Calfornia Dam Uses Emergency Spillway to Control Water



Water flowing over the emergency spillway at Oroville Dam
The massive Oroville Dam in northern California is currently using an emergency spillway to spill excess water from its reservoir after the failure of its concrete lined spillway. Tuesday trouble showed up as the dam operators opened the regular spillway to move excess water more directly into the Feather River. What is normally an impressive flow of water suddenly turned into a turbulent maelstrom halfway down the concrete chute.

Water was shooting out of the concrete pathway and spilling sideways gouging out rocks, dirt and trees.

Workers shut down the spillway to investigate and found that a large hole had opened in the massive chute.

Heavy rains had filled the lake to 98% capacity and more was coming down. If they shut the spillway, the amount that could be released at the base of the dam would not be enough to prevent the lake from overfilling and spill uncontrollably over the top of the 700+ foot dam. So the workers decided to keep the spillway open and hope for the best.

By early Saturday the concrete spillway was badly damaged as the turbulence broke up further pieces of the trackage and water was flowing into the emergency spillway. The emergency spillway is an unpaved part of the hillside. This is the first time in the dam’s history that this has happened.

The 48 year old dam has been declared safe and California officials are not expecting any flooding in the towns downstream.

The Oroville Dam is a major supplier of drinking water, electricity and irrigation water for California’s agriculture industry. Lake Oroville is a popular recreation site.

The repair job won’t be cheap. An initial estimate is at least $200 million will be needed.

Repair to the Feather River is another matter. Direct damage to the river has occurred and a downstream steelhead salmon hatchery may be affected by the turbid water. Steelhead are an endangered species.

More Information:

PBS News Hour            

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