WASHINGTON - Years of legal battles over the Maui’s wastewater treatment plant were front and center in the United States Supreme Court Wednesday.

The central question facing the nine justices: is Maui County violating federal law and the Clean Water Act?

The county, through the Lahaina Wastewater Reclamation Facility, treats millions of gallons of wastewater every day, then injects it into deep underground wells. The water first travels through groundwater before entering the Pacific Ocean.

“I feel the justices were asking all the right questions,” said David Henkin, attorney for Earthjustice representing the environmentalist groups suing Maui County. Those groups include Hawaii Wildlife Fund, Sierra Club Maui Group, Surfrider Foundation and West Maui Preservation Association. “The question is can you evade the Clean Water Act simply by using groundwater as a way to get your pollution into the ocean instead of using a pipe.”

“I think there is an agreement that things other than direct discharges are subject to regulations,” said Lance D. Collins, attorney for the West Maui Preservation Association.

The Hawaii Wildlife Fund, the lead environmental group in the lawsuit, claims the plant was harming a local reef and marine life.

“The justices, some of them, are still looking at how do we define traceability and how do we decide who is the polluter,” said Hannah Bernard, executive director for the Hawaii Wildlife Fund.

Maui Mayor Michael Victorino was among the county officials inside the Supreme Court Wednesday morning during the hour-long oral argument. Victorino declined to comment on-camera to KITV following the hearing.

However, his office sent KITV a this statement defending the wastewater facility, saying Maui County has been an “environmental steward” since these facilities came online in the 1970s.  

“The Lahaina Wastewater Reclamation Facility is a model in employing treatment technologies, including ultraviolet light disinfection, to transform wastewater into the highest quality recycled water in the State of Hawaii,” Victorino said in a statement. “This direction was a conscious decision made more than 40 years ago by visionary leaders in our community, and today, the County’s water reuse program is the most robust in the State of Hawaii.”

The ruling could reach far outside of Maui, potentially impacting environmental standards and wastewater laws for industries such as drilling and fracking.

This is the first major environmental case justices will hear this term, so it’s unclear how they will rule.

A final ruling is expected by June.

You can read each side's oral arguments here.