Wash. Rev. Code § 36.45.040
Whenever any county, by its board of county commissioners, has entered into a contract for the construction of any public improvement for the benefit of the county, whereby the contractor agreed to furnish all labor, material, and supplies necessary for the improvement, and the contractor has proceeded with such improvement and procured from other persons labor, material, or supplies and used the same in the construction of the improvement, but has failed to pay such persons therefor, and such persons have filed claims therefor against the county, and the claims have been audited in the manner provided by law and found to be just claims against the county, and valid obligations of the county except for the fact that they were not filed within the time provided by law; the board of county commissioners may provide funds sufficient therefor, and cause the payment, of such claims in the manner provided by law for the payment of valid claims against the county.
RCW 36.45.040