Allston-based developer The Hamilton Co. is joining the building boom in Somerville’s Union Square with plans for a 200,000-square-foot life science development at a prominent intersection.

The project would replace a cluster of low-rise commercial properties across from the first phase of Union Square master developer USQ’s 2.7-million-square-foot project, which includes a lab building and residential high-rise currently under construction.

The Hamilton Co. submitted rezoning proposal to Somerville officials last week for its project, located at the corner of Somerville Avenue and Prospect Street.

Known as the Union Square South Block, the project would include a 4-story office-lab-R&D building and 6,500 square feet of civic space overlooking a 0.3-acre park. The civic space could include a potential new library branch, The Hamilton Co. said.

The developer has retained Elkus Manfredi Architects to design the class A lab and office building, site improvements and public amenities.

“Union Square is a vibrant and exciting destination rich with culture and a diverse population.  Our One Union Square will be a natural complement to the neighborhood, building on its strengths to create new activity and opportunities,” Hamilton Co. CEO Jameson Brown said in a statement.

The parcels are included in the 17-acre Union Square redevelopment zone created by the city a decade ago, with USQ designated as the master developer in 2014. The Hamilton Co. does not believe it requires USQ’s permission to deviate from the redevelopment plan, Brown said at a meeting last fall, according to a report in the Cambridge Day.

The project does require a zoning amendment and approval of site plans and special permits. Hamilton Co. said it hopes to receive all city permits within 18 months.

According to an application to the Somerville City Council submitted by Reimer & Braunstein LLP, the zoning change would allow the site to be configured to provide more civic and community space than required. The zoning text amendment seeks changes in the building width, floor plate and facade build out regulations.

The site, including a Dunkin’ Donuts and three low-rise commercial buildings, is located a block from the year-old Union Square station on the MBTA Green Line Extension.