The Sacramento District of the U.S. Army Corps of Engineers has awarded a $204 million contract to a joint venture to modify Isabella Lake Dam to deal with overtopping, seismic and seepage concerns.
The Isabella Lake Dam Safety Modification Project is intended to address issues identified with the main and auxiliary dams to reduce the likelihood of dam failure.
Isabella Lake Dam, which impounds Lake Isabella on the Kern River in the U.S. state of California, was completed in 1953 and is about 42 miles northeast of Bakersfield. It impounds water for the 11.95-MW Isabella hydro project. The dam reduces flood risk for Bakersfield and the surrounding region and is a primary water source for Kern County.
The final environmental impact statement for Isabella Lake Dam, released by the Corps in October 2012, proposed a number of improvements to “reduce the risk of dam failure or catastrophic downstream flooding during a large storm.” A panel found in 2006 that the dam qualifies for Corps’ Class I designation, meaning there is an “urgent and compelling” reason to believe that it might have a high risk of failure.
The Flatiron/Dragados/Sukut Joint Venture will work on both the main dam and auxiliary dam. Construction at the main dam will include excavation of a new emergency spillway, modifications to the existing service spillway, raising the dam by 16 feet, and modifying California State Route 155 at the right abutment. Several recreation facilities north of the auxiliary dam will be modified.
Construction will begin this winter and is expected to be complete in 2022, the Corps says.
The contract contains an option to also perform work on the auxiliary dam, including abandoning the Borel outlet works and raising this dam 16 feet. If the Corps decides to exercise this option at a future date, that would bring the total contract award to $241.75 million.
The Corps awarded a $5.7 million contract in December to Spectrum-Straub JV to construct a temporary boat launch and parking at French Gulch Recreation Area as part of the modification project.
For more dam safety news, click here.