Oroville Dam Must Drain 50 Feet by Wednesday

Officials are releasing water from the Oroville Dam, the nation’s highest, at the astonishing rate of 100,000 cubic feet per second, with the goal of lowering the lake’s elevation by 50 feet before a week of rain and snow hits the region Wednesday.

At a press conference Sunday night, law enforcement and California Department of Water Resources officials announced that they had released enough water to stop flow over the emergency spillway, reducing the risk of erosion and structural collapse. The lake dropped below its maximum height of 901 feet above sea level, and was continuing to subside, officials reported.

However, water was continuing to flow into the lake behind the dam at a rate of 40,000 cubic feet per second, the result of runoff and snow melt from weeks of heavy precipitation after five years of drought. As a result, the dam would need to be drained as quickly as possible over the next 72 hours. The maximum release rate is about 150,000 cubic feet per second, though officials are reluctant to release water down the main spillway at that rate because of the risk of structural damage.

Already, the main concrete spillway has developed a large hole, which officials estimate will cost $100 to $200 million to fix. The adjacent emergency spillway, which drains onto an unpaved hillside of soil, rocks and trees, has also developed a hole  that could result in structural failure and that officials may have to plug by dropping rocks from helicopters. If the emergency spillway does collapse, it could lose 30 feet in height, releasing a wall of water into the Feather River below, which drains into the Sacramento River. That poses a severe risk to communities below the dam, including the state capital of Sacramento.

Officials issued an emergency evacuation order Sunday afternoon, warning that the emergency spillway was expected to collapse within an hour. That led to massive traffic jams as residents drove northward towards Chico. Though the spillway remains intact for now, nearly 200,000 residents from Oroville and surrounding communities remain under evacuation.

California Governor Jerry Brown issued an emergency order Sunday evening and indicated that the state was managing the relief effort.

.@JerryBrownGov Issues Emergency Order to Help Response to #OrovilleSpillway https://t.co/RW8XBlLFT6 pic.twitter.com/ULQGjkt1c1

— Gov. Brown Press Ofc (@GovPressOffice) February 13, 2017

Officials also said they were cooperating with the federal government. Separately, Gov. Brown had asked President Donald Trump for federal emergency relief funds to address damage to the state done by storms earlier this year.