Oroville Dam: New time-lapse video shows spillway rising from rubble
Oroville Dam: New time-lapse video shows spillway rising from rubble
Construction crews at Oroville Dam continue to race to rebuild the broken spillway by Nov. 1.
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http://www.mercurynews.com/2017/08/25/oroville-dam-time-lapse-video-shows-spillway-being-rebuilt
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Oroville Dam: Thousands evacuated in California after plans for emergency spillway fail': VIDEO
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By PAUL ROGERS | progers@bayareanewsgroup.com | Bay Area News Group
PUBLISHED: August 25, 2017
New time-lapse video released from the state Department of Water Resources shows the new main spillway at Oroville Dam in Northern California rising from the rubble of the former spillway after one of the nation’s most serious dam accidents earlier this year.
Hundreds of construction workers are working 20 hours a day, six days a week with huge dump trucks, cranes, excavators, bulldozers, concrete pumps and other equipment to demolish and rebuild the 3,000-foot-long main spillway, and shore up the emergency spillway. The goal of the $500 million project to rebuild enough of the main spillway — which is as wide as 15 lanes of freeway — by Nov. 1 so that it can be ready for heavy rains this winter. The entire job is scheduled to be finished in 2018.
This footage was shot by a camera looking down the spillway toward the Feather River. It was shot between June 26 and Aug. 22 by Kiewit Corp., of Omaha, Nebraska, the lead contractor on the job. The most dramatic changes begin to occur at about :30 seconds into the footage, as crews begin laying roller-compacted concrete that will form a base for structural concrete, reinforced with steel, that will be placed on top of it.
This week, state DWR officials said that the job remains on schedule.
Oroville Dam is the tallest dam in the United States, at 770 feet high. It is a critical part of California’s water system, providing water to farmers across the Central Valley and millions of people from San Jose to San Diego.
In February, water flowing down the main spillway during raging winter storms that ended California’s five-year drought ripped a huge hole in that concrete structure. State dam officials closed the gates on the main spillway then to assess the damage, allowing Lake Oroville, California’s second largest man-made reservoir, to fill to to the top.
As water flowed over the dam’s emergency spillway, it violently eroded the base of the hill on which it was built, leading authorities to evacuate 188,000 people over fears that it could collapse and possibly send a wall of water onto Oroville, Marysville, Yuba City and other towns below, which could have killed thousands of people.
To stave off disaster, officials reopened the gates on the main spillway. The waters further tore its concrete apart, but the lake level dropped, allowing the public to return, and averting what could have been one of the worst dam catastrophes in American history.
On Friday, Lake Oroville was 51 percent full. Its water level now has been dropped to 140 feet below where it had been in February, leaving lots of space for winter rains to fill the reservoir before any water would go down the new spillway.
Early investigations show the construction crews that built Oroville’s main concrete spillway in the 1960s made it too thin — only four inches thick in some parts — and didn’t anchor it sufficiently to bedrock or reinforce it enough with steel rebar. Cracks that developed over the years were not fixed adequately by the state Department of Water Resources. A final investigation report by a team of experts is due out this fall.
Meanwhile, numerous class action lawsuits have been filed in recent weeks against the state by farmers, business owners and others who were affected by the evacuation and the damaging water releases in February.
http://www.mercurynews.com/2017/08/25/oroville-dam-time-lapse-video-shows-spillway-being-rebuilt
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