The developers of Maxwell's Green, a $52.5 million development between Magoun Square and Highland Avenue that would contain 184 units of rental housing, announced Wednesday they have cemented their financing and begun construction in earnest.

Kyle Warwick, principal of Davis Square Partners, the developer, said Sovereign Bank is financing the project with a standard construction loan.

Meanwhile, major construction has begun at the site, he said. Commonly known as MaxPac, the development is located at an old industrial site near Clyde Street, Lowell Street and the train tracks that pass under Lowell Street.

Demolition and site-preparation work have been going on at the MaxPac location for months, Warwick said, and over the past two months workers have been constructing a retaining wall for the Green Line. The Lowell Street station of the planned Green Line extension would be next to Maxwell's Green.

Now, Warwick said, the major construction process is under way. The first of four buildings is scheduled to be complete by Sept. 2012, he said, and the entire project is slated for completion during the first quarter of 2013. It's a "fast-track, aggressive timeline," he said.

On Wednesday, Davis Square Partners, a joint venture between K.S.S. Realty Partners and Gate Residential Properties, also announced the hiring of J. Derenzo Company, a construction firm out of Brockton, as a subcontractor to conduct excavation, foundation, backfilling, paving and underground utility work at the site.

Warwick said Callahan Construction is the general contractor for the project.

Wednesday's announcement said the agreement with J. Derenzo Company represents one of the largest contracts for the project and that J. Derenzo works with union labor, including Laborers Local 22 and Operating Engineers Local 4.

Union organizers have criticized the MaxPac project for not hiring union labor and local workers from Somerville. In February, the Somerville Board of Aldermen held a public hearing on the matter after more than 50 people signed a petition requesting the hearing.

Warwick said hiring J. Derenzo is part of an effort to address those concerns, and that it wouldn't be the last gesture.

In terms of hiring local workers, "They"—J. Derenzo—"do make an effort to hire locally on most of their jobs," said Warwick. "They will make an effort to hire locally."

Maxwell's Green
When complete, Maxwell's Green will contain 184 LEED—Leadership in Energy and Environmental Design—certifiable rental units of various sizes: studios and one-, two- and three-bedroom units. The development will contain a fitness center, theater room, yoga studio, roof deck, park, and dining and entertainment area. It will also have 24 units of affordable housing, according to Wednesday's announcement.

The development is being constructed at a former industrial site that was once home to a cardboard and packaging plant and an International Paper facility, among other things.