Officials in Shasta County are preparing to apply for federal emergency management funds to repair a dam from which they can no longer release water, that officials say is in danger of flooding during a major storm event.
Twenty miles west of Redding, near the communities of Igo and Ono, the Misselbeck Dam holds back the Rainbow Lake reservoir. In 2018 the Carr fire burned up the vegetation surrounding the original 113-acre reservoir.
Now decomposing granite, sloughing into the lake has completely clogged the outlet pipes, according to officials. Overflowing winter storm water is weakening the nearby spillway.
“It’s a problem,” says Pat Minturn, the Shasta County Public Works director. “The lake’s been held full all summer. There’s more water coming in right in the heat of summer than there is going out. Now when winter comes, every storm is going to go right over the top of the spillway.”
The potential for a sudden catastrophic failure of the dam or spillway is low, Minturn says, and the floodplain below the dam would likely absorb much of the water if the 100-year-old dam were to break.
But he says there are a handful of houses downstream that could be affected.
“The potential for a sudden catastrophic failure is quite remote but eventually there will be a problem. Eventually there will be a release and the thing is going to start to downcut,” Minturn says.
Water is normally released through 30-inch pipes at the base of the lake, Minturn says. Estimates from the district puts repair costs at between $750,000 and $2.5 million.
The Igo Ono Community Services District is beginning to develop a Hazard Mitigation Plan in order to apply for Federal Emergency Management Agency (FEMA) funds to fix the dam.
Correction: A previous version of this article misstated the size of the Rainbow Lake Reservoir at 12-acres. According to officials its original size was 113-acres, though it has since shrunk from that size.