Iowa Code § 468.137: Levy under reclassification.

If the amount finally charged against a district exceeds twenty-five percent of the original cost of the improvement, the board may order a reclassification as provided for the original classification of a district and upon the final adoption of the new classification and apportionment shall proceed to levy that amount upon all lands, highways, and railway rights-of-way and property within the district, in accordance with the new classification and apportionment. An assessment made under this section on a tract, parcel, or lot within the district which is computed at less than five dollars shall be fixed at the sum of five dollars.