Oroville Dam crisis warns us of need to maintain infrastructure

Oroville Dam Spillway Damage Ca. Dept. of Water Resources

While Department of Water Resources officials have been examining the damage to the emergency spillway since daylight, they have been unable to confirm that the spillway is stable enough to start allowing people to return to their homes.

Water began flowing over the emergency spillway at the dam on Saturday after heavy rainfall damaged the main spillway.

Lake Oroville is the largest reservoir in the State Water Project, a network of canals and pumping stations that move water from Northern California to the Central Valley and Southern California.

Engineers anxious the fast-moving water could undercut the 1,730 foot concrete lip at the top of the emergency spillway, resulting in a collapse of the structure followed by an uncontrolled release of billions of gallons of water into residential areas.

Honea said there is a plan to plug the hole by using helicopters to drop rocks into the crevasse.

Engineers were continuing to assess damage to the emergency spillway that official feared would collapse, triggering the massive evacuation affecting nearly 200,000 residents in Butte and Yuba counties. A mandatory evacuation order was ordered Sunday from authorities after fears the 48-year-old dam's emergency spillway could suffer critical failure and lead to the release of large, uncontrolled amounts of water downstream.

The area had always been in drought, until this year, when heavy rain and snow bombarded the state.

However, late on Sunday Butte County Sheriff Kory Honea said the evacuation orders remained in place.

He said the big worry is not that the dam itself would fail, but that a failure of the spillway could cut into the hillside and potentially release more and more water, leading to a "cascading failure".

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In his letter to the president, Brown says the number of evacuees in shelters on Sunday night was more than 3,200 people and the number is expected to rise. Not the lake draining but a 30-foot wall of water.

The emergency spillway helped for a time to prevent flooding from the crumbling dam.

Officials were concerned the Oroville Dam could overflow and flood the towns below it.

On Sunday afternoon, the Department of Water Resources upped the water flow in the main spillway, which is still damaged by a sinkhole, to 100,000 cfs.

Some people had just a few minutes to prepare to evacuate, in what one Oroville resident described as "pure chaos".

The water levels have since receded, but not to the point to rescind the evacuation order.

The Lake Oroville Dam, completed in 1968, is the tallest in the United States and 12m (40ft) higher than the famous Hoover Dam.

"There was concern that it would compromise the integrity of the spillway, resulting in a substantial release of water", he said.

Residents of Oroville, which has a population of 16,000, are being ordered to head north north towards Chico.

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