CT DEEP Stormwater General Permit: Fees, Filing, and Penalties

The CT DEEP stormwater general permit requirements fall into three tracks — construction, industrial, and municipal (MS4) — and which one applies to you decides your registration category, fee, filing deadline, and ongoing inspection and reporting duties. A new construction general permit took effect January 1, 2026, with higher fees and a phased inspection schedule, so projects moving forward this year need to work from the current rules rather than the prior permit. The authority sits with the DEEP Commissioner under Connecticut General Statutes Sections 22a-430 and 22a-430b.¹

Which Permit Applies to Your Project

Pick the track first. Everything else follows from it.

Construction

Any construction activity that disturbs one acre or more needs stormwater authorization, and that acre threshold includes small lots that are part of a larger common plan of development or sale. A 30-lot subdivision built in half-acre phases is still one covered project.² Connecticut splits construction coverage into three categories:

Small construction between one and five acres with local land-use approval does not require a separate state registration. The local planning and zoning, wetlands, or conservation commission approval satisfies the state permit.
Locally approvable large construction of five acres or more with local approval requires DEEP registration and a Stormwater Pollution Control Plan (SPCP) prepared by a Qualified Professional and certified by a Qualified Professional or a Soil Conservation District. The plan itself is not submitted with the registration.
Locally exempt construction of one acre or more that bypasses local land-use review — state highway work, utility installations, and similar projects authorized under municipal, state, or federal authority — requires DEEP registration and submission of the full SPCP for DEEP review.

If your site was covered under the prior construction permit, you must re-register under the 2026 permit by April 1, 2026, or submit a Notice of Termination. DEEP provides interim coverage while a complete, timely application is pending.

Industrial

The industrial stormwater general permit covers manufacturing, transportation, waste handling, and similar operations where outdoor activities or material storage can contaminate runoff. DEEP uses SIC and NAICS codes to determine which facilities fall in.³ New sites must register at least 90 days before any discharge begins.

A facility that keeps every industrial material, activity, and piece of equipment completely shielded from rainfall can apply for a No Exposure Certification instead of full permit coverage. If approved, the NEC removes the sampling, monitoring, and reporting duties that come with the industrial permit. The moment conditions change and anything industrial becomes exposed to stormwater, the facility must register for full coverage.

MS4 (Municipal)

The MS4 permit covers town-owned storm drainage networks, public universities, and state and federal facilities inside designated urbanized areas. The most recent MS4 permit was issued in September 2023 and was set to expire September 30, 2025. DEEP did not finish reissuance by that date, so the permit is administratively continued, and existing permittees keep their coverage during the extension.⁴ Administrative continuance only protects coverage you already held; a new applicant looking for first-time MS4 coverage during a permit gap may face delays.

The Stormwater Pollution Control Plan

Every permitted site needs a Stormwater Pollution Control Plan. The SPCP documents site conditions, identifies pollutant sources, describes the best management practices you will use, and marks every monitoring location and discharge outfall.²

Who prepares and certifies the plan depends on the construction category. For locally approvable projects of five acres or more, a Qualified Professional must prepare the plan, and either a Qualified Professional or a Soil Conservation District must certify it. For locally exempt projects, a Qualified Professional prepares it and DEEP reviews it directly. State agency projects may use a Qualified Professional for the review step rather than submitting to DEEP.

Before finalizing the plan, check whether the site falls within an area flagged on DEEP’s Natural Diversity Data Base, which maps approximate locations of state-listed species and important natural communities. For projects disturbing ten or more acres, DEEP recommends comprehensive biological surveys across the full site regardless of what the NDDB maps show.⁵

Registration Fees

The 2026 construction fees are higher than many applicants expect, especially for locally exempt projects that go through DEEP review:²

Existing permittee renewal: $1,250
New locally approvable project (any size): $1,250
New locally exempt project, 1 to under 20 acres: $3,000
New locally exempt project, 20 to under 50 acres: $4,000
New locally exempt project, 50 acres or more: $5,000

Municipalities pay 50% of each listed amount. Fees are non-refundable and must be paid at the time of filing to complete the registration.

Industrial registration fees are either $625 or $1,250 depending on the facility’s employee count and gross sales, with the same 50% municipal rate.³

How to Register and When to File

All stormwater registrations go through the CT DEEP ezFile portal. You create a subscriber account, complete a subscriber agreement that authorizes electronic signatures, and upload your SPCP and certification forms. The system takes credit card or electronic check and returns a confirmation receipt that serves as your proof of filing.⁶

Lead time depends on the project. File short, and you cannot legally begin work.²

Locally exempt construction under 15 acres: register at least 60 days before construction starts.
Locally exempt construction of 15 acres or more, projects near tidal wetlands, or discharges to impaired waters: register at least 90 days before construction starts.
New industrial sites: register at least 90 days before initiating discharge.

Inspection and Monitoring After Coverage Begins

The 2026 construction permit replaced the old once-weekly inspection standard with a phased schedule. During the first 30 days of each construction phase, you must conduct at least one inspection confirming the SPCP is being implemented. Within the first 90 days, at least three inspections are required, with seven or more days between each. After the initial period, inspections run at least weekly and within 24 hours of any storm that generates a discharge. A rain gauge is required on site to document rainfall.⁷

If a storm ends on a weekend or holiday and normal working hours will not resume within 24 hours, the 24-hour post-storm inspection is only required for storms of half an inch or more; smaller storms can wait until the next normal workday. Once final stabilization is achieved, inspections drop to at least monthly. Findings go in a site log that must stay available for state inspectors.

When an inspection reveals a failed control or an out-of-spec discharge, federal Construction General Permit standards require corrective action within seven calendar days of discovery. If the repair genuinely cannot be completed in that window, you must document why and set a written schedule to finish as soon as practicable.

Industrial permittees generally must conduct stormwater sampling and turbidity monitoring to confirm discharges meet permit limits. Sample data is submitted electronically through NetDMR, the same portal used for all NPDES discharge monitoring reports in Connecticut.⁸

Reporting Deadlines

Industrial reporting deadlines depend on monitoring frequency:⁹

Quarterly monitoring: due 30 days after each monitoring period ends (April 30, July 30, October 30, January 30)
Semi-annual monitoring: due July 30 and January 30
Annual monitoring: due January 30

MS4 permittees run on a different calendar. Annual reports are due April 1 and must be submitted by mail with a review fee of $375 for institutions or $187.50 for municipalities, and also by email to DEEP’s stormwater staff.

Transferring or Terminating Coverage

If a construction site changes hands, the new owner or operator must obtain their own permit authorization before the original permittee can terminate. Once DEEP authorizes the new permittee, the original permittee has 30 days to submit a Notice of Termination.²

Terminating at project completion is more involved. A project qualifies for termination only after every post-construction stormwater measure is installed, functioning, inspected, and cleaned, and the site has held final stabilization for a full growing season. Connecticut defines a full growing season as two consecutive seeding seasons: April 1 through June 15 and August 15 through October 1.¹⁰ The NOT package must include a Post-Construction Inspection Report and a Final Stabilization Inspection Report, each with timestamped photos.

This timing trips people up. A site that reaches final stabilization in July has already missed the spring seeding season, which pushes the end of the first full growing season out to the following October. Permit obligations continue through that entire stretch after the construction work itself has wrapped.

Penalties for Operating Without Coverage or Breaking the Rules

Operating without required coverage or violating permit conditions carries steep exposure under Connecticut General Statutes Section 22a-438. Penalties scale with the violator’s mental state, and each day of a continuing violation counts as a separate offense.¹¹

Civil penalties up to $25,000 per offense, with the court weighing the severity of the violation, the violator’s history, and any economic benefit from noncompliance.
Criminal negligence: fines up to $25,000 per day and up to one year in prison. A second conviction doubles the fine ceiling to $50,000 per day and raises potential imprisonment to two years.
Knowing violations: fines up to $50,000 per day and up to three years in prison. A second conviction is a Class C felony with fines up to $100,000 per day.
False statements in any application, report, or monitoring data: fines up to $25,000 and up to two years in prison, per violation.

The per-day structure is what makes extended noncompliance ruinous. A facility that discharges without coverage for three months faces potential civil liability over $2 million before criminal exposure even enters the picture.

1
Justia Law. Connecticut Code Title 22a Chapter 446k Section 22a-430b – General Permits Certifications by Qualified Professionals Regulations
2
Connecticut Department of Energy & Environmental Protection. Construction Stormwater General Permit
3
Connecticut Department of Energy & Environmental Protection. Industrial Stormwater General Permit
4
Connecticut Department of Energy & Environmental Protection. Municipal Stormwater
5
Connecticut Department of Energy & Environmental Protection. Requests for Natural Diversity Data Base Environmental Reviews
6
Connecticut Department of Energy & Environmental Protection. DEEP ezFile Portal
7
Connecticut Department of Energy & Environmental Protection. Construction Stormwater General Permit – January 2026
8
Connecticut Department of Energy & Environmental Protection. NetDMR in Connecticut
9
Connecticut Department of Energy & Environmental Protection. Industrial GP Compliance Assistance
10
Connecticut Department of Energy & Environmental Protection. Notice of Termination – Nonsolar Projects
11
Justia Law. Connecticut Code Title 22a Chapter 446k Section 22a-438 – Penalties