ORS § 547.055
No action, suit or proceeding, under ORS 30.570 or otherwise, shall be maintained for the purpose of avoiding, setting aside or otherwise questioning or affecting the validity of the organization of any district organized under the Drainage District Act, unless such action, suit or proceeding is commenced within nine months from the date of the proclamation in such matter made by the county judge; nor for the purpose of questioning the legality of the boundaries established for such corporation in such proclamation unless similarly commenced within nine months therefrom; nor for the purpose of questioning the legality of any altered boundaries of the district which may be subsequently established as provided for by ORS 547.250 to 547.260 unless commenced within nine months from the date of the judgment.
ORS 547.055