Giant rock wall built across Delta river to protect California’s water supply
For the past three weeks, construction crews working 24 hours a day have been stacking boulders across a river in eastern Contra Costa County, building what may be California’s biggest defense yet against the drought: a nearly 800-foot-long rock wall. The state’s emergency project, which was wrapping up Thursday, is designed to prevent San Francisco Bay’s salty flows from pushing into the coveted freshwater supplies of the Sacramento-San Joaquin River Delta. Water levels in the delta’s rivers and sloughs have dropped after two dry years, putting water for almost 30 million Californians at risk of saltwater intrusion. The plan is to keep the wall up until November…