Wash. Rev. Code § 39.04.080
A true copy of such account or record, duly certified by the officer or officers having by law authority to direct such work to be done, to be a full, true, and accurate account of the costs of executing such work shall be filed in the office where the original plans and specifications are filed within sixty days after the completion of the work.
The engineer or other officer having charge of the execution of such work shall execute a certificate which shall be attached to and filed with such certified copy, certifying that such work was executed in accordance with the plans and specifications on file and the times of commencement and completion of such work. If the work is not in accordance with such plans and specifications he or she shall set forth the manner and extent of the variance therefrom.
RCW 39.04.080