Corps of Engineers on Isabella Dam: 'The spillway is in good shape'
LAKE ISABELLA, Calif. (KBAK/KBFX) —
Federal officials say they are watching water levels at Isabella Lake, and though the two dams there are set for big upgrades, there are currently no additional problems.
The engineers are responding to questions, in light of serious issues with the Oroville Dam and its spillway.
The Oroville facility is managed by the California Department of Water Resources, and thousands of people were being evacuated as of Monday due to concerns that the dam's emergency spillway could fail. Water started going over it on Saturday.
Up at Isabella, the U.S. Army Corps of Engineers is getting ready to make that spillway much bigger. Its too-small size was one of three issues identified back in 2005, as Eyewitness News was the first to uncover.
On Monday, the resident engineer for the Isabella Modification Project said they are watching local water conditions, but the spillway there is OK.
"This is probably one of the most-monitored dams in our system," Resident Engineer Julie Martinez said. "This spillway is in good shape, there doesn't seem to be any concern with its structure, it's built -- it's cut -- out of the rock."
But, since it's too small, the Corps plans to build a new one between the Main and Auxiliary dams. Martinez said the new spillway will be much bigger.
"We're making it hardy, it's going to be a concrete labyrinth weir," she added, "So, it's got a lot more science behind it."
It was an engineering analysis in 2005, that identified the problems with the spillway. That report also found earthquake faults which hadn't been identified when the dams were built about 60 years ago, and engineers then found there was too much water "seepage" through the two earth-fill dams.
Since that analysis, the Corps has ordered a restriction on how much water can be in the reservoir. Martinez said with the recent rain and snowmelt, Isabella Lake is now 6 feet below that restriction level.
And she said engineers have 46 wells on the facility that are now being monitored once a week, while they used to be checked every other week.
Things are looking OK at this point.
"We do see the water level's coming up," Martinez said. "Nothing is out of parameters, so we're not alarmed by anything we're seeing right now."
Meanwhile, the work is progressing to make upgrades to the Isabella dams, and putting in the new spillway will be one of the first segments of the repairs.
Martinez said as crews blast out a new spillway, the rock that's removed will be used to build both dams 16 feet taller, and add a layer to the downstream side of the dams.
Already, an electric plant near the dams is being upgraded so it can provide the power for electric machinery to process that rock. Martinez said the rocks will be sorted by size, so they can be used as the correct material to beef up the size of the dams.
"There will be different materials, different strata, depending on what layer you're in," she described. "It's not just a pile of rocks, it's actually quite engineered like a layer cake. Like a diagonal layer cake."
Martinez said the Corps expects to award bids for work on the new spillway this October, and the actual work should start in February 2018.
On Monday, Rep. Kevin McCarthy, R-Bakersfield, issued a statement on conditions at Lake Isabella, saying he's been in contact with Corps Col. David Ray. McCarthy said he was assured Lake Isabella is safe. But, he has questions about the upgrade project.
"Over the years, I have worked to hold the Corps accountable to the timeline needed to expeditiously complete the safety work needed at the Main and Auxiliary Dams, something I reiterated again with Colonel Ray," McCarthy's statement reads. "This weekend's events at Oroville Dam only further demonstrate the need to get the repairs at Isabella done quickly and why I have secured over $85 million to date for the project."
Eyewitness News has also asked why the project is taking so long.
"There's a lot of factors, you can't afford a failure," the Corps' Julie Martinez said. She said designing the best and right repairs took time, and needed to go through several layers of review by several entities.
"You just can't afford not to, as the folks over in Oroville are finding out," she said. "So, there's a lot of consider,"
The latest report from the Corps shows construction on the dams and spillway continuing through 2022.