Future Changes to your Industrial Stormwater Permit

By: Mike Arozarena

After a settlement agreement(1) was entered between the United States Environmental Protection Agency (EPA), industries, and environmental groups regarding needed revisions to the nationwide 2015 Multi-Sector General Permit (MSGP) for industrial stormwater, EPA asked the National Academies of Sciences, Engineering, and Medicine to convene a committee to study certain aspects of the industrial stormwater program, with a focus on stormwater monitoring requirements and stormwater retention standards.

Specifically, the National Academies’ committee was tasked to:

  • Suggest improvements to the 2015 MSGP benchmark monitoring requirements.
  • Evaluate the feasibility of numeric retention standards (e.g., volumetric control standards for a percent storm size or standards based on percentage of imperviousness).
  • Identify the highest-priority industrial facilities/subsectors for consideration of additional discharge monitoring.

EHS Support reviewed a prepublication copy of the consensus study report by the National Academies of Sciences, Engineering, and Medicine 2019(2).  The study made a number of recommendations to EPA, which were grouped into three categories:

  1. Pollutant monitoring requirements and benchmark thresholds
  2. Stormwater sampling and data collection
  3. Consideration of retention standards in the MSGP

The following are the National Academies’ major recommendations by category (excerpted from the National Academy of Sciences, Engineering and Medicine’s study: Improving the EPA Multi-Sector General Permit for Industrial Stormwater Discharges (2019)).

Pollutant Monitoring Requirements and Benchmark Thresholds

Recommendations for improving benchmark monitoring requirements include the following:

  • EPA should require industry-wide monitoring under the MSGP for pH, total suspended solids (TSS), and chemical oxygen demand (COD) as basic indicators of the effectiveness of stormwater control measures employed on-site.
  • EPA should implement a process to periodically review and update sector-specific benchmark monitoring requirements that incorporate new scientific information.
  • EPA should update the MSGP industrial sector classifications so that requirements for monitoring extend to nonindustrial facilities with activities similar to those currently covered under the MSGP.
  • Benchmarks should be based on the latest toxicity criteria designed to protect aquatic ecosystems from adverse impacts from short-term or intermittent exposures, which to date have generally been acute criteria.
  • Additional monitoring data collection on the capacity of stormwater control measures to reduce industrial stormwater pollutants is recommended to inform periodic reviews of benchmark thresholds and identify sectors for which new national effluent limits could help address treatment attainability.
  • Because of the paucity of rigorous industrial stormwater control measure performance data, the development of new Numeric Effluent Limitations is not recommended for any specific sector based on existing data, data gaps, and the likelihood of filling them.

Stormwater Sampling and Data Collection

Recommendations for improving stormwater sampling and data collection requirements include the following:

  • EPA should update and strengthen industrial stormwater monitoring, sampling, and analysis protocols and training to improve the quality of monitoring data.
  • EPA should allow and promote the use of composite sampling for benchmark monitoring for all pollutants except for those affected by storage time.
  • Quarterly stormwater event samples collected over 1 year are inadequate to characterize industrial stormwater discharge or describe industrial structural control measure performance over the permit term.
  • State adoption of national laboratory accreditation programs for the Clean Water Act, with a focus on the stormwater matrix and interlaboratory calibration efforts, would improve data quality and reduce error.
  • To improve stormwater data quality while balancing the burden of monitoring, the EPA should expand its tiered approach to monitoring within the MSGP, based on facility risk, complexity, and past performance.
  • To improve the ability to analyze data nationally and the efficiency and capability of oversight by permitting agencies, EPA should enhance electronic data reporting and develop data management and visualization tools.

Consideration of Stormwater Retention Standards in the MSGP

The factors recognized by the committee that affect the applicability of stormwater retention standards for industrial stormwater include the following:

  • Rigorous permitting, (pre)treatment, and monitoring requirements are needed along with careful site characterization and designs to ensure groundwater protection in industrial stormwater infiltration systems.
  • Site-specific factors and water-quality-based effluent limits render national retention standards for industrial stormwater infeasible within the existing regulatory framework of the MSGP.
  • EPA should consider incentives to encourage industrial stormwater infiltration or capture and use where appropriate.
  • EPA should develop guidance for retention and infiltration of industrial stormwater for protection of groundwater.

Committee’s Report: How it may affect your industrial stormwater permit in the future

The National Academies of Sciences, Engineering and Medicine’s consensus study report will provide valuable input to the EPA as it revises its MSGP for industrial stormwater in 2020. As a reminder, the federal MSGP sets the requirements for industrial stormwater management and monitoring in areas where the EPA is the permitting authority, including most of Indian country and some federally operated facilities, all U.S. territories, the District of Columbia, Idaho, Massachusetts, New Hampshire, and New Mexico.  Although states with delegated permitting authority, which is most of the country, are not subject to the federal MSGP, it serves as a model for states as they develop their own industrial stormwater general permits.  Therefore, once the federal MSGP is re-issued it is likely the states with delegated permitting authority will adopt many of the same requirements.

So, if you’re managing an industrial facility in, for example, Ohio and think these upcoming changes to the federal MSGP will not affect you, think again.  It may take several years until the next state permit cycle, but many of these proposed improvements will likely appear in the next state-issued MSGP.

If you need assistance conducting an evaluation of your company’s compliance, please contact EHS Support’s Mike Arozarena at 513-773-5364 (mike.arozarena@ehs-support.com) or Amy Bauer at 251-533-6949 (amy.bauer@ehs-support.com)

(1)Waterkeeper Alliance v. U.S. EPA. 2016. Settlement Agreement.  Available at http://waterkeeper.org/wp-content/uploads/2016/08/Waterkeeper_Alliance_Settlement_Agreement_08162016-EPA-MSGP.pdf

(2)National Academies of Sciences, Engineering, and Medicine. 2019.  Improving the EPA Multi-Sector General Permit for Industrial Stormwater Discharges. Washington, D.C.: The National Academies Press. https://doi.org/10.17226/25355


Mike ArozarenaABOUT THE AUTHOR Michael Arozarena has over 33 years of technical and project management experience in the environmental field. His diverse work background includes environmental consulting, private industry, and the U.S. Environmental Protection Agency Research Center. His areas of experience include plant-level regulatory compliance; EHS compliance audits; environmental permitting; stormwater and wastewater monitoring; aboveground storage tank testing; ambient air monitoring; and hazardous waste treatment technology evaluations… Read More



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