Rochester, MN Environmental Rules: Stormwater Management (2026)

Chapter 6-4 exists to keep the city's municipal separate storm sewer system, or MS4, in compliance with its National Pollutant Discharge Elimination System permit, and Sec. 6-4-3 applies it to all water entering the MS4 from any developed or undeveloped land in the city unless a specific exemption applies. Sec. 6-4-7 prohibits illegal discharges and illicit connections: no person may throw, drain, or discharge any material other than stormwater into the MS4, though the ordinance exempts routine flows like water line flushing, landscape irrigation, uncontaminated groundwater, air conditioning condensation, and firefighting water, and it bars any sewage connection to the storm system outright.

Sec. 6-4-9 through 6-4-12 require a stormwater management plan, reviewed by the city engineer, for any land-disturbing activity of one acre or more, or smaller projects that are part of a larger common plan of development; those plans must use best-management-practice techniques such as infiltration, green infrastructure, or filtration to capture a water quality volume equal to one inch of rainfall over new and reconstructed impervious surface. Sec. 6-4-12 also bars infiltration systems in sensitive locations, including within 1,000 feet up-gradient or 100 feet down-gradient of active karst features, over Hydrologic Soil Group D clay soils, or in high-vulnerability drinking water supply management areas. The public works department enforces the chapter and holds inspection, sampling, and even search-warrant authority under Sec. 6-4-13 when access is refused.