Oregon Revised Statutes Public Health and Safety § 468A.160

(1) The territory of a regional authority may be expanded in the manner provided for forming regions by inclusion of an additional contiguous county or city if:

(2) Any regional authority may be dissolved by written consent of the governing bodies of all participating counties and cities. Upon dissolution, any assets remaining after payment of all debts shall be divided among the participating counties and cities in direct proportion to the total amount contributed by each. However, all rules, standards and orders of the regional authority shall continue in effect until superseded by action of the commission.