On Sunday, nearly 200,000 people received notice to evacuate their homes immediately, as the nearby Oroville Dam appeared to have been structurally compromised by sudden erosion. An imminent failure of the dam’s auxiliary spillway was anticipated, and though the spillway has held, expected storms this coming week make the future of the area uncertain.
The Washington Post reports that the dam itself is structurally sound, but a hole in the main spillway is still threatening the area. Spillways are meant to lower water levels and release pressure on the dam in a controlled manner. California has been experiencing a record-setting drought for years, but so far in 2017 the rainfall has been at 228 percent above normal for the area. This is the first time in 50 years that water has come down the emergency spillway.
Bill Croyle, acting director of the state’s Department of Water Resources, said that the lake would have to lower about 50 feet to reach the levels at which the dam normally operates. Authorities have stated they plan to use a helicopter to drop rocks into the spillway hole. The California National Guard has committed 8 helicopters to the repair attempt, but Croyle did seem to express some worry over the plan, saying in a press conference on Sunday night that they determined they “could not fix the hole” and stated “you don’t just throw a little bit of rock in it.”
Weather reports indicate it will be dry through Tuesday, but another four inches of rain is expected on Thursday and Friday, giving the state a narrow window of time to attempt repairs and making the possibility of return uncertain for residents of the Oroville area. In addition to people, the California Department of Fish and Wildlife evacuated five million baby Chinook salmon, after brown muddy water from the eroded spillway began to filter downstream into the Feather River Hatchery below.