Developers will break ground on the final building in the first phase of the Assembly Row project on Thursday.
The newest building will feature 100,000 square feet of office space and 30,000 square feet of retail space. The project as a whole is expected to include 800,000 square feet of retail space, about 1.75 million square feet of offices, and more than 2,000 apartments.
The first phase of the project, which includes about 450 apartments, an AMC movie theater, and 330,000 square feet of retail space, is expected to be completed in 2014. A new MBTA Orange Line stop is also expected to be opened next year. A 6-acre park along the Mystic River plans to open this summer.
Undertaken by Maryland-based Federal Realty Trust, the development project has received about $130 million in public funds and more than $1.5 billion in private investment.
Federal Realty owns nearly half of the developable land in the 145-acre area east of I-93 along the Mystic River that makes up the Assembly Square district. The area is the former site of a Ford Motor Co. assembly plant, which operated from 1926 to 1958.
Thursday's ground breaking will be attended by Federal Realty-Boston President Don Briggs; Somerville Mayor Joseph Curtatone; US Senator William "Mo" Cowan; and Jeffrey Simon, assistant secretary of real estate for MassDOT. It takes place at 10 a.m. at Grand Union Boulevard at Assembly Square.