A massive project to revitalize a dormant South Boston power plant is finally underway after the Boston Planning and Development Agency approved it Thursday.

The joint venture of Hilco Redevelopment Partners and Redgate Capital Partners received the go-ahead to undertake a mixed-use development at the former coal-fired Edison Power Plant at 776 Summer St. The approval for the ambitious residential, commercial and hotel development is the culmination of a years-long review process after the partnership bought the site in 2016, the companies said in a statement.

“This is a complex adaptive reuse redevelopment of an obsolete industrial site that has been inaccessible to the public for over 120 years,” Melissa Shrock, senior vice president of mixed-use development at Hilco Redevelopment Partners, said in a statement.

The towering facility at the corner of Summer Street and East First Street was built in 1898 and decommissioned in 2006. Hilco and Redgate pledge to construct 636 housing units, 860K SF of mixed-use space, a 240-room hotel and 5.7 acres of community open space. The billion-dollar plan calls for reusing four former turbine halls to create a total of 1.68M SF of developable space.

The partnership will also contribute more than $10.1M for MBTA investments to improve transit in the City Point neighborhood and will provide $7.3M in linkage payments for affordable housing efforts across the city, according to a pre-approval summary. Of the 636 housing units, 16% will be designated as affordable.

The Hilco and Redgate partnership bought the site for $24M from Exelon Group. The project will be built in phases over the next 10 to 15 years, the developers said.