On September 20, 2024, the Indiana Department of Environmental Management (IDEM) released a draft version of the new Industrial Stormwater General Permit (ISGP). Among many updates when compared to the current Indiana general permit per 327 IAC 15-6 (Rule 6), the new ISGP includes revised stormwater pollution prevention plan (SWPPP) requirements, monitoring requirements and procedures, corrective actions and sector-specific benchmark limitations. Rule 6 has not been updated since 2003.
On January 15, 2021, the United States Environmental Protection Agency (USEPA) issued the 2021 Multi-Sector General Permit (MSGP), which improved the regulation of stormwater discharges from industrial facilities and ensured compliance with the Clean Water Act (CWA). State-specific stormwater discharge regulation programs must meet or exceed the requirements of the MSGP; therefore, the ISGP closely follows the framework of the MSGP.
Key Updates: Rule 6 vs. ISGP
| Current (Rule 6) | New (ISGP) |
| Notice of Intent (NOI) | Submit only the basics | Industrial sectors (A-AD), receiving water type, more detailed site map |
| SWPPP | Implement 365 days after NOI submittal | Implement with NOI submittal |
| Monitoring Parameters | Same 8 for everyone | pH, COD, TSS (plus more depending on Sector listed in Appendix A) |
| Monitoring frequency | Annual | Benchmark, 4 quarters during first 8 quarterly monitoring periods of permit coverage (more if benchmark exceedance). Effluent limitations annually depending on Sector listed in Appendix A. |
| Inspections | Quarterly of BMPs and outfalls | Quarterly of BMPs, outfalls, and runoff sample (color, odor, etc.) |
| No Exposure Certification | Every 5 years | Every 5 years and establish procedures to ensure eligibility for the no exposure exclusion is maintained |
| Reporting | Annual Report | Annual Report, Monitoring Reports |
| Corrective Actions | Improve BMPs as needed | SWPPP and BMP review for exceedances |
Permitting Timeline
Facilities in Indiana that are currently permitted under Rule 6 will be required to apply for permit coverage under the ISGP within 180 days of issuance. If a Rule 6 facility’s coverage were to expire before the issuance of the ISGP, the facility would be required to renew current Rule 6 coverage prior to the due date, then submit an additional permit application upon ISGP issuance. IDEM will continue to be in contact with Rule 6 facilities about the ISGP issuance timeline, as the issuance date may differ between sectors.
For any questions or support, contact Geoffrey Bright at Trinity Consultants’ Indianapolis office.
