Indiana's IDEM administers statewide NPDES stormwater permitting under IC 13-18-3 and 327 IAC 15, requiring MS4 communities, industrial sites, and dischargers to obtain coverage. Local programs must implement state minimum measures.
Under IC 13-18-3 and Indiana Administrative Code Title 327 Article 15, IDEM issues general NPDES stormwater permits regulating municipal separate storm sewer systems (MS4s), construction sites disturbing one or more acres (Rule 5), and industrial activity (Rule 6). MS4 entities must implement six minimum control measures: public education, public involvement, illicit discharge detection and elimination, construction runoff control, post-construction stormwater management, and pollution prevention. Local stormwater ordinances must meet or exceed IDEM standards. Cities cannot reduce protections below the state floor, though they may add stricter local water-quality criteria.
Discharging without an NPDES permit, failing to file Notice of Intent, or violating permit terms can trigger civil penalties up to $25,000 per day per violation under IC 13-30-4 and federal Clean Water Act enforcement.
See how Hamilton County's stormwater management rules stack up against other locations.
Help us keep this page accurate. If you notice an error or outdated information, let us know.