Dam Safety

Corps installs temporary pumps to alleviate seepage at Isabella Dam

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Corps installs temporary pumps to alleviate seepage at Isabella Dam

A new temporary pump system has been installed at Isabella Dam to increase capacity of the existing pump system and redirect seepage back into the lake, according to the U.S. Army Corps of Engineers Sacramento District.

The Corps awarded a contract for installation of the temporary pump system at Isabella Dam in Lake Isabella, Calif., on Sept. 28, 2023. Now that it’s installed, the new system has eliminated downstream flows caused by seepage, the Corps said.

Henri Mulder, a geotechnical engineer who works out of the Isabella Dam Safety Modification Project Resident Office, stressed that the seepage is not a risk to the safety or structural integrity of the dam. “All dams experience seepage,” said Mulder. “However, the elevated seepage levels we’re seeing this year are the result of record precipitation and the higher lake levels that resulted.”

The Sacramento District will continue assessing the Isabella Dam seepage to determine if more permanent changes need to be made to increase the pumping system’s capacity. Mulder said the Corps plans “to install a more permanent solution within six to twelve months.”

The Sacramento District engaged in extensive pre-construction modeling of inflows and outflows at Isabella Lake before the recent modifications to the dam, which included an improved filter and drain system. And although the current collected seepage levels exceed pre-construction estimates, the system is working as designed.

Completed in 1953, Isabella Dam is located about 40 miles northeast of Bakersfield. The reservoir is impounded by two earthen dams on the Kern River and Hot Springs Valley. Isabella Lake and its dams reduce flood risk for Bakersfield and the surrounding region and is a primary water source for water users throughout Kern County. It also impounds water for the 11.95 MW Isabella hydro project.

The Isabella Dam Safety Modification Project addresses overtopping, seismic and seepage issues identified with Isabella Lake’s main and auxiliary dams and spillways, to reduce the likelihood of dam failure. Construction of the dam modifications began in 2017 with the relocation of facilities within the project footprint, and the project achieved substantial completion in 2022, the Corps said.