Mass. Gen. Laws ch. 83 § 15B
A city or town may assess and collect estimated sewer assessments in connection with the construction of water pollution collection, pumping, treatment and disposal facilities. The total amount of such estimated sewer assessments shall not exceed one-half of the municipality's liability under all contracts it has entered into for the construction of such facilities, and the total of such estimated assessments shall be allocated by the same method to be used for the allocation of the actual assessments upon the completion of the work.
When the final costs of construction of the facilities has been determined, the city or town may assess and collect actual sewer assessments. The provisions of chapter eighty relative to the apportionment, division, interest and collection of assessments shall apply to estimated assessments under this section, but the provisions of chapter eighty relating to abatements shall not apply to estimated assessments under this section.
Revenues from estimated assessments under this section shall be dedicated to the payment of the costs of constructing the facilities or to paying the principal and interest on any debt issued in connection with the construction of the facilities, until all such costs and debt service obligations have been paid in full.
Mass. Gen. Laws ch. 83, § 15B