October 05, 2020

The Evolution of Stormwater Regulation

Lisa A. Kirschner

In 1987, Congress expanded the federal Clean Water Act’s National Pollutant Discharge Elimination System (NPDES) program to include stormwater runoff associated with industrial sites. 33 U.S.C. § 1342(p). The U.S. Environmental Protection Agency’s (EPA) implementation of the statutory requirements included the development of NPDES general permits. In 1995, EPA published the first Multi-Sector General Permit (MSGP) addressing stormwater discharges associated with approximately 29 major industrial sectors. Final National Pollutant Discharge Elimination System Storm Water Multi-Sector General Permit for Industrial Activities, 60 Fed. Reg. 50,804 (Sept. 29, 1995). The MSGP has been consistently reissued (and is generally subject to five-year terms); it is effective in areas where EPA is the permitting authority. Each new iteration of the permit can provide a template for stormwater permits in states with delegated NPDES authority. Beginning with that first permit, EPA clarified that it provided the general permit to “NPDES authorized States and encourages such States to consider [the] permit for their permitting needs.” Id. at 50,807. In short, changes in the EPA MSGP and its approach to stormwater compliance obligations can have broad national implications because the permit provisions are often echoed by state versions of the same.

On March 2, 2020, EPA proposed to reissue the MSGP. National Pollutant Discharge Elimination System (NPDES) 2020 Issuance of the Multi-Sector General Permit for Stormwater Discharges Associated with Industrial Activity, 85 Fed. Reg. 12,288 (Mar. 2, 2020). The proposed 2020 MSGP, when finalized, will replace the 2015 MSGP. Coverage over categories of industries was and continues to be based on historic Standard Industrial Classification (SIC) codes (which categories can reflect industries with very diverse operations). While the structure of the proposed permit is not so different from the early MSGPs, its content has shifted from one that reinforces best stormwater practices at sites to more rigorous mandates and specified implementation measures. This article briefly reviews some of the substantive changes in the proposed 2020 MSGP and identifies possible challenges for EPA as it seeks to refine the Clean Water Act program governing industrial stormwater management.

The proposed 2020 MSGP continues long-standing approaches to stormwater regulation including reliance on “benchmark monitoring” for certain dischargers in order to assess the adequacy of stormwater controls. Benchmarks appeared in early iterations of the MSGP. In 2000, EPA explained that benchmarks are the pollutant concentrations that, if exceeded, represent a “level of concern.” EPA described the level of concern as a concentration at which a stormwater discharge could potentially impair, or contribute to impairing, water quality or affect human health from ingestion of water or fish. EPA noted that the benchmarks are an “appropriate level” to determine whether a facility’s stormwater pollution prevention measures are being successfully implemented. EPA stated (and continues to maintain) that the benchmark concentrations “are not effluent limitations and should not be interpreted or adopted as such.” Final Reissuance of National Pollutant Discharge Elimination System (NPDES) Storm Water Multi-Sector General Permit for Industrial Activities, 65 Fed. Reg. 64,746, 64766–67 (Oct. 30, 2000). See also Proposed 2020 MSGP at 4.2.1.

The proposed 2020 MSGP also includes some new approaches to stormwater compliance obligations. Some of the changes stem from requirements associated with the settlement of litigation over the 2015 MSGP. In response to a petition filed in the Second Circuit related to the reissued 2015 MSGP, EPA entered into a settlement agreement with petitioners and industrial representatives that focused on improvements to the MSGP. As part of the agreement, EPA convened and funded a study through the National Academies of Sciences, Engineering and Medicine’s National Research Council (NRC). The NRC Study, completed in 2019, is titled Improving the EPA Multi-Sector General Permit for Industrial Stormwater Discharges (2019 NRC Study). It evaluated, among other topics, MSGP benchmark monitoring requirements, and the feasibility of numeric retention standards, and identified highest priority industrial facilities for consideration of additional discharge monitoring; the NRC Study included some recommendations that have been incorporated into the proposed 2020 MSGP.

In spite of that settlement agreement, neither the proposed 2020 MSGP nor the recommendations from the 2019 NRC Study resolves certain criticisms of stormwater management requirements that date back to the program’s inception. For example, there are long-standing questions regarding the viability of using benchmarks to assess stormwater control measures. The comparison of first-flush stormwater sample analyses with benchmarks (which often are based on water quality criteria for a constituent) may be misleading in the context of a storm event. Specifically, stormwater flow is typically characterized as having widely variable constituent concentrations due to the episodic nature of stormwater flows. The reliance on benchmarks to assess stormwater quality may inadequately incorporate considerations relative to dilution, the short-term effects related to a storm event, background conditions in a receiving water during a storm event, and other water quality considerations that are important to assessing water quality impacts from industrial sites in the context of naturally occurring sediment mobilization. The 2019 NRC Study specifically acknowledged that the unique conditions associated with receiving waters during storm events must be factored into the relevance of benchmarks based on aquatic life criteria. See generally Nat’l Acads. of Scis., Eng’g & Med, Improving the EPA Multi-Sector General Permit for Industrial Stormwater Discharges (2019) at 43. Consistently, the relevance of benchmarks remains controversial in some situations. And, while benchmark exceedances are not permit violations, the evolution of the stormwater program includes potentially enhanced consequences stemming from benchmark exceedances, proposed program changes that could heighten that controversy.

As part of the settlement agreement, EPA agreed to propose additional implementation measures, or AIM, a hierarchal set of stormwater control measures (identified in three tiers) that may include potential new, more onerous implications for permittees who exceed MSGP benchmarks. The AIM tiers “prescribe increasingly robust responses depending on the nature and magnitude of the benchmark exceedance.” 85 Fed. Reg. at 12,288 (link to Proposed MSGP at 5.2). The responses may, however, be based on the wrong metrics. If the benchmarks do not accurately reflect the impacts of a storm event on the receiving waters, the corresponding mandatory approaches to site water management based on benchmark exceedances may also be misplaced.

The proposed 2020 MSGP includes provisions outlining the considerable consequences of not meeting the mandatory AIM obligations; failure to comply with AIM deadlines constitutes permit noncompliance. See, e.g., Proposed 2020 MSGP at 1.6,,, The risk of noncompliance is exacerbated by the specific AIM provisions. The second tier of AIM obligates permittees to implement “all feasible [stormwater control measures] from the relevant sector-specific Stormwater Control Measure Checklist(s) that applies to your facility in Appendix Q of the permit.” Id. at (emphasis added). That checklist includes pages of control measures applicable to each industrial sector. Presumably, permittees will need to evaluate the feasibility of all these measures if they are in the second tier of AIM, a potentially daunting task that may be overly broad when considering actions necessary to protect the beneficial uses of the receiving waters.

EPA has periodically sought input on a regulatory approach that could, in lieu of monitoring (and comparison to benchmark values), better evaluate the overall effectiveness of the industrial stormwater pollution control program. See Proposed Reissuance of National Pollutant Discharge Elimination System (NPDES) Storm Water Multi-Sector General Permit for Industrial Activities, 65 Fed. Reg. 17,010, 17,030 (Mar. 30, 2000). That effort continues. In its proposed 2020 MSGP, EPA recognized that the 2019 NRC Study provided potential recommendations for an alternative approach to “low-risk” facilities that could include site inspections in lieu of monitoring. The NRC Study acknowledged that certain types of sites could be better suited to evaluation through inspection rather than data monitoring. See 2019 NRC Study, supra at 6, 55, 57. EPA sought input on how to develop such an alternative including recommendations on the qualifying conditions for those facilities. 85 Fed. Reg. at 12,288 (link to Proposed MSGP at Although options to benchmark monitoring have been raised over the years, it is not clear whether EPA will finalize such a broad-brush alternative to its stormwater program. Nonetheless, the careful evaluation of defensible alternatives to the benchmark comparison approach seems even more critical in light of the escalating consequences inherent in the proposed 2020 MSGP changes.

Stormwater management of industrial sites is fundamentally important to protecting the quality of receiving waters. That management is an essential component of the Clean Water Act regulatory programs. EPA continues to try to improve the stormwater program through changes to the national MSGP template. That is a daunting task given, among many other variables, the wide variety of industries and receiving waters and the associated geographic and climactic conditions. The 2020 MSGP poses some potential opportunities for EPA to revise the stormwater program and enhance its effectiveness while minimizing the burden and wastefulness of unnecessary monitoring and control measure implementation.


Lisa A. Kirschner

Ms. Kirschner is a water quality attorney at Parsons Behle & Latimer in Salt Lake City, Utah, and a member of the editorial board of Natural Resources & Environment. She may be reached at lkirschner@parsonsbehle.com.