2), and because the City would effectively be participating in possible future regional stormwater projects implemented by Sonoma Water, this option did not undergo any further separate technical analysis.

3.1.6 Efficiency Programs
E-1: Efficiency Programs
Efficiency measures would not provide a new source of drinking water supply to mitigate the impacts of drought and emergencies, but these programs would reduce demand over time as efficiency measures penetrate the City’s customer base. The efficiency program would include a suite of efficiency measures, which are evaluated as a single program, which would be implemented City-wide. These measures are:
• Commercial, industrial, institutional (CII) turf removals, • Single-family residential (SFR) turf removals,
• Toilet direct installs, and
• Fixture direct installs (kitchen aerators, bathroom aerators, and showerheads).

Along with these aggressive efficiency measures, the City’s existing efficiency programs would continue, such as indoor water use efficiency surveys, landscape water use efficiency surveys, and rebates for high- efficiency washing machines, graywater use, and other practices (City of Santa Rosa, 2021). The water savings that can be achieved by the efficiency measures would be limited by factors such as: the number of inefficient toilets and fixtures remaining that could be replaced, the area of turfgrass present, and the extent to which the retrofits/relandscaping could penetrate the market (i.e., number of customers willing/able to participate). For the purposes of this study, program budget was not considered to be a limitation.

The City provided information regarding the estimated costs and water savings that could be achieved via the efficiency program (City of Santa Rosa, 2022) if 100 percent participation were achieved. Full participation voluntarily is unlikely, though the City Code could be updated to mandate changes which may achieve near full participation. In total, up to 5,700 AFY of water savings could be achieved over about the next 40 years with full participation. Descriptions of each efficiency measure, including key assumptions, are summarized below:
• CII turf removals: CII turf removals would remove approximately 16.3 million square feet of turf over about 41 years. A replacement rate of 400,000 square feet per year is assumed (based on 100 sites participating per year, removing an average of 4,000 square feet each). The rebate offered would be $1.50 per square foot of turf removed. Water savings would be about 31 gallons per square foot per year, and the assumed life expectancy of the water savings is 15 years (although this may be higher since customers rarely relandscape back to turf). This measure would yield a lifetime savings of up to 23,000 AF.
• SFR turf removals: SFR turf removals would remove approximately 42.7 million square feet of turf over about 43 years. A replacement rate of 1 million square feet per year is assumed (1,200 homes participating per year, removing an average of 833 square feet each). The rebate offered

City of Santa Rosa (project #0012267.00) 63 Woodard & Curran, Inc.

Feasibility Analysis August 2023
would be $1.50 per square foot of turf removed. Water savings would be about 11 gallons per square foot per year and the assumed life expectancy of the water savings is 15 years (although this may be higher since customers rarely relandscape back to turf). This measure would yield a lifetime savings of up to 22,000 AF.
• Toilet direct installs: The City would replace existing 1.6 gallons per flush (gpf) or greater toilets customers with 0.8 gpf toilets in Santa Rosa residences. It is assumed that 45,600 toilets could be replaced over 15 years, at a rate of approximately 3,000 toilets per year. The life expectancy of the toilet is assumed to be 15 years. In total, toilet replacements would achieve a lifetime water savings of about 6,219 AF. It is assumed that future toilet replacements by residents would maintain the water savings as plumbing codes continue to require greater water efficiency. • Fixture direct installs: The City would replace/install kitchen faucet aerators, bathroom faucet aerators, and 1.5 gpm showerheads. One set of fixtures would consist of one kitchen sink aerator, two-bathroom sink aerators, and two showerheads. It is assumed that 3,000 sets of fixtures could be installed per year over 15 years (about 45,600 households in total). In total, updated fixtures would achieve a lifetime water savings of about 16,000 AF. It is assumed that future fixture replacements by residents would maintain the water savings as plumbing codes continue to require greater water efficiency.

Efficiency program costs would include costs of turf rebates, toilets, and fixtures, labor costs to install toilets and fixtures, and City staff time to implement the program (including outreach to expand the reach of the program). The total lifetime program cost is approximately $169 million, with a lifetime water savings of up to 67,000 AF. At the completion of the program, water savings per year would be up to 5,700 AF. However, given the large levels of uncertainty, an annual savings of 2,145 AFY was assumed, based on estimates of anticipated voluntary participation provided by the City.

Additional detail on data sources and assumptions can be found in Appendix A.

3.2 Screening Analysis Results
All potential water supply options were screened using two key criteria: high-level assessments of cost- effectiveness and scalability. Supply options that performed well in the screening analysis were moved forward to undergo more detailed feasibility analysis and to be scored against each criterion identified in the Study Parameters (Section 2.4).

Table 3-25 summarizes the results of the screening analysis. A total of seven water supply options have been selected to move forward for more detailed feasibility analysis.

City of Santa Rosa (project #0012267.00) 64 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-25: Screening Analysis Results Summary
Category Supply Option
Moving
Forward? Reasoning for Screening Out
Groundwater
GW-1: Add local
groundwater extraction wells
Yes N/A
GW-2: Convert emergency
wells to production wells
Yes N/A
GW-3: Add local ASR wells Yes N/A
GW-4: Regional
groundwater extraction wells
No Regional groundwater extraction is unlikely to be
accepted without including a recharge element,
which would result in a project similar to the local
and regional ASR options. Thus, this option is not
carried forward on its own.

GW-5: Regional ASR wells No Because many project elements and implementation considerations for Regional ASR
would be similar to the local ASR option above,
this option would not undergo separate technical
analysis.

Purified
Recycled
Water
PR-1: DPR AWPF at LTP No Not cost-effective based on City’s current needs.

PR-2: Satellite DPR AWPF Yes Note: Although the option may be less cost- effective than others carried forward, the City
desires to further advance a purified recycled
water option in order to provide a broader suite of
options and greater diversity to potential supplies.

PR3a: IPR AWPF at LTP via
Delta Pond

No Not cost-effective based on City’s current needs.

PR-3b: IPR AWPF at LTP via
Lake Ralphine
No Not cost-effective based on City’s current needs.

PR-3c: IPR AWPF at LTP via
Lake Sonoma

No Not cost-effective based on City’s current needs.

PR-4: Regional DPR AWPF at
LTP
Yes Note: A regional purified recycled water project
appears most promising in terms of cost-
effectiveness. Changing technology, supply needs,
and partnerships could make this option worth
future consideration.

City of Santa Rosa (project #0012267.00) 65 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Category Supply Option
Moving
Forward? Reasoning for Screening Out
Non-potable
Recycled
Water
RW-1: Expand City’s existing
non-potable recycled water
system
No Not cost-effective based on City’s current needs
and does not address potable water needs in
supply-limited circumstances like drought and
catastrophic supply interruptions.

Desalination
DE-1: Regional brackish
desalination
No Not cost-effective based on City’s current needs
and does not reduce reliance on Somona Water
(in the event of a catastrophic supply interruption)
because of the water transfer involved in this
supply option. Implementation is contingent upon
the substantial involvement of partners, including
Sonoma Water. More information on desalination
as a supply and triggers for its reconsideration is
included in Appendix C.

DE-2: Ocean desalination No Not cost-effective based on City’s current needs.

The required pipeline from the ocean to Santa
Rosa’s service area contributes significantly to the
cost. More information on desalination as a supply
and triggers for its reconsideration is included in
Appendix C.

Stormwater
SW-1: Capture stormwater
and store in aquifer for later
potable use
Yes N/A
SW-2: Store in enlarged Lake
Ralphine (or alternate) and
construct water treatment
plant for later potable use
No The space needed to expand Lake Ralphine to
increase the cost-effectiveness of this option is
not available and constructing new surface water
storage is not cost-effective at this time.

Additional work should be completed to confirm
the yield available for this option before
committing to the costs of an additional facility
required to treat the stormwater prior to use.

SW-3: Regional stormwater No Because many project elements and implementation considerations for Regional
stormwater would be similar to the local
stormwater options above and are being carried
forward through other technical teams as present,
this option would not undergo separate technical
analysis. This does not prohibit the City from
continuing to participate in existing regional
stormwater efforts nor does preclude future
partnerships on new regional stormwater efforts.

Efficiency
Programs
E-1: Add aggressive
incentives for efficiency
programs to reduce demand
(in addition to existing
programs)
Yes N/A

City of Santa Rosa (project #0012267.00) 66 Woodard & Curran, Inc.

Feasibility Analysis August 2023

3.3 Feasibility Analysis Results
Upon completion of the screening analysis, the feasibility analysis was completed, which included evaluating and scoring the short-listed water supply options. A numerical system was used for rating (scoring) each short-listed option against each criterion and against each other. The numerical system provides a score of 0 through 2, with 2 being most favorable. The score is based on knowledge of the project area, engineering judgment, and experience on past projects. The evaluation criteria scoring rubric used for the evaluation of the short-listed supplemental supply options is summarized in Table 2-5, a summary of the shortlist supply scores is shown in Table 3-26. Detailed scoring descriptions are found in the following subsections.

City of Santa Rosa (project #0012267.00) 67 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-26: Summary of Supply Option Scores
Criterion
Groundwater Purified Recycled Water Stormwater
E-1:

Efficiency
Programs
GW-1: Add
Extraction
Wells
GW-2:

Convert
Emergency
Wells
GW-3: City
ASR Wells
PR-2:

Satellite
DPR
PR-4: Regional
DPR
SW-1:

Stormwater
Storage in
Aquifer
Cost effectiveness *
[$/AF]
2 [$840/AF]
2 [$540/AF]
2 [$1,100/AF]
0 [$3,900/AF]
0 [$3,200/AF]
0 [$3,500/AF]
1 [$2,800/AF]
Scalability
[Yield in AFY]
2 [5,880 - 10,080
AFY]
0 [1,436 - 2,462
AFY]
1 [2,993 - 5,130 AFY]
2 [3,019 - 10,065
AFY]
2 [3,019 - 10,065 AFY]
1 [1,008 - 10,080
AFY]
1 [2,145 AFY]
Resiliency 1 1 2 2 2 1 1
Equity 1 1 1 1 1 1 2
Environmental
performance 1 2 1 0 1 1 2
Legal, permitting,
and regulatory 1 2 0 0 0 1 2
City control and
interagency
coordination
2 2 1 2 0 2 2
Multi-benefit 0 0 1 0 0 2 1
Total Unweighted 10 10 9 7 6 9 12
Total Weighted 32 26 29 21 22 19 30
* Costs shown reflect a realistic baseline usage scenario and include both capital and operating costs.

City of Santa Rosa (project #0012267.00) 68 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-15 shows cost-effectiveness under baseline operations along with maximum yield and incorporates the weighted scores of each supply option in the bubble sizes (as summarized in Table 3-26).

Figure 3-15: Cost-Effectiveness vs Max Yield (with Weighted Score)

3.3.1 Groundwater Options
The detailed scoring and rationale for the groundwater options are provided in Table 3-27, Table 3-28 and Table 3-29 on the following pages below.

City of Santa Rosa (project #0012267.00) 69 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-27: Detailed Scoring for Option GW-1
Criterion Description Score
Cost effectiveness Under the baseline scenario, actual costs are estimated at $843/AF, making this option one of the least expensive studied, and less expensive than the current Sonoma Water supply which is $1,200/AF. 2 Scalability As evaluated, this option includes construction of 12 wells to meet the City’s supply goals. However, the City need not construct all 12 wells initially, and could potentially build fewer even in the long run if well yield is higher than estimated. Generally, this option could be scaled or phased to best fit City needs.
2 Resiliency Moderate resiliency. Pumping costs would increase with rising power costs. Cost-effectiveness could decrease under certain hydrologic conditions, but groundwater availability may not be severely impacted unless there is a long-term change in hydrology.
1 Equity The additional groundwater supply would have no impact on vulnerable communities. The additional groundwater supply would be available to the City to offset purchased water from Sonoma Water.
1 Environmental
performance
The new extraction wells would be located in the City within the City's Greenway Area. Construction of 12 wells would have moderate potential for environmental impacts.
1 Legal, permitting,
and regulatory
Well construction would likely require some permitting and regulatory compliance but would not require unusual efforts.
1 City control and
interagency
coordination
While coordination with Sonoma Water and the other GSAs in Santa Rosa Plain would be required, the scope and timing of the work would be generally at the City’s discretion.
2 Multi-benefit No other benefits provided. 0

City of Santa Rosa (project #0012267.00) 70 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-28: Detailed Scoring for Option GW-2
Criterion Description Score
Cost effectiveness Based on conceptual analyses, the rehabilitation of the three existing emergency wells would provide up to 2,462 AFY of additional groundwater supply. The baseline scenario average cost of water is approximately $541/AF, the least expensive of all options studied. 2 Scalability This option lends itself to phasing since well rehabilitation could occur one well at a time. However, the overall scale of the project would fall far short of the City’s 7,500 AFY need.
0 Resiliency Moderate resiliency. Pumping costs would increase with rising power costs. Cost-effectiveness could decrease under certain hydrologic conditions, but groundwater availability may not be severely impacted unless there is a long-term change in hydrology.
1 Equity The additional groundwater supply would have no impact on vulnerable communities. The additional groundwater supply would be available to the City to offset purchased water from Sonoma Water.
1 Environmental
performance
The rehabilitation of the existing wells would have minimal potential for environmental impacts.
2 Legal, permitting,
and regulatory
The City has previously completed similar permitting/ regulatory efforts required for approval to convert from emergency use to active supply (i.e., 2005 Farmer's Lane well).
2 City control and
interagency
coordination
No interagency coordination would be required. 2
Multi-benefit No other benefits provided. 0

City of Santa Rosa (project #0012267.00) 71 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-29: Detailed Scoring for Option GW-3
Criterion Description Score
Cost effectiveness Based on conceptual level cost estimates, construction of six ASR wells would provide up to 5,130 AFY of additional groundwater supply. The baseline scenario average cost of water is approximately $2,632/AF which includes purchase of water ASR.
2 Scalability The extraction wells included in this option could be constructed in phases to best fit City needs. At buildout, the option could provide most of the City’s supplemental needs.
1 Resiliency Moderate resiliency. Pumping and injection costs would increase with rising power costs. Cost-effectiveness could decrease under certain hydrologic conditions, but the ability to inject water into the aquifer would improve resiliency relative to extraction-only options. 2 Equity The additional groundwater supply would have no impact on vulnerable communities. The additional groundwater supply would be available to the City to offset purchased water from Sonoma Water.
1 Environmental
performance
The new ASR wells would be located in a less developed area within the City limits. Construction of six wells would have moderate potential for environmental impacts.
1 Legal, permitting,
and regulatory
While ASR projects are increasingly common, they pose more significant permitting and regulatory requirements.
0 City control and
interagency
coordination
Coordination would be required with GSAs in Santa Rosa Plain and with Sonoma Water to coordinate with other ASR programs underway. 1 Multi-benefit This option would enable conjunctive management of surface water and groundwater, which allows for greater flexibility in optimizing surface water and groundwater use (which represents an additional benefit beyond strict water supply).
1 City of Santa Rosa (project #0012267.00) 72 Woodard & Curran, Inc.

Feasibility Analysis August 2023

3.3.2 Purified Recycled Water Options
The detailed scoring and rationale for the purified recycled water options are listed in Table 3-30 and Table 3-31.

Table 3-30: Detailed Scoring for Option PR-2
Criterion Description Score
Cost effectiveness Under the baseline scenario the average cost of water is approximately $3,854/AF, making it the most expensive option.

Additionally, the option involves a financial upfront commitment for capital so even if future circumstances changed the obligation to pay for the project would continue unabated. 0 Scalability The AWPF included in this option could be constructed in phases to best fit City needs. The AWPF could be scaled down 30% in low demand periods.
2 Resiliency High resiliency. The ability to purify tertiary treated water into potable supply would improve resiliency, even in times of drought or future hydrologic uncertainty.
2 Equity The additional purified water supply would have no impact on the City’s vulnerable communities as it will meet or exceed drinking water standards.
1 Environmental
performance
The satellite DPR AWPF would be located in a less developed area within the City limits. Construction of the AWPF and extensive conveyance facilities may have moderate to high potential for environmental impacts.
0 Legal, permitting,
and regulatory
High permitting/regulatory effort would be required as
discussed in Section 3.1.2.1.2. The main challenges in pursuing DPR include the lack of regulatory certainty and the lack of permitting precedents.
0 City control and
interagency
coordination
No significant interagency coordination would be required. 2 Multi-benefit This option would provide a potable supply benefit but would reduce tertiary water availability for the Geysers and for the non- potable customers.
0 City of Santa Rosa (project #0012267.00) 73 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Table 3-31: Detailed Scoring for Option PR-4
Criterion Description Score
Cost effectiveness Under the baseline scenario the average cost of water is approximately $3,166/AF, making it among the most expensive options. Additionally, the option involves a financial upfront commitment for capital so even if future circumstances changed the obligation to pay for the project would continue unabated. 0 Scalability The AWPF included in this option could be constructed in phases to best fit City needs. The AWPF could be scaled down 30% in low demand periods.
2 Resiliency High resiliency. The ability to purify tertiary treated water into potable supply would improve resiliency, even in times of drought or future hydrologic uncertainty.
2 Equity The additional purified water supply would have no impact on the City’s vulnerable communities.
1 Environmental
performance
The DPR AWPF would be located on the City-owned LTP
property. Construction of the AWPF and purified water
conveyance facilities would have low to moderate potential for environmental impacts.
1 Legal, permitting,
and regulatory
High permitting/regulatory effort would be required as
discussed in Section 3.1.2.1.2. The main challenges in pursuing DPR include the lack of regulatory certainty and the lack of permitting precedents.
0 City control and
interagency
coordination
Coordination with a regional partner for the paper exchange would be required in addition to continuing coordination with Sonoma Water if its aqueduct were used for distribution. 0 Multi-benefit This option would provide a potable supply benefit but would reduce tertiary water availability for the Geysers and for the non- potable customers.
0 City of Santa Rosa (project #0012267.00) 74 Woodard & Curran, Inc.

Feasibility Analysis August 2023

3.3.3 Stormwater Capture
The detailed scoring and rationale for SW-1 is listed in Table 3-32.

Table 3-32: Detailed Scoring for Option SW-1
Criterion Description Score
Cost Effectiveness The baseline scenario average cost of water is approximately $3,500/AF, making it among the most expensive options.
0 Scalability While the diversion structure, spreading basins (or injection wells) and extraction wells included in this option could be constructed in phases, the treatment plant, if needed, would require significant cost up-front that could not be recovered even if changes in future conditions reduced the need for the project.
1 Resiliency Moderate resiliency. While the ability to store water in the aquifer would improve resiliency, there are significant uncertainties in the project’s performance, specifically its yield in drought years. 1 Equity The additional groundwater supply would have no impact on vulnerable communities. The recharge areas for the project may tend to focus construction impacts on less-developed, less affluent areas, which could reduce flooding in those areas.
1 Environmental
performance
The new diversion structure, spreading basins and extraction wells would be located in a less developed area within the City limits.

Construction of the twelve wells would have moderate potential for environmental impacts.
1 Legal, permitting,
and regulatory
Some permitting/regulatory effort would be required, but stormwater diversion projects are increasingly common and would not require outsize legal, permitting, or regulatory effort to implement. 1 City control and
interagency
coordination
No interagency coordination would be required.
2 Multi-benefit This option would enable conjunctive management of surface water and groundwater, which allows for greater flexibility in optimizing surface water and groundwater use (which represents an additional benefit beyond strict water supply).
2 City of Santa Rosa (project #0012267.00) 75 Woodard & Curran, Inc.

Feasibility Analysis August 2023

3.3.4 Efficiency Programs
The detailed scoring and rationale for the Efficiency Programs option is provided in Table 3-33.

Table 3-33: Detailed Scoring for Option E-1
Criterion Description Score
Cost effectiveness As summarized above, based on cost estimates provided by the City, efficiency program would provide water savings at a cost of approximately $2,780/AF under the Baseline Scenario. This makes it less expensive than the options involving major costs for water treatment (e.g., PR-2, PR-4, SW-1) but more expensive than the groundwater options.
1 Scalability Water savings could be increased depending on the scale of the program and number of customers that could be reached. Once water savings are achieved, they are considered to be relatively secure because they are built into the landscapes/fixtures, which have typically become more efficient with time due to plumbing codes and price signals. 1 Resiliency Performance of efficiency measures would not degrade with changes in future regulations, energy costs or hydrology. However, the option does not provide “new water” that would help mitigate catastrophic loss of the Sonoma Water supply.
1 Equity Direct installation programs reduce barriers to participation by low- income residents and organizations and agencies managing low-income and subsidized housing that have not been able to participate in rebate programs in the past due to upfront costs.
2 Environmental
performance
The program would have little to no adverse environmental impact and would provide a potential environmental benefit by reducing water consumption.
2 Legal, permitting,
and regulatory
Large-scale construction would not be needed. Physical changes as a result of the project would include toilet and fixture replacements, and relandscaping in existing developed areas. Work would need to be completed by qualified contractors, but additional permitting and regulatory requirements would not be anticipated for this option. 2 City control and
interagency
coordination
No interagency coordination would be required. 2
Multi-benefit In addition to providing water savings, the program would provide a cost savings to customers by helping them to reduce their water use. 1 City of Santa Rosa (project #0012267.00) 76 Woodard & Curran, Inc.

Feasibility Analysis August 2023

3.3.5 Cost Sensitivity Analysis
The screening tool allows the supply option costs to be estimated under a variety of scenarios. The baseline scenario was modified to assess supply option performance under multiple hydrologic scenarios (Figure 3-16), and multiple Sonoma Water dry-year reduction levels (Figure 3-17). In that figure, scenarios SW-35 and SW-40 represent dry-year reductions of 35 percent and 40 percent respectively, versus a base scenario of 30 percent.

In general, most supply options would be more cost-effective in a drier hydrologic scenario because more water would be produced to meet normal demand during Sonoma Water water shortages. The wetter hydrologic scenario contains more wet years than the baseline, but also contains more dry years (as summarized in Table 3-34). Therefore, for some options, the wetter scenario is also more cost-effective than the baseline scenario. All supply options become more cost-effective if greater dry-year Sonoma Water reductions are assumed.

Figure 3-16: Supply Option Cost Performance with Varying Hydrology ($/AF)

Table 3-34: Distribution of Water Year Types in Hydrologic Scenarios Hydrologic Scenario
Year Types by Percent
Wet Normal Dry
Wet 37% 29% 34%
Historic 33% 37% 30%
Dry 23% 30% 47%

City of Santa Rosa (project #0012267.00) 77 Woodard & Curran, Inc.

Feasibility Analysis August 2023
Figure 3-17: Supply Option Cost Performance with Varying Sonoma Water Cutbacks ($M/yr)

SW35: Scenario in which dry-year Sonoma Water supply reduction is 35% of baseline usage rather than the Base assumption of 30% reduction.

SW40: Scenario in which dry-year Sonoma Water supply reduction is 40% of baseline usage.

Although this analysis focused on hydrologic scenarios and Sonoma Water cutbacks, reflecting the City’s goals of addressing climate change and Sonoma Water reliance, future work could use other variables to test cost-sensitivity (such as price of power, interest rate, and demand reduction percent).

4. CONCLUSIONS
This Feasibility Analysis reveals several key considerations for the City to account for as the Water Supply Plan moves forward:
• Future conditions: Depending on the City’s assumptions about future hydrology, Sonoma Water supply reductions, cost of Sonoma Water supplies, and customer demand/conservation, the City may reach different conclusions about the potential best fit water supplies. For example, if the City assumes more optimistic future conditions, the amount of new water needed may be relatively modest, in which case the City would be well served by bridging that gap with a small number of new wells, which could be added one by one as the need arises. On the other hand, if the City assumes more pessimistic future conditions in which existing water supplies decrease, a broader range of options could be considered, including options such as potable reuse that would be run continuously once implemented. Options that could be implemented in phases (e.g., rehabilitating one well at a time, rather than 3 at once) may help provide resiliency against that type of uncertainty while minimizing capital outlay. • Operational assumptions: This analysis has incorporated reasonable operational assumptions into the baseline scenario. The cost per AF of water is sensitive to those assumptions. Generally,

City of Santa Rosa (project #0012267.00) 78 Woodard & Curran, Inc.

Feasibility Analysis August 2023
the cost per AF for a supplemental supply will be reduced as that supply is used more. However, many of the options cost more than the existing Sonoma Water supply. • Sensitivity: This analysis considered the impact of changing hydrology and reduced Sonoma Water dry-year allocations under the baseline scenario. The supply options generally become more cost-effective under more pessimistic scenarios (drier hydrology and higher Sonoma Water cutbacks) because more water is produced via the new options. However, the analysis indicates that the relative rankings of the supply options do not vary substantially with changes to the baseline condition.

The next step of the WSAP will involve a portfolio analysis, which will further assess the water supply options that passed the screening analysis. The portfolio analysis will consider downscaled versions of some supply options and will consider potential groupings of supply options that would allow the City to optimize different areas such as resiliency, supply volume, and cost.

City of Santa Rosa (project #0012267.00) 79 Woodard & Curran, Inc.

Feasibility Analysis August 2023

5. REFERENCES
California Department of Water Resources. (2022, August). The California Department of Water Resources' Statewide Airborne Electromagnetic Survey Project, Report for Survey Area 3.

City of Santa Rosa. (2007). Incremental Recycled Water Program. August 2007 Update to the Recycled Water Master Plan.

City of Santa Rosa. (2018, February). Regional Water Reuse System Master Plan.

City of Santa Rosa. (2021, June). 2020 Urban Water Management Plan.

City of Santa Rosa. (2022, December). WUE Water Savings (Spreadsheet).

City of Santa Rosa. (2023, February). Recycled Water Flows - Volume and User Type by Month 2019-2022.

Marin Municipal Water District. (2021, October 18). Draft Technical Memorandum: MMWD Desalination Supply Study.

Santa Rosa Plain Groundwater Sustainability Agency. (2021, December). Groundwater Sustainability Plan:

Santa Rosa Plain Groundwater Subbasin.

Sonoma Water. (n.d.). Santa Rosa Plain Drought Resiliency Project. Retrieved from https://www.sonomawater.org/DroughtResiliency
State of California Code of Regulations Title 22, Division 4. Environmental Health, Chapter 3 Water Recycling Criteria.

State Water Resources Control Board. (2021, August 17). A Proposed Framework of Regulating Direct Potable Reuse in California Addendum, version 8-17-2021.

City of Santa Rosa (project #0012267.00) Woodard & Curran, Inc.

Feasibility Analysis August 2023

APPENDIX A: COST DETAILS

Appendix A - Cost Details
Santa Rosa Water Supply Options July 2023
Option GW-1a: Groundwater Extraction Wells
Size Units Qty Unit Unit Cost Subtotal
Additional Wells
New Well Construction 500 gpm 12 per well $3,500,000 42,000,000 Product Water Distribution
Product Water Line 20 in 3,000 per inch-dia LF $37 2,225,000 Product Water Pump Station 240 HP $6,500 1,560,000
Potable Connection 1 LS $100,000 100,000
Raw Construction Cost 45,890,000
Construction Contingency 50% 22,950,000
Total Construction Cost 68,840,000
Implementation Cost 40% 27,540,000
Total Capital Cost 96,380,000
Annual Operations & Maintenance Cost (9 mgd production) Annual O&M Variable O&M AFY GPM TDH (ft) kwh-yr Unit Cost
Product Water Pump Station 6,000 118 1,405,080 $0.20 281,016 Extraction Wells 10,080 $54 547,865
Extraction Well Energy Use 10,080 $182 1,834,401
Fixed O&M Construction Cost Unit Cost
Extraction Wells $443,119 443,119
Pump Stations 1,560,000 3.0% 46,800
Pipelines 2,225,000 0.5% 11,125
Total Annual Operations & Maintenance Cost 3,164,326
Annualized Capital Cost 0.03526 3,398,000
Total Annualized Cost 6,562,326
Max Project Yield (AFY) 10,080
MAX $/AF 651
Annual Operations & Maintenance Cost (0 mgd production) Annual O&M Variable O&M AFY GPM TDH (ft) kwh-yr Unit Cost
Product Water Pump Station 0 118 0 $0.20 -
Extraction Wells 0 $54 -
Extraction Well Energy Use 0 $182 -
Fixed O&M Qty Unit Construction Cost Unit Cost
Extraction Wells $443,119 443,119
Pump Stations 1,560,000 3.0% 46,800
Pipelines 2,225,000 0.5% 11,125
Total Annual Operations & Maintenance Cost 501,044
Annualized Capital Cost 0.03526 3,398,000
Total Annualized Cost 3,899,044
Min Project Yield (AFY) 5,880
MIN $/AF 663
Basis of estimate:

Construct additional production wells and wellhead treatment if necessary and tie into the existing distribution system. The no. of wells to meet the demand would be 9 wells for the drought demand of 7,500 AFY and 12 wells for the peak demand of 9 MGD (or 10,000 AFY), based on the well capacity of 500 gpm. The costs were built upon existing City O&M data and well rehab of Leete Well.

Page 1 of 12 ends

Santa Rosa City CouncilOctober 24, 2023

Santa Rosa City Council
October 24, 2023