OXFORD — The Thompson Lake Dam appears to be in good shape.
Town Manager Butch Assselin told selectmen about the dam condition at the board’s September 20 meeting after a diving company spent three days in Oxford, last week completing major repair work on the centuries old dam that controls the level of lake water.
“Joe Kacer (owner) of Commercial Divers said this dam is in good shape overall and that a lot of towns with dams would love to have one as good a shape as this one is,” Asselin said.
Concern grew this summer over several issues in the dam after leaks were detected around the east sluice and water was found seeping into the Robinson Mill on King Street intake tank that went from the dam to the underside of the mill and posed a threat to the mill.
The dam is owned by the Town of Oxford but benefit’s the lake water on which residents from Oxford, Poland, Otisfield and Casco live and recreate.
The former woolen mill, which employed hundreds of area residents in its heyday was purchased by developer Chuck Starbird in 2012 after the town of Oxford foreclosed on the mill property in 2009 due to nonpayment of $244,920 in taxes over a three-year period by previous owner John C. Robinson.
The 7.5-acre property includes the three-story brick mill and a waste treatment plant. The dam, which controls the lake level, is owned by Oxford but the town has a multi-town advisory committee and asks the other three towns to financially contribute to the dam’s upkeep.
The work done last week by Commercial Divers will cost less than $20,000, said Asselin and the cost will be split by the four towns.
Asselin said the Oxford’s Highway Department provided Commercial Divers a hand with equipment, filling sand bags, obtaining supplies and materials, that saved all four town some money.
According to Asselin, leaks have been plugged, corroded anchor bolts on the gate guides have been replaced with stainless steel ones, cement has been placed around the gate guides and the east sluice has been reinforced with additional hemlock planking.
Although some water is still getting through the gate and Asselin said the work is still a temporary fix, he intends to speak with an engineer on an alternative long term solution that the owner of Commercial Divers recommended.
Asselin said the town will not be able to lower lake water levels from the east sluice until the boards have been replaced and the steel plate removed.
In addition to that work, the Robinson Mill intake tank that went from the dam to the underside of the mill has been cleaned out and drained. The gate located on the pad between the mill and the dam was found resting on another old gate preventing it from opening. Accumulations of rust and muck was another problem, Asselin told the selectmen.
Debris was also found piled up three feet behind the gate blocking what flow there was. The gate had to be forced open using a jack, Asselin said.
“What water there is still flowing into the intake tank no longer poses a threat to the mill,” he explained. “Any water that gets by the now open gate (under the pad,) drops down into a rusted out iron tank under the mill and then into the river.”
The gate hoist that controls the water flow from the dam and then into the mill was also repaired and the gate was tested successfully with an emergency release of water from the central sluice to meet annual Maine Emergency Management Association requirements, Asselin said.
He also reported that a diver did an inspection upstream at the base of the dam in front of the central sluice and there does not appear that water is undermining the dam.
According to a report from the Thompson Lake Environmental Association, dam control on Thompson Lake is important because it “significantly reduce(s) the threat of soil erosion dumping phosphates into the water. Maintaining shoreline integrity helps minimize undermining large trees that would fall into the lake as well.
In a study of the water level done several years ago, TLEA said between 1966 and 1986 the average winter water level was 37.1 inches below the top of the dam. In the following years winter water levels were left significantly higher, resulting in spring flooding and erosion. In order to keep the water levels at a safe level it was decided to target the winter level at 32 inches.
The water draw down typically begins around October 1 and is finished by October 20th to the winter level of 32 inches, according to the TLEA report.