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HomeMy WebLinkAboutMINUTES - 04092013 - PR.1RECOMMENDATION(S): ACCEPT presentation by the Contra Costa County Flood Control & Water Conservation District on the commencement of the Upper Sand Creek Restoration and Detention Basin Project, Brentwood and Antioch areas. (No Fiscal Impact) FISCAL IMPACT: There is no fiscal impact with this presentation. BACKGROUND: The Contra Costa County Flood Control & Water Conservation District (District) will soon begin construction of the Upper Sand Creek Restoration and Detention Basin Project (Project), in eastern Contra Costa County. The Project will consist of a 900 acre-foot capacity stormwater detention basin to provide regional flood protection to areas in the cities of Antioch, Brentwood, and Oakley. An acre-foot is the volume of water that covers an acre 12 inches deep, or 325,800 gallons. The capacity of the basin is equivalent to the City of Oakley covered with one inch of flood waters. The basin will detain flood waters, improve water quality through stormwater infiltration, improve groundwater supplies with stormwater infiltration, remove trash using an innovative trash capture device, and restore 3,500 linear feet of Sand Creek. The Project will also create seasonal APPROVE OTHER RECOMMENDATION OF CNTY ADMINISTRATOR RECOMMENDATION OF BOARD COMMITTEE Action of Board On: 04/09/2013 APPROVED AS RECOMMENDED OTHER Clerks Notes: VOTE OF SUPERVISORS AYE:John Gioia, District I Supervisor Candace Andersen, District II Supervisor Mary N. Piepho, District III Supervisor Karen Mitchoff, District IV Supervisor Federal D. Glover, District V Supervisor Contact: Carl J. Roner (925) 313-2213 I hereby certify that this is a true and correct copy of an action taken and entered on the minutes of the Board of Supervisors on the date shown. ATTESTED: April 9, 2013 David Twa, County Administrator and Clerk of the Board of Supervisors By: Stacey M. Boyd, Deputy cc: R. Mitch Avalon, PWD Administration, Mike Carlson, Flood Control, Paul Detjens, Flood Control, Carl J. Roner, Flood Control, Catherine Windham, Flood Control, Betsy Burkhart, County Administrator's Office PR. 1 To:Contra Costa County Flood Control District Board of Supervisors From:Julia R. Bueren, Public Works Date:April 9, 2013 Contra Costa County Subject:Presentation on the commencement of the Upper Sand Creek Restoration and Detention Basin project, Brentwood and Antioch areas. Project No. 7562-6D8518 BACKGROUND: (CONT'D) wetlands and riparian habitat fed by urban runoff. Construction of the Project will also allow the future development of the site as a regional sports park for the City of Antioch and east county residents. The primary purpose of the Project is to prevent flooding along the lower reaches of Marsh Creek between Sand Creek and the Marsh Creek outfall into the Sacramento-San Joaquin River at Big Break in Oakley by reducing peak flows from Sand Creek. Local stormwater runoff generated in the watershed will be conveyed by Sand Creek to the basin where it will be stored and released slowly through the basin outlet, reducing the potential for flooding downstream properties. Secondary purposes of the basin include habitat restoration and water quality enhancements. Construction of the basin will expand an existing interim flood control basin from 41-acres in area to a final constructed area of approximately 62 acres, and increase its flood storage capacity of the basin from 123-acre feet to 900-acre feet with a 35-foot maximum depth. The expansion will be constructed by excavating the existing interim basin floor to create a deeper basin where water will be held and slowly released downstream during major storm events. Excavation depths will range from 0 to approximately 37 feet below existing grade. Soil removed from the excavation will be used to construct an earthen dam on the northeast side of the basin to impound flood waters. Any remaining soil will be hauled off-site, stockpiled in the basin, or preferably placed on adjacent parcel(s) for future use by interested parties to reduce truck traffic impacts. Approximately 3,600 feet of Sand Creek will be reconstructed with a natural creek design to restore and enhance creek flows within the basin. Restoration plantings will include willows, cottonwoods, buckeyes, native roses, and dozens of blue and valley oaks collected by District staff from the existing trees in the basin. The seeds and cuttings were planted in pots by District staff who started a nursery to ensure the restoration plantings were truly native to the project site. These California Sage plants are another example of vegetation salvaged from the site prior to construction. These and other rescued native plant cuttings and seeds are being cultivated in the District’s Volunteer Restoration Nursery located at the Public Works Department in Martinez. When the grading project is completed this coming winter, the District invites the Board of Supervisors and City officials to visit the completed basin, plant these native plants as part of the restoration element of the project, and celebrate the completion of this important regional flood protection project and restoration of Sand Creek. CONSEQUENCE OF NEGATIVE ACTION: The presentation will not be accepted. CHILDREN'S IMPACT STATEMENT: Not applicable.