ORS § 548.335
When any irrigation or drainage district has adopted a plan for refunding and compromising any or all of its outstanding indebtedness, and pursuant to ORS 548.305 to 548.325 has entered into a contract with any governmental agency for a loan for the purpose of carrying out such plan, and the board of directors or board of supervisors for the purpose of carrying into effect the provisions contained in the contract have authorized the issuance of bonds of the district pursuant to ORS 548.315, and such plan of refinancing and compromise has been accepted in writing by the holders of more than 90 percent of such outstanding indebtedness to be refunded and compromised, such irrigation or drainage district may commence and prosecute a proceeding in rem for the purpose of obtaining constructive consent, to the plan, of the unknown holders of the evidences of the indebtedness to be refunded and compromised, and of the known holders of such evidences of indebtedness who have not so given their consent in writing. The proceeding shall be commenced in the circuit court of the county in which the office of the district is located, by filing a petition verified by the oath of the president or secretary of the district.
ORS 548.335