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The Oroville Dam spillway failed miserably, so California is blowing it up

The Oroville Dam's damaged spillway, which threatened massive flooding in February, are now being demolished with controlled explosives. This slow-motion video shows two explosions that took place on May 31. (Video: California Department of Water Resources)

The cause of one of the year’s most memorable weather disasters is getting the boom this month — the spillway on the Lake Oroville Dam in California. In February, the spillway failed spectacularly, to the tune of 200,000 people evacuated from their homes.

After torrential winter storms, water poured over the lake’s spillways. The main spillway, which was ostensibly designed to bear the weight, crumbled on one side and allowed a torrent to flow out of the spillway onto the wall of the dam itself. That’s problematic because this area of the dam is literally just a hill.

If authorities hadn’t unplugged the dam in time to bring the lake level below the spillway, the sides of the dam could have eroded, which would have unleashed the contents of Lake Oroville onto the surrounding communities.

Now that the rainy season is over, the California Department of Water Resources is working to replace the entire spillway infrastructure, which was doomed to fail, according to an independent analysis. That involves using controlled explosions to break up the cement, which you can see in the video above.

Dozens of contractors in concrete, gravel and trucking are working on the project and have been paid millions of dollars by the state, according to the Sacramento Bee.

The department estimates the spillway construction will be completed by Nov. 1.

Lake Oroville holds more than 1 trillion gallons of water, making it one of California’s largest manmade lakes. At 770 feet, the Oroville Dam is the nation’s tallest. Lake Oroville provides water to agriculture, residents and businesses downstream in the Sierra Nevada and Central Valley. Some of its water also makes it down to Southern California, where water resources tend to be fewer.

Correction: This post has been updated to reflect that the spillway being replaced is the main spillway, not the emergency spillway. Thanks to my savvy readers for catching the error!