The Multi-Sector General Permit (MSGP) is an NPDES general permit issued under the Clean Water Act that authorizes stormwater discharges associated with industrial activity from facilities in 29 industrial sectors. The current 2021 MSGP (effective March 1, 2021) requires facilities to develop and implement a Stormwater Pollution Prevention Plan (SWPPP), conduct routine inspections and monitoring, implement corrective actions, and submit annual reports. EPA is the permitting authority in several states (Massachusetts, New Hampshire, New Mexico, and the District of Columbia), federal facilities in some states, and U.S. territories; most other states issue their own industrial stormwater permits modeled on the MSGP. A comprehensive MSGP audit evaluates permit compliance across SWPPP implementation, monitoring, inspections, corrective actions, and reporting requirements.
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2021 MSGP — Multi-Sector General Permit for Stormwater Discharges
The 2021 MSGP authorizes stormwater discharges associated with industrial activity from 29 industry sectors under the Clean Water Act Section 402 NPDES program. The permit requires facilities to develop and implement a SWPPP, conduct visual assessments and analytical monitoring (benchmark and indicator), implement a three-tiered Additional Implementation Measures (AIM) system for benchmark exceedances, perform quarterly facility inspections, submit annual reports, and comply with sector-specific requirements in Part 8. The 2021 MSGP expires February 28, 2026, with a proposed 2026 MSGP under development.
Clean Water Act Section 402 and 40 CFR 122.26
The NPDES stormwater program under CWA Section 402 requires permits for stormwater discharges associated with industrial activity as defined in 40 CFR 122.26(b)(14)(i)-(xi). Eleven categories of industrial activity are regulated including facilities subject to effluent guidelines, heavy manufacturing, mining, hazardous waste facilities, landfills, scrap yards, power plants, transportation facilities, and treatment works. Unpermitted discharges constitute violations of the Clean Water Act subject to civil penalties up to $64,618 per day per violation.
Proposed 2026 MSGP
EPA proposed the 2026 MSGP in late 2024 with a public comment period closing May 19, 2025. Proposed changes include potential PFAS monitoring requirements for most industrial sectors, updated benchmark thresholds, and enhanced stormwater control measures for climate resilience. If the 2026 MSGP is not finalized before the current permit expires on February 28, 2026, the 2021 MSGP will be administratively continued for current permittees.
Permit Coverage and Eligibility
| Audit Item | Expected Finding / What to Evaluate |
|---|---|
| NOI and permit coverage | A Notice of Intent (NOI) was submitted through NeT-MSGP and permit coverage is active. The NOI accurately reflects current facility operations, SIC codes, discharge points, and receiving waters. If facility operations have changed since the NOI was filed, a revised NOI has been submitted. Permit coverage documentation is maintained on-site. |
| Sector identification | The facility’s applicable industrial sector(s) among the 29 MSGP sectors have been correctly identified based on SIC codes and on-site activities. Sector-specific requirements from Part 8 of the MSGP are identified and addressed in the SWPPP. If multiple sectors apply, all applicable sector requirements are addressed. |
| No exposure certification (if applicable) | If the facility qualifies for a No Exposure Certification (NEC) under 40 CFR 122.26(g), a certification has been filed and all industrial materials and activities remain sheltered from precipitation and runoff. The NEC is recertified at least every five years. If any exposure condition changes, an NOI is submitted for MSGP coverage. |
| Permit signage | A sign of permit coverage is posted at a safe, publicly accessible location in close proximity to the facility per Part 1.3.5. The sign uses a font large enough to be readily viewed from a public right-of-way and includes permit number, operator name, NOI tracking number, and contact information. If local ordinances prohibit signage, the prohibition is documented in the SWPPP. |
SWPPP Development and Implementation
| Audit Item | Expected Finding / What to Evaluate |
|---|---|
| SWPPP completeness | A SWPPP has been developed and is available on-site per Part 6. The SWPPP includes all required elements: stormwater pollution prevention team, facility description and site map, summary of potential pollutant sources, description of stormwater control measures (SCMs), schedules and procedures for monitoring, and documentation supporting eligibility determinations. The SWPPP was completed before the NOI was submitted. |
| Site map and drainage | The SWPPP site map identifies all outfall locations, direction of stormwater flow, structural SCMs, areas of industrial activity exposed to precipitation, materials storage areas, vehicle fueling and maintenance areas, receiving waters, and areas of existing or potential soil contamination. The map is current and reflects actual site conditions. |
| Pollutant source assessment | The SWPPP includes a description of potential pollutant sources for each area of industrial activity exposed to stormwater. The assessment identifies industrial activities and associated pollutants, spill and leak history, material handling and storage areas, significant dust or particulate generating processes, and areas where erosion may occur. Non-stormwater discharges are evaluated per Part 1.1.4. |
| Stormwater control measures | The SWPPP documents SCMs implemented to minimize pollutant discharge including good housekeeping, preventive maintenance, spill prevention and response, erosion and sediment controls, management of runoff, and salt/sand storage. SCMs are appropriate for identified pollutant sources and are consistent with sector-specific requirements in Part 8. SCM effectiveness is monitored through inspections and monitoring data. |
| SWPPP availability | The SWPPP is made publicly available per Part 6.5 either as an attachment to the NOI in NeT-MSGP, posted on a public website, or available upon request. The SWPPP is kept up to date and revised to reflect changes in facility operations, control measures, monitoring results, and corrective actions. |
Monitoring Program
| Audit Item | Expected Finding / What to Evaluate |
|---|---|
| Quarterly visual assessments | Visual assessments of stormwater discharges are conducted quarterly per Part 3.2 during daylight hours from each substantially different outfall. Assessments evaluate color, odor, clarity, floating solids, settled solids, suspended solids, foam, oil sheen, and other obvious indicators of stormwater pollution. Results are documented with date, time, outfall, weather conditions, and observations. |
| Benchmark monitoring | If required for the facility’s sector(s), benchmark monitoring is conducted per Part 4.2.1 during the first and fourth years of permit coverage. Samples are collected quarterly from each outfall for applicable parameters (sector-specific). Four-quarter averages are compared to benchmark threshold values. Sampling follows proper protocols for grab or composite samples within the first 30 minutes of discharge (or as soon as practicable). |
| Indicator monitoring | If required for the facility’s sector(s), indicator monitoring for pH, TSS, and COD is conducted quarterly on a report-only basis per Part 4.2.1.1. PAH monitoring is conducted bi-annually (twice per year) in the first and fourth years for applicable sectors. Results are reported but do not trigger AIM requirements. |
| Effluent limitation monitoring | If the facility is subject to numeric effluent limitations (based on EPA effluent limitation guidelines at 40 CFR Parts 405–471 or other permit conditions), compliance monitoring is conducted at the required frequency. All discharge points receiving flows from applicable industrial activities are monitored. The Substantially Identical Discharge Point (SIDP) exception does not apply to effluent limit monitoring. |
| Impaired waters monitoring | If the facility discharges to an impaired water body (listed on the state’s 303(d) list), additional monitoring for the impairment pollutant(s) is conducted annually throughout the first year and in the fourth year for pollutants associated with industrial activity per Part 4.2.3. No discharge of pollutants of concern to impaired waters without an approved TMDL occurs unless consistent with the assumptions of the applicable TMDL. |
Inspections and Corrective Actions
| Audit Item | Expected Finding / What to Evaluate |
|---|---|
| Quarterly facility inspections | Routine facility inspections are conducted at least quarterly per Part 3.1 by qualified personnel. Inspections cover all areas of industrial activity, SCMs, discharge points, and potential pollutant sources. Inspection reports are completed and include date, inspector name, weather conditions, findings, and any corrective actions needed. Inspections are conducted during periods of active discharge when practicable. |
| Corrective action procedures | Corrective actions are initiated within 14 calendar days of identifying any condition requiring correction per Part 5.1. Conditions triggering corrective action include: unauthorized release or discharge, SCM inadequacy, benchmark exceedance requiring AIM, or any other permit noncompliance. The SWPPP is revised to document corrective actions taken. If corrections cannot be completed within 14 days, a plan with timeline is documented. |
| Additional Implementation Measures (AIM) | The three-tiered AIM system is implemented when benchmark thresholds are exceeded per Part 5.2. AIM Level 1: Review SWPPP and control measures, continue monitoring until acceptable levels are obtained. AIM Level 2: Implement additional pollution prevention and good housekeeping measures if exceedance recurs. AIM Level 3: Install permanent structural source controls and treatment controls if exceedance continues. AIM status and actions are documented in the SWPPP. |
Reporting and Recordkeeping
| Audit Item | Expected Finding / What to Evaluate |
|---|---|
| Annual report submission | An annual report is submitted electronically via NeT-MSGP by January 30 each year per Part 7.4. The report summarizes monitoring data, inspection findings, corrective actions taken, AIM status, SWPPP modifications, and any noncompliance incidents. The report is certified by an authorized signatory. |
| Discharge monitoring reports | If required, discharge monitoring reports (DMRs) are submitted through NeT-MSGP for benchmark monitoring, indicator monitoring, and effluent limitation monitoring results per Part 7.2. Data is submitted within the timeframes specified in the permit. |
| Record retention | All records related to permit compliance are retained for at least three years per Part 7.8 including monitoring data, inspection reports, SWPPP revisions, corrective action documentation, and training records. Records are available for review by EPA, state agencies, and the public. Records related to any pending litigation or enforcement action are retained until the matter is resolved. |
| Permit termination procedures | If the facility ceases industrial activities or otherwise no longer requires MSGP coverage, a Notice of Termination (NOT) is filed through NeT-MSGP per Part 1.4. Final site stabilization or transfer of permit coverage to a new operator is completed before termination. A NOT is not required when transitioning to a new version of the MSGP. |
Corrective Actions
Common Issues and Responses
- SWPPP not current: Review and update the SWPPP to reflect current site conditions, industrial activities, outfall locations, and control measures. Revise the site map if any physical changes have occurred. Ensure all required SWPPP elements per Part 6 are addressed and the updated SWPPP is made publicly available.
- Missed visual assessments: Resume quarterly visual assessments immediately. Document the reason for missed assessments and include in the next annual report as a noncompliance incident. If limited rainfall or freezing conditions prevented assessments, document the exception per Part 3.2.4.
- Benchmark exceedance: Initiate the appropriate AIM level response. Review SWPPP and control measures, identify the source of the exceedance, implement additional controls, and continue monitoring. Document all actions in the SWPPP. If at AIM Level 3, consult with the permitting authority on permanent structural controls.
- Late or missing annual report: Submit the annual report through NeT-MSGP immediately. Document the late submission as a noncompliance incident. Establish calendar reminders for the January 30 annual reporting deadline and assign responsibility for report preparation.
- No stormwater pollution prevention team: Designate a stormwater team with clearly defined responsibilities per Part 6.2.1. Team members should include operations, maintenance, and environmental staff. Provide training on MSGP requirements, SWPPP implementation, and their specific roles.
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SWPPP version control, monitoring records, inspection reports, and annual report archives.
