Johnson County, KS Environmental Rules: Flood Zones (2026)
FEMA flood zone rules in Johnson County, KS, also called floodplain regulations or special flood hazard area (SFHA) rules, determine flood insurance requirements and elevation standards for new construction.
Key Facts
- Governing section
- App. B, Ch. II, Art. III, § 5
- Zone covered
- FEMA Special Flood Hazard Zone AE
- Exception
- Wastewater stabilization ponds (lagoons) only
- Existing systems
- Repairs allowed if code otherwise met
- Enforcing agency
- Johnson County Dept. of Health & Environment
- Penalty
- $100-$500 per day, Class G infraction
Summary
Johnson County bars new septic tanks, absorption fields and most onsite wastewater systems from FEMA's Special Flood Hazard Zone AE, the 100-year floodplain, under its Environmental Sanitary Code. Only wastewater stabilization ponds (lagoons) may go inside the zone, and existing systems already there can still be repaired.
Except for wastewater stabilization ponds (lagoons), no portion of an onsite wastewater system shall be constructed within the Special Flood Hazard Zone AE as defined by the Federal Emergency Management Agency (aka: 100-year floodplain) for Johnson County. This does not preclude repairs of existing systems, provided other requirements of this code are met.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Resolutions: Supplement 14).
Full Breakdown
The prohibition sits in Appendix B (Environmental Sanitary Code) of the Johnson County Code of Resolutions, Chapter II, Article III, Section 5, last amended by Resolution No. 058-24 on August 22, 2024. It reads narrowly but firmly: no portion of an onsite wastewater system may be constructed inside the Special Flood Hazard Zone AE, FEMA's designation for the 100-year floodplain in Johnson County. That covers conventional septic tanks, absorption fields, mound systems, holding tanks and alternative treatment systems permitted elsewhere in Appendix B. The single carve-out is for wastewater stabilization ponds, commonly called lagoons, which the county allows inside the zone only if their berms are built at least one foot above the base flood elevation.
The rule also spares systems that already exist in the flood zone from being ripped out: it does not preclude repairs of existing systems, provided other requirements of the code are met, so a homeowner with a legacy septic system in Zone AE can still fix a failing tank or field rather than relocate it. JCDHE administers permits and inspections for every private onsite system in unincorporated Johnson County under this chapter; a permit application for new construction inside Zone AE that is not a lagoon will be denied outright rather than conditioned.
This rule applies only in unincorporated Johnson County: cities within the county, including Olathe, Overland Park, Shawnee and Lenexa, administer their own floodplain development standards separately, and the county's broader zoning floodplain-overlay rules for buildings and fill are published apart from this sanitary code, as Part III of the Code of Resolutions.
Violations & Fines
Constructing or expanding a septic system inside Zone AE without meeting the lagoon exception is a Class G infraction under Chapter I, Article VII, Section 2 of the same code: a fine of $100 to $500, with each day of the violation prosecuted as a separate offense in Johnson County District Court by the county counselor.
Frequently Asked Questions
Can I install a brand-new septic system on flood-zone AE land in Johnson County?
I already have a septic system in the floodplain. Can I repair it?
Does the county's zoning code also restrict building in the floodplain?
Sources & Official References
Other rules in Johnson County
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