Washington County, MN Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Freeboard required
- 2 ft above regional (100-yr) flood
- Lowest floor standard
- At or above RFPE
- Fill minimum
- No lower than 1 ft below RFPE
- Fill extent
- At least 15 ft beyond structure
- Alternative elevation
- Requires Conditional Use Permit
- Certification
- Licensed engineer or architect
Summary
In unincorporated Washington County, new and improved structures in the flood fringe must be built with their lowest floor at or above the Regulatory Flood Protection Elevation, which is two feet of freeboard above the regional (100-year) flood elevation.
Regulatory Flood Protection Elevation. All structures, including accessory structures, additions to existing structures and manufactured homes shall be constructed on fill so that the basement floor or first floor if there is no basement, is at or above the Regulatory Flood Protection Elevation. The finished fill elevation shall be no lower than one (1) foot below the Regulatory Flood Protection Elevation and shall extend at such elevation at least fifteen (15) feet beyond the limits of the structure constructed thereon.
Full Breakdown
1(25) defines the Regulatory Flood Protection Elevation (RFPE) as an elevation no lower than two feet above the elevation of the regional flood, plus any increases in flood elevation caused by encroachments on the floodplain; the regional flood is the local term for the 100-year, or "base," flood used in the FEMA Flood Insurance Study. 4 requires that all structures in the General Floodplain (Flood Fringe), including accessory structures, additions to existing structures, and manufactured homes, be constructed on fill so the basement floor, or the first floor where there is no basement, sits at or above the RFPE.
The finished fill must be no lower than one foot below the RFPE and must extend at that elevation at least 15 feet beyond the limits of the structure built on it. 5 allows alternative elevation methods, such as stilts, pilings, parallel walls, or above-grade crawl spaces and tuck-under garages, in place of fill, but only under a Conditional Use Permit, and the structure's design and as-built elevation must be certified by a licensed engineer or architect. 5.
Violations & Fines
Building below the Regulatory Flood Protection Elevation without qualifying under the Section 8.5 alternative-methods and Conditional Use Permit standards, or without the required engineer/architect certification, is a violation of Chapter Nine. Under Section 14.1, any violation or failure to comply, including breach of conditions attached to a Conditional Use Permit or variance, is a misdemeanor, with each additional day of non-response to the Zoning Administrator prosecuted as a separate violation.
Frequently Asked Questions
How much freeboard does Washington County require above the base flood elevation?
Can a home in the flood fringe be elevated on posts instead of fill?
How far must fill extend beyond a structure built to meet the elevation rule?
Sources & Official References
Other rules in Washington County
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