IPDES Multi-Sector General Permit for Industrial Stormwater Discharges

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Published April 2nd, 2026

Detected April 3rd, 2026

Summary

The Idaho Department of Environmental Quality finalized the Idaho Pollutant Discharge Elimination System (IPDES) Multi-Sector General Permit (MSGP) for stormwater discharges associated with industrial activity. The permit was issued on April 2, 2026, and becomes effective May 2, 2026, replacing the prior 2021 version.

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What changed

DEQ finalized the IPDES MSGP for industrial stormwater discharges, establishing permit requirements for facilities across multiple industrial sectors. The permit includes monitoring requirements, Best Management Practice (BMP) obligations, and response procedures detailed in the Fact Sheet. Public comments submitted between December 19, 2025 and February 2, 2026 were addressed in Appendix L of the Fact Sheet.

Industrial facilities subject to the MSGP must obtain permit coverage and comply with all conditions by May 2, 2026. Operators may challenge permit conditions by filing an action in court or applying for an individual IPDES permit. DEQ advises affected parties to review the final MSGP and Fact Sheet on the department's website and submit Notice of Intent filings as required.

What to do next

Review the final MSGP and Fact Sheet on DEQ's website to determine facility coverage
Submit Notice of Intent (NOI) to obtain MSGP coverage if facility qualifies
Implement required Best Management Practices and monitoring procedures by May 2, 2026

Source document (simplified)

April 2, 2026
News Releases Contact: David Hotz, IPDES General Permit Writer, david.hotz@deq.idaho.gov

BOISE – The Idaho Department of Environmental Quality (DEQ) finalized the Idaho Pollutant Discharge Elimination System (IPDES) Multi-Sector General Permit (MSGP) for stormwater discharges associated with industrial activity.

The public comment period for the draft permit began on December 19, 2025, and closed on February 2, 2026. DEQ’s responses to comments are included in Appendix L of the Fact Sheet. Any resulting changes to the MSGP or Fact Sheet are documented therein.

A final general permit decision constitutes DEQ’s final action to issue, deny, modify, revoke and reissue, or terminate a permit, per IDAPA 58.01.25.107.04. The final MSGP and Fact Sheet are available on DEQ’s website.

Persons affected by an IPDES general permit may not file a petition or otherwise challenge the conditions of a general permit in further DEQ administrative proceedings (IDAPA 58.01.25.204.27.a). Instead, they may:

Challenge the conditions of the general permit by filing an action in court; or
Apply for an individual IPDES permit. The IPDES MSGP was issued on April 02, 2026, and becomes effective on May 02, 2026.