OROVILLE (CBS13/AP) — Officials at the nation’s tallest dam unleashed water down a rebuilt spillway Tuesday for the first time since it crumbled two years ago and drove hundreds of thousands of California residents from their homes over fears of catastrophic flooding.
Water will rush down the spillway and into the Feather River as storms this week and melting snowpack are expected to swell the lake behind Oroville Dam in the foothills of the Sierra Nevada, said Molly White, principal engineer with the California Department of Water Resources.
ALSO: California Free Of Drought For 1st Time Since 2011
The spring storms follow a very wet winter that coated the mountains with thick snowpack, which state experts will coincidentally measure Tuesday to determine the outlook for California’s water supplies. Heavy winter rain and snow has left the state drought-free for the first time since December 2011, experts say.
The dam’s main spillway “was designed and constructed using 21st century engineering practices and under the oversight and guidance from state and federal regulators and independent experts,” Joel Ledesma, deputy director of the department’s State Water Project, said in a statement.
“We spent the last two years restoring full functionality of the spillway. We expect it to run as designed,” Ledesma said during a news conference.
The original spillway on the 770-foot-high (235-meter) dam, which is 150 miles (241 kilometers) northeast of San Francisco, was built in the 1960s.
READ MORE ABOUT THE OROVILLE DAM SPILLWAY
In early 2017, storms drenched the state and the massive spillway broke apart as it carried heavy flows.
Dam operators reduced the flow and allowed water to run down an emergency spillway – essentially a low area on the reservoir’s rim – but the flow began eroding the earthen embankment that had never been used. Authorities suddenly had to order an evacuation of nearly 200,000 people living in communities downstream.
The threat of a dam collapse that would unleash a torrent of water did not happen, however, and people were allowed to go home days later.
ALSO: California Wants To Aim Lasers At Snowpack To Better Predict Runoff
In January 2018, an independent panel of dam safety experts released a nearly 600-page report that blamed the crisis on “long-term and systemic failures” by California dam managers and regulators to recognize inherent construction and design flaws in the dam.
Repairs have cost $1.1 billion. California requested about $639 million from the Federal Emergency Management Agency for the fixes, but the federal government has rejected $306 million of those reimbursements. U.S. officials say the dam’s upper gated spillway was damaged prior to the heavy rain two years ago.
Local water agencies are already paying some of the repair costs, and they would cover anything not paid by the federal government.
Swipe through photos below of the Oroville Dam.
oroville dam spillwayCredit: California Department of Water Resources
oroville dam spillway (credit dwr)
oroville dam spillway ready
Oroville Dam Spillway(Source: California Department of Water Resources)
oroville dam
oroville dam spillway mondayThe new Oroville Dam Spillway on Nov. 28. Work continues on shoring up the spillway. (Credit: California DWR)
Oroville Dam Spillway(Credit: CBS13)
Then And Now: California's Drought Officially Declared To Be OverOROVILLE, CA - APRIL 11: A view of of the heavily damaged spillway at Lake Oroville on April 11, 2017 in Oroville, California. After record rainfall and snow in the mountains, much of California's landscape has turned from brown to green and reservoirs across the state are near capacity. California Gov. Jerry Brown signed an executive order Friday to lift the State's drought emergency in all but four counties. The drought emergency had been in place since 2014. (Photo by Justin Sullivan/Getty Images)
Then And Now: California's Drought Officially Declared To Be OverOROVILLE, CA - APRIL 11: A view of of the heavily damaged spillway at Lake Oroville on April 11, 2017 in Oroville, California. After record rainfall and snow in the mountains, much of California's landscape has turned from brown to green and reservoirs across the state are near capacity. California Gov. Jerry Brown signed an executive order Friday to lift the State's drought emergency in all but four counties. The drought emergency had been in place since 2014. (Photo by Justin Sullivan/Getty Images)
Then And Now: California's Drought Officially Declared To Be OverOROVILLE, CA - APRIL 11: A view of of the heavily damaged spillway at Lake Oroville on April 11, 2017 in Oroville, California. After record rainfall and snow in the mountains, much of California's landscape has turned from brown to green and reservoirs across the state are near capacity. California Gov. Jerry Brown signed an executive order Friday to lift the State's drought emergency in all but four counties. The drought emergency had been in place since 2014. (Photo by Justin Sullivan/Getty Images)
Then And Now: California's Drought Officially Declared To Be OverIn this composite image a comparison has been made between a view of California during severe drought in 2014 (top) and during the week that the majority of the state's drought emergency is due to be lifted (bottom). **TOP IMAGE** OROVILLE, CA - AUGUST 19, 2014: The Oroville Dam spillway stands dry at Lake Oroville on August 19, 2014 in Oroville, California. As the severe drought in California continues for a third straight year, water levels in the State's lakes and reservoirs is reaching historic lows. Lake Oroville is currently at 32 percent of its total 3,537,577 acre feet. As the severe drought in California continues for a third straight year, water levels in the State's lakes and reservoirs is reaching historic lows. Lake Oroville is currently at 32 percent of its total 3,537,577 acre feet. (Photo by Justin Sullivan/Getty Images) **BOTTOM IMAGE** OROVILLE, CA - APRIL 11, 2017: A view of of the heavily damaged spillway at Lake Oroville on April 11, 2017 in Oroville, California. After record rainfall and snow in the mountains, much of California's landscape has turned from brown to green and reservoirs across the state are near capacity. California Gov. Jerry Brown signed an executive order Friday to lift the State's drought emergency in all but four counties. The drought emergency had been in place since 2014. (Photo by Justin Sullivan/Getty Images)
Work Continues To Shore Up The Oroville DamOROVILLE, CA - FEBRUARY 17: In this handout provided by the California Department of Water Resources (pixel.water.ca.gov), Workers look over the diversion pool across from the damaged spillway at Oroville Dam, as work continues to shore up the bank so heavy equipment can remove sediment and debris from the waters on February 17, 2017 in Oroville, California. Last weekend overflow waters from the emergency spillway eroded much of the area below the spillway. The California Department of Water Resources continues to examine and repair the erosion with more than 125 construction crews working around the clock, and placing 1,200 tons of material on the spillway per hour using helicopters and heavy construction equipment at the Butte County site. (Photo by Brian Baer/ California Department of Water Resources via Getty Images)
Work Continues To Shore Up The Oroville DamOROVILLE, CA - FEBRUARY 17: In this handout provided by the California Department of Water Resources (pixel.water.ca.gov), A long line of concrete trucks wait on the top of Oroville Dam to deliver concrete for the erosion repair work at the base of the Oroville Dam emergency spillway on February 17, 2017 in Oroville, California. Last weekend overflow waters from the emergency spillway eroded much of the area below the spillway. The California Department of Water Resources continues to examine and repair the erosion with more than 125 construction crews working around the clock, and placing 1,200 tons of material on the spillway per hour using helicopters and heavy construction equipment at the Butte County site. (Photo by Brian Baer/ California Department of Water Resources via Getty Images)
Work Continues To Shore Up The Oroville DamOROVILLE, CA - FEBRUARY 17: In this handout provided by the California Department of Water Resources (pixel.water.ca.gov), Work continues along the riverbank across the damaged spillway at Oroville Dam, to shore up the bank to allow heavy equipment to remove sediment and debris from the diversion pool on February 17, 2017 in Oroville, California. Last weekend overflow waters from the emergency spillway eroded much of the area below the spillway. The California Department of Water Resources continues to examine and repair the erosion with more than 125 construction crews working around the clock, and placing 1,200 tons of material on the spillway per hour using helicopters and heavy construction equipment at the Butte County site. (Photo by Brian Baer/ California Department of Water Resources via Getty Images)
Work Continues To Shore Up The Oroville DamOROVILLE, CA - FEBRUARY 17: In this handout provided by the California Department of Water Resources (pixel.water.ca.gov), aA worker walks down the damaged roadway near the Oroville Dam emergency spillway on February 17, 2017 in Oroville, California. Last weekend overflow waters from the emergency spillway eroded much of the area below the spillway. The California Department of Water Resources continues to examine and repair the erosion with more than 125 construction crews working around the clock, and placing 1,200 tons of material on the spillway per hour using helicopters and heavy construction equipment at the Butte County site. (Photo by Brian Baer/ California Department of Water Resources via Getty Images)
Work Continues To Shore Up The Oroville DamOROVILLE, CA - FEBRUARY 17: In this handout provided by the California Department of Water Resources (pixel.water.ca.gov), Water continues to move down the damaged spillway at Oroville Dam with an outflow of 80,000 cubic feet per second (cfs) on on February 17, 2017 in Oroville, California. Last weekend overflow waters from the emergency spillway eroded much of the area below the spillway. The California Department of Water Resources continues to examine and repair the erosion with more than 125 construction crews working around the clock, and placing 1,200 tons of material on the spillway per hour using helicopters and heavy construction equipment at the Butte County site. (Photo by Brian Baer/ California Department of Water Resources via Getty Images)
lake oroville damWater being released from the Oroville Dam's spillway on May 10. (Credit: California Department of Water Resources)
butte fireThe smoke plume can be clearly seen from the Oroville Dam. (Credit: CA State Parks)
Thousands Evacuated Near Oroville Dam As Spillway Threatens To FailOROVILLE, CA - FEBRUARY 15: Reconstruction continues in a race to shore up the emergency spillway at Oroville Dam in Oroville, Calif., on Feb. 15, 2017. (Brian van der Brug/Los Angeles Times via Getty Images)
Oroville Dam Spillway
oroville dam spillway
dwr OROVILLE SPILLWAYCrews working on the Oroville Dam's main spillway on Thursday. (Credit: CA DWR)
dwr-orovilleWater flow at the Oroville Dam spillway on Sunday. (Credit: California DWR)
US-DAM-WEATHERThe Oroville Dam spillway releases 100,000 cubic feet of water per second down the main spillway in Oroville, California on February 13, 2017. (Credit: JOSH EDELSON/AFP/Getty Images)
dam-spillway-workCrews working to shore up the Oroville Dam emergency spillway. (Credit: California DWR)
Thousands Evacuated Near Oroville Dam As Spillway Threatens To FailOROVILLE, CA - FEBRUARY 14: A helicopter is seen above the damaged main spillway of the Oroville Dam on February 14, 2017 in Oroville, California. More than 188,000 people were ordered to evacuate after a hole in the emergency spillway in the Oroville Dam threatened to flood the surrounding area. (Photo by Elijah Nouvelage/Getty Images)
Copyright 2019 The Associated Press.