The record-setting high water of last spring's runoff affected more than Big Wood River floodplain neighborhoods.
The Ketchum sewer plant is faced with half a million dollars in repairs from damage inflicted by high groundwater that came along with the record-setting stream levels. The upward pressure from high groundwater cracked the 6-inch concrete floor of one of two clarifiers used to separate solid waste from water.
As part of a normal operational rotation, the level in the clarifier was lowered last spring, and functions were transferred to the other. Without the weight of the sludge pushing down against the rising groundwater, the steel-reinforced concrete cracked.
"In the future, having the knowledge we have now with the fluctuations of the groundwater and what it will do to a concrete floor, the plan is to install numerous dewatering wells," said Ketchum Utilities Manager Steve Hansen.
Engineers estimate repairs will run between $400,000 and $600,000.
The expense is covered, however, by the city of Ketchum's insurance provider, Idaho Counties Risk Management Program.
"It will require some substantial paperwork," said Ketchum City Administrator Ron LeBlanc. "It's not like a fender-bender or typical claim."
Hansen said sewer plant technicians only discovered the problem in October, even though it probably happened last June.
"Once we removed all the water in the tank, then it was pretty obvious," he said. "We noticed a circular crack that ran the entire circumference of the clarifier floor."
Hansen pointed out that the redundancy of having two clarifiers enables the sewer plant to operate at full capacity for up to a year without any problems.
The clarifier allows solids to settle through gravity and removes them from water. Up to 98 percent of wastewater solids are removed this way.
The irony to the clarifier breakdown is that the sewer plant has just undergone $7.4 million in improvements over the past three years. There will be an open house in June, "but it's actually on line now, and it's been on line since the first of the year," Hansen said.
