Wash. Rev. Code § 88.32.250
The joint participation shall be under a contract in writing made in the names of the county, port district, and city, under ordinance or resolution that provides the nature and extent of the work, the extent of the participation of the parties, the division of the costs, and method of payment. The costs shall be paid from any funds of the county, city, or port district designated in the contract.
The control and direction of the work shall be under a joint board consisting of one or more representatives of each party to the contract, as may be agreed upon by the parties. The representatives of the respective parties shall be appointed by the governing body of the respective parties. The joint board shall employ such help and services as may be required and fix the compensation to be paid for the services. The joint board shall consult with the corps of engineers, department of the army, and with the state secretary of transportation and the state director of ecology in furtherance of federal and state of Washington interests in the purposes of RCW 88.32.240 and 88.32.250.
RCW 88.32.250