The Community Services District is facing unexpected bills and a pressing deadline to address a state classification of three of its dams as “high” hazards, though there’s no apparent risk for current Rancho Murieta homes. The CSD is challenging the classifications, a state reaction to last year’s near-collapse of Oroville Dam.
The state Department of Safety of Dams classified the Calero, Clementia and Michigan Bar No. 1 dams as “high” hazards – the second-worst classification.
“If you have a high hazard dam, you have to do an inundation flood study, and this is not easy work,” Paul Siebensohn, CSD director of field operations, told last week’s CSD Improvements Committee meeting. “This is complicated and expensive, and we’re going to have to contract this out.”
The state’s classifications:
- “Extremely high” – not levied against any CSD dam – anticipates considerable loss of human life and major impacts to infrastructure or property.
- “High” anticipates probable loss of human life and economic, environmental and lifeline losses.
- “Significant” does not anticipate any loss of human life, but it does envision the other impacts.
- “Low” anticipates no loss of human life and damage principally to a dam owner’s property.
Here are the state classifications for the CSD’s dams, followed by what the CSD believes the classifications should be:
- Calero: State classification: High | CSD recommendation: Significant
- Chesbro: State classification: Significant | CSD recommendation: Significant
- Clementia: State classification: High | CSD recommendation: Low
- Granlees: State classification: Low | CSD recommendation: Low
- Michigan Bar No. 1: State classification: High | CSD recommendation: Low
- Michigan Bar No. 2: State classification: Low | CSD recommendation: Low
Assessing the state’s action, Siebensohn said Calero is rated high because there’s a single home, outside Rancho Murieta, that might be impacted, even though that home didn’t flood in 1997's floods. Michigan Bar No. 1 has no property that would be impacted, he said. Clementia is rated high because a collapse there could flood the Cosumnes River, he said. Chesbro is rated “significant” because the water treatment plant is below the dam, he said.
Following unanimous Senate and Assembly approval, Gov. Brown last month signed AB 1270, which requires annual inspections of dams classified as significant, high or extremely high hazards, and requires inspections every two years for dams classified as low hazards.
After receiving the state classifications, Siebensohn said he challenged them to the state Department of Safety of Dams. They sent out a representative, who toured the dams with him, Siebensohn said.
Even if the dam called Michigan Bar No. 1 flooded, Siebensohn said, there are no downstream structures or properties likely to flood.
“I pointed this out and took him on the tour. ‘Yeah, it seems to make sense,’” Siebensohn quoted the representative as responding, “but they’re hesitant to change anything, so I’m still waiting on a formal response from them.”
He estimated the cost of studies at an unbudgeted $50,000, and Director Les Clark, a civil engineer by profession, said that estimate is probably at the low end of the possible range.
Siebensohn said his understanding of the filing rules is that if the dam is classified as a high risk, the study is due by year’s end; a lower classification would allow an additional year.
Siebensohn said there are no grants or funding available for this work.