University of Chicago Legal Forum


The distinction between “groundwater” and “navigable waters” has long created legal disputes. The most recent Supreme Court decision to grapple with the boundary between groundwater and navigable waters is County of Maui v. Hawaii Wildlife Fund. Section 301(a) of the Clean Water Act (CWA) prohibits the discharge of any pollutant into navigable waters without a National Pollutant Discharge Elimination System (NPDES) permit. The question in County of Maui is whether the CWA applies to pollutants that travel from a point source through groundwater, before entering navigable waters. The Supreme Court held that the CWA requires a permit when the discharge is the “functional equivalent” of a direct discharge. However, the Court did not define “functional equivalent” and instead provided a list of seven factors for lower courts to evaluate on a case-by-case basis.

This Comment outlines lower courts’ applications of the functional equivalent standard and argues that the functional equivalent standard is inadministrable. Lower courts, endowed with too much discretion, are choosing to apply the functional equivalent standard as if it were a bright-line rule, in ways that are inconsistent and misaligned with the goal of the CWA: protecting our nation’s waters. This misalignment stems from the inconvenient fact that groundwater is hard to trace, and courts are not equipped with the expertise to track water particles through the hydrological system.

This Comment proposes that the functional equivalent standard be replaced with a model based on courts’ interpretations of the Federal Power Act (FPA) and Natural Gas Act (NGA). The FPA and the NGA provide models for how to regulate electricity transmission and natural gas pipelines, respectively, even though electrons and gas particles are hard to track and may cross state lines, much like groundwater. In both cases the default presumption is that the Federal Energy Regulatory Commission (FERC) retains legal jurisdiction to regulate electricity transmission and natural gas pipelines. Our treatment of water is anomalous— the default presumption is that the CWA does not apply to indirect discharges into groundwater. The functional equivalent standard should be replaced with a bright-line rule: all discharges into groundwater require an NPDES permit. This approach to groundwater discharges would provide clarity and stability, which are both essential for the success of the CWA.

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