The Zoning Board of Appeal has approved a plan by two community developers for a 135-unit, six-story apartment building - and two rental townhouses - on what is now an MBTA parking lot at the Mattapan Square T station.

Roughly half of the units in the $57-million complex will be rented as affordable - to people making no more than 60% of the Boston area median income, under the proposal by Preservation of Affordable Housing and Nuestra Comunidad Community Development Corp.

The two have a deal with the MBTA for a 99-year lease for the land needed for the building - and say that once the project is completed, they will start work on nine townhouse condos on an adjoining lot.

The building will have first-floor retail space, a community room and a 70-space garage for residents. The MBTA will continue to have 50 spaces in a lot for commuters.

Of the units, 6 will be studios, 38 one-bedrooms, 81 two-bedrooms and 10 will be three-bedroom units, including the two rental townhouse units.

Developers said they are designing the building to encourage surrounding neighborhoods to walk or bike its grounds - they are planning a bike path to connect to the neighboring Neponset River Greenway.

The two groups hope to finalize financing for the project next year.

Mattapan Station project-notification form (25M PDF).