San Lorenzo River Lagoon Culvert Project

This project offers a multi-benefit solution to protect the neighborhoods surrounding the lower reaches of the San Lorenzo River from disruptive seasonal flooding while ensuring a safe seasonal habitat for endangered steelhead trout and tidewater goby.

ESA led the design and installation of this culvert project in partnership with the City of Santa Cruz, NOAA’s National Marine Fisheries Service, the U.S. Fish and Wildlife Service, the California Coastal Commission, the U.S. Army Corps of Engineers, the California State Water Resources Control Board, and the California Department of Fish and Wildlife.

ESA’s earlier designs with the culvert placement against the eastern banks of the San Lorenzo River.

ESA developed a novel hydrologic model for the San Lorenzo River to understand the influence of the project on the future behavior of the lagoon mouth, and the response of the lagoon water levels. This innovative head-driven pipeline system discharges lagoon water through the beach to the open ocean. The pipe is anchored along the eastern bank at the base of the headland bluff, along San Lorenzo Point. One interesting feature of this design is the below-grade infiltration gallery that extracts saltwater without disturbing lagoon fauna and the surface water intake that limits lagoon water levels to below flood stage.