An interstate district may incur debt and issue its bonds or notes to finance capital projects. Such projects may consist of the acquisition or improvement of land and buildings for school purposes, the construction, reconstruction, alteration or enlargement of school buildings and related school facilities, the acquisition of equipment of a lasting character and the payment of judgments. No interstate district may authorize indebtedness in excess of 10% of the total fair market value of taxable property in its member districts as defined in article VI. The primary obligation of the interstate district to pay indebtedness of member districts shall not be considered indebtedness of the interstate district for the purpose of determining its borrowing capacity under this section. Bonds or notes issued under this section shall mature in equal or diminishing installments of principal payable at least annually commencing no later than 2 years and ending not later than 30 years after their dates.   [PL 1981, c. 693, §§ 5, 8 (NEW).]