In a pair of court cases being watched by the oil and gas industry, the Trump Administration asked the U.S. Supreme Court to decide whether pollution that moves through groundwater before contaminating federally protected waterbodies constitutes a violation of the Clean Water Act (CWA).

Lower courts have been divided over their interpretation of the CWA. In one case, County of Maui, Hawaii v. Hawaii Wildlife Fund et al., the Ninth Circuit Court of Appeals ruled that Maui County had run afoul of the CWA after effluent from four wells at a county wastewater treatment facility seeped into the Pacific Ocean.

But in another case, Kinder Morgan Energy Partners LP et al. v. Upstate Forever et al., the Fourth Circuit Court of Appeals found that two conservation groups that sued parent company Kinder Morgan Inc. (KMI) after a 2014 underground gasoline pipeline rupture were correct in alleging an ongoing CWA violation. In that incident, hundreds of thousands of gallons of gasoline leaked into nearby rivers, lakes and wetlands in South Carolina. The Fourth Circuit had vacated a district court’s decision to dismiss the lawsuit and remanded the case back to the lower court.

Neither Maui County nor the KMI subsidiary had a National Pollutant Discharge Elimination System (NPDES) permit, which is issued by the U.S. Environmental Protection Agency (EPA).

“The courts of appeals are divided on the question of whether a CWA ‘discharge of a pollutant’ occurs when pollutants are released from a point source to groundwater and migrate through, or are conveyed by, groundwater to navigable waters,” Solicitor General Noel Francisco wrote in an amicus brief filed on Jan. 3 in both cases. “The court should resolve that important question.”

The Justice Department asked the Supreme Court to grant a writ of certiorari in the Maui case, and to hold the Kinder case until a decision is made regarding Maui. The department added that EPA said it “expects to take further action, reflecting the results of its review [of the CWA], within the next several weeks.

“If the court grants one or both of the petitions, the parties therefore should have the benefit of the EPA’s views before any brief on the merits is due, and the court can consider those views in deciding the issue on the merits.”

The oil and gas industry has weighed in on the latter case, backing KMI. In an amicus brief filed in October, the American Petroleum Institute (API), the Association of Oil Pipe Lines (AOPL) and the GPA Midstream Association argued that NPDES requirements “were not triggered because there was no discharge from a point source to navigable waters. Instead, the accidental release, which occurred in soil and groundwater, was subject to the authority and oversight of the South Carolina Department of Health and Environmental Control.”

API, AOPL and GPA Midstream contend that if the Fourth Circuit’s ruling were to stand, it would “dramatically expand federal jurisdiction to include regulation of diffuse movements of pollutants in soil and groundwater that Congress explicitly reserved for state oversight.

“The decision exposes pipeline and other petroleum facility operators to unprecedented and unworkable CWA obligations and liabilities, including potentially substantial penalties. Further, the Fourth Circuit’s decision creates significant uncertainty for both industry and state permitting agencies regarding when a permit may be required and how such permits would be implemented.”