Introduction

Stormwater discharge is water from rain or snowmelt that does not immediately infiltrate into the ground and flows over or through natural or man-made storage or conveyance systems. Stormwater picks up industrial pollutants and typically discharges them directly into nearby waterbodies or indirectly via municipal separate storm sewer systems (MS4s).

When facilities allow exposure of industrial activities and materials to stormwater, this can potentially introduce toxic pollutants (e.g., heavy metals and organic chemicals) and other pollutants such as trash, debris, and oil and grease into waterbodies. In addition, accidental spills and leaks, improper waste disposal, and illicit connections to storm sewers may also lead to exposure of pollutants to stormwater.

One way to prevent these pollutants from entering waters of the United States is to require facilities to comply with the requirements set forth in the stormwater permitting process, which is part of a larger permitting program called the National Pollutant Discharge Elimination System (NPDES). This Fact File is meant to provide a basic understanding of the general permitting process as it relates to industrial activity.

Determine if your facility is required to have a permit

While some states, territories, and the Environmental Protection Agency (EPA) do issue Individual Permits based on site-specific or industry-specific concerns, most industrial stormwater discharges are covered under the NPDES General Permit. Compliance under this permit is dependent upon a facility’s Standard Industrial Classification (SIC) code or industrial activity.

Federal regulations at 40 CFR 122.26(b)(14) require stormwater permit coverage from the following categories of industrial activities:

• Category One: facilities subject to federal stormwater effluent limitation guidelines, new source performance standards, or toxic pollutant effluent standards under 40 CFR Subchapter N
• Category Two: facilities within SIC code 24, including heavy manufacturing (e.g., paper mills, chemical plants, petroleum refineries, steel mills and foundries)
• Category Three: facilities within SIC code 10 through 14, including coal and mineral mining and oil and gas exploration and processing
• Category Four: hazardous waste treatment, storage, or disposal facilities
• Category Five: landfills, land application sites, and open dumps with industrial wastes
• Category Six: facilities within SIC code 5015 and 5093, including metal scrapyards, salvage yards, automobile junkyards, and battery reclaimers
• Category Seven: steam electric power generating plants
• Category Eight: facilities with SIC code 40, 41, 42 (except 4221-25). 43, 44, 45, and 5171, including transportation facilities that have vehicle maintenance shops, equipment cleaning operations, or airport deicing operations
• Category Nine: treatment works treating domestic sewage with a design flow of 1 million gallons a day or more
• Category Ten: construction sites that disturb 5 acres or more (mostly permitted separately under a construction stormwater permit)
• Category Eleven: facilities with SIC codes 20, 21, 22, 23, 2434, 25, 265, 267, 27, 283, 285, 30, 31 (except 311), 323, 34 (except 3441), 35, 36, 37 (except 373), 38, 39, and 4221-25, including light manufacturing (e.g., food processing, printing, publishing, electronic and other electrical equipment manufacturing, and public warehousing and storage).

Next steps if you are required to have a permit

Once it has been established that a facility meets the federal regulations requiring stormwater permit coverage, the eligible operator must then read the general permit to under their responsibilities, typically develop a Stormwater Pollution Prevention Plan (SWPPP), comply with the applicable eligibility provisions (including collecting and evaluating stormwater discharge sampling data, and visual inspections and assessments), and then submit a notice of intent (NOI) to the permitting authority. This permitting process must be renewed every five years, or as indicated in the permit.

Special considerations

The EPA regulations recognize that permit-eligible facilities may opt out of the permit by submitting a “No Exposure Certification” (NEC) when all industrial activities are protected from contact with stormwater. The NEC operates under a five-year permit coverage cycle and must be renewed if the conditions of no exposure are still met. It should be noted that industrial materials do not need to be enclosed or covered if stormwater from affected areas will not be discharged to receiving waters or if discharges are authorized under another NPDES permit.

Applicable laws & regulations

40 CFR 122.26

Related definitions

Clean Water Act (CWA): Establishes the basic structure for regulating discharges of pollutants into waters of the United States and regulating quality standards for surface waters.

National Pollutant Discharge Elimination System (NPDES): The national program for issuing, modifying, revoking, and reissuing, terminating, monitoring and enforcing permits, and imposing and enforcing pretreatment requirements, under sections 307, 402, 318, and 405 of CWA. The term includes an “approved program.”

Stormwater Pollution Prevention Plan (SWPPP): A written assessment of potential sources of pollutants in stormwater runoff and control measures that will be implemented at a facility to minimize the discharge of these pollutants in runoff from the site.

Key to remember

Not all facilities are required to follow the stormwater permitting requirements. Those that are must follow the permit criteria, including but not limited to the creation of a SWPPP and filing of an NOI.

Real world example

In March 2021, EPA Region 10 filed a consent agreement and final order to the city administration of an eastern Idaho municipality for violations of the Industrial Stormwater General Permit at its local airport. The city agreed to pay a penalty of $15,000 for failure to conduct quarterly inspections, failure to minimize erosion, failure to implement control measures to minimize exposure of fueling operation to precipitation, and an incomplete Stormwater Pollution Prevention Plan. In addition, the city agreed to modify its facility to correct the violations and agreed to update its SWPPP.