Stormwater NPDES Permit Compliance
Last reviewed · By Chad Griffith
Stormwater discharges from industrial facilities and construction sites are regulated under the Clean Water Act through the National Pollutant Discharge Elimination System (NPDES) permit program. EPA's Multi-Sector General Permit (MSGP) covers industrial stormwater for 29 sectors of operations; the Construction General Permit (CGP) covers construction-related stormwater. Most operators are covered by EPA's general permit or an equivalent state-issued permit. Both permit types require a Stormwater Pollution Prevention Plan (SWPPP), routine inspections, and in some cases discharge monitoring.
Industrial Stormwater (MSGP)
EPA's Multi-Sector General Permit covers industrial stormwater discharges from 29 industry sectors including manufacturing, transportation, scrap and recycling, hazardous waste TSDFs, and food processing. Operators must submit a Notice of Intent (NOI) to be covered, develop and implement a Stormwater Pollution Prevention Plan, conduct routine and quarterly visual inspections, perform benchmark monitoring (sector-dependent), and file annual reports. Many states have authorized state-equivalent permits with similar but not identical requirements.
Construction Stormwater (CGP)
EPA's Construction General Permit covers stormwater discharges from construction sites disturbing one or more acres (or smaller sites that are part of a larger common plan of development). Operators must submit a Notice of Intent, develop a SWPPP specific to the project, install and maintain erosion and sediment controls, conduct routine inspections (typically every 7 calendar days plus after qualifying storm events), and submit a Notice of Termination upon project completion when stabilization is achieved.
SWPPP Required Content
A Stormwater Pollution Prevention Plan must include: pollution prevention team identification; site description and drainage maps; potential pollutant source inventory; control measures and design specifications; routine and post-storm inspection procedures; spill prevention and response procedures; employee training requirements; record retention procedures; and signature certification. Industrial SWPPPs include sector-specific elements; construction SWPPPs include phase-specific control measures.
Inspection and Monitoring
Industrial facilities under MSGP conduct quarterly visual inspections of stormwater discharge points and routine inspections of pollutant source areas. Some sectors require benchmark monitoring (sampling and analysis of pollutants of concern). Construction sites under CGP conduct inspections at least every 7 calendar days plus within 24 hours after qualifying storm events (typically 0.25 inches or greater). Inspection records must be maintained on-site or at the construction office for the duration of the project.
Frequently Asked Questions
Which industries need stormwater permits?
EPA's MSGP covers 29 sectors including: timber products, paper products, chemical manufacturing, asphalt and concrete, glass and clay, primary metals, metal mining, coal mining, oil and gas extraction, mineral mining, hazardous waste TSDFs, landfills, automobile salvage, scrap recycling, steam electric power, land transportation, water transportation, ship building, air transportation, treatment works, food and kindred products, textile mills, leather tanning, fabricated metal products, transportation equipment, and waste recycling and resource recovery.
How big does a construction site need to be to require a CGP?
Construction sites disturbing one or more acres of land require coverage under the EPA Construction General Permit (or an equivalent state permit). Smaller sites that are part of a 'larger common plan of development or sale' that exceeds one acre cumulatively also require coverage. Sites under one acre that are not part of a larger plan are typically exempt.
How long must SWPPPs and inspection records be retained?
MSGP industrial: 3 years from the date of expiration of the permit. CGP construction: 3 years from the date of submission of the Notice of Termination. SWPPP must be available on-site or at a central office during the period of permit coverage. Inspection records must be retained on-site during the construction project plus the 3-year post-termination period.
What are common stormwater violations?
Frequent EPA citations: failure to obtain coverage (no NOI submitted), missing or outdated SWPPP, inadequate or missing inspections, failure to maintain control measures (erosion controls washed out, spill kits empty), discharge of non-stormwater (illicit discharge), failure to submit benchmark monitoring data, and improper disposal of dewatering water from excavations.
Authoritative sources