Evacuation ordered for Oroville; dam spillway expected to fail
By Melody Gutierrez and Evan Sernoffsky, San Francisco Chronicle
Updated 5:17 pm, Sunday, February 12, 2017
OROVILLE, Butte County — Butte County officials ordered residents in low-lying areas of Oroville to immediately evacuate on Sunday afternoon due to a “hazardous situation” with the Oroville Dam emergency spillway.
The Butte County Sheriff’s Office said a failure of the spillway may cause “uncontrolled release” of flood waters from Lake Oroville.
The state Department of Water Resources did not elaborate on the emergency, but said just before 4:45 p.m. that the “auxiliary spillway at the dam was predicted to fail within the hour.” Officials have increased water releases out of the primary spillway to 100,000 cubic feet per second.
The amount of water gushing over Lake Oroville’s emergency spillway had begun to decrease before the emergency Sunday as state officials pushed ahead with urgent measures to make room in the state’s second-largest reservoir to avoid a repetition of the weekend’s extraordinary event.
The emergency spillway — an open hillside that drains to the Feather River below — had never been used since the Oroville Dam was completed in 1968. The discharge that began early Saturday raised concerns over how the backup channel would hold up, and whether debris would threaten fish and levees downstream.
The primary concrete spillway just south of the overflow area, meanwhile, was thought to have stabilized after a gigantic hole emerged in its 3,000-foot-long channel last week. The gash forced operators to reduce the outflow, which set the stage for this weekend’s unprecedented situation.
Another wet-weather system, in what has been a soaking winter, is on deck to hit Northern California on Wednesday, requiring water managers to make still more room in Lake Oroville for another surge.
The series of Pacific storms is expected to bring up to 4 inches of rain to parts of the Central Valley, said Idamis Del Valle, a meteorologist with the National Weather Service’s Sacramento office.
“We need to do everything we can to maximize our ability to move water our of this reservoir — not just for the coming storm but for the coming storms,” said Bill Croyle, acting director of department of water resources. “Our planning is both short term and long term.”
At its peak over the weekend, water was cascading over the emergency spillway at 12,600 cubic feet per second.
Teams were dredging an area composed of silt, rock and hunks of concrete debris that has formed under the primary spillway following recent erosion.
The blockage forced water in the diversion pool to back up toward the dam and has threatened the Edward Hyatt Power plant at the base of the concrete behemoth.
The power station, which was closed late Friday due to the threat, serves as a third release point for the reservoir when it is operational. The facility expels up to 14,000 cubic feet of water per second downriver.
Officials had stressed earlier Sunday that the structural integrity of the 770-foot Oroville Dam — the tallest in the country — had not been compromised by the damaged spillway.
Once the dredging is completed, crews must rewire overhead power lines that were taken out of service after support towers were threatened by erosion.
Operators first detected the hole in the primary spillway Tuesday. Subsequent releases down the slide made the hole grow dramatically, exposing bedrock even beyond the 180-foot-wide channel.
Officials stabilized the hole and stopped further erosion by slowing the outflow to 55,000 cubic feet per second. But 90,000 cubic feet of water per second continued to dump into Lake Oroville and pushed the reservoir over capacity on Saturday.
“The problem is we don’t have that flexibility right now,” Croyle said. “Our bowl is full. So, what comes in comes out.”
By Sunday, the rate of inflow had fallen to 41,400 cubic feet of water per second, officials said.
The estimated cost of repairing the concrete spillway has soared to as much as $200 million, and officials are debating whether it can be patched when the rains end, or if a new chute will be needed altogether.
Under clear skies, many residents from nearby communities headed to Oroville on Sunday in hopes of seeing the raging Feather River or the damaged spillway. They parked and walked along streets overlooking the murky water, but public access to the spillways next to the dam was blocked.
The reservoir is the second largest in the state behind Lake Shasta and supplies water to Central Valley along with districts in the Bay Area and Southern California.
On Sunday, the cause of the hole in the main spillway was still being investigated. But experts noted repairs had been made to the spillway in 2013 near where the hole emerged.
Robert Bea, a U.C. Berkeley engineering professor, reviewed 2015 inspection reports that made note of the earlier repairs to the concrete slabs.
“From what I can tell from the photographs, it appears that the water pressures from the recent releases were great enough to cause failure of the repairs made to the base slabs,” he told The Chronicle.
Downstream from the dam at the Feather River Fish Hatchery in Oroville, officials with the California Department of Fish and Wildlife had moved nearly all their salmon hatchlings into nearby holding ponds due to brown and silty water that threatened the fish.
Chronicle staff writer Peter Fimrite contributed to this report.
Your collective inability to acknowledge this obvious truth makes you all look like fools.
Signs Of Hope At Oroville Dam, After Overflow Sparked Large Evacuation Sunday
The area around a huge dam at California's second-largest reservoir is in a state of emergency, with some 180,000 residents ordered to evacuate the area Sunday out of fears that part of Oroville Dam could fail. A glimmer of hope arrived late Sunday night, when officials said water had finally stopped pouring over the dam's emergency spillway.
The secondary spillway was in use because the main spillway had developed a huge hole, stressed by the need to release water accumulated from California's wet winter — and brought to a new crisis point by last week's heavy rains.
"So the lake rose 50 feet in just a few days," Dan Brekke of member station KQED tells Morning Edition, "and got up to this emergency spillway which had never been used since the dam went into service in 1968. And on Saturday morning, it began pouring over there."
Residents of the area some 70 miles north of Sacramento were placed under evacuation orders around 4:30 p.m. Sunday, after the reservoir rose to a record level — more than a foot above what's considered "full" — and its main spillway struggled to provide relief and its auxiliary spillway was seen at risk of failing. At the time, officials said that dangerous flooding could be just hours away.
Even as the evacuation orders were issued, officials had reason to hope that Lake Oroville would soon begin to recede, due to a drop in the amount of runoff water entering the lake and a dry weather forecast. But the reservoir's infrastructure was struggling to cope.
"The lake is considered full at 901 feet [above sea level], and it's at that level that it began pouring over an emergency spillway early Saturday," KQED reports.
The lake kept rising, surpassing its "full" level by more than a foot. Last night, Lake Oroville's water level finally dropped below 900 feet around midnight, in a trend that has continued into Monday morning.
Overnight, evacuation centers and shelters were still being outfitted with beds and blankets. Gov. Jerry Brown issued an emergency order last night to help with the process, which saw shelters erected at fairgrounds to handle the thousands of people leaving Oroville and other downstream areas.
While the waters are receding and dry weather is expected for Monday and Tuesday, the region in Northern California could get another round of rain later this week, when forecasts are calling for several days of rain.
The Oroville Dam incident has sparked questions about how to repair the dam's spillways — and whether other structures in California and beyond are similarly vulnerable. After the main spillway developed a 200-foot hole, the auxiliary spillway also began to erode, sparking Sunday's evacuation.
Flood control expert Jeffrey Mount, of the Public Policy Institute of California and the University of California Davis, says the auxiliary spillway at Oroville had never been tested — always a challenge with emergency equipment — and that it will be very expensive to repair.
"The weaknesses were revealed immediately in the design, and it threatened to collapse," Mount tells Morning Edition.
"I can tell you that this event will cause us to do some soul-searching about the amount of money we're spending on infrastructure — maintenance, particularly — here in California," Mount says.
Well, I suppose that after nearly fifty years of never being needed, and 5 years of drought, it's understandable that "how good a shape are the emergency spillways in our dams? " wasn't at the top of the state government's list of priorities...
Moonbeam's "choo-choo to nowhere" would take the top spot.
When you look at the amount of cost involved in creating that; a high speed rail between San Francisco and Los Angeles... (including, unlike in Europe, the cost of having every single local municipality get on board...so to speak...and all the legal challenges towards every foot of the rail line etc.)versus the relatively inexpensive cost of flying back and forth between Northern and Southern California...
The numbers just don't add up...
It's not a good investment for the state...
It would make a lot more sense to put that money into de-salinazation plants as an investment against the next drought...
It would make a lot more sense to put that money into de-salinazation plants as an investment against the next drought...
Perhaps, a more realistic idea is more dams (like Oroville) to hold (or not) billions of gallons of water.
There is no reason that any territory that shares a coastline with an ocean, (Like California, or Australia) should ever suffer from a drought..
As long as they are willing to pay the higher prices for desalinated water and find a way to produce the electricity and water crops with higher-priced water. &c.
dales wrote:
Next in line is "the tunnel project" to divert NorCal's water to those in SoCal .....a STUPID idea!
Isn't that where the failing Oroville dam's water ends up now - in the frickin' aqueduct built under Moonbeam's father's administration?
You are just chock-full of ignorant insults aren't you?
The California water project connects the places where we had a lot of water, in the north, with the places which needed it, in the south. Rather like the California aqueduct and the federal water projects which watered the central and Imperial valleys.
"Governor Moonbeam" is one of the most effective and intelligent governors we have ever had. "We" meaning the United States. He is universally respected by Republicans and Democrats for balancing the budgets and making the tough choices.
I agree that humanity will have to get serious about desalinization or face a massive die-off, probably within the next 50 years. Viewing the future of the technology through the lens of the present, limited, technology is a mistake. Even with the present electricity-intensive technology, though, massive reductions in the cost and massive increases in the availability of solar-generated power holds out some hope.
People who are wrong are just as sure they're right as people who are right. The only difference is, they're wrong.
— God@The Tweet of God
The Israelis have developed very sophisticated and remarkably efficient desal. systems which were used to build a large plant in San Diego.
And in Sweden they have pioneered a system which can run either way: Salt water can be desalinated with an input of electrical energy and the reverse system of combiningof fresh water flowing into salt water can be used to generate electricity. So that a location with high seasonal river flows can run one direction and generate power and the other and generate fresh water. Rather like a Hybrid car which uses braking to regenerate electricity.
But no matter which choice we make we will have to make cultural changes in how we view and use the water we have.
For the last 4 months we have averaged 25 gal per person per day without any sense of deprivation.
