Oroville Dam: A race to brace spillway for storms arriving tonight


Crews worked through the night to shore up the emergency spillway at troubled Oroville Dam, racing to fortify the structure before a series of storms arrive Wednesday night.

Three storm systems will hit Northern California during the next six days, according to the National Weather Service. The first system will drop about an inch of rain in Oroville between 10 p.m. Wednesday and 4 p.m. Thursday. Greater amounts of precipitation will fall in the mountains northeast of Lake Oroville.

Forecasters are confident that the first two storm systems will not cause huge inflows into Lake Oroville. They are less confident about the third system, which is due around Tuesday. That storm could be bigger and warmer, meaning more rain and snowmelt streaming into Lake Oroville.

“The third wave is looking like our problem child,” said Michelle Mead, warning coordination meteorologist at the National Weather Service in Sacramento.

Officials continued to release water from Lake Oroville’s fractured main spillway at 100,000 cubic feet per second Wednesday to make room for the storms. The main spillway, which has a jagged crater in its midsection that formed last week, is holding under the strain, said Chris Orrock, state Department of Water Resources spokesman. The water flowing from the spillway is clear, indicating the midsection isn’t further eroding.

Engineers want to keep lake levels well below 901 feet, the depth at which water begins to flow over an adjacent emergency spillway. Concern over apparent erosion on the emergency spillway after it activated over the weekend led officials to evacuate almost 200,000 people in Butte, Sutter and Yuba counties Sunday night.

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