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Vital power plant shut down after Oroville spillway erosion could be tested Friday, officials say

Construction crews clear rocks away from Oroville Dam's crippled spillway Feb. 28, 2017. California water authorities stopped the flow of water down the spillway Monday, allowing workers to begin clearing out massive debris that's blocking a hydroelectric plant from operating.
(Rich Pedroncelli / AP)
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A power plant at the foot of the Oroville Dam, closed last month after a portion of the reservoir was overwhelmed by rising waters, could begin tests as early as Friday in anticipation of reopening, state water officials said.

The Hyatt power plant, which provides drinking water and power and helps the Department of Water Resources control water levels at the state’s second largest reservoir, has been offline since the emergency that led to evacuations.

In a rapid chain of events in early February, powerful storms eroded the reservoir’s main flood control spillway, forcing its brief closure; that allowed the reservoir to reach capacity. When that happened, water poured over a concrete weir onto the reservoir’s emergency spillway – an unlined hillside – which quickly eroded to the point engineers feared it would collapse, triggering sweeping evacuations in Butte County.

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The erosion of the two spillways dumped an estimated 1.5 million cubic yards of brush, sediment and rock into a pool at the foot of the dam, or almost enough debris to fill the Houston Astrodome. The debris raised the water level of the pool, preventing the power plant from operating. The Department of
Water Resources relies on Hyatt to control water flowing out of the reservoir. Without it, there is greater reliance on the main, severely damaged spillway which officials fear could erode further.

Crews have so far pulled out an estimated 110,000 cubic yards of debris, said DWR spokeswoman Lauren Bisnett. When enough debris is pulled out, the water around the power plant will be low enough for Hyatt’s turbines to be tested, she said.

The work underway at Oroville, which feeds the Feather River, is a delicate balance between maintaining water levels in the river to support marine life but also ensuring the water in the reservoir doesn’t climb to levels engineers consider unsafe. If the water rises too high before the plant comes online, engineers would again have to use the damaged spillway, which has been dry since Monday morning.

joseph.serna@latimes.com

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