The Hetch Hetchy Aqueduct is a conveyance of Tuolumne River water runoff from federal lands in Yosemite National Park to San Francisco and its client municipalities in the greater San Francisco Bay Area. The system, completed in 1934, is a 167 mi (269 km) gravity-driven network of dams, reservoirs, tunnels, aqueducts and pipelines that delivers 31,900,000 cubic feet per day (900,000 m3/d), from the Hetch Hetchy Reservoir behind O'Shaughnessy Dam.
The aqueduct splits into four separate Bay Division pipelines at the point where it reaches the city of Fremont. These are called Bay Division Pipelines (BDPL) 1, 2, 3, and 4, with nominal pipeline diameters of 60, 66, 78, and 60 inches (1.5, 1.7, 2.0 and 2.4 m, respectively). All four pipelines cross the Hayward fault. Pipelines 1 and 2 cross the San Francisco Bay to the south of the Dumbarton Bridge. Pipelines 3 and 4 run to the south of the bay.
Read more about Hetch Hetchy Aqueduct: Infrastructure