Does the Clean Water Act Regulate Discharges of Pollutants to Hydrologically Connected Groundwater?

The Clean Water Act (“CWA”) prohibits the discharge of pollutants into “waters of the United States” without a valid National Pollutant Discharge Elimination System (“NPDES”) permit. The statute offers notoriously scant guidance as to what “waters of the United States” actually means. As a result, whether the CWA applies to a given water body is often the subject of controversy and confusion. The EPA and the U.S. Army Corps of Engineers’ Clean Water Rule—currently beset by political, legal and legislative challenges—attempts to clarify this important term. But the Clean Water Rule is silent on an important question that continues to divide federal courts: does the CWA apply to releases of pollutants into groundwater that eventually migrate into waters of the United States?

Federal district courts have held that the CWA governs discharges into groundwater that is hydrologically connected to jurisdictional waters of the United States and would permit CWA jurisdiction over groundwater discharges in far more limited circumstances. Still other courts view the CWA as inapplicable to groundwater, no matter its ultimate connection to surface water bodies. (Marten Law)