Section 18. Any request for a change order shall be processed promptly, in compliance with regulations promulgated by the commissioner, and otherwise according to the requirements of section 39P of chapter 30. Requests shall be submitted to the project manager, who shall, after consultation with the designer and the using agency, approve or disapprove the request. The project manager shall, after obtaining any other required approvals or disapprovals, notify in writing the designer, the using agency and the requesting party of the request and shall issue a written change order or written notice of disapproval to the contractor. If the approval or disapproval would result in a deviation, as defined by regulations of the commissioner from (a) any study or program which must be prepared in accordance with section 59 or (b) any other pre-design document which must be prepared in accordance with any other statute, appropriation or authorization or administrative directive consistent therewith, the decision made shall be subject to appeal by the using agency to the secretary of administration and finance. Such appeal shall set forth in writing the reasons therefor and a copy thereof shall be furnished to the commissioner at the time the appeal is filed with the commissioner. The commissioner shall, within 10 days following the receipt of such appeal, render a written decision thereon, which shall be final and conclusive.