Stormwater NPDES Permit
Last reviewed · By Chad Griffith
Stormwater NPDES (National Pollutant Discharge Elimination System) permits regulate stormwater discharges to surface waters under the Clean Water Act. Two permits cover most operators: EPA's Multi-Sector General Permit (MSGP) for industrial stormwater from 29 covered sectors, and the Construction General Permit (CGP) for stormwater from construction sites disturbing one or more acres. Both require a Stormwater Pollution Prevention Plan (SWPPP), routine inspections, and in some cases discharge monitoring. Implementation is at 40 CFR Part 122. Many states have authorized state-equivalent permits.
Frequently Asked Questions
Who needs a stormwater permit?
MSGP industrial: operators in 29 sectors including manufacturing, transportation, scrap and recycling, hazardous waste TSDFs, food processing, and warehousing. CGP construction: anyone disturbing one or more acres of land (or part of a larger common plan exceeding one acre cumulatively). State-issued permits cover similar populations under state-administered NPDES programs.
What is a SWPPP?
A Stormwater Pollution Prevention Plan is the site-specific document required by NPDES general permits. It identifies pollution prevention team, site description, drainage maps, pollutant sources, control measures, inspection procedures, training, recordkeeping, and signature certification. SWPPPs must be available on-site (or at construction office) during the period of permit coverage.
How often do construction sites need stormwater inspections?
Per the Construction General Permit, at least every 7 calendar days plus within 24 hours after qualifying storm events (typically 0.25 inches or greater of rainfall). Inspection records must be maintained on-site for the duration of the construction project plus 3 years after Notice of Termination.
What are common stormwater violations?
Failure to obtain coverage (no Notice of Intent submitted), missing or outdated SWPPP, inadequate or missing inspections, failed control measures (erosion controls washed out, spill kits empty), illicit discharge (non-stormwater entering the storm drain), failure to submit benchmark monitoring data for industrial facilities, and improper dewatering practices on construction sites.
Authoritative sources
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