Okla. Stat. tit. 61, § 19

A. A municipality or rural water district may enter into a multi-year contract for painting and other maintenance of water storage tanks and appurtenant facilities if the contract contains a contingency provision whereby the municipality or district is not obligated to make any payment, in any year, in an amount exceeding the income and revenue provided for such year. B. Notwithstanding the provisions of Section 101, et seq., of Title 61 of the Oklahoma Statutes, a municipality or rural water district contemplating entering into a multi-year contract for painting and other maintenance of water storage tanks and appurtenant facilities may or may not, at its option, require that the work be bid pursuant to the provisions of the Public Competitive Bidding Act of 1974.