Mass. Gen. Laws ch. 83 § 1C
After commencement of operations of the sewer system authorized pursuant to section 1A, additional connections shall be permitted within the final area of concern by such board or officer having charge of the maintenance and repair of sewers, subject to available capacity, only upon certification by the board of health that the on-site subsurface sewage disposal system on land abutting upon a private or public way in which a common sewer has been laid cannot comply with the provisions of 310 CMR 15.000, et seq., or in the case of new construction, expansion of an existing structure, a change in use, or increases in flow from said land, such expansion, change in use, or increase in flow does not result in sewage flow in excess of the amount of said regulations flow capacity or actual flow resulting from a legal use of said land, whichever is greater, which existed on the date of adoption of this act as determined by the board of health. Notwithstanding anything to the contrary contained herein, the board or officer having charge of the maintenance and repair of sewers may at any time permit extensions, new connections or increases in flow to the sewer system, subject to capacity, to serve municipal buildings, public restrooms, or other public service uses, including but not limited to housing of which at least 15 per cent of the housing units are deed restricted to residents with incomes no greater than 80 per cent of the area median income paying no more than 30 per cent of their income towards housing.
Mass. Gen. Laws ch. 83, § 1C