ORS § 523.350
No improvement assessment shall be rendered invalid by reason of a failure of the improvement report to contain all of the information required by ORS 523.210, or by reason of a failure to have all of the information required to be in the improvement resolution, the assessment ordinance, the lien docket or notices required to be published and mailed, nor by the failure to list the name of, or mail notice to, the owner of any property as required by ORS 523.210 to 523.380, or by reason of any other error, mistake, delay, omission, irregularity or other act, jurisdiction or otherwise, in any of the proceedings or steps specified, unless it appears that the assessment is unfair or unjust in its effect upon the person complaining. The district board may remedy and correct all such matters by suitable action and proceedings.
ORS 523.350