RBS Citizens Financial Group has closed on a "substantial" construction loan with The Fallon Co. to partially finance the development of 100 Northern Ave., which will house the new headquarters of global law firm Goodwin Procter LLP. The amount of the loan was not disclosed.

Once complete, the 17-story, build-to-suit tower will be 515,000 square feet, 375,000 square feet of which will be leased to Goodwin Procter.

RBS Citizens underwrote the transaction and is serving as administrative agent and sole arranger. Other lenders include TD Bank, Santander Bank, First Niagara Bank and People’s United bank.

"We’re excited to help Joe Fallon implement the next phase of his vision for Fan Pier," Jerry Sargent, Massachusetts president for RBS Citizens and Citizens Bank, said in a statement. "The continuing transformation of the Seaport District is a great indicator of the economic vitality of the city of Boston, and we are pleased to be participating in this effort."

In addition to financing the Fan Pier construction, the Citizens Bank Foundation recently donated $30,000 to Pine Street Inn, a Boston-based nonprofit that works to reduce homelessness in the city.

The donation will support a housing model that is in the midst of a 300-unit housing expansion. It will also help the nonprofit pilot its "Phases of Care" tool, which assesses clients using a broad spectrum of medical, mental health, legal and substance abuse indicators.