RCW 39.34 Interlocal Cooperation Act and RCW 39.34.040 permits local governmental units to cooperate and contract with other localities on a basis of mutual advantage and thereby to provide services and facilities in a manner and pursuant to forms of governmental organization that will accord best with geographic, economic, population and other factors influencing the needs and development of local communities. These agreements shall be filed with the county auditor or, alternatively, posted on the public agency’s website.