Rising sea levels, as well as droughts and earthquakes, threaten the levees protecting the Sacramento-San Joaquin river delta, which supplies 25 million Californians with fresh water. But the state’s solution isn’t to build higher but lower—150 ft below the earth.
California’s Dept. of Water Resources plans to dig two gravity-fed, 40-ft-dia tunnels under the delta to move fresh water from the Sacramento River to federal pumping stations in the southern delta. First proposed in the 1960s as a peripheral canal skirting the delta, the $15.7-billion delta tunnel project received an environmental certification from the state in late July.