Iowa Code § 357.15: Inadequate assessment.

When bids have been received, if it is apparent that the final assessment will need to be increased more than ten percent over the preliminary assessment, the board of supervisors shall, at its option, reject bids and readvertise for bids as provided herein, or reject bids and revise the dummy assessment. If the dummy assessment is revised, another election shall be held within the district in the same manner and with the same notices as the first, except that the candidates for trustees shall not be voted for.