Industrial Stormwater Permits (NPDES) are Clean Water Act permits that control pollutants washed off industrial sites by rain and snowmelt. When precipitation runs across loading docks, scrap piles, fueling areas or outdoor equipment, it can carry oil, metals, sediment and chemicals into storm drains and nearby waters.
The rules reach steel mills, chemical plants, trucking terminals, scrapyards, landfills and food processors. For most, the permit means a year-round routine of inspections, sampling, corrective action and recordkeeping.
What Are Industrial Stormwater Permits?
The Clean Water Act prohibits discharging pollutants to waters of the United States without a National Pollutant Discharge Elimination System (NPDES) permit. EPA's stormwater regulation at 40 CFR 122.26 extends that requirement to "stormwater discharges associated with industrial activity" and defines which facilities fall into that group.
Most facilities obtain coverage under a general permit written for many similar facilities: they prepare a Stormwater Pollution Prevention Plan (SWPPP), file a Notice of Intent (NOI) and follow the permit's conditions.
Who issues the permit
Most states are authorized to run their own NPDES programs and issue their own industrial stormwater general permits, so most facilities get coverage through their state. State permits often follow EPA's model, but parameters, deadlines and forms differ.
EPA's own general permit, the Multi-Sector General Permit (MSGP), applies only where EPA remains the permitting authority. EPA lists this as Massachusetts, New Hampshire and New Mexico, the District of Columbia, most U.S. territories, most Indian country lands and certain federal facilities and other specific activities. The MSGP groups facilities into lettered sectors with sector-specific requirements.
Current status of EPA's MSGP
The 2021 MSGP expired on February 28, 2026. Because EPA did not reissue it in time, it was administratively continued under 40 CFR 122.6: facilities covered before expiration remain covered under the 2021 terms.
EPA published a proposed 2026 MSGP in the Federal Register on December 13, 2024, and the comment period closed May 19, 2025. In a February 27, 2026 memo, EPA said Endangered Species Act consultation and water quality certifications were still pending. As of our latest review in late 2026, we found no announcement that a final 2026 MSGP had been issued.
Key changes in the proposal include:
- PFAS monitoring: quarterly, report-only indicator monitoring for PFAS, using EPA Method 1633, for 23 sectors. The proposal sets no benchmark for PFAS and does not tie results to corrective action.
- Benchmark changes: some sectors would move from indicator to benchmark monitoring, with new benchmarks for parameters such as ammonia, nitrate, nitrite and certain metals.
- Impaired waters: quarterly monitoring for detected impaired-water pollutants throughout the permit term.
- Public SWPPPs: the plan would have to be posted as a standalone document or on a public webpage.
The final permit may differ; the SBA Office of Advocacy urged EPA to withdraw the proposal.
For new facilities that began discharging on or after March 1, 2026, EPA issued a no action assurance. It requires following the 2021 MSGP's conditions, emailing an NOI to EPA before discharging and filing under the next MSGP within 90 days of its effective date. It ends on February 28, 2027, or 120 days after the next MSGP takes effect, whichever comes first.
Who Must Comply?
Section 122.26(b)(14) lists 11 categories of industrial activity. Several are defined by Standard Industrial Classification (SIC) code, while others are defined by the activity itself:
- Facilities subject to stormwater effluent guidelines or similar standards.
- Heavy manufacturing, such as paper, chemicals, refining and primary metals.
- Mining and oil and gas operations (SIC 10 to 14) with contaminated runoff.
- Hazardous waste treatment, storage or disposal facilities.
- Landfills, land application sites and open dumps that receive industrial waste.
- Recycling facilities, including scrapyards, salvage yards, battery reclaimers and auto junkyards (SIC 5015 and 5093).
- Steam electric power plants, including coal handling sites.
- Transportation facilities with vehicle maintenance, equipment cleaning or airport deicing.
- Domestic sewage treatment works with a design flow of 1.0 million gallons per day or more, or with a required pretreatment program.
- Construction disturbing five or more acres, which is permitted separately under construction general permits.
- Light manufacturing, such as food processing, printing, electronics and warehousing.
The regulation uses SIC codes, though some permits also reference NAICS. For transportation facilities, only the areas used for vehicle maintenance, equipment cleaning or deicing are covered, which matters for fleet operators.
The no exposure exclusion
Under 122.26(g), a facility in any category except construction can avoid permit coverage if all industrial materials and activities are protected by a storm-resistant shelter, so nothing is exposed to rain, snow, snowmelt or runoff. The operator must submit a signed no exposure certification to the permitting authority and recertify at least once every five years. The exclusion applies to the whole facility, not individual outfalls, and the permitting authority may inspect to confirm conditions. See EPA's no exposure guidance.
Key Requirements
The details below follow the 2021 MSGP, still in effect through administrative continuance. State permits use similar building blocks.
Stormwater Pollution Prevention Plan
The SWPPP must be developed or updated before you submit the NOI. It identifies the pollution prevention team, describes the site and drainage, inventories potential pollutant sources and spells out the control measures, schedules and procedures you use. Typical controls include housekeeping, maintenance, spill prevention, erosion control and training. It must be kept current and publicly available.
Routine facility inspections
Qualified personnel must inspect areas of industrial activity exposed to stormwater, and the control measures, at least quarterly. At least one routine inspection each year must take place while a discharge is occurring.
Quarterly visual assessments
Once each quarter, you collect a sample from each discharge point within the first 30 minutes of an actual discharge, from a storm at least 72 hours after the previous discharge unless you document a shorter interval. The sample is checked for color, odor, clarity, floating, settled and suspended solids, foam, oil sheen and other obvious signs of pollution. Evidence of pollution triggers corrective action.
Benchmark and other monitoring
Many sectors must sample for benchmark parameters quarterly in their first and fourth years of coverage. An exceedance triggers review through the permit's Additional Implementation Measures (AIM), which escalate across three levels if exceedances continue.
Corrective action
When inspections, assessments or monitoring reveal a problem, you must document the condition within 24 hours and the action taken or planned within 14 days. Repairs and new controls must generally be completed within 14 days, or within 45 days if 14 days is infeasible. AIM Level 3 allows longer installation timelines.
Reporting and Recordkeeping
- Electronic reporting: under the MSGP, NOIs, annual reports, no exposure certifications and Notices of Termination go through EPA's NPDES eReporting Tool (NeT-MSGP). Monitoring results are submitted as electronic discharge monitoring reports through NetDMR.
- Monitoring data: discharge monitoring reports are due within 30 days of receiving complete lab results.
- Annual report: due by January 30 each year, summarizing inspections, visual assessments and corrective actions.
- Records: keep the SWPPP, inspection reports, visual assessments, lab results and corrective action documentation for the retention period your permit specifies.
State programs use their own portals and deadlines, so confirm both with your state agency.
Common Compliance Mistakes
- Assuming you are not covered. Fleet maintenance yards and warehouses often miss that their SIC code is listed.
- A shelf SWPPP. Plans that do not match current site layout, materials or controls are a frequent finding.
- Missed quarters. Skipped inspections or visual assessments, with no documented reason, are hard to defend.
- Undocumented fixes. A repair without timely documentation is still a violation.
- Missing permit renewals. Watch for the final 2026 MSGP or your state's renewal and file new NOIs on time.
Unpermitted discharges and permit violations can lead to administrative orders, civil penalties assessed per day of violation and, for knowing violations, criminal enforcement.
How to Comply: Step by Step
- Confirm applicability. Compare your primary SIC code and activities against 122.26(b)(14).
- Identify your permitting authority. Determine whether your state or EPA issues the permit.
- Evaluate no exposure. If everything is under cover, consider certifying instead of seeking coverage.
- Prepare the SWPPP. Map drainage and outfalls, inventory sources and select control measures.
- File the NOI. Submit before discharging and allow for the permit's review period.
- Schedule recurring work. Set quarterly inspections, visual assessments and monitoring.
- Track corrective actions. Assign owners and due dates that match permit deadlines.
- Report on time. Submit DMRs and the annual report; update the SWPPP after changes.
How SMS360 Helps
SMS360's Audits & Inspections module lets you build digital checklists for quarterly facility inspections and visual assessments, complete them on a mobile device and attach photos. Findings can be turned into corrective actions, assigned and tracked against due dates.
Inspection records and SWPPP revisions can be stored centrally, and dashboards show overdue items across sites, giving you a complete audit trail. It also supports related EHS programs such as the SPCC rule and hazardous waste generator requirements.
Frequently Asked Questions
Does my facility need an industrial stormwater permit?
If your facility falls into one of the 11 industrial activity categories in 40 CFR 122.26(b)(14) and discharges stormwater to a storm sewer or surface water, it generally needs permit coverage or a valid no exposure certification. Coverage usually comes through your state's general permit.
Is the 2026 MSGP in effect?
As of our latest review in late 2026, EPA had proposed the 2026 MSGP but had not announced a final permit. The 2021 MSGP expired on February 28, 2026, and was administratively continued for facilities already covered. Once a new permit takes effect, existing permittees are expected to have a set period, 90 days in the proposal, to file a new NOI.
Will PFAS monitoring be required?
The proposed 2026 MSGP would require quarterly, report-only PFAS monitoring for 23 industrial sectors. Report-only means results are submitted to EPA but do not trigger benchmark exceedances or corrective action. State permits set their own monitoring.
What is the difference between a benchmark and an effluent limit?
An effluent limit is an enforceable cap; exceeding it is a violation. A benchmark is a target showing whether controls are working. Exceeding a benchmark requires review and, under the MSGP, additional implementation measures.
