Minnetonka, MN Environmental Rules: Stormwater Management (2026)

The Minnetonka City Council regulates stormwater in Section 1205 of Chapter 12. Section 1205.015 defines an illicit discharge as any direct or indirect non-storm water discharge to the storm drain system, and an illicit connection as any drain or conveyance that lets one enter, including indoor drains and sinks, even if the connection was previously allowed, permitted or approved. Commercial or industrial drains that were never documented in plans, maps or equivalent records and approved also count. The MS4 means the city's roads with drainage systems, streets, catch basins, curbs, gutters, ditches, man-made channels and storm drains used to convey storm water rather than sewage.

The core rule in subdivision 2 is that no person can throw, drain or otherwise discharge, or cause or allow others under its control to do so, any pollutants or waters containing pollutants into the MS4, other than storm water. The pollutant definition is long and specific: paints, varnishes and solvents, oil and other automotive fluids, yard wastes, refuse and litter, pesticides, herbicides and fertilizers, animal wastes, and wastes and residues from constructing a building or structure, among others.

Subdivision 3 exempts a defined list, including water line flushing, landscape irrigation, foundation and footing drains, air conditioning condensation, lawn watering, individual residential car washing, dechlorinated swimming pool discharges, and water used in street sweeping. Firefighting discharges are exempt. Dye testing is exempt but requires verbal notification to the city engineer or designee before the test. A discharge allowed under a National Pollutant Discharge Elimination System (NPDES) permit is exempt only if the discharger is in full compliance and written approval has been granted for the discharge to the storm drain system.

Subdivision 4 prohibits the construction, use, maintenance or continued existence of illicit connections, including connections made in the past that were lawful at the time. Connecting a sewage line to the MS4, or letting that connection continue, is a violation. Improper connections must be disconnected and redirected to an approved onsite wastewater management system or the sanitary sewer system with approval of the city engineer or designee. An owner or occupant who receives written notice of violation must locate any undocumented drain and identify its outfall within a reasonable time the notice specifies.

Two companion sections apply. Section 1205.005 bars blocking, obstructing or impeding the flowage of waters through the city storm sewer system, or to or from a lake, pond, detention area, stream, creek, ditch or mapped wetland, without prior approval of the city engineer, and the engineer cannot approve action that violates the standards in city code sections 300.23, 300.24 or 300.25. Section 1205.010 makes every property owner responsible for a proportionate share of storm sewer costs through utility charges, which are a lien against the property.