California Gov. Gavin Newsom’s administration unveiled a 3,000-page draft version of an environmental impact report for a scaled-down version of the California Water Fix tunnel. The new plan includes a single tunnel that would divert water from California’s Sacramento River and route it under the Sacramento-San Joaquin Delta to farms and cities in southern California. The newest version of the plan, now called the Delta Conveyance — which is a trimmed-down version of tunnel scenarios proposed by the administrations of Govs. Arnold Schwarzenegger and Jerry Brown — would grab excess water delivered by big storms and divert some of those Sacramento River flows.

All along, the Metropolitan Water District of Southern California has been a major driver of this replumbing, the Los Angeles Times reported.
As a historic drought intensifies its grip, and sea-level rises threaten to make the delta more salty, water managers in California’s most populated urban areas are growing increasingly concerned about the existing system for pumping supplies through the delta. The area is not only a hub for conveying water but also an estuary that is home to rare species, some on the brink of extinction.

The Sacramento Bee reported that two massive, arena-sized pumping stations built in the south Delta near Tracy decades ago are so powerful they alter the currents inside the estuary and cause problems for migrating fish. As fish numbers have dipped closer and closer to extinction over the years, regulators have forced the pumping stations to ratchet back the amount of Delta water that gets pumped into state and federal canals. To address the growing Delta water-delivery bottleneck, both Newsom’s and Brown’s plans would build intakes a few miles south of Sacramento that would siphon off a portion of the Sacramento River’s flows during heavy storms and route it under the Delta so that fresh, clean water could head to the south state without as many environmental harms.

The state’s favored proposal outlines the construction of a tunnel — 11 m (36 ft) in diameter on the inside — crossing the eastern side of the delta, whereas an earlier version went down the middle. It would capture water from the Sacramento River, just 27 km (17 miles) south of the state capital, and deliver it to the Bethany Reservoir, northwest of Tracy, where the existing State Water Project pumps are.

If constructed, it would be the state’s largest infrastructure venture since the high-speed rail system, a project that has faced numerous delays, cost overruns and litigation — hurdles that could also hobble the water tunnels. It would also create thousands of jobs — one reason the state’s powerful labor unions have backed versions of it for decades, along with numerous governors.

Cost estimates are running around $16 billion — $3 billion less than the previous iteration, a double-tunnel system proposed in 2018, during Brown’s administration.

Large water districts, including the Metropolitan Water District and the Santa Clara Valley Water District in San Jose, have been funding the planning of the tunnel system for years. They are joined by 14 other water agencies that receive water from the State Water Project.

Between 2021 and 2024, that group of water agencies, known as the Delta Conveyance Design and Construction Authority, planned to spend about $360 million on the effort. The Metropolitan Water District is footing about 44 percent — roughly $160 million.

The single tunnel project is smaller than iterations proposed during the Brown and Schwarzenegger administrations. This new one has a maximum capacity of 6,000 cubic feet per second, whereas Brown’s plan called for a capacity 50 percent higher. Schwarzenegger’s plan was even bigger — 15,000 cubic feet per second.