On February 19, 2021, the U.S. Environmental Protection Agency (EPA) published notice of its issuance of the final 2021 National Pollutant Discharge Elimination System (NPDES) Multi-Sector General Permit (MSGP) for stormwater discharges associated with industrial activity. The MSGP covers stormwater discharges from industrial facilities in 30 business sectors in states where EPA is the NPDES permitting authority. States who have been delegated NPDES permitting authority often incorporate requirements from the MSGP into their own general permits. The final permit became effective on March 1, 2021, and replaces the existing MSGP issued on June 4, 2015, which expired on June 3, 2020 but has been administratively continued until the issuance of the new MSGP.

As we reported here when EPA requested public comment on the proposed MSGP, many of the proposed changes in the MSGP stem from the settlement of litigation over the 2015 MSGP. The settlement called for a study to be conducted by the National Academy of Sciences, Engineering, and Medicine’s National Research Council (NRC) on changes that could be made to the MSGP. The study suggested changes focused primarily on monitoring requirements for consideration in the 2021 MSGP. Among the changes arising from the study and settlement agreement included in the 2021 MSGP are:

Indicator monitoring for pH, TSS, and COD for certain subsectors without benchmark monitoring: Certain operators must conduct indicator analytical monitoring for pH, Total Suspended Solids (TSS), and Chemical Oxygen Demand (COD) quarterly for the duration of the permit. Indicator monitoring is “report only” and does not have a threshold or baseline value for comparison. No follow-up action is triggered or required based on the sampling results.

Indicator monitoring for PAHs for certain sectors/activities: Certain operators must conduct report-only indicator analytical monitoring for polycyclic aromatic hydrocarbons (PAHs) bi-annually during their first and fourth year of permit coverage. The operators to which this requirement applies are operators with discharges from surfaces sealed with coal-tar sealcoat, and facilities that manufacture, use, or store creosote or creosote-treated wood. Also included are other operators in named sectors which EPA determined are likely to have industrial activities with potential petroleum hydrocarbon exposure to precipitation that could result in the discharge of PAHs.

Updating the benchmark monitoring schedule: Operators conducting benchmark monitoring must do so quarterly in their first and fourth years of permit coverage. In the 2015 MSGP, operators who conducted four quarters of benchmark monitoring with no exceedances for a given parameter could discontinue benchmark monitoring for that parameter for the remainder of the permit term. In the 2021 MSGP, benchmark monitoring must continue in the fourth year of permit coverage.

Updating benchmark values: Benchmark monitoring thresholds for aluminum and cadmium, and copper and selenium for discharges to freshwater, have been updated based on current CWA section 304(a) national recommended aquatic life water quality criteria. The 2021 MSGP also suspends the benchmark monitoring thresholds for magnesium and iron based on a lack of documented acute toxicity.

Additional Implementation Measures: Repeated benchmark exceedances are subject to a proposed Additional Implementation Measures (AIM) protocol, which involve the implementation of varying stormwater controls dependent on the degree, or tier, of benchmark exceedances. The final AIM requirements create stepwise, sequential advancement through the AIM levels with resets to baseline status if benchmark thresholds and responses are met within the required deadlines. The AIM requirements would replace corresponding sections regarding benchmark exceedances in the 2015 MSGP.

Impaired waters monitoring: Operators discharging to impaired waters without an approved or established total maximum daily load must complete annual monitoring for discharges of certain pollutants to impaired waters. Monitoring must be completed during the first year of permit coverage and must continue into the second and third year if the relevant pollutants are detected. Monitoring must then occur during the fourth year of permit coverage and must continue into the fifth year if the relevant pollutants are detected.

In addition to new monitoring requirements, the 2021 MSGP requires operators to consider implementing enhanced stormwater control measures for facilities that could be impacted by major storm events. EPA is requiring only that operators consider the benefits of selecting and designing control measures that reduce risks posed by the potential impact of pollutants in stormwater discharges caused by a major storm event. No additional controls are necessarily required.

The 2021 MSGP does not include a number of requirements that were originally proposed in the 2020 notice. For example, universal benchmark monitoring for pH, TSS, and COD for all sectors has been scrapped in favor of requiring only certain operators to conduct quarterly indicatory analytical monitoring. Sector specific benchmark monitoring has not been included in the final 2021 MSGP for Sectors I (Oil and Gas Extraction), P (Land Transportation and Warehousing), and R (Ship and Boat Building Repair Yards), as had been initially proposed.

States which implement and enforce their own permitting programs for stormwater discharges, which include Pennsylvania and New Jersey, must ensure that their permitting programs are in compliance with the Clean Water Act. Accordingly, although states may issue permit requirements that differ from EPA’s, many state-issued permits follow the requirements in EPA’s permits. To that end, the changes featured in EPA’s 2021 MSGP may forecast potential changes to state-implemented permitting programs when those permits must be reissued. More focus on enhanced pollution prevention measures for facilities that could be impacted by major flooding events, and additional monitoring requirements, for example, could be forthcoming to Pennsylvania and New Jersey general permits for stormwater discharges associated with industrial activity.