Section 62. Pursuant to sections 61 to 69, inclusive, a governmental unit may enter into contracts for the inspection, maintenance, repair or modification of a water storage facility to maintain adequate services to users and to ensure that the water storage facility is in compliance with federal, state and local laws. All contracts shall be awarded in accordance with section 6 of chapter 30B and approved by a 2/3 vote of the local legislative body of the governmental unit. An approved contract may provide that the governmental unit: (i) may make annual payments to fund capital modifications, repairs or installation of equipment and systems at a water storage facility that have been completed or are to be completed pursuant to the terms of the request for proposals; provided, however, that costs shall be amortized over a period that shall not be longer than the useful life of the modifications or repairs or the equipment and systems installed; and (ii) may make payments for future capital modifications, repairs or installation of equipment and systems or a second interior or exterior coating at a water storage facility pursuant to the terms of the request for proposals based on estimated costs of such capital modifications, repairs or installation of equipment and systems at a water storage facility, only if the payments for the full accumulated amount are guaranteed by a bond, letter of guaranty or other form of guaranty to be submitted on an annual basis and approved by the governmental unit for the 100 per cent accumulated amount.