IDEM Industrial Stormwater General Permit Issuance
/On December 30, 2025, the Indiana Department of Environmental Management (IDEM) issued and made effective the Industrial Stormwater General Permit (ISGP).
The issuance of the ISGP is the first step in establishing a new paradigm for stormwater compliance in Indiana. Once fully established, the ISGP will replace the existing Rule 6 program for regulation of industrial stormwater discharges in Indiana.
As it relates to notification to the agency, IDEM indicates the following:
Existing Permit Holders will be notified when a new Notice of Intent is ready for submission. Until that time, renewals should be completed as required under the Rule 6 regulations.
Existing Facilities Operating and a "No Exposure" Exclusion will be notified when renewal under the new program can occur. Until that time, renewals should be completed as required under the Rule 6 regulations.
Unpermitted Facilities should review applicability requirements to determine whether a Notice of Intent or No Exposure is required to be submitted for the facility. These can be submitted under the existing Rule 6 format until IDEM has initiated compliance under the ISGP paradigm.
While notification to IDEM is not required at this time, there are several actions that should be initiated now.
Review the ISGP: There are significant changes from the Rule 6 requirements to the ISGP. It is important for each permit holder to understand these changes.
Conduct Sampling for New Parameters: Evaluate the ISGP to determine the specific sampling requirements for facilities in your SIC Code. If your facility does not have adequate data for these parameters, including receiving stream hardness, collecting data now will allow you to assess compliance under the new paradigm.
Update your Stormwater Pollution Prevention Plan (SWP3): Updating your plan will be required in order to submit an updated Notice of Intent (NOI). The ISGP contains numerous requirements for the SWP3 not contemplated under the current Rule 6 regulations. Update your plan now to address these new requirements.
Register for the Regulatory Services Portal: Once IDEM has fully established this new program, all data submissions will occur through the Indiana Regulatory Services Portal. Register early to be prepared for this change.
Read the full IDEM Notice of Final Issued NPDES General Permit.
KERAMIDA, a member of IDEM's Advisory Group on the development of the ISGP, is uniquely qualified and prepared to assist you with all of these activities. Please contact Mack Overton, SVP, EHS Compliance Services, at moverton@keramida.com with any questions as to how your company should proceed to comply with these requirements.
Contact:
Mack Overton
Senior VP, EHS Compliance Services
KERAMIDA Inc.
Contact Mack at moverton@keramida.com.
