State keeps water flowing
Officials must leave damaged spillway open while waiting for spring before making repairs
OROVILLE — With the scarred and crippled main spillway of Oroville Dam blasting out water at a rate faster than the flow of Niagara Falls, state water officials Wednesday said there’s no need for concern about a series of storms coming in over the next week.
But the crisis is far from over. Even after the rainy season ends, water officials will be under pressure to keep California’s second-largest man-made lake from filling up as the larg-
est northern Sierra Nevada snowpack in more than two decades begins to melt, cascading billions of gallons of runoff back into the reservoir.
“If all the cards line up wrong, they may not see lower flows coming in until the middle of summer,” said Jan Null, owner of Golden Gate Weather Services in Saratoga. “If it’s a season that warms up gradually and without variation, it’s much more manageable.”
The state Department of Water Resources is draining Lake Oroville as fast as it feels comfortable, and after overflowing last weekend, the lake was at 92 percent of capacity on Wednesday. About 100,000 cubic feet of water is now hurtling through the gates of the spillway every second and tumbling down a broken chute — something the department didn’t want to do last week because of its deteriorating condition.
Officials say that’s faster than the new storms will be able to fill it up, but the flow has got to slow and eventually cease because the spillway desperately needs to be repaired. The department intends to do that before the next rainy season begins in the fall.
“The dilemma that the Department of Water Resources faces is they need to fix the damaged main spillway — but they also need to use it through the rest of the wet season,” said Peter Gleick of the Pacific Institute, an Oakland-based think tank that focuses on water issues. And with snowpack levels that haven’t been seen since 1995, it’s hard to predict how long that “wet season” will last.
A warm, sunny week early in the spring could trigger a massive melt, filling the reservoir as fast as a big storm. Or a cool walk-up to summer could preserve those snowpacks long into the year — potential trouble if water officials decide to shut down the main chute to fix it, only to be inundated with runoff.
The other available drain runs through the dam’s power plant, and Chris Orrock, a DWR spokesman, said officials don’t want to run that any faster than 13,000 cubic feet per second. In 1995, flows from melting snow were higher than that up until late June. Officials say that while the emergency spillway is being shored up in a round-the-clock effort, it will remain a last resort.
Repairs to the main spillway won’t be an easy job.
“It’s going to take a long shutdown to fix,” Orrock said, “but there is a way to fix it, and it’s going to be fixed.”
He said the department has “very, very smart people working on that, putting a plan together right now” with various options, but he would not elaborate.
Orrock acknowledged that it’s hard to tell exactly what needs to be done when the spillway is masked by an omnipresent cloud created by rushing water.
“With those things putting out 100,000 cfs right now, you can’t see what’s going on at the bottom of that hole,” he said. “As we are able to take a lot more water out of the lake and feel comfortable about the flood control levels, we’ll be able to shut down the flow so they can go in there and take a look.”
Bill Croyle, the department’s acting director, said officials want to “ramp down” the flow over that spillway as soon as possible.
“The idea is we don’t want to tear up the flood control structure any more than we already have,” he said.
Gleick said the key will be the direction any continued damage spreads down the chute. If it spreads downstream toward the river, it might be acceptable. If it goes the other way, that could be very bad news — jeopardizing a key part of the flood control facility.
“If there’s erosion moving uphill toward the dam’s gates, they’re in trouble,” he said. “If they lose the main spillway, they have no more control, and then they’re at the mercy of the climate.”
Croyle said the repairs could cost as much as $200 million, but the state has yet to identify a funding source.
Recent years have seen only patchwork repairs done on the main spillway, and federal officials have ordered the state to create an independent panel to investigate what went wrong.
About 200,000 people were ordered to evacuate Feather River communities downstream from the dam on Sunday after the emergency spillway was used for the first time since the project was completed in 1968. Parts of the unreinforced hillside were quickly washed away by waters topping over the concrete lip of the backup spillway, and officials feared it could fail and send a deadly 30-foot-tall wall of water downstream.
After a three-day, twonight exodus, residents were allowed to return to their homes Tuesday, but they were told to be ready to flee again if the situation changes.
Despite the potential problems, there’s “reason to be optimistic” about the prognosis for the dam, Gleick said. ”Hopefully Mother Nature and Father Engineering will continue to cooperate.”