Washington County, UT Environmental Rules: Erosion Control (2026)

Washington County Code Title 10, Chapter 24 (Hillside Development Standards) requires a grading development permit for any development on slopes exceeding twenty percent (20%), granted by the county commission after review by county staff and the land use authority under section 10-24-5. The permit application must include a drainage control plan and report under section 10-24-6(F), which spells out erosion and sediment obligations for the construction phase itself, not just the finished grading: crews must prevent erosion and scour at every point of discharge and at the face of every cut or fill slope, and during grading or construction, including off-site work, the developer must control both construction water and storm runoff so adjoining properties are not affected and no silt or debris reaches any storm drain, wash, channel, or roadway.

The application must also include a drainage plan showing all surface and subsurface drainage systems, walls, cribbing, or other erosion protection devices, plus a geology and soils report addressing slope stability and erosion, and the drainage plans and construction drawings must be approved by the public works director before final plat or site approval and before any building permit issues. Under section 10-24-7, projects disturbing more than one acre (or smaller sites the public works director flags) must post a cash bond or irrevocable letter of credit before the permit issues, sized to cover soil stabilization, grading, planting, and maintenance; if restoration is not completed within one year, the county can call the bond and finish the work itself.

Retention and detention basins are barred outright on hillsides under 10-24-6(F)(12), and independent storm systems triggered by street-capacity overruns must be sized for a 10-year storm at minimum, with a 12-inch minimum storm drain. Chapter 24 exempts strictly mining or mineral-development grading under section 10-24-12 unless the public works director requires compliance anyway.