LAKE ISABELLA, Calif. (KERO) — The Lake Isabella Dam was originally constructed in 1953. In 2005, the dam was brought to the top of a national list of dams in critical need of attention, and as a result has been undergoing a multi-phase upgrade project over recent years. Phase 2 of 3, which started 6 years ago, is finally wrapping up.
23ABC visited the dam for an update on the upgrade work, as well as to find out how the 70-year-old structure has handled the recent heavy rains.
Phase 2 of the current upgrade addresses the risks of failure that put the dam in such critical need in the first place, including a seepage problem, earthquake impacts, and water overtopping. According to Evan Nelson, a project manager for the U.S. Army Corps of Engineers, this part of the work is more than 90 percent complete.
"We're standing on the upstream side of what we call the Labyrinth Weir, and it is a control structure that we built at the head of the new emergency spillway," said Nelson.
The 28-foot-tall zig-zag wall helps with flood risk mitigation by slowing and controlling the water so that downstream communities like Bakersfield are protected in the event of flooding.
On the other side of the structure, more work continues.
"We raised both dams by 16 feet and excavated the new emergency spillway to prevent both dams from being overtopped," Nelson said.
Nelson says they also added a thick layer of sand where the Kern Count Fault runs to mitigate seismic failure, and added filter and drain layers to control the water moving through the dams.
The Corps of Engineers completed these parts of the project in October, which put the project under substantial completion, bringing them closer to that initial fill of the lake.
"Right now, we think we are in good shape to fill the lake this next spring. The recent storms we have had had great impact. We doubled the amount of water in the lake since the start of January, but we still have a ways to go," said Nelson.
All of these goals are dependent on Mother Nature and how much rain the area gets before the spring. Initially, February 1 was the set goal date to raise the water limit to 240,000 acre feet, but that is not the case, since they are not even at the ideal normal operation average of 170,000 acre feet.
"Our goal is to get permission to go above restricted pool this spring. If we don't get enough runoff to do that, we will roll that exception over to next year and try again," said Nelson.
In the meantime, the final touches to Phase 2 continue and will tentatively wrap up in spring, with Phase 3 starting the more operational aspect getting ready to roll out with just managing the dam.
"Starting our Phase 3 of the project, we're going to be building a new operations building for the Corps of Engineers, a visitor center in Lake Isabella for the U.S. Forest Service, and also doing some restoration work on a campground downstream of the main dam," said Nelson.
Construction for Phase 3 is around the corner, but the expected end date for all of the work on the Isabella Dam is expected sometime in mid-2025.
