Nervous wait for 188,000 evacuated over fears dam will burst
Stormwaters receded yesterday behind the United States’ tallest dam, in Northern California, as engineers raced to drain the rain-swollen reservoir and shore up a crumbling overflow channel before new storms sweep the region this week.
Authorities said they had averted the immediate danger of a catastrophic failure — one capable of unleashing a wall of water three storeys tall on towns below.
But evacuation orders for some 188,000 residents remained in effect indefinitely, Butte County Sheriff Kory Honea said. The risk to those living in the Feather River valley below the Lake Oroville Dam, 100km north of Sacramento, was still being reviewed, he said.
“We need to have time to make sure that before we allow people back into those areas it is safe to do so,” Honea said.
Residents below the dam were ordered from their homes on Monday when an emergency spillway that acts as an automatic overflow channel appeared on the brink of collapse from severe erosion during what is on track to be Northern California’s wettest winter on record after years of drought.
Environmental groups had warned for more than a decade that the dam’s spillway was not safe.
In October 2005, as the Oroville Dam was going through a relicensing process, three groups filed a motion urging a federal regulatory agency to require state officials to armour the emergency spillway with concrete so that in case of extreme rain and flooding, water would not freely cascade down and erode the hillside. The upgrade would have cost millions of dollars and no one wanted to foot the bill, said Ronald Stork, senior policy Evacuation
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Pop: 16,000 Dam advocate for Friends of the River, one of the groups that filed the motion.
California Governor Jerry Brown said yesterday: “Infrastructure is profoundly important, and in our complex society, whether it’s electricity or gas or water or roads or bridges, there’s a lot to be done.”
Brown yesterday sent a letter to President Donald Trump requesting he issue an emergency declaration, which would open up federal assistance for the affected communities.
The immediate aim, however, is to lower the reservoir’s overall water level by 15m — and prevent further spillover down the emergency hillside channel — before more rain arrives in the coming days and snowmelt runoff begins in the spring, acting state water resources director Bill Croyle told reporters. He said he hoped to achieve that goal within two weeks.