In January 2023, the U.S. Army Corps of Engineers Sacramento District acquired the former Bank of America property at 6212 Lake Isabella Boulevard in Lake Isabella for relocation of the U.S. Forest Service visitor center after USFS selected the location as the preferred site for their new location following a rigorous USACE environmental study and planning process.

Earlier this year the Bank of America building was demolished by USACE contactors. Construction of the new USFS visitor center is expected to begin in 2024, with completion by spring 2025.

The former visitor center was displaced by construction of a new emergency spillway as part of the Isabella Dam Safety Modification Project and a temporary visitor center has been co-located with the USFS Lake Isabella fire station in the interim.

For more information, visit the Lake Isabella Visitor Center Webpage.

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

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 had multiple deficiencies that required correction which increased the time required to understand and to start the fixes.

We also took great effort to comply with the National Environmental Protection Act and the Endangered Species Act which requires significant time to ensure that all requirements are met.

The project team has accomplished these, as well as other actions:

• 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 with a labyrinth weir.

Phase I construction was completed in Fall 2017. It included relocation of the USFS fire station in Lake Isabella and the USFS administrative building in Kernville, as well as construction of an interim boat launch at French Gulch to replace Boat Launch 19 until Phase II was complete, when Boat Launch 19 was reopened.

Phase II construction began in October 2018 and was substantially completed in 2022. Phase II included 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.

Phase III construction is currently underway. It includes the construction of a new USFS Visitor Center, as well as other facilities.

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 Isabella@usace.army.mil.