Crews race to fix California dam before more rain falls

Because of recent rainfall and extreme erosion the Oroville emergency spillway is at risk of catastrophic failure

Workers installed flashboards atop the dam's gates to increase reservoir capacity before closing and rebuilding the spillways. Engineers can release excess water through these chutes in a controlled manner in order to prevent flooding. The rising water topped over the earthen back-up spillway, which has a concrete top, for the first time in the dam's 50-year history over the weekend.

Officials had managed to avert an expected structural collapse of the top portion of the dam's emergency spillway by releasing massive amounts of water via the damaged mail spillway, lowering the level of the lake so that it no longer poured over the concrete berm at 901 feet above sea level.

Dump trucks and helicopters have dropped thousands of tons of rocks and sandbags over the past couple of days to shore up the dam's spillways, and avoid what officials had warned could be a catastrophic failure and flood downstream.

ABC10 received a comment about the possibility of there being boils on the dam's emergency spillway.

This left the emergency spillway badly eroded with a gaping hole.

More rain was forecast for as early as Wednesday and through Sunday, according to the National Weather Service, but the state Department of Water Resources said the upcoming storms were unlikely to threaten the emergency spillway.

Those fears had ebbed by Tuesday, when the evacuation order was lifted.

Downstream of the dam, flooding has been reported in Marysville and several roads and highways have been closed by the California Department of Transportation, including at least one that is impassable due to flooding.

Crews race to fix California dam before more rain falls
Crews race to fix California dam before more rain falls

If the main spillway remains in operation forecast storms aren't likely to put water into the reservoir faster than it can be drained, neither is snowmelt alone.

Jeffrey Kightlinger, the general manager of the Metropolitan Water District of Southern California, the water utility for Los Angeles and its environs, said the issue was not cost but federal guidelines, the Los Angeles Times reported. "This was a new, never-happened-before event".

The Federal Emergency Management Agency relief package that covers Butte, Sutter and Yuba counties is for public assistance and does not cover individuals or businesses.

"The situation is a textbook example of why we need to pursue a major infrastructure package in Congress", Spicer said at a daily briefing on February 14.

Is the situation still risky?

Robert Bea, professor emeritus of civil and environmental engineering at University of California, Berkeley, said it's "obvious those repairs didn't work".

"We have crews out there putting giant boulders into some of the erosion spots, putting aggregate and then filling that with slurry so that it stops the erosion", said Orrock.

While fears of such a disaster have largely been alleviated, crews are continuing repairs by dropping rocks into the gouged hole in the emergency spillway.