Iowa Code § 468.270
When the levee or drainage district embraces land in two or more counties, a duplicate of the petition of any owner of land to be affected or benefited by such improvement shall be filed with the county auditor of each county into which said levee or drainage district will extend, accompanied by a duplicate bond to be filed with the auditor of each of the said counties as provided when the district is wholly within one county, in an amount and with sureties approved by the auditor of the county in which the largest acreage of the district is situated, which bond shall run in favor of the several counties in which it is filed.
Iowa Code § 468.270
Referred to in §468.305
Procedure for converting several intracounty districts into one intercounty district, see subchapter II, part 2