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Quonnipaug Dam Likely to Need Major Work or Replacement

Posted on December 8, 2020

The town is expecting the Lake Quonnipaug dam to either need a rebuilding or total replacement in the near future, according to Town Engineer Janice Plaziak, with formal inspection by the state Department of Energy & Environmental Protection (DEEP) this spring likely to result in a mandate for some major work.

Plaziak told the Board of Selectmen (BOS) and Board of Finance (BOF) last month at a capital budget hearing that the dam is leaking, and has seen issues with weed growth, sediment, and other structural challenges. She added what she characterized as a very preliminary cost forecast of $300,000 in fiscal year 2021-’22, with another $3.5 million in 2023-’24 for dam-related work.

Plaziak told the Courier that the $300,000 was to “get started” on design work, and emphasized both numbers are very rough estimates ahead of any formal assessments or inspections.

She also told the BOS it was possible there were funding sources out there, but that it would take more work to identify them, as the project is still in its very earliest stages.

Even without the upcoming DEEP review, however, it has become abundantly clear that the dam is an issue that needs addressing, as it continues to overflow regularly and shows significant signs of erosion, according to Plaziak.

“I’m pretty confident now is the time to start doing something about the dam,” she said. “I’m anticipating that it’s in the best interest of the town to move forward with a replacement project.”

Earlier this year, the Inland Wetlands Commission approved repairs to three culverts near the dam, which Plaziak warned were in bad enough shape that the road above might collapse without that work. Any work on the dam would also almost certainly include more work on surrounding infrastructure like these, Plaziak said, though the precise scope of a potential project still must be determined by the BOS and other stakeholders.

DEEP can mandate specific work be done based on the upcoming inspection, including scope within certain parameters, Plaziak told the Courier. It also can assess environmental concerns, though she said the dam wasn’t a cause of some of the other issues Lake Quonnipaug has faced with invasive species and overgrowth of aquatic plants.

A 2009 study looked at various options for the dam and related problems, including replacement of the dam, dredging the lake waters, and raising nearby roads. Plaziak said the estimated costs are based loosely on these numbers, while again emphasizing that a lot has changed in the last decade and actual dollar amounts will almost certainly vary.

“That’s the opportune time to take care of any of these other things, if that’s the will of the community,” Plaziak said. “If there is the idea to dredge, to create deeper water in that southern section to deal with that problem they’re having with too many plants…that would be the time to deal with it, because you’re going to have to de-water to build the dam.”

The 2009 study estimated about $1.7 million for the dredging, according to Plaziak, out of a total of $3.3 million for a more comprehensive project that included rebuilding the dam—though again, Plaziak said she anticipated those numbers changing for a project today.

A total failure of the dam, while not catastrophic due to the gradient of the surrounding floodplain area and the dam’s size, still “wouldn’t be fun” and could have a significant impact on nearby roads and property, according to Plaziak First Selectman Matt Hoey said there is a long history of disputes over ownership and responsibility for the lake. The state has a boat launch at the north end of the lake, while Guilford’s Parks & Recreation Department oversees the beach and parking on the west side.

Former first selectman Joe Mazza said publicly back in 2016 that DEEP “will not let us touch the lake,” despite former town engineer Jim Portley recommending a rebuilding of the dam.

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