A recent Ninth Circuit decision has expanded Clean Water Act (“CWA” or the “Act”) liability, holding that discharges to groundwater are actionable if there is a “fairly traceable” connection between the groundwater discharge and pollutants reaching other jurisdictional surface waters. See Hawaii Wildlife Fund et al. v. County of Maui, Slip Op. (Feb. 1, 2018). The case represents the first appellate decision to apply directly the “conduit” theory and impose CWA liability for discharges through groundwater. This decision will encourage and bolster citizen suits—and potentially other enforcement actions—seeking to impose liability for groundwater discharges.

Following the Ninth Circuit’s decision, EPA formally requested comment on whether the agency should clarify its position regarding the regulation of discharges through groundwater and, if so, what form that clarification should take. See EPA, Clean Water Act Coverage of ‘‘Discharges of Pollutants’’ via a Direct Hydrologic Connection to Surface Water, 83 Fed. Reg. 7126 (Feb. 20, 2018). Comments are due by May 21, 2018.