A gaping hole in the spillway of the Oroville Dam is causing problems after chunks of concrete flew off the nearly mile-long spillway, creating a 200-foot-long, 30-foot-deep hole in the structure.

The Oroville Dam is located about 150 miles northeast of San Francisco. The Oroville Lake is one of the largest man-made lakes in California, while the 770-foot-tall Oroville Dam is the nation’s tallest water structure.

Officials said that the critical flood control structure is @ 90% of its capacity, but the dam is still safe and so are Oroville’s 16.000 residents.

The lake is a central piece of California’s government-run delivery network, supplying water for agriculture in the Central Valley and residents and businesses in Southern California. After years of drought Northern California has endured several months of exceptional heavy rains.

Oroville and other lakes are brimming and have begun releasing water to make room for more runoff. The repair costs to plug the Oroville Dam spillway could approach $100 million, that could save them from having to use an emergency spillway for the first time in the reservoirs 48-year history.

The initial damage to the spillway occurred Tuesday, about 3.000 feet downstream from where water enters from the lake. Lake Oroville would naturally flow over a ungated concrete crest into the mostly unlined emergency spillway once the reservoir reaches 901 feet elevation.

The reservoir came within a foot from flowing over in January 1997.

AP / Crickey Conservation Society.


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