To: Board of Directors, Sonoma County Water Agency
Department or Agency Name(s): Sonoma County Water Agency
Staff Name and Phone Number: Aaron Fulton (707) 547- 1974
Vote Requirement: Majority
Supervisorial District(s): Countywide
Title:
Title
Central Sonoma Watershed Project
End
Recommended Action:
Recommended action
A) Authorize Sonoma County Water Agency’s General Manager to request assistance from the United States Department of Agriculture Natural Resources Conservation Service (NRCS) to plan for the rehabilitation of the Central Sonoma Watershed Project Piner, Brush, and Santa Rosa Creek reservoir facilities under the Watershed Rehabilitation Program.
B) Adopt a resolution authorizing Sonoma County Water Agency’s General Manager to sign a Local Sponsor Statement of Commitment when requesting assistance from the NRCS Watershed Rehabilitation Program.
C) Direct the Sonoma County Water Agency General Manager and Director of Engineering to develop and analyze a range of flood reduction alternatives in the Natural Resources Conservation Service Watershed Rehabilitation Program, including those which reestablish the 100-year level of flood protection in the Central Sonoma Watershed Project.
D) Direct staff to return to the Board of Directors with results of the Watershed Rehabilitation planning process before entering into a Watershed Agreement for rehabilitating Brush, Piner, or Santa Rosa Creek flood detention facilities.
E) Receive an update on the Matanzas Dam Rehabilitation Project.
end
Executive Summary:
The Central Sonoma Watershed Plan was developed in 1958 to protect the City of Santa Rosa and surrounding communities from flooding. Sonoma Water served as the local sponsor for this federally-funded infrastructure and continues to operate and maintain the project. Several facilities were constructed as part of the overall project and have served the community for approximately 60 years, exceeding their original 50-year design life. Recent planning efforts supported by Sonoma Water’s federal partner, the Natural Resources Conservation Service (NRCS), have identified several vulnerabilities and deficiencies with respect to state and federal dam safety criteria. Sonoma Water proposes to request assistance from the NRCS Watershed Rehabilitation Program (WRP) which focuses on rehabilitating aging dams that no longer meet state and federal safety and performance criteria to complete planning and identify alternatives that address current vulnerabilities. This work is needed to leverage the current Flood Control Zone 1A budget and position Sonoma Water to obtain federally funded design and construction assistance for flood and seismic risk mitigation projects.
Discussion:
Background
In 1958, the Sonoma County Flood Control and Water Conservation District (now Sonoma Water) and the United States Soil Conservation Service (now Natural Resources Conservation Service) developed the Central Sonoma Watershed Work Plan (1958 Plan) to combat recurring flood damage within the Santa Rosa Creek subwatershed. The 1958 Plan resulted in implementation of a network of 21 miles of improved channels, four detention reservoirs, two diversion structures, and numerous bridges and culverts (flood facilities) between 1962 and 1988, collectively known as the Central Sonoma Watershed Project (CSWP). The objective of the CSWP was to establish a 100-year level of flood protection along Santa Rosa Creek and its primary tributaries Matanzas, Paulin, Piner, Spring, and Brush Creeks. The CSWP has provided substantial flood protection to the City of Santa Rosa and surrounding communities for the past 60 years.
Despite ongoing maintenance by Sonoma Water, several CSWP facilities have exceeded their original 50-year design life, requiring flood planning and feasibility assessments to identify seismic, geotechnical, climatic, and hydraulic vulnerabilities, and to develop alternatives that would bring the CSWP system into compliance with current state and federal design and performance criteria. Sonoma Water is advancing two flood planning and feasibility studies to identify needed actions for the CSWP to reliably protect the community for the next 50 years; the Central Sonoma Watershed Project and Matanzas Dam Rehabilitation Project.
Central Sonoma Watershed Project
In 2016, all CSWP dams were assessed by NRCS for compliance with contemporary state and federal hydraulic performance criteria. The assessments indicated Piner, Brush, and Santa Rosa creek reservoirs did not have hydraulic deficiencies. After these initial assessments, Sonoma Water and NRCS secured $1.2 million in federal funding with a Cooperative Agreement under the Watershed and Flood Prevention Operations Program (WFPO) to evaluate sediment, climate, seismic, structural, and hydrologic vulnerabilities within the system. The Cooperative Agreement includes baseline feasibility and vulnerability assessments and development of a Watershed Plan-Environmental Assessment (Plan-EA) for NRCS National Environmental Policy Act (NEPA) compliance that must occur prior to issuing federal design funding. The NRCS Plan-EA will develop alternatives that mitigate vulnerabilities and rectify deficiencies while evaluating project impacts in accordance with NEPA. Sonoma Water serves as the local sponsor for the flood planning and feasibility project with technical and financial assistance from NRCS, the lead federal agency under NEPA.
The Cooperative Agreement Baseline feasibility and vulnerability assessments are complete. Based on updating the systemwide hydrology and hydraulic model with new datasets and calibration data, Sonoma Water has determined that Brush, Piner, and Santa Rosa dam facilities do not meet state or federal hydraulic dam safety and performance criteria. In addition, other deficiencies related to sediment, seismic, and structural components were identified. A summary of deficiencies identified in the baseline feasibility and vulnerability assessments is provided in Table 2.
Table 2 Summary of Identified Deficiencies
|
|
Hydraulic |
Sediment |
Seismic |
Structural |
|
|
|
|
|
|
|
Matanzas1 |
ü |
ü |
ü |
- |
|
Brush |
ü |
ü |
ü |
ü |
|
Piner |
ü |
ü |
ü |
ü |
|
Santa Rosa (Spring Lake) |
ü |
- |
ü |
ü |
1 - See Matanzas Creek Rehabilitation Project Update (below)
Before developing alternatives to mitigate vulnerabilities and rectify deficiencies, Sonoma Water and NRCS conducted an initial baseline economic analysis to determine if rectifying deficiencies and incorporating additional flood protection improvements could meet the WFPO program requirements of providing 20% of total project benefits to agriculture and rural communities. Despite incorporating direct damage reduction benefits to agriculture and extending benefit categories to housing, agritourism, and agriculture support businesses, it was determined that rehabilitating the identified deficiencies would not provide the statutorily required 20% agricultural and rural benefits given the degree of urbanization that has occurred over the life of the CSWP. Rehabilitating the deficiencies would not provide additional benefits because the actions would maintain current flood protection levels and increasing flood protection would overwhelmingly benefit urban areas where land and improvement values exceed the limited size and distribution of agriculture, rural communities, and agriculture-related benefit categories.
Given the outcome of the baseline vulnerability assessment and economic analysis, it is not feasible to develop a Plan-EA that meets the WFPO program requirements. Sonoma Water and NRCS intend to cease further planning efforts under the WFPO and not develop alternatives that mitigate vulnerabilities and rectify deficiencies under the current Cooperative Agreement. This strategy will avoid the additional costs of evaluating environmental effects for alternatives that cannot be funded under the WFPO program. Of the $1.2 million in federal funding, Sonoma Water will be reimbursed $980,000 and will relinquish the ability to request reimbursement for approximately $220,000 of planning costs attributed to alternatives generation and development of NRCS’s Plan-EA that have yet to commence. Future planning and feasibility activities would need the support of an alternative funding program that does not require a 20% benefit to agriculture and rural communities.
Because specific deficiencies with respect to federal and state dam safety and performance criteria have been identified, Sonoma Water is now eligible, and upon Board approval, will request assistance from the NRCS Watershed Rehabilitation program (WRP) which focuses on rehabilitating aging dams that no longer meet state and federal safety and performance criteria. The WRP is currently supporting the Matanzas Dam Rehabilitation Project and does not require a 20% agriculture and rural net benefit and is therefore better suited for rehabilitating flood protection facilities that primarily benefit urban areas. Alternatives that mitigate vulnerabilities and rectify deficiencies can be developed in the WRP to ensure the potential for future NRCS design and implementation funding. Upon Board approval, Sonoma Water will sign and submit a Local Sponsor Statement of Commitment to request NRCS WRP assistance.
Sonoma Water has been actively supporting NRCS’s National Environmental Policy Act (NEPA) planning process. Since October of 2021, Sonoma Water has filed formal notices in the Press Democrat, coordinated with local interest groups and the City of Santa Rosa, circulated notices to affected landowners and entities, provided updates to the Flood Control Zone 1A Advisory Committee, and led regulatory and public scoping meetings.
Staff Recommendation
Sonoma Water seeks to address vulnerabilities and rehabilitate aging infrastructure at Piner, Brush, and Santa Rosa Creek flood detention facilities which do not meet current federal dam safety and performance criteria. Rehabilitating these facilities is critical to protecting the residences, businesses, and infrastructure throughout the City of Santa Rosa for the next 50 years and cannot be supported by the Flood Control Zone 1A budget. The NRCS provides federal financial and technical assistance to local sponsors such as Sonoma Water seeking to rehabilitate facilities that are reaching the end of their design life and no longer meet federal or state criteria. NRCS provides 100% of the costs to evaluate and plan for rehabilitation actions. To be considered for federal assistance, Sonoma Water must submit a letter request and sign a Local Sponsor Statement of Commitment. Therefore, staff recommends adopting a resolution authorizing Sonoma County Water Agency’s General Manager to request assistance and sign a Local Sponsor Statement of Commitment as required under the NRCS WRP to continue vulnerability and flood planning in the Central Sonoma Watershed. Staff recommends evaluating a range of flood protection levels and to return to the Board for discussion before entering a Watershed Agreement requesting federal design assistance for Brush, Piner, or Santa Rosa flood detention facilities.
The recommended action allows Sonoma Water to leverage the baseline vulnerability assessments completed at Piner, Brush, and Santa Rosa detention facilities under the WFPO Cooperative Agreement and limited Flood Control Zone 1A funding to develop planning alternatives under the WRP that will ensure the CSWP system continues to protect the community for the next 50 years. Most importantly, if federal assistance is granted, Sonoma Water will have the necessary funding to conduct critical work while leveraging locally programmed funds to support flood planning and feasibility analyses in Flood Control Zone 1A. Depending on the outcome of the rehabilitation planning phase, Sonoma Water may request additional final design and construction assistance from NRCS in subsequent years.
Matanzas Creek Dam Rehabilitation Project Update
The 2016 NRCS dam CSWP assessments identified Matanzas Creek Dam as one of numerous high hazard dams in the nation that did not meet contemporary NRCS standards. In February of 2019, Sonoma Water requested technical and financial assistance from the NRCS WRP to investigate the deficiency, develop alternatives to bring the dam into compliance with NRCS standards, and facilitate future final design and construction funding requests. Disposition of WRP funds for final design and construction is considered a Federal Action subject to NEPA. Therefore, in addition to analyzing vulnerabilities and developing alternatives to rectify deficiencies, the NRCS is responsible for developing a Watershed Plan-Environmental Assessment (Plan-EA) to determine whether the Project has the potential to cause significant environmental effects in accordance with NEPA.
The Project commenced in October 2020 and is led by NRCS with Sonoma Water as the Local Sponsor. NRCS completed the feasibility and planning analyses for the Project and will present a Locally Preferred Alternative (LPA) in the Draft Plan-EA in the Summer of 2023 for public review. The LPA (Alternative 3) will rectify hydrologic design, sediment storage, and seismic design deficiencies at Matanzas Creek Dam. Consistent with the 1958 Plan, the LPA will establish 100-year flood storage as documented in the 1958 Plan, is consistent with required design flows in the Sonoma County Flood Management Design Manual adopted by Board Resolution on May 19, 2020, and will meet NRCS and State Division of Safety of Dams design criteria. The three preliminary alternatives identified in the Plan-EA differ by their primary components, flood storage, and design and construction costs as summarized in Table 1.
Table 1 Summary of NRCS Plan-EA Alternatives
|
|
Sediment Removal |
Seismic Stability Berms |
Lined Spillway |
Dam Crest Raise (ft) |
Flood Storage |
Design and Construction Cost1 |
|
|
|
|
|
|
|
|
|
Alternative 1 |
ü |
ü |
ü |
- |
~25-Year |
$47 M |
|
Alternative 2 |
ü |
ü |
- |
ü (3.4) |
~50-year |
$33 M |
|
Alternative 31 |
ü |
ü |
- |
ü (7.4) |
~100-year |
$35 M |
1 - Locally Preferred Alternative
NRCS will circulate the Draft Plan-EA for a 30-day public comment period in the summer of 2023 with a goal of responding to comments and developing a Final Plan-EA in late 2023. If, after completion of the Final Plan-EA, NRCS files a Finding of No Significant Impact, Sonoma Water will return to the Board for authorization to enter a Watershed Agreement and request 100% NRCS-funded final design assistance. Sonoma Water will comply with CEQA, obtain project approvals, and secure local permits during final design when the level of Project details and alternatives are commensurate with a CEQA-level impact analyses. If the final design phase results in an implementable project and local match funds can be secured for construction, NRCS would provide up to 65% of construction costs. Sonoma Water is actively seeking funding opportunities to meet our 35% construction cost share obligation.
Sonoma Water has been actively supporting NRCS’s NEPA planning process. Since October of 2021, Sonoma Water has filed formal notices in the Press Democrat, coordinated with local interest groups and the City of Santa Rosa, circulated notices to affected landowners and entities, provided updates to the Flood Control Zone 1A Advisory Committee, and led regulatory and public scoping meetings. Sonoma Water anticipates the following project milestones and schedule, which are subject to change based on the NRCS Plan-EA, outcomes of future phases, and Sonoma Water’s ability to secure local match funding.
• Draft Watershed Plan-EA released by NRCS: Summer2023
• Watershed Plan-EA Public Review Period: 30 Days
• Final Plan-EA and Finding of No Significant Impact: Winter 2023
• Enter Watershed Agreement for Design Funding: Winter 2023 (Requires Board Approval)
• Commence Final Design, CEQA, and Permitting: Spring 2024
Sonoma County Strategic Plan
This item directly supports the County’s Five-year Strategic Plan and is aligned with the following pillar, goal, and objective.
Pillar: Resilient Infrastructure
Goal: 5: Support, fund, and expand flood protection.
Objective: 3: Evaluate the feasibility, creation, and/or update of Flood Protection Plans and seek out financing mechanisms to establish protection zones countywide by 2026.
Sonoma Water Strategic Plan Alignment
Goal: Planning and Infrastructure - Implement comprehensive, integrated, and innovative infrastructure planning to strengthen existing services, minimize life cycle costs, and prepare for the future.
The current flood planning activities will result in implementation actions that improve community resilience to seismic events and climate change, reduce life and property risk from aging flood protection structures, and ensure continued and improved flood protection services in the Santa Rosa Creek watershed for future generations.
Prior Board Actions:
7/20/2021: A) Authorized Sonoma County Water Agency’s General Manager to execute an agreement with a consultant selected by Sonoma County Water Agency’s technical review panel for engineering and planning services related to the Central Sonoma Watershed Plan, through June 30, 2023, in the not-to-exceed amount of $1,400,000; B) Authorized Sonoma County Water Agency’s General Manager to amend the agreement to extend the term and make modifications to the scope of work provided the amendments do not increase the total cost to Sonoma County Water Agency beyond the not-to-exceed amount of $1,400,000; C) Adopted a Resolution Authorizing Adjustment to the Board Adopted Budget for Fiscal Year 2021-2022 for the Flood Control Zone 1A Fund in the amount of $875,000 for the Central Sonoma Watershed Plan - Environmental Assess
9/15/2020: A) Authorized Sonoma County Water Agency’s General Manager to execute a Cooperative Agreement with the United States Department of Agriculture Natural Resources Conservation Service in the amount of $1,200,000 in federal funding received to prepare a Watershed Plan and Environmental Assessment for the upgrade and rehabilitation of the Central Sonoma Watershed Project; B) Adopted a Resolution authorizing adjustments to the Board Recommended Budget for Fiscal Year 2020-2021 for the Flood Control Zone 1A Fund, in the amount of $82,000 for the Watershed Plan & Environmental Assessment for Central Sonoma Watershed Project.
5/19/2020: Adopted a Resolution approving the Updated Flood Management Design Manual Revised March 2020 to provide guidance and criteria for the conveyance of storm water.
Fiscal Summary
|
Expenditures |
FY 22-23 Adopted |
FY23-24 Projected |
FY 24-25 Projected |
|
Budgeted Expenses |
$250,000 |
$260,000 |
$250,000 |
|
Additional Appropriation Requested |
|
|
|
|
Total Expenditures |
$250,000 |
$260,000 |
$250,000 |
|
Funding Sources |
|
|
|
|
General Fund/WA GF |
|
|
|
|
State/Federal |
|
|
|
|
Fees/Other |
$250,000 |
$260,000 |
$250,000 |
|
Use of Fund Balance |
|
|
|
|
Contingencies |
|
|
|
|
Total Sources |
$250,000 |
$260,000 |
$250,000 |
Narrative Explanation of Fiscal Impacts:
Central Sonoma Watershed Project: Budgeted amount of $250,000 is available in Flood Control Zone 1A. Upon Board approval of submitting a Local Sponsor Statement of Commitment to NRCS, and upon NRCS granting assistance under the Watershed Rehabilitation Program, Sonoma Water will continue to expend budget for staff support of the NRCS Watershed Rehabilitation planning phase by reviewing environmental documents, scheduling and completing public meetings, and reviewing technical reports. NRCS will provide 100% of the costs to evaluate and plan for rehabilitation actions.
With NRCS’s assistance, Sonoma Water’s share of costs to support NRCS’s work will be budgeted in FY 2023/2024 and subsequent years. Without NRCS’s financial and technical support, the project would be delayed until Sonoma Water obtained alternative sources of funding to continue the planning and feasibility analyses.
Matanzas Creek Dam Rehabilitation Project: There is no fiscal impact associated with the Board update.
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Staffing Impacts: |
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Position Title (Payroll Classification) |
Monthly Salary Range (A-I Step) |
Additions (Number) |
Deletions (Number) |
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Narrative Explanation of Staffing Impacts (If Required):
None
Attachments:
Resolution
Related Items “On File” with the Clerk of the Board:
PowerPoint Presentation