ORS § 547.265
Where the works set out in the plan for reclamation of any drainage district are found insufficient to reclaim in whole or in part any or all of the land of the district, the board of supervisors may formulate new or amended plans containing new ditches, levees or other works, and additional assessments may be made in conformity with the provisions of ORS 547.225, the same to be made in proportion to the increased benefits accruing to the lands because of the additional works. If it should be found at any time that the total of the charges made under ORS 547.455 to 547.485 is insufficient to pay the cost of works set out in the plan for reclamation or additional work done under this section, the board of supervisors may impose an additional charge to provide funds to complete the work, provided the total of all charges does not exceed the total amount of benefits assessed.
ORS 547.265