After a historic 5-year drought in California a massive storm took locals and infrastructure by surprise. A Water Deeply article written by Ian Evans about the Oroville Dam in Butte County, California details what happened, why, and what’s next.
The wettest winter in California’s recent history threatened to collapse the dam and send billions of gallons of water through dozens of California communities. The heavy rainfall filled the reservoir to dangerous levels which caused the state to relieve some of the pressure by releasing water down the main spillway at rates of up to 54,500 cubic feet per second (cfs). Shortly after the state’s effort to ease the pressure, a 250-ft crater formed after a crack appeared in the spillway.
On February 11, the reservoir’s water rose high enough to flow over the emergency spillway (901ft). The next day, the water flowing down began to erode the hillside which endangered the entire dam to possibly collapse and send a 30ft wall of water into the valley and communities below. That same day, California officials ordered 188,000 people to evacuate the Feather River Basin the reservoir now threatened to flood. Luckily, the dam held up and water levels dropped below 850ft and residents cautiously reentered their homes.
“According to Martin McCann, Jr., the director of the National Performance of Dams Project at Stanford University, Oroville may have been an institutional failure as well as a structural one. Problems with the dam-building industry not paying attention to data on dam safety and structure, bad communication between groups – like engineers and geologists – and a failure to catch the signs of impending failures during routine inspections, all contributed to the Oroville Dam incident. They may point to a much larger problem.”
Repairs will cost California upwards of $700 million and a race against the clock to beat the rainy weather in November.
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