ORS § 553.320
After the creation of a subdistrict, the board shall secure an engineering plan for the improvements requested in the petition for the creation of the subdistrict. The board may adopt as an engineering plan for a subdistrict any plans theretofore made by any department or agency of the federal government or the State of Oregon or a project work plan proposed for any soil and water conservation district in which lands within the subdistrict are located, or the board may employ a qualified engineer to make such engineering plan. Upon completion of the plan the board shall cause notice thereof to be given to the owners of the tracts of land within the subdistrict and shall permit the inspection of the plan at the office of the subdistrict by all landowners. The notice may be given by mail or by publication, as may be determined by the board. The notice shall fix a time and place for a hearing before the board of all objections to the plan, which hearing shall be held not less than 20 nor more than 30 days after the date of mailing or the date of the last publication of the notice. At the hearing the board shall make such changes in the engineering plan as it deems necessary in the light of any objections or suggestions made by any person appearing at the hearing. After the hearing, the board shall approve the plan as corrected or changed, by adopting an order of approval. However, if the owners of more than 50 percent of the lands within the subdistrict file written objections to the order approving the engineering plan with the secretary of the district within 15 days after the date of such order, no further action shall be taken under the order and the plan shall be considered to have been rejected by the landowners. Whenever an engineering plan for a subdistrict is so rejected by the landowners the board may obtain a new engineering plan and present it to the landowners in the manner above provided or the board may dissolve the subdistrict.
ORS 553.320