October 24, 2018

The Groundwater Conduit Theory: Expanding the Scope of the CWA?

Rachel Jacobson, Sarah Judkins, and Zach Lass


The Clean Water Act (CWA) prohibits the discharge of any pollutant from a point source into navigable waters. 33 U.S.C. §§ 1311(a), 1362(12). However, a party that obtains a National Pollution Discharge Elimination System (NPDES) permit is exempt from the general prohibition on point source pollution so long as those discharges are in compliance with the NPDES permit limits. Id. § 1311(a). Although the meaning of “navigable waters” is the subject of multiple court cases—including a series of decisions by the US Supreme Court—and is currently undergoing regulatory review, the term has generally been limited to surface waters and wetlands. By contrast, groundwater—typically subject to state jurisdiction—is not a navigable water for the purposes of federal CWA jurisdiction. However, when discharges of pollutants into groundwater eventually reach navigable waters, there is uncertainty as to whether a NPDES permit is required. Under the so-called groundwater conduit theory, discharges into groundwater that eventually make their way to navigable water could be subject to the CWA’s NPDES permitting regime, depending on the jurisdiction where the discharge takes place. 

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