Two years ago, the Oroville Dam's main spillway failure forced 200,000 people to evacuate from rural northern California. Yesterday, after the state spent $1.1 billion on repairs, floodgates opened and water poured from a spillway into the Feather River for the first time since 2017.
The main spillway is not operating at full strength yet. It started off releasing 3,300 cubic feet per second (cfs), and by the afternoon the flow was up to 8,300 cfs. That may sound like a lot of water, but consider that in 2017, when its spillway had failed, it was releasing 100,000 cfs. That's the equivalent of 748,000 gallons every second.
“It’s operating as expected,” said Erin Mellon, communications manager for the Oroville Recovery project for the California Department of Water Resources, a small statement that belies the massive reconstruction project that went into rebuilding the main spillway. According to the , "visual reminders of the crisis abounded" at the restart, with bulldozers still working even as the water rushed through to the river.
On February 17, 2017, a crack opened up along the Dam's spillway, a 3,000-foot-long concrete chute meant to guide water into the river. To lessen the burden on the spillway, engineers limited the amount of water it would release daily. However, this had the side affect of letting Lake Oroville, the second-largest reservoir in California, rise to extraordinarily high levels.
The hillside holding the reservoir quickly began to dissolve under the pressure, threatening not only the dam itself but 188,000 residents nearby. Officials began to ratchet up the amount of water released as an evacuation plan went underway. The worst fears were staved off, but it took months before the spillway could be safely turned off for repairs. When the water finally stopped flowing on May 19, 2017, most of the lower half of the spillway's structure was gone.
With 1.2 million cubic yards of concrete poured in since then, the spillway has a new state-of-the-art drainage system. The $1.1 billion price tag far exceeds the initial price of $400 million, which shows how paying for infrastructure later often ends up costing more. While the emergency backup spillway hasn't been completed yet, officials say that the dam will be able to function safely through next winter.
“We’re prepared; we’ve spent the last two years restoring full functionality,” said Joel Ledesma, the deputy director of California Department of Water Resources, the Bee. “The industry has learned a lot since this (dam) was built 50 years ago.”