Interconnection of Large-Diameter Transmission Pipelines

The East Bay Municipal Utility District (EBMUD) is a major metropolitan water district located near San Francisco, California. Approximately 90% of the EBMUD water supply is conveyed by three 82 mi (132 km) long pipelines, the Mokelumne Aqueducts, from the Sierra Nevada to EBMUD's service area. For approximately 10 mi (16 km), the three parallel pipelines are elevated on pile-supported bents across the islands of the Sacramento-San Joaquin Delta, where there is significant risk of flooding and seismic hazards. A significant flood or seismic event in the Delta would likely damage the two oldest and most vulnerable aqueducts, and only the newer aqueduct, which has been seismically upgraded, would survive. To mitigate the risk of failure of one or more aqueducts, interconnections were constructed on both sides of the Delta. The interconnections will increase transmission capacity of the system by 50% by utilizing the capacity of the surviving portions of aqueduct outside of the Delta.