In accordance with section three hundred seventeen, a contract may be awarded according to another procurement procedure established by rule of the procurement policy board, under circumstances, defined by rule of the procurement policy board, in which the use of such procedures is in the best interest of the city. An agency determination to utilize such an alternative procurement procedure for a particular procurement or for a particular type of procurement shall require the written approval of the mayor prior to seeking bids or proposals. The agency contract file shall contain the determination to use an alternative procurement procedure which shall state (1) which circumstances defined by the board to be in the best interest of the city apply to the procurement, including the basis upon which the agency made such determination, and (2) which procedure, as defined by the board pursuant to this section, was used in awarding the contract.