Repairs to Isabella Dam power plant completed; Kern River flows to ramp back up

Repairs to a damaged tunnel inside the power plant at the base of Isabella Dam were completed Saturday, just seven days after the project began, according to an attorney for Water Audit California, a public interest group suing to keep water in the Kern River.

Releases from the dam had been reduced to about 100 cubic feet per second during the repairs and are now expected to ramp back up, according to attorney William McKinnon who has been coordinating with the Army Corps of Engineers and power plant owner Isabella Partners.

Roger Kirk, the manager of the power plant, referred questions about the project to McKinnon.

Flows in the river had been set to drop to almost nothing during the repair project, which was originally scheduled to begin Dec. 18 and last potentially three weeks, according to a previous interview with plant operator Rush Van Hook.

That would have dried up the river downstream, resulting in a massive fish kill.

Water Audit and several other public interest groups had won an injunction against the City of Bakersfield Oct. 30 to keep water in the river to protect fish populations that had re-emerged with the high flows brought on by last winter’s storms. That injunction, however, does not apply to the Army Corps, nor Isabella Partners, which were both unaware of the ongoing legal issues downstream.

After McKinnon and the other plaintiffs learned of the impending repair project in early December, McKinnon began working with Isabella Partners to find a way to keep at least 200 cfs in the river.

Isabella Partners postponed the project while it worked with the Army Corps to find a way to do the repairs and keep the river flowing. The workaround  involved “a lot of engineering,” according to McKinnon.

There are two portals through the power plant, a main outlet and one that takes water through the generator room. The portal through the generator room suffered “spalling,” or erosion, during heavy flows last spring.

To repair that portal and keep water flowing through the main portal, the Army Corps briefly stopped releases while Isabella Partners crews sealed off the generator portal using a unique “muscle wall” welded in place and covered with a membrane.

The Army Corps and Isabella Partners had hoped to keep releases through the main portal at 200 cfs but that amount of water created some “cavitation,” or vibrations, against the membrane covering the muscle wall, so releases had to be cut back to about 100 cfs for the duration of the repairs, McKinnon said.

The repairs were completed in just seven days with crews working round the clock, according to McKinnon. Dam releases had to be brought down to near zero midday Sunday for crews to remove the muscle wall and were expected to go back up in the afternoon.

“A noble amount of effort went into keeping the river wet,” McKinnon said in praise of the Army Corps and Isabella Partners. “The engineering and organization not to mention the focus and courage of the people to get that task finished in just seven days…wow.”