The work of restoring a safe functional spillway for Lake Oroville is a massive undertaking estimated to cost nearly $300 million dollars. The lower 1,400 feet of the spillway is being demolished as part of the reconstruction. Much of this was destroyed this past winter when the spillway was needed to keep the lake from overtopping and flowing over the emergency spillway, an area that had never been used since the dam was built in the 1960’s.
What might be the most dramatic weather event in the U.S. last winter began with the high rainfall in Northern California and a seemingly wonderful amount of water filling Lake Oroville, a large reservoir behind the world’s tallest earth-filled dam (770 feet). One month later a series of decisions (past and present) resulted in an OMG emergency evacuation of nearly 200,000 people living downstream of the spillway when DWR saw that the water flowing over the emergency spillway might undercut the area and release a wall of water. A forensic report released recently by the Center for Catastrophic Risk Management found that “design and construction flaws compounded by inadequate upkeep and maintenance” created the “all but inevitable” near-disaster. (Area residents and environmental groups have been saying this for years but no one in authority from the DWR to the state and federal government gave credence to their warnings.)
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All that leads to today when construction work maintains a 10-hour workday in an attempt to re-establish a safe functional spillway before the onset of winter rains in November. The lake water is being held at low enough levels to ensure adequate space for snow melt run-off that is
higher this year than seen since 1998. The June 21st
Lake Oroville Spillways Emergency Recovery Project update from DWR reports multiple levels of work occurring simultaneously. For example —
- demolition of the lower portion of the spillway (that was severely damaged during the winter resulting in water moving onto the hillside and gouging out an alarming canyon)
- preparations for patching and reinforcement of the damaged but intact upper portion of the spillway
- installation of eight additional time-lapse cameras at various locations in the construction zone
- continuous air quality monitoring, which includes dust monitors and an asbestos sampling apparatus
Here is the latest video overview of the reconstruction. For the most informative and dramatic view,
go to youtube and watch this full screen to see the scale of this site. First half of the video is looking up towards the spillway gates at the lake and then the view reverses to look down the chute where the spillway used to be towards the channel at the base.
The work won’t be finished this year. The goal is to have the lower spillway area that was damaged last winter rebuilt this summer and then next summer (dry season) demolish and rebuild the upper 1,000 feet. By time the project is completed, workers will have placed approximately 800,000 cubic yards of roller-compacted concrete, 146,000 cubic yards of concrete, and installed 8.5 million pounds of reinforcing steel. DWR is aiming to have a spillway capable of releasing 100,000 cubic-feet-per-second by November 1, 2017.
The photo below is from early March 2017 after primary spillway water flows were halted so damage could be evaluated. More information on that phase is reported here.
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This is the biggest news (still) in my part of the world. We’re also watching the snow melt in the Sierras and wondering when some of the higher elevation roads will be open.