OROVILLE, Calif. — Nearly 200,000 Northern Californians who live downstream of the country’s tallest dam were allowed to return home Tuesday after two nights of uncertainty, but they were warned they may have to again flee to higher ground on a moment’s notice if hastily made repairs to the battered structure don’t hold.
The fixes could be put to their first test later this week with the first of a series of small storms forecast for the region.
But the real test is still to come in the weeks ahead when a record amount of snowfall melts.
“There is the prospect that we could issue another evacuation order if the situation changes and the risk increases,” Butte County Sheriff Kory Honea said Tuesday, telling residents they could return home but to remain vigilant.
Residents living below the Oroville Dam were ordered to evacuate Sunday afternoon after water authorities had assured them for nearly a week that the dam was sound despite a gaping and growing hole found in the structure’s main spillway. The order came after authorities feared an earthen emergency spillway used when the lake behind the dam overflows its capacity appeared ready to fail Sunday because of erosion.
Over the weekend, the swollen lake spilled down the unpaved emergency spillway for nearly 40 hours, leaving it badly eroded. The problem occurred six days after engineers discovered a growing hole in the dam’s main concrete spillway.
State and federal officials ignored calls in 2005 from environmental groups to armor the earthen spillway in concrete to prevent erosion. Federal regulators concluded the earthen spillway could handle a large amount of overflow after water agencies that would have had to pay for the upgrade argued it was unnecessary.
On Tuesday, U.S. Rep. John Garamendi, a Democrat who represents an area near Oroville, called the government’s failure to coat the spillway in concrete “a classic case of woulda, coulda, shoulda.”
He said that if the state had listened to the 2005 warnings and installed the concrete a decade ago, “This problem would not have occurred. But they didn’t, and there are probably multiple reasons why,” with cost a crucial one.
The California Department of Water Resources said the lake was ready to take on rain and melting snow. State water officials said they have drained enough of the lake behind Oroville Dam that the emergency spillway will not be needed to handle runoff from an approaching storm.
Forecasts call for 2 inches to 4 inches of rain and snow in the foothills and mountains starting tonight. But the storm was looking colder than initially projected, meaning less rain and less runoff than last week’s storms.
