Environmental Rules in Story County, IA (2026)
4 rules for unincorporated Story County, Iowa.
Verified from official government sources
Stormwater Management
Unincorporated Story County requires a Stormwater Management Plan before construction on any development that disturbs one acre or more, or that splits land into more than four lots. The plan must meet numeric water-quality, channel-protection and peak-runoff criteria under Story County Code of Ordinances § 88.05(4) and be certified by an Iowa-licensed professional engineer before Planning and Development will issue permits.
Story County Stormwater Management Plan Rules
Some RestrictionsStory County Code of Ordinances § 88.05(4)
Post-Construction Stormwater Management. Stormwater runoff increases nonpoint source pollution, flooding, siltation, stream temperatures, and streambank erosion. ... Development that meets any of the following thresholds shall be required to submit a Stormwater Management Plan, in addition to other applicable development permit applications, prior to commencing development activities: ... Devel...
Erosion Control
Any development or land-disturbing activity in unincorporated Story County must control erosion and sedimentation under § 88.05(3). Sites disturbing one acre or more also need an NPDES permit and Stormwater Pollution Prevention Plan from the Iowa DNR, and disturbed ground has to be stabilized immediately once grading permanently stops.
Story County Construction Erosion & Sediment Control
Some RestrictionsStory County Code of Ordinances § 88.05(3)
Construction Site Erosion and Sediment Control. Sedimentation and erosion pollute water, degrade land, cause the loss of native vegetation and habitats, and impair drainage. ... Any development that disturbs one or more acres is required to also obtain a National Pollutant Discharge Elimination System (NPDES) Permit from the Iowa Department of Natural Resources. The Stormwater Pollution Prevent...
Flood Zones
Any development in a mapped floodway, floodway fringe, or general floodplain district in unincorporated Story County needs a floodplain development permit from the County Floodplain Manager before work starts, per Code of Ordinances § 80.16. The application must include the project's elevation data, the lowest-floor elevation, and, for remodels, the structure's pre-improvement market value under § 80.17.
Floodplain Development Permits, Story County
Some RestrictionsStory County Code of Ordinances §§ 80.16, 80.17
A floodplain development permit issued by the Floodplain Manager shall be secured prior to any floodplain development as defined in Section 80.02 Definitions. ... Application shall be made on forms furnished by the Floodplain Manager and shall include the following: ... ... 4. Elevation of the one percent annual chance or greater flood. ... ... 6. For structures being improved or rebuilt, the e...
Flood Elevation Requirements
In unincorporated Story County, new or substantially improved residential structures in the floodway fringe must have the lowest floor, including any basement, elevated a minimum of three feet above the one percent annual chance flood level. Compacted fill supporting the structure must hold that same three-foot freeboard and extend at least 18 feet beyond the structure. The Floodplain Manager enforces the standard under Chapter 80.
Flood Elevation Freeboard Rules, Story County
Some RestrictionsStory County Code of Ordinances § 80.13(3)(C)
All new or substantially improved residential structures shall have the lowest floor (including basements) elevated a minimum of three (3) feet above the one percent annual chance or greater flood level. Construction shall be upon compacted fill meeting the requirements in Subsection 80.13.3.A which shall, at all points, be no lower than three (3) feet above the one percent annual chance or gre...
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