California's governor has restarted a project to build a giant, underground tunnel that would pump billions of gallons of water from the San Joaquin Delta to the southern part of the state.

Gov. Gavin Newsom's administration on Wednesday issued a Notice of Preparation for the project, which is the first step in the state's lengthy environmental review process.

Last year, Newsom halted a similar project that would have built two tunnels for the same purpose. The new project will have only one tunnel, and it will carry less water. State officials don't know how much it will cost.

“This project would help safeguard a vital source of affordable water for millions of Californians,” said Karla Nemeth, director of the California Department of Water Resources.

The tunnel would be a major addition to the State Water Project, the complex system of reservoirs, aqueducts and pumping plants that deliver water to more than 27 million Californians and 3 million acres of farmland. The water comes from rain and snow in the Sierra Nevada mountains.