Connecticut Statewide Rule

Connecticut Stormwater MS4 General Permit Standards

Heavy RestrictionsApplies statewide across Connecticut (2026)

Key Facts

Permit: MS4 General Permit
Lead agency: DEEP
Construction threshold: 1+ acre disturbed
Civil penalty: Up to $25,000 daily
Design manual: 2004 Stormwater Quality Manual

Last verified: September 5, 2026Source: State of Connecticut

Summary

Connecticut DEEP issues a statewide MS4 general permit requiring municipalities to control stormwater discharges. Standards for illicit discharges, post-construction controls, and the 2004 Stormwater Quality Manual apply uniformly.

No person or municipality shall initiate, create, originate or maintain any discharge of water, substance or material into the waters of the state without a permit for such discharge issued by the commissioner. Any person who initiated, created or originated a discharge prior to May 1, 1967, and any municipality which initiated, created or originated a discharge prior to April 10, 1973, for which a permit has not been issued pursuant to this section, shall submit an application for a permit for such discharge on or before July 1, 1987.

Source: State of ConnecticutView official code

Full Breakdown

Under Conn. Gen. Stat. Sec. 22a-430 and the Clean Water Act, DEEP administers the MS4 general permit governing municipal stormwater systems. Cities and towns must enforce illicit discharge detection and elimination, public education, post-construction stormwater management, and good housekeeping practices. The 2004 Connecticut Stormwater Quality Manual and 2002 Erosion and Sediment Control Guidelines establish baseline design standards. Construction sites disturbing one or more acres require a separate Construction General Permit. Municipal ordinances must meet or exceed state minimums but cannot weaken them.

Violations & Penalties

Unpermitted discharges may incur civil penalties up to $25,000 per day under Sec. 22a-438. DEEP can issue cease-and-desist orders and require remediation of contaminated runoff.

Frequently Asked Questions

Do I need a stormwater permit for my home construction project?

Projects disturbing less than one acre typically do not need the state Construction General Permit, but local erosion control approval is still required and best management practices apply under municipal ordinances.

Can towns adopt weaker stormwater rules than the state?

No. Connecticut municipalities must implement at least the minimum control measures required by the MS4 general permit. Local rules may be stricter but never less protective than state standards.

Sources

See something wrong?

Help us keep this page accurate. If you notice an error or outdated information, let us know.