AgdaPkt 2011-09-12 - Laserfiche WebLink

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8.A. - Page 1 REPORT To the Honorable Mayor and City Council From the City Manager September 12, 2011 SUBJECT Bayfront Canal Drainage Improvement RECOMMENDATION This is an information -only staff report. BACKGROUND The Bayfront Canal was originally built by Leslie Salt Company (currently Cargill) in 1945. It extends from Douglas Court to Marsh Road just south of Cargill's salt ponds. The Canal, maintained by Redwood City through easement, is the single stormwater collection canal that collects runoff from the Atherton Channel and six drainage basins and discharges through a single outlet to Flood Slough then out to the Bay. In addition to Redwood City, various neighboring jurisdictions, such as unincorporated areas administered by the County of San Mateo, the cities of Atherton and Menlo Park, and the Town of Woodside, all contribute runoff to the Bayfront Canal through flows to the Atherton Channel and /or other drainage basins. A tide gate structure, located at the Canal outlet off Marsh Road, was installed to eliminate backflow of bay water into the Canal at periods of high tide and to allow outflow at periods of low tide. Flooding has occurred in the neighborhoods and communities around and near the Bayfront Canal and Atherton Channel. During storms that coincide with high tides, the Canal and Channel cannot discharge stormwater to the Bay due to hydraulic constraints at the tide gates, and at times they do not have enough detention capacity to prevent flooding in low lying areas. Excess runoff from the Fifth Avenue basin, the County's Second Avenue basin, and Atherton's Selby Lane basin overflows to the adjacent Douglas drainage basin, and overwhelms Redwood City's Douglas pump station. These conditions can cause wide spread flooding throughout the low -lying areas adjacent to the Bayfront Canal, in the Fifth Avenue basin, the Douglas basin, and the Haven Avenue area in Menlo Park. On November 22, 2010 the City Council held a study session on the Bayfront Canal drainage system, and formed a Storm Drainage Subcommittee comprised of Council Members Bain, Gee, and Pierce to provide policy directive and facilitate regional collaboration.