February 16, 2017
A swarm of trucks and helicopters dumped 1,200 tons of material per hour onto the eroded hillside that formed the dam’s emergency spillway. One quarry worked around the clock to mine boulders as heavy as 6 tons. An army of workers mixed concrete slurry to help seal the rocks in place.
“This is an aggressive, proactive attack to address the erosion,” said Bill Croyle, acting director of the state Department of Water Resources. “There’s a lot of people, a lot of equipment, a lot of materials moving around, from the ground and from the air.”
At the main spillway, a different and riskier operation was underway: Despite a large hole in the concrete chute, officials have been sending a massive amount of the swollen reservoir’s water down the chute to the Feather River in a desperate attempt to reduce the lake’s level.
The structure continued to hold Tuesday without sustaining more significant damage, officials said.
The idea is to get the reservoir’s water level low enough that it can take in rain from an upcoming series of storms without reaching capacity. If the reservoir filled up again, water would automatically flow down the emergency spillway, which on Sunday appeared to be nearing collapse, forcing the evacuation of more than 100,000 people downstream.
I don’t think “proactive” means what acting Department of Water Resources director Bill Croyle thinks it means. A proactive effort would have fixed the damaged spillway during the drought, when the water level was far below the danger zone.