HATFIELD — Work on taking out an historic 19th century dam next to the Old Mill Inn could start in late 2028, based on preliminary, pre-permitting plans presented to the Select Board this week.
Even though the D.F. Riley Grist Mill Dam is on the National Register of Historic Places, Tighe & Bond is working with the Connecticut River Conservancy and the property owners, Old Mill Enterprises and Mill River Storage, to develop a way to remove the deteriorating structure located off School Street.
Candice Constantine, senior project manager and engineer with Tighe & Bond, told the Select Board Tuesday that the dam removal is the alternative being pursued by the dam owners, after they received a certificate of non-compliance from the state’s Office of Dam Safety.
While the owners have explored keeping intact the dam, which forms a waterfall on the Mill River, for use as hydropower, gifting to the town or rehabilitating it, removal has been determined as the best option.
“It’s quite a heavy cost burden for the owners,” Constantine said.
The dam is unsafe and its substantial deficiencies have been documented since 2019, Constantine said. The spillway is missing concrete, there is some cracking on the spillway, there’s been a loss of masonry on abutments and there is leakage through the former sluiceway under the building.
The dam, considered intermediate size but high hazard due to the risk to properties and public safety should it fail, also has been identified by the National Inventory of Dams as at risk of failing.
Constantine said the proposal is to move the spillway itself, leaving the abutments on both sides. There would also be bank reconstruction on one side, using “fabric-encapulated soil lifts,” and filling in the existing intake.
Becky Budd, restoration program manager at Connecticut River Conservancy, came on board at the request of the dam owners. Budd said she then solicited assistance from Tighe & Bond, using a $250,000 grant from the Executive Office of Energy and Environmental Affairs’ Dam and Seawall program.
Tighe & Bond is now progressing through the pre-permitting design. Permitting could happen in fall 2027, a final design in spring 2028, bidding in fall 2028 and then work that winter into 2029.
Select Board member Luke Longstreeth said he is concerned about freshwater mussels and other fish moving upstream that have been prevented from doing so, and the potential impact on the habitat from not having the dam in place.
Longtsreeth said he worries about moving too fast on removal. “It just seems there are a lot of negatives to this for a dam that could be repaired,” Longstreeth said.
Constantine said the problem is repairs usually can’t get grants, while removal can. “A lot of times costs are not that different … but what’s different is there’s no grant funding to pay for the dam repair option,” Constantine said.
Dam owners are also responsible for periodic inspections and ongoing maintenance and repairs.
Isobel Arthen-Long, environmental scientist with Tighe & Bond, said an examination of the habitat before permitting will determine if there are any concerns for the fish in the river.
The removal of the dam could also lead to decisions on the Prospect Court Bridge, which has been closed to pedestrians and vehicles for a number of years. Constantine said this bridge could be removed as part of the project.
The dam was originally built as part of the 10,000-square-foot grist mill in 1880-1881 on the site of the Shattuck Gun Factory. A dam has been at the site, though, since 1661.
The D.F. Riley Grist Mill Dam is the only standing dam on the mainstream Mill River, blocking fish from accessing valuable upstream habitat.
According to the watershed group, the dam removal will benefit migratory species such as American shad and sea lamprey, and improve the overall ecological health of the river system, as well as its resilience to climate change.