This weekend the water level in Isabella Lake is expected to reach — and maybe even exceed — the restricted pool allowed by the U.S. Army Corps of Engineers.
And that means it might be time for residents who reside below the lake’s troubled dam to review their risks.
County emergency officials even recommend developing a plan for how to get out of town in the unlikely event that the dam fails due to something like a massive earthquake.
A dam failure could send a wall of water down the Kern River Canyon that would flood downtown Bakersfield under as much as 20 feet of water.
Much of urban Bakersfield would be flooded. Only east and northeast Bakersfield, Oildale and the far northwest of the city would be spared, according to Corps of Engineer models.
Kern River Watermaster Dana Munn said so much water is being allowed out of the Isabella Lake dam that it’s causing damage to riverbanks and levees downstream.
At 5,400 cubic feet per second, it’s the highest flow in the lower Kern since 1983, he said.
Chevron has recently had to reinforce river banks and levees in the Kern River Oil Field, he said.
John Ryan, water resources superintendent for the City of Bakersfield, said the city had to bolster the riverbanks under the Westside Parkway bridge with slabs of broken concrete called rip-rap.
Homes along Goodmanville Road have had parts of their lawns flooded, though no structures have been damaged.
All up and down the river, there is erosion and damage, he said.
“We are managing it right now,” Ryan said. “If it went any higher, we would be having problems.”
There are no plans to increase the flow into the lower Kern River.
But even that high flow can’t keep up with the torrents that Mother Nature is pouring into Isabella Lake from the mountains around Mount Whitney.
Ryan said 6,452 cubic feet was roaring into the lake from the upper Kern River on Friday, down a bit from recent days but still a massive flow.
The bottom line, Ryan said, is that Isabella Lake is nearly as full as the engineers who maintain it are willing to let it get.
The magic number, set by the Army Corps of Engineers, is 361,250 acre-feet of water.
On Friday morning, Ryan said, the lake level was about 354,000 acre-feet and creeping upward.
It’s expected to peak on Sunday, he said.
Munn said the Corps has “kind of consented to let it go above” the restricted pool level.
Kern County Emergency Services Manager Georgianna Armstrong said the Corps has been asked if the restriction can be exceeded but has not yet replied.
Ryan said modeling shows the lake won’t get that full, at least not for too long.
But, he said, if you can predict where the lake level is going to end up, it might be time to take a shot at the Powerball jackpot.
The worry in having the lake so full comes from the fact it was identified in 2006 as one of the most dangerous dams in the nation.
An active earthquake fault runs along the spine of rock between the main and auxiliary dams.
And the Corps has recorded evidence of water damage that, if it remained under full pressure, could increase the risk of dam failure.
That’s why the restricted pool was put in place.
“What they have told us is that, at 66 percent of capacity, the dam meets current dam safety standards,” Armstrong said.
However, that limit has been exceeded once before with minimal impact, Ryan said.
In 2011, the last high water year, the water level increased to 368,000 for 10 days in July.
It wasn’t a problem, he said.
“I’m not a dam safety guy. But we didn’t really have a problem,” Ryan said.
The Isabella Lake dam is watched like a hawk, Armstrong said.
“The Isabella Dam is monitored in real time in Sacramento,” she said. And the Corps of Engineers has people who walk the dam every day looking for signs that it has been compromised.
Any suspicious activity, leak, earth movement or other clue triggers a five-step system that could lead, if it escalates, to the evacuation of everyone in Bakersfield.
A dam failure, the Corps has said repeatedly, is very, very unlikely.
But the sheer number of human lives that would be in danger if the dam collapsed with a full pool of water behind it makes it a critical priority for repair.
And Armstrong said the scope of the destruction that would fall on Bakersfield if even the 361,250 acre-feet of water were released by a failing dam would be massive.
At a restricted pool, you have 20 feet of water in downtown Bakersfield. With a full pool, it’s 30 feet.
Repair is coming.
The window for companies to bid on construction of the main improvements to the dam — increasing its height 16 feet and constructing a new spillway, as well as an option to improve the auxiliary dam — closed in May.
That work could begin as soon as this year.
In the meantime, there is a plan for evacuating people from Bakersfield in the event the dam begins to fail or, in the worst case, collapses in a seismic event.
At alert level 1, the county would be notified that there might be a concern.
At level 2, with additional signs of trouble, first responders, hospitals, schools and other critical agencies would be directed to begin activating their emergency plans.
At level 3, the general public would be alerted and, Armstrong said, some evacuations would likely begin.
At level 4, the likelihood of a dam failure would top 50 percent and a full evacuation of Bakersfield, Lake Isabella and the Kern River Canyon would be ordered.
The dam breaks at level 5 and the water begins its eight-hour run into northeast Bakersfield.
The county’s emergency plan for Isabella Lake — including maps of where the city would flood and how long it would take water to get to each part of town — is available at the Kern County Fire Department website at KernCountyFire.org; go to the “Operations” tab and click on “Emergency Plans.”
Residents, Armstrong said, should be ready for the worst.
Different parts of the city would be evacuated in different directions.
Families should talk and develop a plan for when to evacuate. They should, she said, arrange for a place to meet up if different family members have to flee in different directions.
“It’s not something to blow off. Water carries tremendous power. Just look at the river,” Armstrong said.