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February 27, 2019
NAS recommends sweeping update of Multi-Sector General Permit

In a 2016 settlement agreement with 10 environmental groups, the EPA committed to providing funds to the National Academy of Sciences, Engineering, and Medicine (NAS) to convene a committee to study the effectiveness of the Agency’s Multi-Sector General Permit (MSGP). The NAS has now published its final report, which includes recommendations to put the MSGP more in step with the latest advances in stormwater management.

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“In general, the adoption of new knowledge into revisions of the MSGP program has been slow,” said the chair of the NAS committee. “Both permitted facilities and the nation’s waters would be best served by a progressive and continuously improving MSGP based on focused data-gathering efforts and analysis of new data, advances in industrial stormwater science and technology, and structured learning.”

Under the agreement, the EPA must consider all recommendations included in the NAS report as the Agency develops the next MSGP, which is scheduled for issuance in 2020. In addition, the agreement specifies that the EPA must solicit public comment on certain recommendations the NAS makes (e.g., pertaining to industrial sectors covered by the MSGP, as well as MSGP provisions affecting pollutant monitoring).

All this may result in a 2020 MSGP that both differs considerably from the current MSGP, which was issued in 2015, and imposes additional and possibly significant new requirements on facilities that choose to be subject to the MSGP.

The NAS report is available at no cost here.

29 sectors covered

The EPA issued the first MSGP in 1995 as a 5-year permit. The MSGP provides that a facility may meet its Clean Water Act (CWA) National Pollutant Discharge Elimination System (NPDES) permitting requirements through submittal of a Notice of Intent to be covered by the general permit, self-certified implementation of a stormwater pollution prevention plan (SWPPP), and implementation of stormwater control measures (SCMs) to reduce pollution levels in discharges. The 2015 MSGP is available to 29 specific types of facilities plus any other unspecified facilities where industrial activity is exposed to rain, snow, snowmelt, and/or runoff.

The EPA may impose requirements beyond those in the MSGP for some facilities. Certain large or complex facilities may be required to obtain an individual NPDES permit. Also, any facility may apply for an individual NPDES permit.

The MSGP is available in areas of the country where the EPA is the permitting authority, including in four states (Idaho, Massachusetts, New Hampshire, and New Mexico); in most of the Indian country; and for other designated activities in specific states (e.g., oil and gas activities in Oklahoma and Texas).

2015 lawsuit

In 2015, an environmental coalition led by Waterkeeper Alliance filed suit against the Agency for alleged deficiencies in the 2015 MSGP. Among their complaints, the groups said that the MSGP lacks numeric effluent limits required by the CWA; does not require that facilities monitor for many pollutants they commonly discharge; and provides no opportunity for the public to comment on industry permit applications before coverage is granted.


One major concern raised in the report is the current MSGP’s benchmark monitoring requirements, which, says the NAS, are not consistently applied. (A benchmark is a threshold value against which pollution control or pollutant concentrations can be measured.) For example, in several sectors where stormwater pollutants are expected, little or no benchmark monitoring is required, while other sectors with similar industrial activities may have multiple benchmarks.

“Therefore, EPA should implement a process that uses new scientific information to periodically review and update sector-specific benchmark monitoring requirements,” recommends the NAS. “This process should consider updated industry fact sheets, published literature and industry data, advances in monitoring technology, and other available information, so that the monitoring programs adequately address the classes of pollutants used on site [sic] and their potential for environmental contamination.”

Other recommendations

The NAS also recommends:

  • That the EPA require industrywide monitoring for pH, total suspended solids (TSSs), and chemical oxygen demand (COD) as basic indicators of the effectiveness of stormwater control measures employed on-site. These parameters can serve as indicators of poor site management, insufficient stormwater control measures, or failures of these measures, which can lead to high concentrations of these and other pollutants. Industrywide monitoring of these pollutants would also provide a baseline understanding of industrial stormwater management across all sectors.
  • A tiered approach to monitoring that recognizes the varying levels of risk among different industrial activities, which balances the overall burden to industry and permitting agencies. Low-risk facilities could opt for a permit-term inspection by a certified inspector in lieu of monitoring. Those that do not qualify as low risk would conduct industrywide monitoring for pH, TSSs, and COD. Facilities in sectors that merit more pollution monitoring would also monitor for sector-specific benchmark parameters. Facilities that have repeatedly exceeded benchmarks or large, complex sites with high potential for pollutant discharges would conduct more rigorous monitoring, potentially taking advantage of additional advanced monitoring and modeling strategies to assess the impacts of these sites.
  • That benchmark thresholds for pollutants be based on the latest toxicity criteria designed to protect aquatic ecosystems from adverse impacts from short-term or intermittent exposures, given the episodic nature of stormwater flow.
  • That the EPA suspend or remove the benchmarks for magnesium and iron until acute aquatic life criteria are established or benchmarks are developed based on long-term effects from intermittent exposures.
  • That the EPA update and strengthen protocols, training, and data management tools for industrial stormwater monitoring, sampling, and analysis to improve the quality of monitoring data.

Nonindustrial facilities

Furthermore, says the NAS, the EPA should update the MSGP industrial sector classifications so that monitoring requirements extend to nonindustrial facilities with activities and pollution risks similar to those currently covered.

“Many facilities generating pollutants of concern in stormwater, such as school bus transportation facilities and fuel storage and fueling facilities, currently are not included in the MSGP because they are not considered industrial,” says the NAS. “EPA should examine other facilities with activities similar to regulated facilities and include them in the MSGP so that pollutant risks from these sites can be appropriately reduced.”