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A Supreme Court dispute involving a coral reef off Hawaii could impose major limits on the U.S. Clean Water Act, giving mines and coal-fired power plants what environmental advocates say would be a new license to pollute.

The justices are set to hear arguments Wednesday in the case, which centers on treated wastewater that makes its way into the waters off a picturesque Maui beach.

Maui County officials, backed by the Trump administration and business groups, are urging the court to say the treatment facility doesn't need a federal permit because it pumps its wastewater into the ground, not directly into the ocean. David Henkin, an Earthjustice lawyer challenging the discharges, said the county's position would "blow an enormous hole in the Clean Water Act."

But the Chamber of Commerce says environmentalists are trying to stretch the permit requirement so far it could apply to home septic systems. It would be "a massive expansion of the law," said Aaron Streett, a lawyer who filed a brief for the business group.

The dispute comes as the Trump administration moves to restrict federal jurisdiction over wetlands and waterways. The Environmental Protection Agency said in September it would repeal an Obama administration rule that broadly defined what qualifies as "waters of the United States" under the Clean Water Act. Trump administration officials are drafting a replacement rule now, as environmental groups challenge the repeal.

The treatment facility, near the town of Lahaina, releases 3 million to 5 million gallons of treated water a day into four underground pipes, known as injection control wells. The discharged fluid then mixes into the groundwater.

A federal-state study using dye showed that much of the water reaches the Pacific through small fissures in the ocean floor. Environmental groups say decades of discharges have devastated a once-pristine coral reef off nearby Kahekili Beach.

The groups say nutrients in the discharges have stimulated the growth of algae that smother the coral by blocking photosynthesis. The county says it sent an expert to the beach in 2014 and found no evidence the reef had sustained any damage.

Environmental groups led by the Hawaii Wildlife Fund sued the county in 2012. Although the Maui County Council has approved a proposed settlement, the county's mayor has balked, keeping the high-court showdown on track.

The Ninth U.S. Circuit Court of Appeals said Maui County needs a permit to continue disposing of water through its underground wells. At issue is whether the Clean Water Act governs pollution that travels through groundwater before emerging in an ocean, river or other major body of water.

At the Supreme Court, Maui County says the Clean Water Act requires a permit only when a "point source" — a specific conveyance such as a pipe, ditch or well — discharges pollution directly into a body of water. The county says the test is whether the point source is the "means of delivery."

"The county's wells are not the means that deliver pollutants to navigable waters," Maui County argued. "It is the groundwater that conveys to the ocean." The Trump administration doesn't go that far. But the government says that when it comes to discharges into groundwater, polluters don't need a permit under the National Pollutant Discharge Elimination System.