Hamilton County, IN Environmental Rules: Stormwater Management (2026)

Under the county's illicit discharge ordinance, no person may discharge or cause to be discharged, directly or indirectly, any pollutant-bearing material other than stormwater into the municipal storm drainage system, a regulated drain maintained by the Hamilton County Drainage Board, or any watercourse. Exempt discharges include water line flushing, landscape irrigation, rising groundwater, foundation and sump pump drainage, air conditioning condensation, non-commercial vehicle washing, firefighting water, and dechlorinated swimming pool water (generally under one part per million chlorine), plus any discharge covered by a valid NPDES permit.

Illicit physical connections to the storm system are separately prohibited outright, even ones built legally years ago. Property owners must also keep any watercourse crossing their land free of trash, debris, and excessive vegetation, and maintain structures near it so they don't become a hazard. Anyone who discovers a spill that could reach stormwater must immediately contain and clean it up, notify emergency dispatch for hazardous releases, notify the Surveyor's Office for illicit discharges, and, if the release came from a commercial or industrial site, keep a written on-site record for at least three years.

The Surveyor's Office can issue a notice of violation requiring monitoring, cleanup, or a cease-and-desist, and can suspend a violator's storm sewer access without prior notice in an emergency.