On this page
In this lesson
What you'll learn
- Explain how the Clean Water Act regulates stormwater discharges
- Describe the NPDES program and who issues permits
- Compare general permits and individual permits
- Identify the three main NPDES stormwater programs
The Clean Water Act
The Clean Water Act (CWA) makes it unlawful to discharge pollutants from a point source into waters of the United States without a permit. Section 402 creates the permit program: the National Pollutant Discharge Elimination System (NPDES).
For decades NPDES focused on pipes from factories and sewage plants. In 1987 Congress amended the CWA to address stormwater, and EPA's stormwater regulations at 40 CFR 122.26 followed:
- Phase I (1990): construction disturbing 5 acres or more, medium and large MS4s, and listed industrial activities.
- Phase II (1999): extended coverage to small construction sites disturbing 1 to 5 acres and small MS4s in urbanized areas.
That's why today the threshold for construction stormwater permit coverage is one acre, including smaller sites that are part of a larger common plan of development or sale.
Who issues the permit
EPA can authorize states to run the NPDES program. Most states are authorized, so for most projects the permit comes from a state agency. EPA remains the permitting authority in a handful of places, including Massachusetts, New Hampshire, New Mexico, the District of Columbia, most U.S. territories, and most Indian country lands. Check our state permit requirements table for your state.
General permits vs. individual permits
- A general permit covers many similar dischargers under the same terms. Construction sites usually get coverage by filing a Notice of Intent (NOI) under a Construction General Permit (CGP).
- An individual permit is written for one facility. It's uncommon for construction, but a permitting authority can require one for a large or high-risk project.
EPA's current CGP is the 2022 CGP, which took effect on February 17, 2022, was modified in 2025, and expires at 11:59 p.m. on February 16, 2027. EPA has proposed a replacement 2027 CGP, so check EPA's site for the current version.
The three NPDES stormwater programs
| Program | Who it covers | Key document |
|---|---|---|
| Construction | Operators of sites disturbing 1+ acre (or part of a common plan) | Stormwater Pollution Prevention Plan (SWPPP) |
| Municipal (MS4) | Cities, counties, DOTs, universities and other operators of separate storm sewer systems | Stormwater management program |
| Industrial | Facilities in listed industrial categories, such as manufacturing, recycling and transportation | Industrial SWPPP under a multi-sector general permit |
You'll meet the MS4 and industrial programs in lesson 12.
What the permit requires, in one sentence
Construction general permits typically require operators to prepare a SWPPP, install and maintain erosion, sediment and pollution prevention controls, inspect regularly, fix problems by set deadlines, stabilize the site, keep records, and terminate coverage when the work is done.
Key takeaways
- CWA section 402 creates NPDES; discharging pollutants from a point source without a permit is unlawful.
- Phase I (1990) covered 5+ acre construction; Phase II (1999) extended coverage to 1 to 5 acres.
- Most states issue their own permits; EPA is the permitting authority in a few states, DC, most territories and most Indian country.
- Construction sites usually get coverage under a general permit by submitting an NOI.
- EPA's 2022 CGP expires February 16, 2027; your governing permit controls.
Knowledge check
Lesson 2 quiz: 8 questions
Choose one answer for each question, then select Check my answers. Score 80% or higher to pass. Your answers stay in your browser and are never saved.
Sources and official references
Last reviewed: October 25, 2026 · Free general education based on the Clean Water Act, EPA NPDES rules and the EPA Construction General Permit. Your governing permit (EPA, state, tribal or local) controls. This is not legal advice, not EPA-approved, and not a California QSP/QSD or other state credential, and it does not issue a certificate. Nothing you enter on this page is saved or sent.