Oregon Revised Statutes Public Health and Safety § 450.870

(1) All assessments made pursuant to ORS 450.855 (3) shall be determined and made by an order of the board adopted in accordance with such procedures as shall be established by a general ordinance adopted by the board. Such general ordinance shall establish a procedure for assessing property directly benefited by the installation, making supplementary assessments and rebates, notice of the proposed assessment, provide for correction of errors, establish the form of the assessment order and such other procedures as are necessary to the adoption of the assessment order. It shall not be necessary to issue a separate order for each parcel of land, and any number of parcels in the same area and the same county may be included in one order. A copy of the order making an assessment, certified and acknowledged by the manager of the authority, shall be filed with the county clerk of the county in which the land is located. Upon being filed, the assessment shall constitute a lien against the land assessed.

(2) Notice of all assessments levied by an authority shall be given to the landowner by mail and shall be payable on the 30th day after such notice is mailed unless agreements for payment of such installments are made pursuant to ORS 223.205 and 223.210 to 223.295. All assessments shall be paid to the authority and a receipt shall be issued therefor. From time to time the board shall order the satisfaction of the liens against lands on which assessments have been paid, and a copy of such order shall be filed with the county clerk of the county in which the lands are located.