The 9th U.S. Circuit Court of Appeals on Friday, for the second month in a row, dealt Maui County a setback in the legal defense of its Lahaina sewage treatment plant injection wells.

The court in San Francisco rejected the county’s petition to have the full court take a second look at an appeals panel’s February ruling that the county has been violating the U.S. Clean Water Act since the Lahaina Wastewater Reclamation Facility was built in the early 1980s.

Maui County spokesman Rod Antone said the ruling would be appealed to the U.S. Supreme Court.

The rejection is another victory for Maui community groups that have been trying to protect coastal waters off Kahekili Beach Park from pollution for at least a decade.

The Lahaina Wastewater Reclamation Facility, which serves West Maui, injects 3 million to 5 million gallons of treated sewage into the ground each day.

In 2011 an EPA-funded study used tracer dye to link Lahaina sewage to nearshore waters off Kahe­kili Beach. And in November a U.S. Geological Survey study found that discharge from the sewage treatment plant has been drastically undermining the coral reefs off Kahekili.

Four Maui community groups — Hawai‘i Wildlife Fund, Sierra Club Maui Group, Surfrider Foundation and West Maui Preservation Association — sued the county in 2012, accusing it of polluting in violation of the Clean Water Protection Act.

In court, attorneys representing Maui County argued that Clean Water Act permits are unnecessary because pollutants are discharged from injection wells a half-mile from the ocean and flow into the ocean only indirectly in groundwater.

In addition, they argued that the treatment plant isn’t the only source of pollution contributing to impaired coastal waters.

But a three-judge panel of the appellate court in February disagreed, saying the case is about preventing the county from doing indirectly what it cannot do directly.

In its opinion, the panel noted that the county could not build an ocean outfall to dump pollutants directly into the ocean without a Clean Water Act permit, and to let it do it indirectly would make a “mockery” of the law.

In rejecting the county’s request Friday, the court also spurned 18 conservative state attorneys general, who joined industry groups and government organizations in asking that the ruling be overturned.

Many of the friend-of-the-court briefs argued that Congress did not include groundwater when writing the act that aims to prevent polluting the nation’s waters. They said the ruling, as it stands, extends the scope of federal regulatory authority too far.

But Earthjustice’s David Henkin, attorney for the Maui groups, called those claims “outlandish.”

“When Congress passed the Clean Water Act, it did not create a loophole for Maui County to pollute the Pacific Ocean by using the groundwater underneath the Lahaina facility as a sewer,” he said.

In 2015 the county agreed that if it lost its appeal, it would pay a $100,000 fine and invest $2.5 million in infrastructure upgrades to allow treated effluent from the Lahaina facility to be reused for irrigation.

On March 20 a Maui County Council committee authorized paying its private attorneys up to $3.8 million to litigate the case.

“It’s time for the county to stop spending taxpayer money on lawyers and to start focusing on fixing the problem,” Henkin said.

Last month Maui Mayor Alan Arakawa said the county is “at the forefront of water reuse advocacy” with many projects in the works.

“In Lahaina we plan to utilize high-level reservoirs that can pump and store recycled water so we can redistribute and reuse it all. We can accomplish this in about a year,” he said.