OROVILLE (CBS SF) – California Congressman John Garamendi on Monday painted a grim picture of how catastrophic the failure of the Oroville Dam’s emergency spillway could have been.
Engineers were continuing to assess damage to the emergency spillway that official feared would collapse, triggering the massive evacuation affecting almost 200,000 residents in Butte and Yuba counties.
Officials said 37,000 cubic feet per second of water is flowing into Lake Oroville, but 100,000 cubic feet per second is being released from the main spillway.
That means the lake’s water levels that were contributing to the erosion of the emergency spillway are starting to come down.
Evacuation orders remain in effect for towns below the spillway, including Oroville, Gridley, Live Oak, Marysville, Yuba City, Olivehearst, Linda, and Wheatland.
As soon as officials saw the craters in the auxiliary spillway Sunday, they realized they had an emergency on their hands. The holes were in the base of the spillway, creating the serious danger of the spillway collapsing onto itself and sending a tsunami downstream.
“If it had collapsed — a catastrophic collapse — there would be a 30-foot wall of water descending on the town of Oroville,” said U.S. Rep. John Garamendi, the Democratic congressman for District 3. “And then very quickly, Gridley, Live Oak, Yuba City and Marysville. The calculations are the water in Oroville would have been 100 feet deep within an hour.”
Months of heavy rain created a 200 foot-long gash in the Oroville Dam’s main spillway last week. Then on Sunday, the back-up emergency spillway showed signs of weakening as erosion became worse.
Video shot by Chopper 5 shows the extent of the damage to the emergency spillway and offers a clearer picture as to why it prompted mass evacuations.
Water rushed over the spillway, gouging huge craters out of the hillside, taking out a road, altering the landscape.
However, because water officials were able to divert water away from the emergency spillway by increasing the flow out of the main spillway, the auxiliary spillway did not fail.
Now, officials are using helicopters to drop rocks at the base of the damaged spillway, hoping to plug the massive holes.
No water is spilling over the emergency spillway at this time. That’s an important thing, said Butte County Sheriff Kory Honea.
But with more rain is on the way later this week and a huge surplus of water in the reservoir behind the dam, officials with Department of Water Resources are continuing to release water downstream to lower the level of the lake.
“We’re not out of the woods. The water is still up against that emergency spillway,” said Garamendi. “That’s pressure. Heavy, heavy pressure against a damaged emergency spillway.”
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.