Story County, IA Environmental Rules: Erosion Control (2026)

Story County Code of Ordinances § 88.05(3), Construction Site Erosion and Sediment Control, applies to all development and land-disturbance activity in unincorporated Story County. Applicants must submit a site plan showing the disturbed area, slopes, watercourses, floodplain and other erosion-prone features along with the Best Management Practices chosen to meet the chapter, plus a construction and grading schedule showing when temporary and permanent BMPs go in. Any development disturbing one acre or more must also obtain a National Pollutant Discharge Elimination System permit from the Iowa Department of Natural Resources and submit a Stormwater Pollution Prevention Plan to the Planning and Development Department.

BMPs must follow the Iowa Statewide Urban Design and Specifications Design Manual or other accepted design criteria and be maintained so they keep functioning. Disturbed area has to be minimized through staging and delineated, flagged or fenced limits, and natural plant cover retained where practical. Final stabilization, seeding or sodding, must begin immediately once clearing, grading or excavation permanently stops on any part of the site; if final stabilization can't happen right away because of season or weather, temporary stabilization such as temporary seeding, geotextiles, mulches or vegetative filter strips must start immediately, and any area left idle more than 14 calendar days needs temporary stabilization. Development in the floodplain is discouraged and must also comply with the county's Floodplain Management Ordinance, Chapter 80. Land primarily used for agricultural purposes while so used is exempt from the grading-permit and erosion-control submission requirements, except to the extent Iowa Code § 335.2 requires otherwise.