The goal of the federal Clean Water Act (CWA) is to restore and maintain the chemical, physical and biological integrity of our nation’s waters. To date, the CWA has been effective in improving water quality in many waterbodies. The water quality benefits from limiting discharges of pollutants from industrial facilities, municipal wastewater treatment facilities and, to a lesser extent, construction sites and municipal separate storm sewer systems (MS4s), continue to be realized. But despite these achievements, controlling pollution carried by stormwater runoff remains a vexing problem.

Litigation concerning the continuing impairment of the water quality of the Accotink Creek, a 20-mile tributary of the Potomac River in Virginia, illustrates the challenges that the U.S. Environmental Protection Agency faces in regulating stormwater-related pollution. Virginia Department of Transportation v. EPA, C.A. 1:12-cv-775 (E.D. Va. January 3, 2013) (VDOT), involved a total maximum daily load (TMDL) that the EPA established to address excess sedimentation in the creek. The EPA determined that stormwater carried the sediment to the creek, and chose to regulate stormwater flow as a surrogate for sediment.

The U.S. District Court for the Eastern District of Virginia granted the motion for judgment on the pleadings filed by plaintiffs Virginia Department of Transportation and Fairfax County Board of Supervisors on the ground that the CWA does not authorize the EPA to establish a TMDL for stormwater flow. To understand why the court concluded that establishing a “flow TMDL” violated the CWA, some background is helpful.

The CWA requires each state to establish water quality standards for waterbodies within the state. Thereafter, pursuant to Section 303(d) of the CWA, each state must identify those waters within its boundaries for which the technology-based effluent limitations (ordinarily imposed through permits) are not stringent enough to implement the applicable water quality standards. In practical terms, this statutory language requires the state to identify those impaired waterbodies that are likely to remain impaired unless the ongoing pollutant loadings reaching the waterbody are reduced. Once a state lists a waterbody as impaired, Section 303(d) requires the state to establish what the EPA has termed a “pollution diet” for the waterbody.

To do so, the state determines the maximum amount of the pollutant causing the impairment that the waterbody can assimilate without violating water quality standards. The state then allocates this total load by assigning wasteload allocations to each discharger from a point source (i.e., a discrete conveyance such as a pipe or channel) and assigning load allocations to nonpoint source dischargers. The allocations must take into account seasonal variations that affect water quality and include a margin of safety.

The CWA is silent about transforming the TMDL into an enforceable document or implementing TMDL allocations. Wasteload allocations, however, affect the numeric effluent limitations imposed on point source dischargers pursuant to the CWA’s National Pollution Discharge Elimination System (NPDES) permitting program. Although effluent limits in NPDES permits are ordinarily technology-based, the permits may include more stringent water quality-based effluent limitations when necessary to attain water quality standards. EPA regulations in practice implement TMDLs by requiring NPDES permit limits to be consistent with the assumptions and requirements of the TMDL. To comply with this requirement, the permitting authority translates the wasteload allocation assigned to each discharger in the TMDL into a water quality-based effluent limitation in the NPDES permit.

Implementation of load allocations assigned to nonpoint sources may be much more difficult, because nonpoint sources are generally not subject to the CWA’s permitting regime. The EPA requires that there be “reasonable assurance” that the nonpoint source load allocation will be achieved and that water quality standards will be attained. The paucity of enforceable mechanisms in the CWA makes reasonable assurance in many instances hard to demonstrate.

As the EPA developed the flow TMDL for the Accotink Creek, it confronted the difficult task of controlling sediment from point and nonpoint source dischargers. The poor state of benthic (bottom-dwelling) organisms in the creek caused the creek to be included on Virginia’s list of impaired waters. The EPA, not Virginia, established the TMDL for the creek pursuant to the terms of a consent decree requiring the EPA to establish TMDLs for all waters on Virginia’s 1998 Section 303(d) list if Virginia failed to do so by certain deadlines.

EPA studies determined that the benthic impairment in the creek resulted from sediment carried to the creek bottom by stormwater runoff or scoured from the creek bottom by stormwater flow. According to the EPA, the amount of sediment impairing the creek is a function of the amount and timing of excess stormwater flow. Under the CWA, sediment is classified as a pollutant, but stormwater is not so classified. Nevertheless, rather than allocate sediment loadings directly, EPA decided that it would be most efficient to allocate the flow of stormwater carrying sediment to the creek and thereby indirectly reduce the sediment impacting benthic organisms.

VDOT alleged that EPA’s approach constituted a major shift from EPA’s prior practice of regulating pollutants directly and an unauthorized regulation of water quantity. The court noted that the EPA has attempted to regulate stormwater flow through the TMDL process on only four occasions nationwide, all of which have been challenged. The court viewed flow TMDLs as an unauthorized effort by the EPA to expand its own authority.

In a November 12, 2010, guidance issued by EPA’s Office of Wastewater Management, the EPA developed the rationale for regulating stormwater as a surrogate for a pollutant such as sediment. The guidance noted that Section 402(p) and other provisions of the CWA authorize the EPA to control the discharge of pollutants in stormwater. The guidance recommended that where feasible, state permitting authorities should include numeric water quality-based effluent limitations in stormwater permits issued to MS4s and to operators of small construction sites. In this respect, the guidance marked a departure from the previous practice of including limitations on stormwater discharges expressed only as best management practices.

Most relevant to flow TMDLs, the guidance further explained that numeric limitations may include not only parameters such as pollutant concentrations and pollutant loads, but also numeric parameters acting as “surrogates” for pollutants. The guidance offered several examples of surrogates such as stormwater flow volume and percentage or amount of impervious cover. The guidance noted that where the wasteload allocation in a TMDL is expressed as a surrogate pollutant parameter, the same surrogate can be used in the corresponding discharge permit limitation.

In support of the use of surrogate parameters, the guidance cited to a report by the National Research Council noting that regulating flow is a “more straightforward” way to regulate stormwater contributions to the waterbody impairment and would “automatically” achieve reductions in pollutant loading. The guidance also found support in EPA regulations that allowed TMDLs to be expressed in terms of mass, time, toxicity or “other appropriate measure.” The guidance concluded that a surrogate parameter may be an appropriate measure if the linkage between the surrogate parameter and the documented impairment is demonstrated.

The EPA advanced these arguments to the VDOT court, which rejected them. The court cited to the familiar two-step analysis in Chevron USA v. NRDC, 467 U.S. 837 (1984). The Chevron court held that when interpreting a statute, a court should first determine whether Congress addressed the precise question at issue. If so, Congress’ clear intent resolves the matter. If ambiguity or gaps in the statute exist, the court must give deference to any reasonable statutory construction by the agency charged with administering the statute.

The VDOT court determined that Congress spoke clearly as to which parameters a TMDL may utilize. Section 303(d)(1)(C) of the CWA references establishing a TMDL “for those pollutants which the administrator identifies … as suitable for such calculation.” Pollutant is defined in the statute to include sediment, not stormwater. On this basis, the court concluded that the EPA may not allocate stormwater flow rates, even if the EPA believes such allocation to be superior to a direct allocation of sediment load.

As further support for its conclusion, the court cited the decision by the U.S. Court of Appeals for the D.C. Circuit rejecting EPA’s expression of TMDLs as annual loadings. In Friends of the Earth v. EPA, 446 F. 3d 140 (D.C. Cir. 2006), EPA policy justifications for specifying annual loadings in a TMDL were deemed insufficient to overcome Congress’ use of the term “daily” loads. Similarly, notwithstanding EPA’s policy reasons for using stormwater as a surrogate for sediment, the VDOT court held that Congress’ use of the defined term “pollutant” foreclosed use of nonpollutant surrogates.

The court’s reading of the statutory language is not without plausible rebuttal. In VDOT, the EPA argued that the CWA does not expressly foreclose use of surrogates. The EPA therefore viewed its use of surrogates as “gap-filling” the statute. The EPA studies had concluded that “the dynamic relationship between the biological impairment and pollutant (sediment) in Accotink Creek is best characterized through the relationship of flow to sediment transport within the waterbody.” In EPA’s view, given the causal connection between flow and sedimentation, the flow TMDL is a means of addressing sediment, not an attempt to characterize stormwater as a pollutant.

The VDOT case arose in the TMDL context and calls into question the validity of any TMDL based on a surrogate parameter rather than on the pollutant itself. It is unclear from the decision whether the statutory language cited by the court limits state flexibility under delegated programs, or whether states may establish a flow TMDL based on state authorities. In addition, outside the TMDL context, the VDOT decision may complicate EPA’s efforts to impose runoff controls in NPDES permits to regulate the discharge of pollutants. The EPA has announced an intent to propose a rule to strengthen the national stormwater program by June 10 and to complete a final action by December 10, 2014. The VDOT decision, if it withstands any appeal that may be filed, may affect whether the proposed rule may limit stormwater runoff or must directly address the pollutants themselves. •

Kenneth J. Warren is a shareholder in the environmental practice group at Hangley Aronchick Segal Pudlin & Schiller. He is a former section chair of the American Bar Association Section of Environment, Energy and Resources.