The groundwater conduit theory
The on-going regulatory dispute over the Waters of the United States rule and scope of Clean Water Act (CWA) jurisdiction over streams and wetlands has been well publicized and discussed. Simultaneously, a much less publicized battle has been brewing over the application of the CWA to the discharge of pollutants through groundwater. The outcome of this dispute over discharges through groundwater could have far reaching consequences for defining CWA jurisdiction.
The CWA prohibits the discharge of pollutants from a point source into navigable waters. A National Pollution Discharge Elimination System (NPDES) permit is required to receive an exemption from the general prohibition on point source pollution. Any allowable discharges must comply with the NPDES permit limits. Groundwater is not a navigable water for the purposes of federal CWA jurisdiction.
An unresolved question is whether (or when) the discharge of a pollutant into groundwater that eventually reaches navigable waters requires a NPDES permit. At least two recent federal circuit courts have held that discharges into groundwater that eventually reach navigable waters could be subject the CWA’s NPDES permitting requirements. This concept of pollutant discharges through groundwater into navigable waters is often referred to as the groundwater conduit theory.
Recently, several federal circuit courts issued contradicting holdings on the applicability of the CWA to discharges to groundwater when that groundwater flows into navigable waters. One set of recent opinions effectively expand the scope of the CWA to require NPDES permits for discharges that did not previously require permits—including coal ash discharges and pipeline spills. Conversely, other recent circuit court decisions rejected the need for NPDES permits in such situations. Such courts determined that discharges into groundwater fall outside the jurisdictional reach of the CWA.
Under current law in the Ninth and Fourth Circuits, NPDES permitting requirements may apply when pollutants are discharged from a point source through groundwater into a navigable water. In Hawaii Wildlife Fund v. County of Maui, 886 F.3d 737 (9th Cir. 2018) and Upstate Forever v. Kinder Morgan, the Ninth and Fourth Circuits each held that the CWA requires NPDES permits for discharges of pollutants into groundwater when those pollutants reach navigable water. On the other hand, in Kentucky Waterways Alliance v. Kentucky Utilities Company, No. 18-515 (6th Cir. 2018) and Tennessee Clean Water Network v. Tennessee Valley Authority, No. 17-6155 (6th Cir. 2018), the Sixth Circuit held that NPDES permitting requirements do not apply to the discharge of pollutants into groundwater prior to flowing into navigable waters. The Second Circuit has already heard arguments on this same issue; however, the court has not yet issued an opinion. Given the existing circuit split, it will be interesting to see which way the Second Circuit rules.
Whether discharges to navigable water through groundwater (serving as a conduit) are subject to CWA NPDES permitting requirements has significant and potentially expansive regulatory consequences for many entities and industries. Following Hawaii Wildlife and Upstate Forever, there is strong authority that groundwater discharges that are “fairly traceable” from a point source to navigable waters will require a NPDES permit, at least in the Fourth and Ninth Circuits.
The Supreme Court may decide to take up the issue given the recent and stark circuit split. It is also possible the EPA may issue a rulemaking or guidance document on the issue. EPA has already requested and received comments on whether the CWA should apply to discharges from point sources that eventually reach navigable waters through groundwater. It is yet to be seen how the EPA will decide and/or act on the issue after completing its review of the comments received. Regardless, resolution of this issue is important for those entities and industries seeking regulatory certainty on the extent and jurisdiction of the CWA.
 The regulation of groundwater is typically subject to the jurisdiction of the individual states.
 Both of these decisions were issued on the same day—September 24, 2018.
 See Hawaii Wildlife Fund v. County of Maui, 886 F.3d 737 (9th Cir. 2018)
 See 83 Fed. Reg. 7126 (February 20, 2018). EPA received approximately 60,000 comments on the issue.
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