For decades, the precise scope of the Clean Water Act’s point source permitting program has been the subject of much controversy. Over the past several years, the question of whether that program—known as the National Pollution Discharge Elimination System (“NPDES”)—regulates discharges to groundwater that is hydrologically connected to surface water has produced a number of conflicting decisions and a torrent of commentary and public debate. The Fourth and Ninth Circuits recently concluded that the NPDES program regulates such discharges under certain circumstances, while the Sixth Circuit reached the opposite conclusion, setting up potential review of the issue in the United States Supreme Court. See Upstate Forever v. Kinder Morgan Energy Partners, L.P., 887 F.3d 637 (4th Cir. 2018); Haw. Wildlife Fund v. Cty. of Maui, 886 F.3d 737 (9th Cir. 2018); Ky. Waterways All. v. Ky. Utils. Co., No. 18-5115, 2018 WL 4559315 (6th Cir. Sept. 24, 2018); Tenn. Clean Water Network v. Tenn. Valley Auth., No. 17-6155, 2018 WL 4559103 (6th Cir. Sept. 24, 2018).

In the meantime, certain groups are looking to further expand the Clean Water Act’s NPDES program to regulate releases of pollutants into the air. In particular, in a citizen suit filed in August 2018 in the Eastern District of North Carolina, an environmental group has alleged that emissions from a manufacturing facility’s stacks violate the Clean Water Act because they enter nearby surface water (1) through the air; and (2) through hydrologically connected groundwater. Cape Fear River Watch v. Chemours Co. FC, LLC, No. 7:18-cv-00159-D (E.D.N.C.).

Should the district court uphold these claims, the ramifications could be drastic, with the NPDES program potentially reaching commonplace activities such as emissions from vehicles, airplanes, and household chimneys. Fortunately, however, the Clean Water Act contains an express limitation on its reach—it only applies to discharges of pollutants into “navigable water” from a “point source,” which is defined as “any discernible, confined and discrete conveyance.” In this definition, Congress drew a distinct line between regulation of point source pollution and nonpoint source pollution, leaving the latter to be regulated by the states. S. Rep. No. 95-370, at 8-9 (1977) (Congress drew a “clear and precise distinction between point sources, which [are] subject to direct Federal regulation, and nonpoint sources, control of which was specifically reserved to State governments” because those are “the level[s] of government closest to the sources of the problem”).

EPA has repeatedly recognized that stack emissions are a form of nonpoint source pollution. Nonpoint source pollution “generally results from land runoff, precipitation, atmospheric deposition, or percolation.” EPA Office of Water, Nonpoint Source Guidance (1987) (emphasis added). In addition, EPA has explained that emissions from stacks constitute nonpoint source pollution, which would not be subject to the NPDES program.

Smokestack industries such as fossil-fueled electric generating plants could be considered point sources of air pollution. But the diffuse deposition of pollutants emitted by such facilities is a form of nonpoint source in the context of water pollution.

EPA, Introduction to the Clean Water Act. Likewise, “common sense dictates that … stack emissions constitute discharges into the air—not water—and are therefore beyond the CWA’s reach.” Chemical Weapons Working Group, Inc. v. U.S. Dep’t of the Army, 111 F.3d 1485 (10th Cir. 1997).

Of course, this does not mean that air emissions are unregulated. To the contrary, these emissions are heavily regulated under other laws, including the Clean Air Act. Under that law, states and EPA issue permits to facilities authorizing the release of pollutants into the air up to levels designed to protect human health (with an adequate margin of safety). Moreover, in the Clean Air Act, Congress specifically directed EPA to evaluate the effects of “air pollution on water quality,” recognizing that such pollution should be addressed under the Clean Air Act, not the Clean Water Act. See, e.g., 42 U.S.C. § 7403(e)(4). Finally, permitted air emissions under the Clean Air Act may not be challenged in a civil action in federal court when those emissions could have been challenged through an administrative appeal of the permit. 42 U.S.C. § 7607(b)(2) (“[a]ction of the Administrator with respect to which review could have been obtained … shall not be subject to judicial review in civil … proceedings”).

The defendant in the citizen suit has until October 31 to answer or otherwise respond to the complaint. Because of the potential implications of the suit, companies and industries involved in the emission of pollutants into the air should watch this case closely.