Idaho finalizes industrial stormwater general permit

The Idaho Department of Environmental Quality has finalized its Idaho Pollutant Discharge Elimination System (IPDES) Multi-Sector General Permit (MSGP) for stormwater discharges associated with industrial activity, completing a rulemaking process that included a public comment period from December 2025 through early February 2026.

The updated permit establishes requirements for industrial facilities to manage stormwater runoff and comply with discharge regulations. According to DEQ, responses to public comments and any resulting revisions are detailed in the permit’s fact sheet, which is now available alongside the final rule.

Issued April 2, 2026, the MSGP will take effect May 2, 2026. Under state rules, affected parties cannot challenge general permit conditions through further administrative proceedings but may pursue legal action in court or apply for an individual IPDES permit. For stormwater professionals, the finalized permit signals updated compliance expectations for industrial sectors and reinforces the role of general permits in standardizing stormwater management practices statewide.