The dam project

Lorraine Briscoe

The new dam will be ready early in 2023, about a month late. It was delayed by heavy rainfall in mid September which washed away some of the temporary bariers. The new dam will recreate the beloved Mill Pond, which is so much a part of the look of old Knowlton captured on so many postcards.

The dam site is where Paul Holland Knowlton built his grist mill in 1836, a project that was instrumental in developing the town of Knowlton. The new dam will look different from the old one that was built in 1951.

While the width of the dam will remain the same, the new one will be U-shaped giving the water more place to flow in heavy rain. The dam’s height will be restored by 1.2 m, to where it was prior to 2011 when Hurricane Irene passed through damaging the wooden retaining gates that were subsequently removed. The level of Mill Pond will rise, part of the revitalization plan for the downtown core. A new fence will be installed around the dam area making it safe to observe up close. However, it won`t be possible to walk across the dam as was many years ago.

The big setback in construction was the heavy rainfall the week of September 18. “It set back the dam project”, says the TBL engineer, Marc-André Boivin, who has been involved in the project’s planning for several years. The first step was building a cofferdam with large white plastic sandbags, filled on site, behind the old dam to narrow the water flow to one third of the dam width. These sandbags weren’t able to hold back the water after the heavy rain and the water found its way over the other two thirds of the dam’s width. Work had to be halted until the cofferdam was built up to narrow the flow of water again. The next step was the placing of steel anchors in the bedrock surrounding the cofferdam, around which new concrete has been poured. “The new dam should last 100 years”, says Mr. Boivin. The new dam will be stronger and able to retain 30,000 cubic meters of water, double the current capacity. Also, the dikes will be rebuilt and upgraded, the vegetation will be mowed, and the pond will be dredged.

In the province of Quebec, dams are heavily regulated under various laws including the Dam Safety Act, the Watercourses Act, the Environment Quality Act as well as the Act respecting the conservation and development of wildlife. Hence the years of planning. “The dam construction could only begin on Aug. 15th after spawning season”, Mr. Boivin explained.

Couillard Construction of Coaticook, won the contract, which will cost approximately $3,000,000. They will have a team of about 12 on site through its completion. Take a look when you drive by. Maybe you will catch them mowing the pond vegetation which they hope to finish before the snow comes.