Wash. Rev. Code § 85.12.010
Whenever, under the provisions of any act of the congress of the United States, the corps of engineers of the United States army, or any other agency of the United States, shall be authorized to reconstruct, improve, repair or maintain any system of improvements of any diking, drainage or sewerage improvement district under the laws of the state of Washington, the board of county commissioners of the county in which such district is situated, on behalf of such district may consent to and permit the United States, or any agency thereof, to perform any work or service upon or with regard to such district's system of improvements which shall by the board be found to be for the benefit of such district and the property therein, or, if the enlargement, betterment or other improvement of such district's system of improvements, or the performance of extraordinary maintenance work upon or with respect to its existing system of improvements shall have been authorized, the board may contract, on behalf of said district, upon such terms as may be agreed upon by the United States and the board for the performance of the work so authorized by said corps of engineers, or other agency of the United States. No bond shall be required by the district for any work performed by or under the supervision of said corps of engineers, or other agency of the United States.
RCW 85.12.010