A proposal to replace the Plymouth Iron Foundry with a new, larger boat repair facility has some residents concerned the town could lose a historic building along the Plymouth Harbor waterfront.

The proposal, by Dallas-based Safe Harbor Marinas, calls for a larger marina facility to replace the existing foundry structure at the corner of Water and Union streets. The location is directly across the street from Brewster Gardens, a gem of a park that runs along both sides of Town Brook, and a few minutes walk to tourist spots like Plymouth Rock and the replica ship Mayflower II.

The existing structure — parts of which date back to the 1860s — is in poor condition, with roof leaks, damaged ceilings, rotted structural elements, and deteriorated brick, according to project filings.

Tim Moll, the Northeast regional vice president for Safe Harbor Marinas, said the company has been working with residents to address their concerns, and the yard’s general manager has taken residents on tours of the property.

“We have hosted two neighborhood meetings that were very positive,’’ Moll said in an e-mail. “It’s been a working boatyard for many years that has strived to be a good neighbor.’’

Jessica McHugh, who is with a neighborhood group dubbed the Bradford Area Commission, said the group is calling on Safe Harbor to work more closely with residents about the project and try to preserve parts of the historic structure.

Residents who raise concerns about the project have also questioned its potential impact on the environment, and whether it could increase the risk of flooding in the area, she said.

Residents want the marina business to succeed, but are concerned with the scope of the company’s proposal, said McHugh, who lives near the property.

“It’s going to completely change the everyday look and feel of what this part of the town looks like,’’ McHugh said in a phone interview. “And this is going to impact us for generations to come.’’

Safe Harbor Marinas owns and operates marina facilities in 24 states and Puerto Rico, with its Massachusetts facilities located in Edgartown, Hull, Marshfield, North Falmouth, Quincy, Salem, and Vineyard Haven, along with the marina in Plymouth.

The roughly 2½-acre property is already a boatyard with 100 berths that services yachts and small commercial vessels, and the proposed project will provide Safe Harbor a more efficient work service space, Moll said.

The existing foundry building, which is about 31,000 square feet, varies in height between one and two stories, with a single-story section facing the corner of Water and Union streets. The structure is made up of several buildings that have been connected over the years, Moll said.

The proposed replacement would be about 38,000 feet and as much as 35 feet tall — the ­additional height is needed to accommodate boats during ­servicing, according to Moll. ­Another existing building on the property, which was built in 2003, is currently 35 feet high, he said.

“The current building is very tired and it’s not cost-effective to rebuild it,’’ Moll said. “The combination of structures that make up the building [is] very inefficient and makes it difficult to accommodate and service today’s boats.’’

The marina project would also remove aging underground fuel tanks and install new above-ground storage, and improve access to the waterfront with a new public walkway where Town Brook meets the harbor.

The proposed building is designed to meet local and federal requirements for flood-prone areas and handle storm water, according to filings. It will also incorporate a new system for collecting oil.

Moll said the property has not flooded in the past, including during storms like Hurricane Sandy and the Blizzard of ‘78.

The project, which was proposed late last year, needs the approval of several agencies, including Plymouth’s Conservation Commission and Historic District Commission, as well as the state Department of Environmental Protection.

The proposal will also be reviewed by the town’s public works and fire departments, as well as its Planning Board, according to Lee Hartmann, Plymouth’s acting town manager.

Concerns over demolishing the foundry led the Historic District Commission in late February to impose a one-year delay on any knockdown of the structure. Moll said that, before the decision, Safe Harbor had intended to start demolition in the fall.

The historic commission can lift the delay at a later date if the applicant comes back with something to preserve the building’s historical value, according to Tara Brennan, the board’s ­administrative secretary.

The Conservation Commission, which also met to review the project last month, is due to continue its discussion in April.

Michael McKenna, who also lives near the project, said he wished Safe Harbor would work more closely with neighbors, and do more to address concerns like flood control and questions about potential environmental issues due to the project.

He said the existing building is in poor condition, but wished that the company would incorporate its facade into a new structure. He said a new building should reflect the “historic environment’’ of the surrounding area.

“That would be a nice gesture for the neighborhood,’’ he said in a phone interview.

Lea Filson, the president and chief executive of See Plymouth, which promotes local tourism, said in a phone interview the project is important to the town, given its proximity to Brewster Gardens and waterfront location.

“I just think it’s a vitally important thing that we get this right, because after all, tourism is the number one industry for the town and county of Plymouth,’’ said Filson, who lives near the site.

“That’s why we have to be so careful not to overbuild it, not to underbuild it, but to keep the product as beautiful and as accessible as possible.’’

Moll said the company is willing to discuss the project further with residents.

McHugh said the move to delay demolition and the ongoing conservation review gives residents more time to raise their concerns with the company.

“A project of this scope isn’t just an abutters’ issue, or a neighborhood issue,’’ McHugh said.

“It’s a conversation for our town.’’

John Hilliard can be reached at john.hilliard@globe.com.