To: Board of Directors, Sonoma County Water Agency
Department or Agency Name(s): Sonoma County Water Agency
Staff Name and Phone Number: John Mendoza 707-547-1929
Vote Requirement: Majority
Supervisorial District(s): Countywide
Title:
Title
Engineering Support for the Lake Sonoma Forecast Informed Reservoir Operations Final Viability Assessment
End
Recommended Action:
Recommended action
Authorize Sonoma County Water Agency’s General Manager to execute an agreement with HDR Engineering, Inc., in a form approved by County Counsel, for Lake Sonoma Forecast Informed Reservoir Operations engineering support services through January 31, 2027, in the not-to-exceed amount of $165,000.
end
Executive Summary:
Sonoma County Water Agency (Sonoma Water) currently works with the United States Army Corps of Engineers (Corps) to operate water storage facilities at Lake Sonoma/Warm Springs Dam. In coordination with state and federal agencies, Sonoma Water is exploring methods to better balance flood control and water supply needs by utilizing modern rainfall observation and prediction technology to implement Forecast Informed Reservoir Operations (FIRO) at Lake Sonoma. The goal of this effort is to develop reservoir operations that will be authorized into a Water Control Manual update which will improve the water supply reliability and flood control operations at Lake Sonoma, while potentially reducing flood risk to communities downstream of Warm Springs Dam. Sonoma Water requires engineering support in completing the studies and analyses for the Lake Sonoma FIRO Final Viability Assessment (FVA).
Discussion:
HISTORY OF ITEM/BACKGROUND
Lake Sonoma is located on Dry Creek in Sonoma County, California. Created in 1984 by Warm Springs Dam, it provides flood control, water supply, recreation, and stream flow regulation. The Corps owns and operates the dam in accordance with the Lake Sonoma Water Control Manual, 1984 (Manual). Sonoma Water is the local partner that manages water stored in Lake Sonoma for water supply. The Manual specifies elevations for an upper volume of reservoir storage that must be kept available for capturing storm runoff and reducing flood risk and a lower volume of storage that may be used for water supply. During a flood event, runoff is captured by the reservoir and released soon after to create storage space in the reservoir for another potential storm. The Manual is based on typical historical weather patterns - wet during the winter, dry otherwise.
The Manual utilizes gross estimates of flood potential to establish reservoir storage and release requirements. It does not account for changing conditions in the watershed, such as increased variation in dry- and wet-weather patterns associated with climate change. Also, the Manual’s reservoir operational procedures were developed decades ago, without the benefit of current science that more accurately predicts weather and streamflow.
Given reduced supplies, changed hydrologic conditions, and technological advances, some adjustments to the current reservoir operating procedures may be possible to better achieve the goals of maintaining, or possibly improving, flood control while bolstering water supply reliability for downstream users and the environment (e.g., to support recovery of endangered and threatened fish). Modern observation and weather forecasting technology could be used to reduce flood risk by supporting decisions of greater reservoir level drawdown if the forecast predicts a large storm, and improve supply reliability by permitting more water to be retained in the reservoir if the forecast is dry.
In 2015, a multi-agency committee consisting of the University of California San Diego, Scripps Institute, Sonoma Water, the California Department of Water Resources, the Corps, the National Oceanic and Atmospheric Administration, and other agencies (Steering Committee) was formed to explore methods for using weather forecasts to better balance flood control and water supply needs at Lake Mendocino. After completing a FIRO FVA in 2020 at Lake Mendocino, which demonstrated the benefits of FIRO operations for water supply and flood control, the Steering Committee reformed in 2022 to develop a FIRO Workplan for Lake Sonoma that was completed in 2023. Based on the FIRO Workplan, the Steering Committee is currently working on a FVA to determine whether FIRO at Lake Sonoma can improve water supply, maintain and improve current flood protection, and achieve additional ecosystem benefits.
As part of the Lake Sonoma FIRO FVA, a scenario that includes a new outlet structure at Lake Sonoma will be analyzed. The outlet structure could potentially divert water from Lake Sonoma into the upper Alexander Valley, providing water supply benefits to communities along the Russian River, ecological benefits to the Endangered Species Act-listed species along the Russian River and Dry Creek, and flood control operational flexibility. The new outlet scenario will not be part of the current Lake Sonoma Manual update being completed by the Corps concurrent to the Lake Sonoma FIRO FVA, but will be used as a feasibility study in long-term planning for Lake Sonoma.
SELECTION PROCESS
HDR Engineering, Inc. (Consultant) was selected from a list of qualified consultants developed from a competitive selection process. Attached is a memo that explains the competitive selection process.
Consultant was selected for the subject work because of Consultant’s previous experience providing engineering support for the Lake Mendocino FIRO FVA completed in 2020, and Consultant’s assistance with developing the Lake Sonoma FIRO Workplan completed in 2023.
Sonoma Water may seek to amend or enter into subsequent agreement(s) with Board approval if required, relying upon this competitive selection process, after the preliminary or initial work is completed.
SERVICES TO BE PERFORMED
Consultant will evaluate scenarios as part of the Lake Sonoma FVA, including a new outlet structure in Lake Sonoma that can divert water into the Russian River in northern Alexander Valley. Consultant will develop a technical memorandum evaluating model results of the scenarios against agreed-upon metrics.
The cost of services will not exceed $165,000; the term end date is January 31, 2027.
The agreement includes authorization for the General Manager to make changes to lengthen time schedules or make minor modifications to the scope of work, which do not increase the amount paid under the agreement, in a form approved by County Counsel.
The agreement includes two options for Sonoma Water to extend the term for a period of one year each by providing written notice to Consultant thirty days in advance of the expiration date of the agreement and of the first extension option. The extension will be formalized in an amended agreement or amendment signed by Sonoma Water and Consultant.
County of Sonoma Strategic Plan Alignment
N/A
Sonom Water Strategic Plan Alignment
This item directly supports the County’s Five-year Strategic Plan and is aligned with the following pillar, goal, and objective.
Goal: Planning and Infrastructure
Strategy: Conduct planning that integrates and balances operational, maintenance, and infrastructure priorities
Acton: Continue to engage in planning efforts to support reliable wastewater and flood management services
The FIRO method conducted under the proposed agreement uses data from watershed monitoring and state-of-the-art weather and water forecasting to adaptively manage reservoir storage levels by incorporating forecasts of available water to meet the goals of improving water supply reliability without impairing flood protection to downstream communities.
Racial Equity:
Was this item identified as an opportunity to apply the Racial Equity Toolkit?
No
Prior Board Actions:
05/12/2020: Approved first amended agreement between Sonoma Water and HDR Engineering, Inc., for hydrologic and hydraulic engineering support for the Lake Mendocino forecast informed reservoir operations final viability assessment. Cost $270,000; term end March 31, 2022.
07/23/2019: Approved agreement between Sonoma Water and HDR Engineering, Inc., (formerly David Ford Consulting Engineers, Inc.) for hydrologic and hydraulic engineering support for the Lake Mendocino forecast informed reservoir operations final viability assessment. Cost $430,000; term end March 31, 2021.
10/23/2018: Approved fifth amended agreement between Sonoma Water and HDR Engineering, Inc., for forecast-informed reservoir operation design, development, deployment, and related services. Cost $83,915, term extended for a new not-to-exceed agreement total of $363,915 and end date of June 30, 2019.
10/25/2016: Approved fourth amended agreement between Sonoma Water and David Ford Consulting Engineers, Inc., for forecast-informed reservoir operation design, development, deployment, and related services. Cost $150,000, term extended for a new not-to-exceed agreement total of $280,000 and end date of June 30, 2019.
10/25/2016: Approved second amended agreement between Sonoma Water and David Ford Consulting Engineers, Inc., for forecast-informed reservoir operation design, development, deployment, and related services. Cost $36,000, term extended for a new not-to-exceed agreement total of $130,000 and end date of April 30, 2017.
10/13/2015: Approved first amended agreement between Sonoma Water and David Ford Consulting Engineers, Inc., for forecast-informed reservoir operation design, development, deployment, and related services. Cost $69,000, term extended for a new not-to-exceed agreement total of $94,000 and end date of December 31, 2016.
Fiscal Summary
|
Expenditures |
FY23-24 Adopted |
FY24-25 Projected |
FY25-26 Projected |
|
Budgeted Expenses |
$165,000 |
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Additional Appropriation Requested |
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Total Expenditures |
$165,000 |
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Funding Sources |
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General Fund/WA GF |
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State/Federal |
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Fees/Other |
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Use of Fund Balance |
$165,000 |
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General Fund Contingencies |
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Total Sources |
$165,000 |
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Narrative Explanation of Fiscal Impacts:
Budgeted amount of $165,000 is available from FY 2023/2024 appropriations for the Russian River Projects fund. No additional appropriation is required.
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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):
N/A
Attachments:
Competitive Selection Process Memo
Related Items “On File” with the Clerk of the Board:
None.