Understanding Connecticut’s Groundwater & Stormwater Permits: What Manufacturers Need to Know

Connecticut manufacturers are facing several important updates to state water permitting requirements that affect how stormwater and wastewater are managed and discharged. These updates, issued by the Connecticut Department of Energy and Environmental Protection (CT DEEP), are intended to modernize permitting, improve tracking and reporting, and ensure water quality across the state.

While the official permit documents are lengthy and highly technical, the key takeaway is simple: many manufacturers may need to review, renew, or update one or more water-related permits to remain in compliance. Below is an overview of the four major permits manufacturers should be aware of. 

Industrial Stormwater General Permit (IGP)

Who this applies to: Manufacturers whose operations involve outdoor industrial activity and whose facilities fall under certain Standard Industrial Classification (SIC) or North American Industry Classification System (NAICS) codes.

What this permit covers: Stormwater runoff that may come into contact with industrial materials, equipment, or activities before leaving the site.

What’s new:

• A newly reissued permit became effective October 1, 2025
• Registration opened November 1, 2025 via CT DEEP’s ezFile portal
• Effective January 1, 2026, facilities are required to monitor under the new permit standards, even if they have not submitted for the new permit
• Existing permit holders must re-register by April 1, 2026
• Facilities claiming a “No Exposure” exemption must also re-register to maintain compliance
• Stormwater Pollution Prevention Plans (SWPPPs) should be reviewed and updated

Why it matters: Stormwater permits are one of the most common compliance gaps for manufacturers—especially when outdoor operations change over time. If any industrial activity occurs outside, including mobile equipment used for loading and unloading, then a stormwater exposure exists, and a permit needs to be applied for.

Comprehensive General Permit (Non‑Stormwater Discharges)

Who this applies to: Facilities that discharge certain types of non‑stormwater wastewater to surface water or groundwater and do not qualify for a more specific permit.

Common covered discharges include:

• Non-contact cooling or geothermal water
• Boiler blowdown (to groundwater only)
• Hydrant flushing
• Water treatment wastewater
• Pressure washing (newly added)

What’s changing:

• Electronic reporting through DEEP’s NetDMR system
• New online noncompliance reporting tools
• Removal of some previous eligibility thresholds
• Additional planning requirements for some groundwater discharges

Important timing:

• Public comments on the proposed permit renewal are due January 23, 2026
• Final permit requirements may affect future compliance obligations
• Why it matters: This permit acts as a “catch‑all” for discharges that are often overlooked—but still regulated. This permit is scheduled to expire, and the new permit be issued, on April 1, 2026. This timeline could change based on the number and content of the comments.
  

Pretreatment Permit for Significant Industrial Users (SIU)

Who this applies to: Larger manufacturers that discharge industrial wastewater to a municipal sewer system (Publicly Owned Treatment Works, or POTW) and meet federal criteria for a Significant Industrial User.

Typical examples:

• Metal finishers and electroplaters
• Chemical and food manufacturers
• Discharges more than 25,000 gallons per day

What’s new:

• Permit reissued on October 29, 2025
• Updated monitoring, sampling, and reporting requirements
• Transition required from the previous SIU permit

Key deadline:

• Existing SIU facilities must apply for the updated permit by March 1, 2026
  

Pretreatment Permit for Non‑Significant Industrial Users (NSIU)

Who this applies to: Smaller manufacturers and facilities that discharge lower volumes of process wastewater to a municipal sewer system.

Examples include:

• Small manufacturing shops
• Maintenance and repair facilities
• Labs and testing operations

What’s new:

• Replaces the former “Miscellaneous Industrial Users” permit
• Registration opened December 1, 2025

Key deadline:

• Facilities previously covered must register by March 1, 2026
  

What Manufacturers Should Do Now

If your facility uses water in its operations—indoors or outdoors—it’s important to:

• Identify whether you discharge stormwater, wastewater, or both
• Determine which permit(s) apply to your operations
• Review permit renewal deadlines and reporting requirements
• Update required plans, such as SWPPPs or pretreatment documentation

Facilities may require more than one permit, depending on the type of discharges involved.

How CONNSTEP Can Help

Water permitting requirements can be complex, and compliance missteps can result in costly penalties or operational delays. CONNSTEP and our trusted third-party providers, like Walden Environmental Engineering, work with Connecticut manufacturers to:

• Understand permit applicability
• Identify compliance gaps
• Connect you with trusted technical resources
• Streamline the permit application, renewal, and re-registration process
  

“The simplest way to reduce regulatory risk is to keep registration, monitoring, and documentation aligned with the new permit requirements,” said David Garner, EHS director at Walden Environmental Engineering.

“Falling behind on registration is one of the easiest ways to draw extra attention, especially if monitoring and documentation don’t reflect the new permit standards.”

Staying compliant helps ensure your operations run smoothly. If you’re unsure whether your facility is properly permitted, now is the time to review your requirements.

Contact CONNSTEP today or call us at 860-513-3200.