US Army Corps of Engineers
Sacramento District


Isabella DSMP Timeline
Isabella DSMP Timeline as of Aug. 1, 2018

Supplemental EA #7, Water Control Manual Deviation 
To All Interested Parties Letter - Sept. 19, 2017
Draft SEA - Sept. 19, 2017
Final SEA - Oct. 31, 2017

Supplemental EA, SR 155 at French Gulch Rec Area
Final SEA/FONSI - Sept. 18, 2017
Draft SEA - July 10, 2017

Contact Information

For more information on the
Isabella Dam Safety Modification Project,
please contact us at the following:



Mailing Address:
U.S. Army Corps of Engineers,
Sacramento District
Isabella Dam Safety Modification Project
1325 J Street, Room 1513
Sacramento, CA 95814

Isabella Lake Dam Safety Modification Project

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. The project is expected to be complete in 2022.

Ask a Dam Question

The hottest question at the moment ...

Construction of the new emergency spillway between the main and auxiliary dams will include a 28-foot-tall, roughly 1,300-foot-wide "Labyrinth Weir" at the top of the spillway. The zig-zag-patterned pseudo-dam is designed to help regulate water flow through the emergency spillway rather than to hold it back like the main and auxiliary dams are designed to do.

Check out this video of the model our team constructed at Utah State University's Water Research Laboratory in Logan, Utah, during the planning and design phase of the project. It allowed our engineers to review the final hydraulic design—including the Labyrinth Weir—before construction of the thing begins.

We want to answer your questions! If you’re curious about the process or have specific questions for us, please email us at

News Updates

Here's an update to the overall project timeline - 

Isabella Dam Safety Modification Project Timeline as of August 1, 2018

Construction work to extend the interim boat launch at French Gulch to 2544 feet elevation is complete and will remain available - lake levels permitting - for the duration of the Isabella Dam Safety Modification Project. The interim ramp replaces Boat Launch 19, which is closed for the duration of the project.

The U.S. Forest Service now has operational control of the French Gulch facility and will determine appropriate seasonal opening and closing dates, if necessary, for the ramp.

Frequently Asked Questions

Collapse All Expand All

The project includes:

  • Sealing the Borel conduit through the auxiliary dam.
  • Raising the main and auxiliary dams 16 feet to minimize the risk of over-topping.
  • Adding a filter and drain on the downstream slope of both dams to increase stability.
  • Improving stability of the existing spillway.
  • Creating an additional 300-foot-wide emergency spillway.

Safety remains our #1 priority – we have to reduce the risk from a potential failure for the people living below these dams. We feel this is the best way to do that.

The Corps acquired the Borel easement from Southern California Edison in September 2018. The easement is that portion of the Borel Canal that runs immediately upstream, through (the conduit), and immediately downstream of the Auxiliary Dam. All other portions of the canal, upstream and downstream, are not on Corps property or our project area and, therefore, we have no authority to determine what is done with those portions of the canal.

The Corps has sealed the conduit through the Auxiliary Dam with concrete and filled those portions of the easement directly upstream of the dam with soil and rock. This work was completed in February 2019. As a result, the low-water restriction has been lifted and lake levels will be allowed to rise once again to restricted pool - 361,250 acre-feet - weather permitting.

Sealing the conduit has permanently cut off water supply to the Borel Hydroelectric Project. SCE will be responsible for determining any actions (including potential decommissioning) related to the canal and power station. SCE could also negotiate for another agency to take the lead in the decommissioning process.

Regardless of who takes that lead, other agencies would then partner together to ensure a smooth and appropriate process. For example, the California Public Utility Commission would be responsible for approving any change in power plant status to ensure local ratepayers and private landowners are not unfairly affected.

The Federal Energy Regulatory Commission, which permits hydropower production at Borel, would require that actions related to decommissioning be taken in a timely manner and that the canal not be left to create a safety hazard.

Finally, the US Forest Service and Bureau of Land Management, who own much of the land underneath the canal, would provide input into the final state of the canal.

As you can see, between USACE, FERC, CPUC, USFS, and BLM, there are several federal and state agencies working together with SCE and the public to put together the best environmental and economic plan for the fate of the Borel Canal, and regardless of the final decision, the public will have a chance to review the proposed action and provide comment.

Given the multiple purposes of this dam facility and the long-term benefits it provides, we require thorough analysis of any modification to assure public safety and benefits are not compromised by modification to the dam.

Dam analysis and designs are complex technical efforts. Risk assessments must be performed to understand the extent of a problem and to evaluate options to fix the dams. In this case the dam has multiple deficiencies that require correction which increases the time required to understand and to start the fixes.

We also take great effort to comply with the National Environmental Protection Act and the Endangered Species Act which does require significant time to assure that all requirements are met.

Kern County and the U.S. Forest Service are working together to determine specific agreements, timing, and location of the permanent visitor center. Once those determinations are made, the Corps will move forward with construction at the agreed upon location.

Phase I is already complete. Phase I included relocation of the USFS fire station in Lake Isabella and the USFS administrative building in Kernville, and construction of an interim boat launch at French Gulch to replace Boat Launch 19 until the project is complete in 2022. Once the project is complete, Boat Launch 19 will be reopened.

Phase II construction began in October 2018. Phase II includes 16-foot raises to both the Main and Auxiliary Dams, along with improvements to both dams and the existing Service Spillway; and construction of a new 1,500-foot-long, 300-foot-wide, and 100-foot-deep Emergency Spillway where the former USFS fire station and USACE operations office once stood between the Main and Auxiliary Dams. 

The project is expected to be complete in 2022.

The workforce on this project will vary throughout the life of this project. Our prime contractor is responsible for hiring any work force needed to complete the job.

You can reach out to the contractor directly -

Flatiron/Dragados/Sukut Joint Venture
2959 Eva Ave
Lake Isabella, CA, 93240

More information regarding project contracts can be found in the “Contract Opportunities” section below.

Contract Opportunities

No contract opportunities at this time. Please visit the Isabella Archive page for past contracts.

Recreation and Water Levels

Collapse All Expand All
The Isabella reservoir offers fishing, boating, water sports, camping, and picnicking. Close proximity to Los Angeles and Bakersfield makes this lake a popular yearround vacation spot for southern Californians. The lake is one of the state’s most popular windsurfing areas; reliable afternoon winds, from 35-50 miles an hour, create ideal conditions for intermediate to advanced windsurfers. Enjoy shoreline camping and day use activities at Auxiliary Dam, Old Isabella Road, or South Fork Recreation Area with the purchase of a Southern Sierra Pass or other Interagency Pass. South Fork Wildlife Area, one of the most extensive riparian woodlands remaining in California, provides fishing, hunting, canoeing, and hiking opportunities; no developed recreation facilities are located here. When operating on the lake, every boat, personal watercraft, and sailboard must display a permit from Kern County. These permits may be obtained at any lake marina or at various locations throughout the Kern River Valley. Be sure to check for required safety equipment.

More information on Annual, Senior, Access, Volunteer, and the Southern Sierra Passes including Fee-Free Days in 2017 can be viewed here:

Information is also available for Campfire Permits, River Permits, and Wilderness Permits at the same website. For more information, please contact the U.S. Forest Service at (760) 376-3781.

Weather information, including current temperature, wind speed, rainfall and humidity, as well as live weather webcams around Lake Isabella can be viewed here: 
From farmer's markets to firework displays, Lake Isabella is full of community events. For more information on events, visit: 
Current pool levels, inflow and outflow levels for Lake Isabella can be viewed here: You can view the elevation levels here: 
Information on developed campgrounds at Lake Isabella, managed by the U.S. Forest Service, can be viewed here: 
Water safety tips from the Kern County sheriff's office can be viewed here.