California’s second largest reservoir filled with so much water last week that officials at the Oroville Dam, the nation’s tallest dam, were forced to open the main spillway, a long concrete chute that releases and reroutes water when the lake level is too high.
The release of water cratered the spillway, making a 200-foot-long, 30-foot deep hole, sparking fears that further erosion would cause the spillway to collapse. As the lake continued to swell, engineers opened the emergency spillway — a dirt hillside nearby — which also began to erode and was in danger of failing.
Fears of the structure collapsing and inundating communities in and around Oroville prompted officials to evacuate nearly 200,000 residents on Sunday. The evacuation order was lifted Tuesday.
