Environmental Rules in Washington County, MN (2026)
4 rules for unincorporated Washington County, Minnesota.
Verified from official government sources
Stormwater Management
New subdivisions in Washington County cannot increase runoff: Development Code Chapter Three, Section 10.3 caps post-development peak discharge at pre-development rates for the 2-year, 10-year and 100-year storms. Applicants must install a drainage system, dedicate easements, and prioritize natural infiltration before engineered ponds, and the same standard governs the Shoreland Management Overlay District by cross-reference.
Washington County Subdivision Stormwater Rules
Some RestrictionsWashington County Development Code, Chapter Three, § 10.3(4), (6) (Subdivision Regulations)
Storm Water Drainage. (4) The rate of surface runoff within the boundaries of a proposed subdivision shall not, in any event, be greater than the rate of runoff existing on the proposed subdivision prior to the proposed development... (6) An applicant shall install or construct, on or for the proposed land disturbing or development activity, all storm water management facilities necessary to m...
Erosion Control
Washington County requires erosion and sediment control on construction sites under Development Code Chapter Three, Section 10.4. Bare disturbed ground left inactive 14 or more days must be stabilized, and sites disturbing 10+ acres need a sedimentation basin while smaller sites use silt fences or straw bales.
Erosion Control During Construction, Washington County
Some RestrictionsWashington County Development Code, Chapter Three (Subdivision Regulations), Section 10.4
10.4 Erosion Control During Construction. (1) Erosion control shall be implemented in accordance with the recommended practices of the Washington Conservation District and the applicable Watershed Management Organization. All Best Management Practices shall be consistent with the Minnesota Construction Site Erosion and Sediment Control Planning handbook. (2) The following criteria apply only to...
Flood Zones
Washington County regulates development in mapped floodplains across its unincorporated areas under Development Code Chapter Nine, Ordinance No. 211. A Zoning Administrator permit is required before building, filling, excavating or changing land use within the mapped floodplain.
Washington County Floodplain Development Rules
Significant RestrictionsWashington County Development Code, Chapter Nine, Section 2.1
This Ordinance applies to all lands within the unincorporated areas of Washington County, Minnesota shown as being located within the floodplain in the documents titled "Flood Insurance Study, Washington County, Minnesota and Incorporated Areas," the "Flood Insurance Rate Map, Map Indexes numbered 27163CIND1A and 27163CIND2A," and all Flood Insurance Rate Map Panels noted therein... Dated Febru...
Flood Elevation Requirements
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.
Washington County Base Flood Elevation & Freeboard
Significant RestrictionsWashington County Development Code, Chapter Nine, Section 8.4
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 Protectio...
All Washington County ordinances
See every category we cover for Washington County: parking, noise, fences, fires, animals, pools, and more.
Washington County Ordinance Hub →