Water & Drought

One year later: The crisis at Oroville Dam

Oroville Dam spillway: 'It's not supposed to do that'

As engineers tested the damaged Oroville Dam spillway in February 2017, Eric See of the Department of Water Resources explains what workers saw after the hole formed.
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As engineers tested the damaged Oroville Dam spillway in February 2017, Eric See of the Department of Water Resources explains what workers saw after the hole formed.

The water was a furious, foaming, boiling mess. Things would only get worse.

One year ago, when the main flood-control spillway at Oroville Dam cracked in two on Feb. 7, 2017, the crater sent concrete chunks flying and water shooting off in all directions. The crisis at America’s tallest dam peaked five days later, with the frantic evacuation of 188,000 residents of Butte, Sutter and Yuba counties.

In February 2017, Oroville Dam's main and emergency spillways were significantly damaged, eventually prompting the evacuation of more than 180,000 people living downstream along the Feather River. The beginning of the crisis was caught early on in

The fractured spillway posed a huge challenge for the California Department of Water Resources. It wanted to limit the water releases on the spillway to contain the damage to the 3,000-foot-long concrete chute. But the rainy weather made a mockery of that strategy, and Lake Oroville filled up.

Approximately 188,000 people were evacuated due to the threat of the emergency spillway of the Oroville Dam, the United States' tallest dam, failing and unleashing flood waters. Here's drone footage from the California Department of Water Resource

On Feb. 11, the lake was so high that water started pouring over the adjacent emergency spillway for the first time ever. DWR officials initially said the structure was holding up fine. But one day later they noticed that the unpaved hillside below the emergency spillway was rapidly eroding, triggering fears that a “wall of water” would swamp much of Oroville and other downstream communities. Mandatory evacuations were ordered late in the afternoon of Feb. 12, clogging Highways 99 and 70 and creating havoc throughout much of the region.

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A California Highway Patrol officer, Ken Weckman, directs traffic during the Feb. 12 evacuation on Highway 70 in Marysville. Paul Kitagaki Jr. pkitagaki@sacbee.com

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Grace Moxley takes shelter at the Silver Dollar Fairgrounds in Chico the night of the Feb. 12 evacuation as the Oroville Dam emergency veered out of control. Paul Kitagaki Jr. pkitagaki@sacbee.com

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DWR Acting Director Bill Croyle, far right, became the “face” of the crisis, at first assuring residents that all was well but later conceding that the emergency spillway was in danger of failing. Butte County Sheriff Kory Honea, center, ordered the evacuations. This press conference took place Feb. 13. Paul Kitagaki Jr. pkitagaki@sacbee.com

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To keep the emergency spillway from crumbling, DWR dramatically ramped up water releases on the battered main spillway, bringing lake levels down and effectively ending the crisis. Water continued pounding the main spillway for days afterward, carving a giant crevice in the nearby hillside. This photo was taken Feb. 20. Hector Amezcua hamezcua@sacbee.com

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The sudden shutdown of water from Oroville Dam caused environmental havoc downstream. State biologists Alana Imrie, left, and Kevin Moncrief examine fish rescued in side pools from the receding water of the Feather River eight miles from the dam near Gridley on Feb. 28. Randy Pench rpench@sacbee.com

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The sheer power of the water being released from Oroville Dam’s fractured main spillway is evident in this Feb. 24 aerial photo. Heavy pounding on the concrete chute left the structure a shambles. Randy Pench rpench@sacbee.com

Bill Croyle, acting director of Department of Water Resources, explains the current plans to fix the Oroville spillway and the emergency spillway.

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The crisis deepened the festering resentment Oroville residents have held for DWR, which had failed to deliver on promises of state-of-the-art recreational facilities at the reservoir. Assemblyman James Gallagher, R-Yuba City, speaks at an Oroville town hall meeting on May 2. Jose Luis Villegas jvillegas@sacbee.com

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Fixing the two spillways turned into an $875 million job that wouldn’t be finished until the fall of 2018, although DWR promised the structures would be safe enough for the 2017-18 rainy season. Here, crews work on the repaired wall of the main spillway in mid-October. Randy Pench rpench@sacbee.com

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As the sun sets, workers place roller-compacted concrete onto the sidewall between the upper and lower chutes of the main spillway in late October. Kelly M. Grow California Department of Water Resources

Crews lay the last layer of concrete on the Oroville Dam spillway before the state Department of Water Resources’ deadline to have the structure ready to pass flows of 100,000 cubic-feet per second. This video was taken October 30, 2017, just two

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A worker from Kiewit Corp., the general contractor in charge of Oroville Dam repairs, cleans a joint between two rebuilt sidewall panels along the lower end of the main flood control spillway in November. The spillway will be used Tuesday for the first time since the February 2017 crisis. Ken James California Department of Water Resources

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A controlled blast clears rock for the placement of concrete on the lower end of the Oroville Dam main spillway on Dec. 12. Ken James California Department of Water Resources

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Kiewit Corp. workers connect drain pipes to the outer sidewalls of the upper chute of the main Oroville Dam spillway in December 2017. The spillway, rebuilt at a cost of $1.1 billion, could be used for the first time in early April. Ken James California Department of Water Resources

State officials say the Federal Emergency Management Agency will pay for three-quarters of the $875 million repair, although FEMA has indicated it might not pay to fix structures that were poorly maintained. A forensic investigation showed that the spillways were poorly designed and maintained over the years. Any repair costs not covered by FEMA will be shouldered by the local water agencies that belong to the State Water Project and store water behind the dam.

This compilation of drone footage from May 20, 2017 through November 1, 2017 highlights the transformation of Lake Oroville’s main spillway during repairs. Kiewit Infrastructure has led the massive construction effort to repair and reconstruct the

Note: An earlier version of this story incorrectly said that a sudden increase of water caused a negative impact on fish downstream. The negative impact was actually caused by a sudden decrease of water which left fish stranded in side pools.

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