ORS § 547.605
The board of trustees of any drainage or levee district having an outstanding indebtedness of not less than $3 per acre for each acre of land included in the district, evidenced by bonds or warrants of the district, may, if the board considers it for the best interests of the district, fund or refund the same or any part thereof and issue bonds of the district therefor in sums of not less than $100 nor more than $1,000, each having not more than 20 years to run, and bearing a rate of interest determined by the board of trustees, payable semiannually. Both principal and interest may be made payable at a place named by the board. The bonds shall be negotiable in a form to be selected by the board of trustees, numbered consecutively, signed by the president of the board and countersigned by the clerk of the county in which payable, who shall thereto affix the official seal. Interest coupons shall be attached to each bond. The bonds shall then be delivered to the treasurer of the district, who shall stand charged upon the official bond for all bonds delivered to the treasurer and the proceeds thereof.
ORS 547.605