TOWNSEND — When everything is done, people will not see much change in the waterways around the historic district in Townsend Harbor. Work on the dam and mill raceway is scheduled to begin in early July.

“We’re well aware of the historic significance of the area. The design is such that it has minimal impact on the historic district,” said Bob Kimball, project manager at Hollingsworth & Vose Co.

The manufacturing firm, which has a branch in West Groton, owns the dam and is responsible for making the repairs. Leslie Gabrilska, acting conservation agent in Townsend, said the dam failed a safety inspection in 2008.

Deteriorating concrete in the raceway and trees growing on the crest of the earthen dam were the problem, Kimball said.

“The dam isn’t in any danger of immediate failure,” he said.

The repair work will benefit the surrounding buildings. “Some of the work will help protect the cooperage and the grist mill from flooding,” he said.

The cooperage hangs over the dam. Laura Bradley, owner of the antique co-op in the structure, said the building was sandbagged this spring during the floods. The previous owner of the shop was rescued during a spring flood several years ago.

The safety of the surrounding area will increase, but there will be little impact on appearances from the work. “There’ll be a few trees cut down. When it’s all said and done it will look pretty much like it does now,” Kimball said.

He expects the work to take approximately six weeks. Some of the work will be done on land owned by the Townsend Historical Society and on the privately owned land beside the former tavern.

A cofferdam will be installed while work is done on the raceway. The temporary dam will divert water from the canal and over the dam.

The water behind the dam will not be drained away for the work. Riprap, a stone filling used for erosion prevention, will be installed but will not be visible from the street.

Hollingsworth & Vose Co. is headquartered in Walpole. The facility in West Groton, four miles downriver from the dam, employs a significant amount of people, according to Kimball.

Engineering work was done by the Pare Corp. of Lincoln, R.I., and Foxboro, and construction will be done by MAS Building & Bridge, Inc., of Franklin.

Both companies are well-regarded. “Boy, they are on their toes,” Gabrilska said of the engineering company.

Gabrilska said changes were made in the original plans when an area identified as wetlands was found to be stormwater runoff.

MAS is a New England-based company that has worked on other water-related projects for Hollingsworth & Vose Co.