Water & Drought

California unveils environmental blueprint for Delta tunnels

Aerial photo of the region to be affected by the Delta tunnels, near Courtland and Clarksburg.
Aerial photo of the region to be affected by the Delta tunnels, near Courtland and Clarksburg. Sacramento Bee file

California officials Tuesday released a detailed environmental blueprint for Gov. Jerry Brown’s controversial Delta tunnels project, saying the $15.5 billion plan “minimizes potential effects” on endangered fish species whose populations have dwindled following decades of water pumping.

The Department of Water Resources unveiled its so-called “biological assessment” for the proposed tunnels, which are designed to re-engineer the plumbing of the battered Sacramento-San Joaquin Delta in order to improve reliability of water deliveries to the San Joaquin Valley and Southern California.

The assessment, which runs hundreds of pages, is a necessary step in the lengthy planning process. Two federal agencies responsible for overseeing the Delta’s fish population, the U.S. Fish and Wildlife Service and National Marine Fisheries Service, now have to take the document and decide whether the tunnels would violate the Endangered Species Act.

The agencies received a draft version of the assessment last fall. State officials are eager to secure a decision before President Barack Obama leaves office in January. Otherwise, the process would essentially have to start over with a new administration, potentially squandering years of work.

The project would divert a portion of the Sacramento River’s flow near Clarksburg, and send that water via twin tunnels 30 miles to the Delta pumping stations near Tracy. Planners say the new system would alter the Delta’s current flow patterns in a way that would protect the Chinook salmon and Delta smelt from harmful effects of the pumps.

Critics say diverting the water at Clarksburg would greatly diminish the amount of fresh water at critical points in the Delta, hurting agriculture and damaging water quality.

Dale Kasler: 916-321-1066, @dakasler