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A boater travels in front of Isabella Lake's main dam in this Californian file photo.

Casey Christie / Californian file

The dam is getting fixed.

Construction on Isabella Lake Dam, which has lingered in the study, planning and environmental process for more than a decade, will begin this winter.

On Monday the U.S. Army Corps of Engineers approved a $204 million contract with a collection of Bay Area construction companies to build a new emergency spillway, modify the existing spillway, raise the height of the dam by 16 feet and adapt surrounding roads and recreation facilities to accommodate the remade dam.

The contract with a trio of contractors — Flatiron, Dragados and Sukut — includes the option to modify the auxiliary dam as well, bringing the total cost of the work up to $241.75 million, according to a press release from the Corps of Engineers.

The five-year construction process will begin this winter and finish in 2022, the press release stated.

Tyler Stalker, spokesman for the Corps of Engineers, said a notice to proceed is expected to be issued to the contractors at the end of October and people will begin seeing heavy equipment on-site by November.

The contractors will have to set the stage for the work and implement their traffic control plans, site plans and environmental compliance plans before construction launches.

Work is expected to take 42 months to complete and will start with a $81.5 million allocation in this fiscal year, Stalker said.

The rest of the money for construction will be funded annually through the Corps’ portion of the federal budget.

THE THREAT

Concerns about the safety of the Isabella Lake Dam began to rise in 2006 when serious seepage was discovered in the earthen dam.

Scientists also learned that the Kern River Fault, which runs along a ridge between the main and auxiliary dams, was active. It had previously been thought to be a dead fault.

A major earthquake on the obscure fault while the dam was full could spell disaster.

The risk of a catastrophic failure of the dam has always been extremely remote, according to the Corps.

But Lake Isabella Dam was ranked as the most dangerous in the nation because of the dramatic damage it could do if the dam failed when it was full of water.

The Kern River canyon would quickly channel a wall of water down through the town of Lake Isabella and into Bakersfield.

Computer models show that most of Bakersfield would be flooded within hours if that happened and some areas could be covered in between 10 and 20 feet of water.

To mitigate the risk to Bakersfield, the Corps of Engineers imposed a restriction on the amount of water that can be stored in Isabella Lake.

Kern River Watermaster Dana Munn said those restrictions have, this year, made it difficult to bring in cheap water from other parts of the state to help Kern County recover from years of drought.

Water recharge areas in the San Joaquin Valley had to be used to store Kern River water rather than storing that water in Isabella Lake and buying Friant-Kern Canal water, for example, on the cheap.

But the restrictions were an important precaution to keep people safe.

Other precautions were put in place by Kern County emergency agencies.

They developed an aggressive notification plan and evacuation model for metro Bakersfield and installed dam sirens around the small communities clustered near the dam to alert residents to flee for higher ground.

THE LAST DECADE

In the past decade, the Corps worked to plan an exhaustive study of Isabella Lake Dam and developed a unique series of solutions that — when built — will eliminate the threat of a dam failure and allow Isabella Lake to be filled again.

Those solutions include an impressive accordion-shaped labyrinth weir on the main spillway that was tested with a scale model at the Utah Water Research Lab at Utah State University.

Stalker said the design is important for Isabella Lake Dam because it requires less excavation and earthwork and it handles large volumes of water well in a smaller amount of space.

James Burger can be reached at 661‑395-7415. Follow him on Twitter: @KernQuirks.

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