USEPA’s 2021 Multi-Sector General Permit Updates – What it Means for the Wood Sector

On January 15, 2021, the United States Environmental Protection Agency (USEPA) issued the 2021 Multi-Sector General Permit (MSGP) for industrial stormwater discharges. The MSGP becomes effective on March 1, 2021.


The USEPA established National Pollutant Discharge Elimination System (NPDES) permit requirements for industrial stormwater discharges in 1990 and the agency first issued the MSPG for those facilities in 1995. The new 2021 MSGP replaces the 2015 MSGP, which was issued on June 4, 2015.

The MSGP applies in areas of the country where USEPA is the NPDES permitting authority and has made the permit available for coverage. These areas include:

  • Massachusetts, New Hampshire, New Mexico, Idaho, and the District of Columbia
  • All U.S. territories except the Virgin Islands
  • Federally-operated facilities in Colorado, Delaware, Vermont, and Washington
  • Most Indian country lands
  • Other designated activities in specific states

USEPA held a 90-day comment period for the proposed MSGP from March 2, 2020, to June 1, 2020. A total of 195 total comment letters and 1,895 unique comments were received and considered in the development of the new MSGP. The 2021 MSGP includes new or modified requirements compared to the 2015 MSGP, as outlined below.

Significant General Changes in the 2021 MSGP

The following list summarizes the most significant changes to the 2021 MSGP:

  1. Streamlining of Permit: USEPA streamlined and simplified the language throughout the permit to present the requirements in a more clear and readable manner.
  2. Public Sign of Permit Coverage: MSGP operators are required to post a sign of permit coverage at a safe, publicly accessible location close to the facility.
  3. Consideration of Stormwater Control Measure Enhancements for Major Storm Events: Operators are required to consider implementing enhanced stormwater control measures for facilities that could be impacted by major storm events, such as hurricanes, storm surge, and flood events.
  4. Monitoring Changes
    1. Indicator Monitoring for pH, TSS, and COD: A new provision requires operators to conduct indicator analytical monitoring for pH, total suspended solids (TSS), and chemical oxygen demand (COD) quarterly for the duration of the permit. This requirement applies to all operators in the following subsectors that do not have sector-specific benchmark monitoring requirements in the 2021 MSGP: B2, C5, D2, E3, F5, I1, J3, L2, N2, O1, P1, R1, T1, U3, V1, W1, X1, Y2, Z1, AB, AC, and AD. This monitoring requirement does not apply to the Wood Products Sector (Sector A).
    2. Indicator Monitoring for Polycyclic Aromatic Hydrocarbons (PAHs): This new provision requires certain operations to conduct “report-only” indicator analytical monitoring for PAHs bi-annually during the first and fourth years of permit coverage. This applies to operators in all sectors with stormwater discharges from paved surfaces that will be sealed or re-sealed with coal-tar sealcoat, or operators in sectors A, C, D, F, H, I, M, O, P, Q, R, and S. This requirement includes the Wood Products Sector (Sector A).
    3. Updating Benchmark Threshold Values: USEPA modified the benchmark monitoring thresholds in the 2021 MSGP for aluminum; copper and selenium for discharges to freshwater; and cadmium based on revised current Clean Water Act section 304(a) national recommended aquatic life water quality criteria. Additionally, the 2021 MSGP suspended the benchmark monitoring thresholds for magnesium and iron based on a lack of documented acute toxicity.
    4. Updating the Benchmark Monitoring Schedule: Applicable operators are required to conduct benchmark monitoring quarterly in their first and fourth years of permit coverage.
    5. Impaired Waters Monitoring: Operators discharging to impaired waters without a USEPA-approved or -established total maximum daily load (TMDL) must complete annual monitoring for discharges of certain pollutants to impaired waters. Monitoring is required for one year at each discharge point for all pollutants for which the water body is impaired, after which the operator can discontinue monitoring for the next two years for any pollutant that is not detected.
    6. Additional Implementation Measures (AIM): This provides new revisions to the AIM requirements for benchmark monitoring exceedances that were included in the proposed 2020 MSGP. USEPA revised these provisions to address concerns raised in public comments. Both the proposed 2020 MSGP and the final 2021 MSGP maintain a three-level structure of advancement and responses triggered by benchmark exceedances. The final 2021 MSGP AIM requirements reduce costs and complexity from the proposal by creating a stepwise, sequential advancement through the AIM levels with a clear “resetting” to baseline status if benchmark thresholds and responses are met within the required deadlines.

2021 MSGP Changes Impacting the Wood Sector

Sector A – Timber Products of the 2021 MSGP covers general sawmills, planing mills, log storage facilities, and wood preserving facilities. Sector-specific requirements for the Timber Products Sector are provided in Part 8, Subpart A of the 2021 MSGP. Before finalization of the 2021 MSGP, comments were submitted to USEPA on its proposed 2020 MSGP to address concerns of the Timber Products Sector by the Treated Wood Council (TWC) and the Federal Water Quality Coalition (FWQC). Key changes to the MSGP impacting the Timber Products Sector are outlined below.

  1. Stormwater Control Measures for Major Storm Events: The requirement to implement enhanced stormwater controls for major storm events has been removed. The 2021 MSGP only requires discharges to consider implementing enhanced control measures for facilities that could be affected by major storm events, such as hurricanes, storm surge, and flood events. USEPA is not requiring operators to implement additional controls if the operator determines such controls to be unnecessary, but USEPA is requiring operators to consider the benefits of selecting and designing control measures that reduce risks to their industrial facility and the potential impact of pollutants in stormwater discharges caused by major storm events.
  2. Removal of Universal Benchmark Monitoring for pH, TSS, and COD: Under the 2021 MSGP, the requirement for universal benchmark monitoring for pH, TSS, and COD in the Timber Products Sector has been removed. Instead, there will be non-benchmark monitoring of those parameters required only for those subsectors that currently have no sector-specific benchmark monitoring requirements. Benchmark monitoring for COD and TSS is required under Subsectors A1 (General Sawmills and Planing Mills) and A4 (Wood Products Facilities not elsewhere classified). Additionally, TSS monitoring is required in Subsector A3 (Log Storage and Handling).
  3. Modification of Copper Benchmarks: Benchmark monitoring for copper is required under Wood Preserving Subsector A2. The 2021 MSGP updated the Total Recoverable Copper Benchmark for copper discharges to freshwater to 5.19 micrograms per liter (µg/L). The Copper Benchmark for discharges to freshwater were previously hardness-dependent in the 2015 MSGP.
  4. Modification of AIM Requirements: The modification of the AIM requirements in the 2021 MSGP addresses some concerns posed by the TWC and FWQC, by ensuring that a discharger has the opportunity to take compliance steps at one AIM level before being moved to the next level. All operators subject to benchmark monitoring requirements begin in the baseline status at the start of their permit coverage. An operator would progress linearly through the three AIM levels (AIM Level 1, Level 2, and Level 3) if an exceedance triggering event occurs and continues. The operator is required to respond with increasingly robust control measures and continued benchmark monitoring with each subsequent AIM level. The following exceptions to the AIM requirements are offered in the 2021 MSGP for an exceedance triggering event at any AIM Level:
    1. Natural background sources
    2. Run-on
    3. One-time abnormal event
    4. Demonstration that discharges of copper and aluminum do not result in an exceedance of facility-specific criteria using the national recommended water quality criteria in-lieu of the applicable MSGP benchmark threshold
    5. Demonstration that the benchmark exceedance does not result in an exceedance of an applicable water quality standard
  5. Coal-Tar Sealants: The restrictions on permit eligibility if a facility uses coal-tar sealants have been removed. The 2021 MSGP requires indicator monitoring for PAHs for all facilities in the Timber Products Sector with stormwater discharges from paved surfaces sealed or re-sealed with coal-tar sealcoat, or that use or store creosote or creosote-treated wood in areas exposed to precipitation. The indicator monitoring is a “report-only” requirement in the first and fourth years of permit coverage. No thresholds or baseline values were established for these parameters.

What’s Next?

The 2021 MSGP is currently frozen for review by the new administration. If approved, the 2021 MSGP will become effective on March 1, 2021.

Learn More

EHS Support’s compliance experts can assist you with preparing your facility for the updates in the 2021 MSGP and can answer any questions you may have about this update. Please reach out to Bruce Martin for:

  • Questions related to changes to the 2021 MSGP
  • Compliance concerns with the 2021 MSGP
  • Assistance navigating new AIM requirements

Any other MSGP related questions!



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