09.17.2021  |  News

EPA Issues an Updated National Industrial Stormwater Permit


The U.S. Environmental Protection Agency (EPA) issued the updated 2021 National Pollutant Discharge Elimination System (NPDES) Multi-Sector General Permit (MSGP) for stormwater discharges from industrial activity, effective on March 1, 2021. Continue reading for a summary of the key changes to the 2021 MSGP and their broader impacts on the regulated community. [NOTE: The authors adapted the information in this blog post from the EPA’s 2021 MSGP Fact Sheet.]

EPA’s 2021 MSGP

The 2021 MSGP contains provisions that require industrial facilities in 29 different industrial sectors to, among other things, implement control measures and develop site-specific stormwater pollution prevention plans to comply with NPDES requirements. EPA’s 2021 MSGP is the governing industrial stormwater permit for facilities in areas where EPA is the permitting authority and has made the permit available for coverage. These areas include:

  • Massachusetts
  • New Hampshire
  • New Mexico
  • Idaho (until July 1, 2021)
  • The District of Columbia
  • Puerto Rico
  • All U.S. territories except for the Virgin Islands
  • Federally operated facilities in Colorado, Delaware, Vermont, and Washington
  • Most Indian country lands
  • Other designated activities in specific states (e.g., oil and gas activities in Texas and Oklahoma).

Several other states delegated authority by EPA to implement their own permits may also look to the MSGP as a guiding reference. For example, according to the California Stormwater Quality Association, the California State Water Resources Control Board relied heavily on the 2015 MSGP in developing their latest state Industrial General Permit (CASQA Water Quality Newsflash, March 2019).

National Academy of Sciences Report

EPA’s industrial stormwater permitting requirements have come under scrutiny since the program’s inception in 1995. Concerns about the effectiveness of efforts to date resulted in a legal agreement between EPA, industry organizations, and environmental groups to review and improve certain aspects of the EPA’s 2015 MSGP. In 2019, the National Academy of Sciences (NAS) issued a report offering guidance to inform the 2021 MSGP. Please refer to our earlier blog post for more information on the NAS report. EPA agreed to consider all recommendations suggested in the NAS report when drafting the 2021 MSGP.

The 2021 MSGP did not implement the following NAS report recommendations:

  • The 2021 MSGP does not cover any new industrial sources beyond those named in 40 CFR 122.26(b)(14).
  • The 2021 MSGP does not require additional monitoring specific to stormwater control measure performance beyond that included in the 2015 MSGP.
  • The 2021 MSGP does not offer an inspection option at low-risk facilities as an alternative to benchmark monitoring.
  • The 2021 MSGP does not allow infiltration as an alternative to permanent stormwater controls.

Key Changes to the 2021 MSGP

The following are areas where the 2021 MSGP differs significantly from the prior 2015 MSGP.

Additional Implementation Measures (AIM)

The 2015 MSGP required sampling and comparison of results against numeric benchmarks. Exceedances of benchmarks do not represent permit violations, but do require corrective actions. These corrective actions were broadly defined in the 2015 MSGP and generally left to the discretion of the permittee.

The 2021 MSGP includes new Additional Implementation Measure (AIM) requirements for benchmark monitoring exceedances that are more specific and prescriptive than the 2015 MSGP. AIM requirements include a three-level structure of advancement and responses triggered by benchmark exceedances. According to the 2021 MSGP Fact Sheet, the EPA believes that this structure will “keep follow-up actions clear, timely, and proportional to exceedance frequency and duration.”

  • Permittees subject to benchmark monitoring requirements begin in baseline status at the start of their permit coverage.
  • If an exceedance triggering event occurs while in baseline status, a permittee enters AIM Level 1 and must review their stormwater plan and stormwater control measures and implement additional control measures.
  • If a triggering event occurs while in Level 1, a permittee proceeds to AIM Level 2 and must review their stormwater plan and implement stormwater control measures beyond what they did in their AIM Level 1 response.
  • If a triggering event occurs while in Level 2, a permittee proceeds to AIM Level 3 and must install structural source controls and/or treatment controls.

Indicator Monitoring for pH, TSS, COD, and Polycyclic Aromatic Hydrocarbons (PAHs)

45% of 2015 MSGP permittees did not have benchmarks assigned, and therefore were not required to conduct benchmark monitoring. The 2021 MSGP includes a new provision that requires permitees without assigned benchmarks conduct “report-only” indicator analytical monitoring for pH, Total Suspended Solids (TSS), and Chemical Oxygen Demand (COD) quarterly for the duration of the permit. Certain permittees must also conduct “report-only” indicator analytical monitoring for polycyclic aromatic hydrocarbons (PAHs) twice per year during their first and fourth years of permit coverage. EPA may use the indicator monitoring data to develop benchmarks in the future.

Updated Benchmark Values

EPA modified the benchmarks in the 2021 MSGP for aluminum, cadmium, copper for discharges to freshwater, and selenium for discharges to freshwater. EPA also removed the benchmarks for magnesium and iron. The 2021 MSGP also allows permittees who exceed the revised benchmarks for discharges to freshwater for aluminum and copper to demonstrate to EPA that their discharges do not exceed a facility-specific value, which can be calculated by the permittee using the national recommended water quality criteria multi-variable models.

Updated Monitoring Schedule

The 2021 MSGP requires that applicable permittees conduct monitoring in their first and fourth years of permit coverage. This requirement is different from the 2015 MSGP, where a permittee that did not exceed limits in the first year permit coverage could discontinue monitoring for that parameter for the remainder of the permit term. Under the new schedule, regardless of when the permittee halted monitoring for any parameter, monitoring resumes for all parameters for four quarters in the fourth year of permit coverage.

Public Signage Indicating Permit Coverage

The 2021 MSGP includes a new requirement that permittees must post a sign of permit coverage near the facility. This notice must consist of information about the facility, how to request the facility’s stormwater plan, and how to contact the facility and EPA if the interested public observes stormwater pollution.

Next Steps

Permittees already covered under the administratively-extended 2015 MSGP have until May 30, 2021, to submit a new permit application. Eligible new dischargers are required to apply for permit coverage at least 30 days before commencing discharge. EPA intends share several updated guidance documents in the upcoming weeks, such as the SWPPP template, SWPPP guide, and the monitoring and sampling guide. As other delegated states and territories revise their own industrial stormwater permits, they may adopt changes from the 2021 MSGP.

Need Help?

KJ’s Stormwater Community of Practice staff closely track changes to the MSGP and state industrial stormwater permits on behalf of our clients. We comment on proposed revisions to these permits and help our clients plan for upcoming permit changes. We help clients obtain general and individual permit coverage when necessary. If benchmark monitoring shows a need for improvements, we can help with pollutant source assessments and operational, structural, and treatment improvements. Contact us for more information on how we can help you obtain and stay in compliance with your NPDES permit.

If you are interested in more information on our stormwater services, don’t forget to subscribe to our blog! Or email us at stormwater@kennedyjenks.com.


For more information, visit EPA’s Industrial Stormwater website: https://www.epa.gov/npdes/stormwater-discharges-industrial-activities


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