San Vicente Pipeline Tunnel

The San Vicente Pipeline Tunnel is part of the San Diego County Water Authority’s (SDCWA) Emergency Storage Project, the largest element of a $1.2 billion Capital Improvement Program. This pipeline will help sustain the region during a major earthquake. As prime consultant, Jacobs Associates served as tunnel and shaft designer. We are currently providing construction engineering support to SDCWA in its efforts to complete the project in a cost-effective manner while balancing community and environmental concerns.

This project involves the construction of a pipeline connecting San Vicente Reservoir, one of San Diego County’s major water storage facilities, and the Second Aqueduct, which delivers water from Northern California to San Diego County. In an emergency, this new connection will allow water to be distributed to agencies in the southern half of the county.

Most of the pipeline is being constructed in a tunnel about 11 miles (17.1 km) long with a finished inside diameter of 102 inches (2.6 m). This high-pressure water conveyance facility will have internal hydrostatic pressures ranging from about 200 to 250 psi (1.38 to 1.72 MPa).

Various tunneling methods are being used: an 11.5-foot (3.5 m) hard rock tunnel boring machine to bore through 5,255 feet (1.6 km) of granitic rocks, and two 12-foot (3.7 m) digger shields to excavate remaining sedimentary formations; drill-and-blast methods are being used in one reach, and the New Austrian Tunnel Method is being applied to a mixed face reach. Tunnel excavation is being staged from three shafts and one portal. Various rock support methods are being employed, including rock dowels, steel sets, and expanded precast segments. The final lining consists of systematic welded steel pipe.