Me. Rev. Stat. tit. 30-A, § 3518

A municipality may withdraw from the district at the end of a fiscal year provided that it has given the board of directors at least one year's written notice of its intention to do so. The municipality must pay its proportionate share of the current indebtedness of the district before withdrawal and must agree by appropriate written document to pay its proportionate share of any long-term indebtedness of the district as that indebtedness becomes due and payable. During the period of notice, the withdrawing municipality does not become liable for any capital expenditures or borrowings which may be made by the district. The proportionate share of the withdrawing municipality in any current and long-term indebtedness of the district shall be in accordance with the formula then in effect for payment of the current and long-term indebtedness.