It was a story of ineptitude, willful ignorance, and oncoming catastrophe. But that didn’t stop civil engineers in the state of California from bouncing back and rectifying what had been neglected. In February 2017, Oroville Dam’s main and emergency spillways were damaged due to heavy rains which exposed the ill maintenance and general corrosion of the main and emergency spillways.
The reservoir is California’s second-largest provider of water. The dam’s capacity is 4.363537 km3, which equates to 1.75 million Olympic swimming pools. During the crisis, more than 190,000 people had to be evacuated from Oroville and the surrounding counties due to fears that the concrete weir of the dam could collapse and send water flooding into the regions.
Thankfully, there was no collapse in Oroville, but extensive repairs were needed. The Department of Water Resources’ engineers went to work and began a repair project that would see some impressive work done. On the 2nd of April 2019, it opened for the first time after the crisis.
On the main spillway, every 5 minutes, a dump truck would place 19 cubic meters of roller-compacted concrete onto the main spillway. They would eventually lay over 100 thousand cubic meters of concrete for the repair of both spillways. They utilized 16,000 feet of drainage pipe, which is equivalent to 500 Olympic swimming pools. And to keep everything in place? Five million kilograms of reinforcing steel.
The engineers constructed a secant wall out of reinforced concrete piles for the emergency spillway. The wall, in length, was just four feet shorter than the height of the Empire State Building.
It was initially thought that the repair work would only cost $400 million USD, but the final number was much larger. The final repair bill weighed in at $1.1 billion USD. Speaking to the Sacramento Bee, Joel Ledesma, the deputy director of the California Department of Water Resources said:
“We are prepared; we’ve spent the last two years restoring full functionality. The industry has learned a lot since this dam was built 50 years ago.”
They reopened the spillway and began pushing water at 3,300 cubic feet per second down the newly repaired spillway on its first day of operation.
Joel also told the media that the new spillway was ‘designed and constructed using 21st century engineering practices and under the oversight and guidance from state and federal regulators and independent experts’. Below, is a video that shows the rebuilding process:
Caraccio, David. “Enough Concrete to Pave from Oroville to Texas, and Other Facts about Oroville Dam Repair.” Sacbee, The Sacramento Bee, 5 Apr. 2019, www.sacbee.com/news/state/california/article228890254.html.
Pedroncelli, Rich, et al. “$1.1B Oroville Dam Spillway Repairs Put to Test.” Construction Equipment Guide, Construction Equipment Guide, 10 Apr. 2019, www.constructionequipmentguide.com/11b-oroville-dam-spillway-repairs-put-to-test/44557.