The U.S. Army Corps of Engineers has released its final environmental impact statement for the Isabella Dam on California’s Kern River.
The report, titled “Isabella Lake Dam Safety Modification Project Environmental Impact Statement,” is part of the Corps’ Sacramento District’s efforts to improve the safety of the 60-year-old structure.
A panel found in 2006 that Isabella Dam qualifies for the Corps’ Class I designation, meaning there is an “urgent and compelling” reason to believe that it might have a high risk of failure.
The Corps has proposed a number of improvements to the structure in order to “reduce the risk of dam failure or catastrophic downstream flooding during a large storm,” including:
- Improvements to the existing spillway;
- A new 900-foot emergency spillway;
- Auxiliary dam modifications that would raise the dam’s crest by 16 feet;
- Replacement of Borel conduit through the right abutment of the auxiliary dam; and
- Relocation of Highways 155 and 178 to accommodate the crest raise.
The Corps’ most recent report is intended to address the project’s environmental impact and its effects on nearby residents, with three public response meetings scheduled throughout mid-November.
The cost of the project has an estimated price tag of US$400 million to $600 million, with construction beginning in 2015 and finished by 2022.
HydroWorld.com reported in March that the Corps was seeking bulkhead work at Isabella Dam’s accompanying 11.95 MW hydropower project.