Isabella Reservoir is located forty miles northeast of Bakersfield, Kern County, California, and consists of an earthfill main dam and auxiliary dam across Kern River and Hot Springs Valley, respectively. The dam was authorized under the Flood Control Act of 1944 and construction was completed in 1953. The reservoir provides flood-risk management, irrigation and recreational benefits. With more than 300,000 people living and working below the dams, primarily in the town of Lake Isabella and the city of Bakersfield, the U.S. Army Corps of Engineers began a dam safety modification study in 2006 to address seismic, hydrologic (potential over-topping during an extreme flood event) and seepage issues at the dams.

An operating restriction is currently in place, limiting the lake’s normal storage capacity and reducing the risk of the seepage and seismic concerns while a permanent solution is implemented. USACE has increased surveillance and monitoring; stockpiling of emergency materials; warning sirens in the town of Lake Isabella; installation of additional instrumentation for monitoring; and continued public outreach with Kern County and the local public. 

Following the signing of the Record of Decision in December 2012, the Corps entered the Pre-Construction Engineering and Design phase of the project, and from 2013 to 2016, focused on design improvements to the existing dams and the relocation of U.S. Forest Service buildings located in the excavation footprint. Construction of the USFS warehouse/administrative buildings in Kernville and the USFS fire station in Lake Isabella were completed in 2017. 

In September 2017, the Corps awarded a $204 million contract to Flatiron/Dragados/Sukut Joint Venture of Benicia, California, to construct the Phase II dams and spillways modifications. Phase II reached substantial completion in late 2022, and the phase is expected to be fully complete in 2023.