Wash. Rev. Code § 47.08.130
The state treasurer is hereby authorized and directed to receive and have custody of such funds and warrants drawn by the secretary of transportation or other authorized agent of the United States as are made available for payment by the secretary of the treasury of the United States under the provisions of the federal aid road act approved July 11, 1916, and all acts amendatory or supplementary thereto, disbursing the same under such terms and conditions as may be prescribed by the secretary of transportation or by the secretary of the treasury or other authorized agent of the United States. The state treasurer is further authorized and directed to pay from the motor vehicle fund for the use of the department such funds as may be necessary upon any project in anticipation of reimbursement by the government of the United States.
RCW 47.08.130