ORS § 551.130
Owners of land already diked may organize districts for the repair and maintenance of the dikes and dams thereof by complying with the procedure prescribed in this chapter, except that the petition need not be signed by more persons than the owners of more than one-half of the acreage embraced in the limits of the proposed district. The board of viewers shall provide for placing the dikes and dams in thorough repair and up to a uniform standard, and shall levy the cost of such repairs in the first instance, not upon the assessed valuation of the lands, but in proportion to the benefits conferred. The value of the dikes and dams as they stand shall be estimated and due credit given to the lands which have borne the original cost of construction; provided, such credit shall entitle the land to no consideration greater than release from the cost of repairs in the first instance.
ORS 551.130