Mass. Gen. Laws ch. 83, § 18: Method of assessment

Section 18. The city council of a city or a town which itself is, or the officers of which are, entitled, under sections fourteen to seventeen, inclusive, or under any special act, to assess upon land the whole or a part of the cost of laying, making, maintaining or repairing main drains or common sewers, may determine that such assessments shall be made by two or more of the methods provided in said sections or special acts, and may determine what part of the expense or estimated average cost shall be paid under each method.