CLAREMONT — The dam on the reservoir that supplies about 70% of the city’s drinking water supply is in need of structural repairs, an engineer told the City Council Wednesday.
There are maintenance-level repairs that have to be undertaken on the Whitewater Reservoir Dam, but there are “no imminent structural concerns,” said Jason Gallant with the firm Wright-Pierce of Bedford, N.H.
The 150-million-gallon reservoir is located on the Claremont/Cornish line.
“The dam is safe,” Gallant said in response to questions from a few councilors.
Still, before any of the “observed deficiencies become structural deficiencies,” concrete repairs to restore the abutment spillway structure of the 60-year-old earthen dam should be completed, Gallant said.
“It needs some repairs that are in the normal course of operating these types of structures,” Gallant said.
A report on the dam’s condition, issued in August, builds upon earlier inspections and subsequent reports by the New Hampshire Department of Environmental Services, or DES, in 2023 and Waysville Engineering of Springfield, Vt.
The dam is in “fair condition,” Steve Doyon, chief dam safety engineer with the DES, said in April. The dam has concrete deterioration on the spillway’s right abutment and downstream embankment wall, although he said the deterioration appeared to be non-structural and “not jeopardizing the safe operation of the dam.”
The dam is in “general compliance” with dam safety standards, but completing recommended repairs will ensure it will continue to meet those standards, Doyon said.
The estimated cost of a little more than $1 million would include repairs to the left embankment wall, primary spillway and pedestrian walkway railing, as well as mobilization of materials and equipment and engineering and construction costs, Gallant said in his report.
To help cover the cost, the city could tap into a capital reserve fund and a fund balance in the drinking water fund and state assistance and grants could also be sought, Acting City Manager Nancy Bates said.
Repairs to the left embankment wall and northeast return wall recommended in Gallant’s report “are required for long-term structural stability and water tightness of the dam,” Gallant wrote.
A second recommendation is to complete repairs to the remaining one-third of primary spillway that was partially repaired in 2019 by refacing it with concrete to a depth of eight inches. The procedure will be similar to what was done in 2019.
Fallen stone and riprap should be repositioned at the base of the dam slope and vegetation removed and maintained, Gallant said. He noted that the city has been monitoring and removing vegetation.
The project is slated to go to bid in October, followed by the necessary permitting. The start of construction has not been decided.