Lemon Street Flood Control Predesign and Design
Vallejo Sanitation & Flood Control District
West Yost prepare a detailed design and specifications for flood control improvements to address flooding following a December storm event. The project involved addressing changes within the watershed since the District’s Storm Drainage Master Plan was prepared. West Yost developed updated modeling which closely reproduced the actual flooding observed from the December storm, and conducted a detailed evaluation of alternatives, resulting in recommendations and ultimately design of a 2,600 feet of 96-inch bypass pipeline through a congested industrial area (in soft bay mud).
The project design also included clearing sediment and cattails from the Lake Dalwigk detention basin, adding open water and wetlands habitat around the perimeter, and modifying the lake outlet to lower the permanently ponded water within the basin. In support of the environmental review (conducted by others) two alternatives to the proposed project were evaluated, however, neither performed as well as the recommended project, and both alternatives were more costly. A formal benefit to cost evaluation for the proposed project was prepared using the FEMA software.
Other components included a diversion structure, modification of an existing pump station/weir, removal of nuisance vegetation and restoration with suitable native California grasses and trees, replacement of undersized culverts with a 14 feet by 7 feet box culvert, and other culvert and ditch improvements at two sites. West Yost divided the project into three bid packages to allow phasing of the construction and potential coordination of some of the project elements with future redevelopment along Sonoma Boulevard.
For the Lemon Street Flood Control Project, a formal benefit to cost evaluation for the proposed project was prepared using the FEMA software.