200-Foot Hole Growing In Oroville Dam Spillway; No Threat To Dam, But Lake Rising 6"/Hour
A gaping hole in the spillway for the tallest dam in the United States has grown and California authorities said they expect it will continue eroding as water washes over it but the Oroville Dam and the public are safe. Earlier this week, chunks of concrete flew off the nearly mile-long spillway, creating a 200-foot-long, 30-foot-deep hole. Engineers don't know what caused cave-in that is expected to keep growing until it reaches bedrock.
But faced with little choice, the state Department of Water Resources resumed ramping up the outflow from Lake Oroville over the damaged spillway to keep up with all the runoff from torrential rainfall in the Sierra Nevada foothills. Officials said the critical flood-control structure is at 90 percent of its capacity. But the dam is still safe and so are Oroville's 16,000 residents.
"The integrity of the dam is not jeopardized in any way because the problem is with the spillway and not the dam," department spokesman Eric See said.
Located about 150 miles northeast of San Francisco, Oroville Lake is one of the largest man-made lakes in California and 770-foot-tall Oroville Dam is the nation's tallest. The lake is a central piece of California's government-run water delivery network, supplying water for agriculture in the Central Valley and residents and businesses in Southern California.
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http://abcnews.go.com/Technology/wireStory/gaping-hole-spillway-tallest-us-dam-growing-45396597
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