California Attorney General Xavier Becerra has sued Westlands Water District to block it from helping plan and build a project to raise the height of Shasta Dam.

The project poses “significant adverse effects on the free-flowing condition of the McCloud River and on its wild trout fishery, both of which have special statutory protections under the California Wild and Scenic Rivers Act,” Becerra’s office said in a statement.

The Act prohibits any California agency—including Westlands—from assisting or cooperating with actions to raise the Shasta Dam, Becerra said.

The suit joins another filed by an environmental coalition represented by Earthjustice that includes Friends of the River, Pacific Coast Federation of Fishermen’s Associations, Institute for Fisheries Resources, Natural Resources Defense Council, Defenders of Wildlife, Sierra Club, and Golden Gate Salmon Association.

The U.S. Bureau of Reclamation, which operates the dam, wants to raise it by 18.5 feet, and has been studying the idea of raising it and enlarging the reservoir since the 1980s. Most of the water would go to Westlands and its members in Fresno, Calif.

Congress in 2018 approved $20 million in the Water Infrastructure Improvements for the Nation Act to help with studies for the $1.4 billion project.

The 602-foot-high structure was completed in 1945. The site is also home to the 633-MW Shasta hydroelectric plant, with five turbine-generator units.