(Adds quotes from justices)
By Lawrence Hurley
WASHINGTON, Nov 6 (Reuters) - U.S. Supreme Court justices on Wednesday wrestled over whether a wastewater treatment plant in Hawaii is subject to a landmark federal law aimed at curbing water pollution in an important environmental case, with justices on both sides of the ideological divide appearing to be searching for a compromise.
In a case that could limit the scope of 1972 Clean Water Act, the nine justices heard arguments in an appeal by Maui County of a lower court ruling siding with the Hawaii Wildlife Fund in its 2012 lawsuit accusing local officials of violating that law.
The San Francisco-based 9th U.S. Circuit Court of Appeals last year found that a Clean Water Act program - one that requires property owners responsible for polluted water discharged from pipes, drains or other "point sources" to obtain federal permits - should apply to discharges from the county wastewater facility that end up in the Pacific Ocean.
The justices court seemed receptive to concerns raised by environmentalists that a ruling for the county could allow for polluters to easily evade federal jurisdiction. But several of them appeared worried that a ruling favoring the environmental group could allow a massive increase in the number of people, including individual homeowners, who could require permits.
The legal question is whether the county needs a permit even though the waste reaches the ocean via groundwater and is not discharged directly into the ocean through a pipe or other means.
Liberal Justice Stephen Breyer said that polluters could simply construct a pipe that terminates 35 feet (10 meters) before a river, knowing full well the polluted water would eventually reach it even if it was not conveyed directly by the pipe.
"You have an absolute road map for people who want to avoid the 'point source' regulation," Breyer said, calling for a legal test that would "prevent evasion."
Conservative Justice Samuel Alito said he was concerned about an individual homeowner with a septic tank that discharges pollution into the groundwater being faced with federal enforcement, which can lead to daily financial penalties.
Fellow conservative Justice Brett Kavanaugh said that a "clear line for the property owner is really important here" so they would know if a permit was needed.
The Hawaii Wildlife Fund and other environmental groups accused the county of violating the Clean Water Act because several million gallons of treated wastewater from the Lahaina Wastewater Reclamation Facility ends up in the Pacific every day.
President Donald Trump's administration sided with the county, noting that the U.S. Environmental Protection Agency, which oversees enforcement of the Clean Water Act, concluded in April that any discharges into groundwater are not covered by the federal permit program.
The Trump administration has rolled back numerous environmental regulations. One of its plans is to reduce federal jurisdiction over waterways, reversing the approach taken by the administration of Trump's Democratic predecessor Barack Obama.
The EPA did not go as far as to endorse Maui County's view that all discharges that indirectly reach a waterway from a point source are excluded from the permit program.
States have separate authority to regulate discharges into groundwater.
A ruling is due by the end of June. A decision in favor of the county could limit the ability of environmental groups to sue for Clean Water Act violations in certain cases. After the Supreme Court agreed to hear the case, the county council agreed to a settlement but the county's mayor refused to sign off on it.
(Reporting by Lawrence Hurley; Editing by Will Dunham)