Section 19. If any change order under section 17 causes any change in the contractor's cost of performance of any work under the contract, whether or not that work is changed by any order, either the contractor or the project manager may request an equitable adjustment in the contract price. A request for such an adjustment shall be in writing and shall be submitted by the party making such claim to the other party before commencement of the pertinent work or as soon thereafter as possible, and in any event within 30 days of receipt by the contractor of an approved change order or the mailing or furnishing to the commonwealth by the contractor of written notice that the contractor regards an order as a change order. Except for claims on defective specifications, no claim for any change under this section shall be allowed for any costs incurred more than 20 days before the contractor gives written notice as required by this section. In the case of defective specifications for which the commonwealth is responsible, the equitable adjustment shall include any cost reasonably incurred by the contractor in attempting to comply with such defective specifications.

The project manager and the contractor shall by negotiation agree upon an equitable adjustment in the contract price before commencement of the pertinent work or as soon thereafter as possible. Notice of the adjustment shall be given to the director. In the absence of agreement by the parties on an equitable adjustment in the contract price, the project manager shall unilaterally determine the costs attributable to the change order. Unilateral equitable adjustments of the project manager shall be reduced to writing and a copy mailed or otherwise furnished to the contractor. Such adjustments shall be final and conclusive unless, within 30 days from the date of receipt of such copy, the contractor mails or otherwise furnishes to the project manager a written appeal addressed to the commissioner, and otherwise complies with the requirements set forth in section 39Q of chapter 30. Said section shall govern further appeal to the division of hearing officers.