A Miami developer has begun mobilizing construction equipment at the site of a planned 414-unit apartment complex on a long-vacant parcel in Boston’s Seaport District.

Crescent Heights paid $36 million in 2016 to acquire the fully-permitted site at 399 Congress St., nicknamed “the sausage parcel” because of its unusual shape.

Union Labor Life Insurance Co. of Silver Spring, Maryland provided $157 million in construction financing on May 16, according to Suffolk County Registry of Deeds records.

A previous developer, Boston-based Madison Properties, acquired the property in 2006 for $5.65 million from Boston Edison Co. in the wake of the Central Artery Tunnel project, which extended a new highway ramp that terminates next to the property. Madison Properties gained approval for a 505-room hotel but was unable to obtain financing during the recession; it switched gears to a residential complex, approved by the former Boston Redevelopment Authority in 2013.

A Crescent Heights executive declined to comment this week, but referred to a new website providing ongoing construction updates and a timetable for foundation work, which begins this month, with a completion date of fall 2019.

The complex would be built on a 30,435-square-foot parcel. The project site, part of a planned development overlay district allowing greater density, also includes a 27,502-square-foot patch of vacant land owned by Massport between three highway ramps.

The parcel is across the street from Cottonwood Management’s $900 million Echelon development. Echelon,  which broke ground in June and is scheduled for completion in 2019 and 2020, contains 448 condominiums, 285 apartments and 125,000 square feet of retail and restaurant space.