Iowa Code § 357C.12
The owner of any property in an unincorporated area immediately contiguous to the boundaries of any established benefited street lighting district may petition the board of supervisors to be included in the district. Upon receipt of such petition the board shall submit the request to a competent disinterested civil engineer to investigate the feasibility of adding such additional territory and to make a report to the board. If the board agrees that said property should be added to the district, the tax levy for the next year shall be applied to said property and on the first day of the said next year said property shall be considered a part of the district. If the benefited street lighting district lies in more than one county the joint action of the boards of supervisors shall be required to add additional territory.
Iowa Code § 357C.12