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    U.S. Supreme Court rules that the Clean Water Act regulates groundwater

    In a 6-3 opinion issued on April 23, 2020, the U.S. Supreme Court ruled that the Clean Water Act regulates activities that release pollutants that are eventually conveyed through groundwater to navigable water. The ruling is contrary to Maui County and the federal government’s position that the Clean Water Act does not regulate pollutants that travel through groundwater. Justice Breyer, joined by Chief Justice Roberts and Justices Ginsburg, Sotomayor, Kagan and Kavanaugh, wrote the Court’s opinion. Justices Thomas, Alito and Gorsuch dissented. 

    Creating a new test, the majority ruled that a permit is required when there is a direct discharge from a point source into navigable waters or when there is the “functional equivalent of a direct discharge.” 

    In the underlying County of Maui case, several environmental groups sued Maui County, alleging that the county’s discharge of treated municipal wastewater into underground injection wells without a National Pollutant Discharge Elimination System (NPDES) permit violated the Clean Water Act when the contaminants migrated through the groundwater to the ocean. The Ninth Circuit agreed with the environmental groups, holding that the county must get an NPDES permit for the discharge of pollutants to navigable waters that are “fairly traceable” from a point source to navigable waters. 

    The Court’s decision represents an attempt to strike a middle ground between the lower Ninth Circuit decision and the position of the county and the federal government. The Court noted that the Ninth Circuit’s “fairly traceable” test could cover the release of pollutants that reach navigable waters even many years after their release, constituting a broader grant of authority to US EPA than that which Congress intended. Yet, the Court also noted that the total exclusion of all discharges through groundwater from Clean Water Act regulation, as the county and federal government asserted, is also not within the intent of the statute.

    Federal government position

    After the U.S. Supreme Court granted certiorari in County of Maui on February 19, 2019, on April 15, 2019, US EPA issued an interpretive statement seeking to clarify its position in anticipation of the U.S. Supreme Court’s ruling in County of Maui. US EPA expressly rejected the idea that Clean Water Act jurisdiction includes discharges to groundwater. According to US EPA, “the Act is best read as excluding all releases of pollutants from a point source to groundwater from NPDES program coverage and liability under Section 301 of the CWA, regardless of a hydrologic connection between the groundwater and a jurisdictional surface water.” 

    Circuit split

    The U.S. Supreme Court granted certiorari in County of Maui in light of decisions out of the Fourth and Sixth Circuits on this same question of whether the NPDES permit program applies to activities that cause pollutants to be conveyed through groundwater to navigable water. Similar to the Ninth Circuit, the Fourth Circuit in Kinder Morgan Energy Partners LP v. Upstate Forever held that Clean Water Act jurisdiction does extend to pollution caused by unpermitted discharges that reach surface water through groundwater. Case No. 17-1640, 887 F.3d 637 (April 12, 2018).

    The Sixth Circuit, on the other hand, conversely ruled that discharges of a pollutant to surface waters through groundwater do not require a NPDES permit pursuant to the Clean Water Act. In both Kentucky Waterways Alliance v. Kentucky Utilities Co., Case No. 18-5115, 905 F.3d 925 (Sept. 24, 2018), and Tennessee Clean Water Network v. Tennessee Valley Authority, (Case No. 17-6155, 905 F.3d 436 (Sept. 24, 2018), the Sixth Circuit considered claims brought by environmental groups via citizen suits alleging that power plants violated the Clean Water Act by failing to obtain NPDES permits for the discharge of pollutants from coal ash ponds to groundwater that subsequently migrated into surface waters. The Sixth Circuit found that in order to fall within the Clean Water Act’s reach, pollution must enter navigable waters via a point source discharge to constitute the “discharge of a pollutant” under the Clean Water Act and that a discharge to groundwater – even if the groundwater is hydrologically connected to a navigable water – is not a point source discharge. In its decision, the Sixth Circuit emphasized that the Clean Water Act intended for such non-point source discharges of pollution to be regulated by the states. 

    Likely impacts

    The Court’s decision is likely to have far reaching implications for permitting and enforcement pursuant to the Clean Water Act. Critics of the decision, including the dissenting Justices, assert that it provides no clear guidance and, instead, creates an amorphous standard that will lead to arbitrary and inconsistent application.

    Notably, some states already regulate groundwater at the state level. Under Ohio law, the definition of “waters of the state” includes groundwater, and Ohio EPA has taken the position that impacts to groundwater are subject to regulation under Ohio Rev. Code Chapter 6111. 


    This is for informational purposes only. It is not intended to be legal advice and does not create or imply an attorney-client relationship.

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