RCW 47.08.060
RCW 47.08.060: Contracts with United States—Disposal of funds from the United States.
Whenever any moneys shall be realized by the state of Washington as a result of any agreement authorized by RCW 47.08.040 , the same shall be deposited in the treasury of the state of Washington to the credit of the motor vehicle fund, and shall be available for highway purposes only.