Mass. Gen. Laws ch. 30B, § 3

A procurement officer who awards a contract in the amount of $10,000 or more shall maintain a file on each such contract and shall include in such file a copy of all written documents required by this chapter. Written documents required by this chapter shall be retained by the governmental body for at least six years from the date of final payment under the contract. Except as provided by paragraph (d) of section six, the records shall be open to public inspection.