Sauk County, WI Environmental Rules: Stormwater Management (2026)

Sauk County enacted its stormwater ordinance under Wis. Stats. §§ 59.693 and 281.33(3m), and Sec. 51.03 limits it to unincorporated lands within the county plus all county-owned land regardless of which municipality it sits in, including highway right-of-way. Section 51.14 triggers a land use permit for any land disturbance of one acre or more, any smaller disturbance that is part of a larger development, any new or reconstructed public or private road, and any project that cumulatively adds 20,000 square feet of impervious surface. The Zoning Administrator, housed in the Department of Land Resources and Environment, reviews applications under Sec.

51.16, which requires peak-flow calculations, site plans stamped by a professional engineer for ponds, swales and basins, and a financial guarantee escrowed to cover third-party plan review. Performance standards in Sec. 51.17 require best management practices to cut total suspended solids by 80 percent for new development and 40 percent for redevelopment of parking areas and roads, and to hold post-development peak discharge at or below pre-development rates for the one-, two-, ten- and 100-year, 24-hour storm events. Infiltration BMPs must replace 60 to 90 percent of pre-development infiltration volume depending on how much of the site is paved.

Permits run 24 months, with a one-time 12-month extension, and a long-term maintenance agreement must be recorded with the Register of Deeds. Violators face a fine of $200.00 to $1,000.00 per offense under Sec. 51.23, with each day of violation counted separately.