To: The Contra Costa County Flood Control and Water Conservation District Board of Supervisors
From: Warren Lai, Public Works Director/Chief Engineer
Report Title: APPROVE the Marsh Creek Reservoir Restoration and Total Mercury Reduction Project, and take related actions under the California Environmental Quality Act, Brentwood area.
☒Recommendation of the County Administrator ☐ Recommendation of Board Committee
RECOMMENDATIONS:
Acting as the governing body of the Contra Costa County Flood Control and Water Conservation District, APPROVE the Marsh Creek Reservoir Restoration and Total Mercury Reduction Project (Project), Brentwood area. DCD-CP# 23-25, and
FIND, on the basis of the whole record, including the proposed Initial Study/Mitigated Negative Declaration and any comments received and staff responses thereto, that there is no substantial evidence the Project may have significant effect on the environment, and that the Mitigated Negative Declaration (MND) reflects the independent judgment and analysis of the lead agency, Contra Costa County (County).
ADOPT the MND and Mitigation and Monitoring Reporting Program for the Project.
SPECIFY that the Chief Engineer, or designee, is the custodian of the documents and other material that constitute the record of proceedings upon which the Board’s decision is based, and that the record of proceedings is located at 255 Glacier Drive, Martinez, California.
DIRECT the Director of the County Department of Conservation and Development, or designee, to file a Notice of Determination (NOD) with the County Clerk, and,
AUTHORIZE the Chief Engineer, or designee, to arrange for payment of $3,043.75 for California Department of Fish and Wildlife fees and a $50 fee to the County Clerk for filing the NOD.
FISCAL IMPACT:
The Project planning is 52% funded by the Flood Control District Zone 1 Funds and 48% State Grant Funds (Proposition 1 Ecosystem Restoration and Water Quality Grant Program provided by Delta Conservancy). Project No. 7521-6D8495
BACKGROUND:
The Marsh Creek Reservoir, located approximately four miles southwest of the City of Brentwood in Contra Costa County, was constructed in 1962 to provide flood protection to the downstream communities of Brentwood and Oakley. Over the past 60 years, mercury-laden sediment accumulation has diminished reservoir capacity and degraded water quality. The source of mercury is from an abandoned mercury mine at the base of Mount Diablo, several miles upstream of the Project location. The Project intends to improve reservoir capacity, restore and increase ecosystem functions and values, increase reservoir and habitat resilience to climate change, reduce mercury output to downstream Sacramento-San Joaquin Delta habitats, and improve aesthetic value.
The Project would excavate excess accumulated sediment and debris from the wet pool of the Reservoir adjacent to the dam, dry the removed material, store the material on site for potential future reuse, create a high-flow diversion, restore riparian habitat, clean and maintain the existing primary outfall, and install cattle exclusion fencing.
CONSEQUENCE OF NEGATIVE ACTION:
Delay in approving the Project may result in a delay of design and construction of the Project.