Johnson County, KS Environmental Rules: Flood Elevation Requirements (2026)

This freeboard standard lives in Appendix B of the Johnson County Code of Resolutions, the county's Environmental Sanitary Code, Chapter II (Wastewater Disposal), Article III (Private Onsite Wastewater Treatment and Disposal Systems), Section 5, adopted by Resolution No. 058-24 on August 22, 2024. It targets one specific system type: wastewater stabilization ponds, commonly called lagoons, which JCDHE permits for larger lots without soil suited to a conventional septic field. Ordinary septic tanks and absorption fields cannot be built inside the Special Flood Hazard Zone AE at all; lagoons are the sole exception, and the trade-off is the one-foot freeboard requirement on their berms.

Where FEMA has not published a base flood elevation for the site, Section 5 shifts the burden onto the property owner: a registered professional engineer or licensed surveyor must determine and certify the base flood elevation before JCDHE will approve the lagoon design. The rule reaches only private onsite systems in unincorporated Johnson County; cities such as Olathe, Overland Park, Lenexa and Shawnee administer their own floodplain and building codes for lots inside city limits. It also does not cover general construction setbacks, finished-floor elevations, or fill placement for houses and other structures in the floodplain: those standards sit in the county's separate Zoning and Subdivision Regulations, adopted as Part III of the Code of Resolutions and published independently by the Johnson County Planning Department, not in this sanitary code.

Anyone who cannot meet the one-foot freeboard figure can apply for a rule exception under Chapter I, Article VIII of the same code, filed with the JCDHE director on the county's approved variance form.