Client: San Luis Obispo County
Questa completed the design of a comprehensive flood management project to protect the coastal town of Cambria in San Luis Obispo County. This area experiences frequent flooding from Santa Rosa Creek, in part due to development on the floodplain and the influence of the Coast Highway 1 Bridge. Questa was the lead consultant for the project, which took a multi-faceted approach to solving the flooding problems of the community. The scope of work included detailed biologic, geomorphic, and geotechnical studies, as well as the development and calibration of a HEC-HMS watershed runoff model using stream gauge data, completion of detailed channel hydraulic analysis using HEC-RAS, and development and presentation of alternatives to the County, community, and regulatory agencies. A flood bypass system, levee modifications, pressure storm drain, a new pump station, and a new Highway 1 bridge, including roadway elevation, were designed for the project. Initial conceptual design alternatives examined included upstream detention, channel modification, use of floodwalls, channel diversions, and pump systems, as well as bridge modifications. These design concepts were then turned into construction plans for review and approval by the County and Caltrans.
Since the creek supports a run of southern steelhead, as well as a population of California red-legged frog and tidewater goby, an important part of the work scope was to develop a plan that minimized aquatic habitat impacts and provided aquatic habitat enhancement; this was done in consultation with U.S. Fish and Wildlife Service and National Marine Fisheries Service. The project also entailed obtaining permits from the California Department of Fish and Game, National Marine Fisheries Service, U.S. Army Corps of Engineers, and the Regional Water Quality Control Board. Questa prepared the CEQA documentation and obtained a Coastal Development Permit.
Questa also completed final plans, specifications, and cost estimate for this project.