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

Chapter 238 of the Code of Washington County, adopted under §§ 59.693 and 281.33, Wis. Stats., applies to all unincorporated lands in the County unless a town enforces its own equivalent ordinance or has an intergovernmental agreement with the County for administration. The Land Conservation Committee, through the Land and Water Conservation Division of the Planning and Parks Department, administers the chapter.

Section 238-6A triggers the construction-site erosion control permit whenever land-disturbing activity meets any of five thresholds: disturbing 4,000 square feet or more of land surface; excavating or filling more than 400 cubic yards; disturbing 300 linear feet of roadway ditch or open drainage channel; maintaining an existing stormwater best management practice; or any other activity the administering authority determines carries a high risk of erosion or water pollution. Once a project crosses a threshold, § 238-7 requires the erosion control plan to hold the site's sediment discharge, by design, to no more than five tons per acre per year from sheet and rill erosion until the site is stabilized, using practices such as silt fence, diversions, sediment traps and temporary mulch; if that standard cannot be met, the plan must explain in writing why and reduce the load to the maximum extent practicable.

Certain sites are exempt or partially exempt, including one- and two-family homes disturbing less than an acre, agricultural land use, and activity already covered by shoreland or nonmetallic-mining permits. Violations are enforced by the administering authority through forfeitures, stop-work orders, permit revocation or emergency action.