Image courtesy of HGA

Despite the region’s historic lab vacancy rate, Boylston Properties is planning a new 175,000-square-foot life science building next to its Arsenal Yards property in Watertown.

The Boston-based developer has been steadily repositioning the retail property with office, lab and residential space over the past decade. The new lab building would occupy a portion of the parking lot behind the Home Depot building, 

Boylston Properties bought the 10-acre Home Depot property in 2022 for $96 million.

It’s now seeking to amend the Arsenal Yards master plan special permit, adding the Home Depot parcel into the master plan area, according to documents submitted to the town of Watertown.

The proposed 6-story lab building, known as 300 Forge, would occupy 1.5 acres in the rear parking lot bordering the Charles River. 

The Arsenal Yards redevelopment currently contains 227,500 square feet of lab space leased to nine tenants, according to Boylston Properties.

Following approval of the master plan changes, Boylston Properties plans to submit a site plan for the new lab building, according to the application.

The Home Depot property currently contains 577 parking spaces and the new lab building would include 392 below-grade parking spaces.

East Watertown emerged as a life science destination in recent years, when vacancies in Cambridge dwindled and growing companies leased space at new developments such as Arsenal Yards and Alexandria Real Estate Equities’ Arsenal on the Charles.

But amid declining investment in the industry since 2022, life science leasing in Greater Boston hit a post-pandemic low of 505,000 square feet in the second quarter, CBRE reported.