MSGP 2020: National Academy of Sciences Study and Recommendations to EPA

The effectiveness of the Multi-Sector General Permit (MSGP), a Clean Water Act stormwater permit program aimed at industrial stormwater, is under fire. Per a legal agreement between the Environmental Protection Agency (EPA), industry, and environmental groups, the EPA funded a study conducted by the National Academy of Sciences (NAS) to identify potential improvements to the MSGP. The results of NAS’s study were published in a February 2019 report, which makes several suggestions for strengthening the MSGP and provides intended environmental protection while balancing the overall burden of monitoring. EPA is required to consider all NAS recommendations as it moves to reissue MSGPs in 2020. These recommendations, if accepted, will have a direct impact on facilities covered by such permits.  

Improving Monitoring and Benchmarks

The NAS encourages consideration of scientific evidence when reassessing benchmark thresholds for pollutant concentrations. Updated industry fact sheets, published literature, industry data, and advanced monitoring technology should also be considered when adjusting benchmark monitoring requirements. Some existing benchmarks are based on chronic criteria despite the episodic and unpredictable nature of stormwater. NAS recommends revisiting some of these benchmarks to consider acute criteria. It also suggests suspending or removing certain benchmarks with no current established acute criteria and little evidence of causing adverse effects to aquatic organisms at common concentrations. The report states: “In general, EPA has been slow to adopt new knowledge into its MSGP permit revisions, but the MSGP should not be a static enterprise.”

The report suggests that EPA and state agencies should utilize industry-wide monitoring to better understand and support new or modified benchmarks. Currently, only 55 percent of MSGP holders are required to conduct chemical-specific benchmark monitoring. NAS advocates for industry-wide monitoring of certain pollutants, such as pH, TSS, and COD, to serve as general indicators of problems with site management practices. This will help identify correlations with other common benchmarks, such as metals, nutrients, and toxins. If the EPA accepts this advisement and requires all permit holders to conduct monitoring, it would result in a more complete data set to inform future decision making and build a better understanding of industrial stormwater conditions. However, industry-wide benchmark monitoring would obviously impact permit holders not currently required to monitor. 

The NAS further recommends the EPA consider a training or certification program for stormwater collection and monitoring to ensure information obtained adequately represents stormwater runoff. The NAS also favors composite sampling over grab sampling for benchmark monitoring. Given the temporal and variable nature of pollutant concentrations in a single stormwater event, composite sampling could be a game changer for many regulated dischargers as it would more accurately represent total loads of stormwater pollutants from a site, as opposed to a single snapshot in time that may entirely misrepresent total loads. 

Finally, one of the most interesting recommendations is the development of a tiered approach to monitoring based on the potential risk associated with the range of industrial activities covered under the MSGP. NAS proposes four tiers of monitoring for different types of facilities based on their risk potential, ranging from inspection only for low-risk facilities to enhanced monitoring for high-risk facilities. Facilities in the middle tiers may be required to monitor for designated industry-wide parameters (pH, TSS, and COD) only, or for industry-wide parameters plus sector-specific benchmarks. The NAS report suggests this approach would improve the overall quality of monitoring data while balancing the burden to industry and permitting agencies.

The Potential Impact 

As the EPA drafts a revised MSGP for 2020, it will review and consider the NAS report and recommendations. Industrial facilities covered under the revamped permit can expect to see changes in compliance obligations in 2020, including new or different requirements related to benchmark monitoring parameters, concentrations, and frequencies. Some facilities may be subject to less burdensome requirements while others may have substantial new requirements. The EPA is expected to publish a draft MSGP for public comment prior to issuing the 2020 MSGP. Additional information, including a link to the NAS report, is available  

Watch for EPA to publish a draft MSGP for public comment prior to reissuing the permit. Additional information, including a link to the NAS report, is available on the EPA’s website.



Zach Henderson Senior Technical Leader Stormwater & Flood Resiliency

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