The project will upgrade the Vista Grande storm drain system, a regional stormwater system that drains northwest Daly City and an adjacent portion of San Mateo County within the watershed of Lake Merced. The existing system, built in the 1890’s, consisting of a canal and a tunnel that drain to the ocean, does not have adequate capacity to convey peak storm flows. The upgrades will reduce flooding and provide a water source for Lake Merced. The project includes: • Partial replacement of a 3,600-ft-long canal that will include a solids screening device, a constructed treatment wetland, and diversion and discharge structures • Replacement of the existing 3,000 ft long tunnel, expanding the internal diameter to 10.5 ft • Modifications to an existing effluent gravity pipeline • Modifications of the existing Lake Merced overflow structure • Replacement of the existing ocean outflow structure and a portion of the existing 33-inch-diameter submarine outfall pipeline across the beach • Additional civil, mechanical, electrical, and instrumentation work to support the above
