The State of California recommends building a USD 12.7bn tunnel to bring water from the San Francisco Bay, south to the Sacramento-San Joaquin Delta.

A report issued by the Bay Delta Conservation Plan (BDCP) Steering Committee, a collaboration of state, federal and local agencies, recommends a 5mi (8km) single bore tunnel, with a 29ft (8.8m) i.d. from the Sacramento River to an intermediate forebay. Another 35mi (56km) dual bore tunnel with 35ft (10m) i.d. would then connect to a new forebay and pumping plant. Tunnels would run as deep as 150ft (45.7m).

The tunnel option is said to be the best for bringing needed drinking water to the Central Valley, while protecting the delta’s ecosystem. The final size of the tunnel will depend on future analysis of costs versus benefits and further assessment of environmental effects.

A coordinated federal report issued on the same day calls for the construction of a new water conveyance system, and restoration of tens of thousands of acres of marshes, wetlands and habitat.

“After years of drought, growing stress on water supplies, and with the Bay-Delta in full environmental collapse, it has become clear to everyone that the status quo for California’s water infrastructure is no longer an option,” said Ken Salazar, secretary of the interior.

The tunnel is estimated to cost approximately USD 12.7bn, and will be paid for by state and federal water contractors. A Public Review Draft BDCP should be available for public review and comment in fall 2011.