(1) An authority may be formed by two or more members pursuant to this chapter by execution of a joint municipal utility services agreement that materially complies with the requirements of RCW 39.106.050. Except as otherwise provided in RCW 39.106.080, at the time of execution of an agreement each member must be providing the type of utility service or services that will be provided by the authority. The agreement must be approved by the legislative authority of each of the members. The agreement must be filed with the Washington state secretary of state, who must provide a certificate of filing with respect to any authority. An authority shall be deemed to have been formed as of the date of that filing. The formation and activities of an authority, and the admission or withdrawal of members, are not subject to review by any boundary review board. Any amendments to an agreement must be filed with the Washington state secretary of state, and will become effective on the date of filing.

(2) An authority is a municipal corporation. Subject to RCW 39.106.040(3), the provisions of a joint municipal utility services agreement, and any limitations imposed pursuant to RCW 39.106.050: (a) An authority may perform or provide any or all of the utility service or services that all of its members, other than tribal government members, perform or provide under applicable law; and (b) in performing or providing those utility services, an authority may exercise any or all of the powers described in RCW 39.106.040(1).

(3) An authority shall be entitled to all the immunities and exemptions that are available to local governmental entities under applicable law, including without limitation the provisions of chapter 4.96 RCW. Notwithstanding this subsection (3), if all of an authority's members are the same type of Washington local government entity, then the immunities and exemptions available to that type of entity shall govern.

(4) Nothing in this chapter shall diminish a member's powers in connection with its provision or management of utility services, or its taxing power with respect to those services, nor does this chapter diminish in any way the authority of local governments to enter into agreements under chapter 39.34 RCW or other applicable law.

(5) Nothing in this chapter shall impair or diminish a valid water right, including rights established under state law and rights established under federal law.