CANAAN — In order to conduct repairs this winter to the dam at Goose Pond, the New Hampshire Department of Environmental Services’ Dam Bureau plans to significantly lower the water levels of the lake.

Beginning Oct. 9, the dam bureau is scheduled to lower the water level by one foot a day until it’s around 22 feet below normal surface levels. The drawdown is expected to remain in place for about a year, allowing for repairs that are scheduled to be completed in 2025.

If it were to fail, “it would be pretty catastrophic,” said Corey Clark, chief engineer for the dam bureau.

Cracks in the concrete dam are the primary concern, Clark said. The dam bureau is scheduled to host a public meeting on the project on Tuesday at 6 p.m at the Canaan Emergency Operations Center on Route 118.

In the winter, NHDES typically drops the water level of the lake by about eight feet to prevent ice damage to the shoreline and create space for springtime runoff. But this fall’s dramatic drawdown is of another order of magnitude.

“People who live on the lake will no longer be living on a lake,” said Michael Riese, president of the Goose Pond Lake Association.

The lake, which typically covers around 600 acres in Canaan and Hanover, will shrink to about a quarter of its size. There are around 180 homes directly on or across the road from the pond, with under 50 that are used by year-round residents, according to the lake association’s website.

“Water’s going to go down,” Riese said. “Some animals are going to go upstream, some downstream, some will die.” Though the state wildlife biologists that Riese has talked to have all said the same thing about the long-term impact on wildlife, he said. “It’s that: Nature heals itself.”

The 31-foot tall concrete dam at the lake was poured in 1918 to replace a wooden dam. Repairs are set to include the installation of 20 “relief wells” around the base of the dam that will ease pressure from groundwater, Clark said. A pipe system also be installed at the time that should allow the water to discharge into Goose Pond Brook.

New Hampshire received more than $29 million in federal funds from the American Rescue Plan Act, or ARPA, to put toward the rehabilitation of state-owned dams. Engineers on the Goose Pond project estimate costs at $5 million.

“But even if it’s above that, we should have sufficient funding to cover it,” Clark said.

The repair at Goose Pond is the only active dam rehabilitation effort in the Mascoma River watershed, which flows empties into the Connecticut River.

The project also will include repairs to the dam’s spillway, the concrete chamber that discharges water into Goose Pond Brook. Additionally, a trio of wooden floodgates at the bottom of the dam that allow for draining are set to be replaced with a single, stainless steel gate.

“We’ve determined those floodgates are more of a risk than a benefit,” Clark said. “The risk being that they’re made of wood. If it were to rot and fail, there would be unexpected discharge of the pond and possible flooding downstream.”

The stability of Goose Pond is crucial to safeguarding habitat and municipalities along the watershed.

In the event the dam failed, homes along Goose Pond Brook in Canaan would likely be impacted, Clark said, as well as low-lying property along the stream, especially where it crosses Route 4 and discharges into Mascoma River.

“As the Mascoma River moves through Enfield, the downtown area in town would also likely be impacted,” he said. “It then discharges into Mascoma Lake, and could create a flooding event downstream of the lake into Lebanon. Impacts could be seen all the way from Mascoma Lake dam down to the Connecticut River.”

In 2014, the dam bureau identified cracks in the Goose Pond dam’s concrete.

In 2018, the bureau installed test wells and monitoring instruments in order to begin drafting a rehabilitation plan.

Repairs made to the dam by the department in the 1990s weren’t sufficient, Riese said.

The project went out to bid last week.

“I just hope that the contractor they pick is conscientious, starts on time, works hard, and finishes on time,” Riese said. “We can’t control nature, but we can hopefully control the contractor.”

Frances Mize is a Report for America corps member. She can be reached at fmize@vnews.com or 603-727-3242.