Beer is mostly water — more than 90 percent, in some cases. Which is why the craft brewing industry is increasingly concerned about the Trump administration’s attempt to deregulate the 1972 Clean Water Act.

Sixty craft breweries from across the country filed a brief in July in support of environmental advocates who are fighting the deregulation attempt in a case before the Supreme Court. They claim that weakening the protections around American waterways directly threatens their livelihoods — as well as one of America's favorite adult beverages.

"The cleanliness and flavor profile of the water is really at the heart of making great beer,” said Heather Sanborn, who opened Rising Tide Brewery in Portland, Maine, with her husband nine years ago. “We need to protect our water and make sure we have access to clean water to make great beer here in Maine and across the country.”

The Supreme Court case starts with a wastewater station in Maui County, Hawaii, that is pumping waste into underground injection wells. The trouble, environmental groups argue, is that the effluent then moves into groundwater before traveling into the Pacific Ocean, which they say undermines the Clean Water Act. The groups are suing to stop the station from dumping waste into the groundwater, claiming that the polluted ocean water led to algae blooms that cause corral reefs and their unique ecosystems to deteriorate.

A 2013 dye test conducted by University of Hawaii researchers supported that position, concluding that 64 percent of the wastewater injected into the wells ended up in the ocean. That plant produces 4 million gallons of wastewater per day via 40,000 inhabitants.

The breweries, spread throughout the United States, are supporting the case for fear that a win for Maui County could allow wastewater treatment plants and other industrial facilities in their vicinity to pollute their local waterways and undermining the consistency of their beer.

A favorable ruling for the county and a recent change to an EPA policy, they argue, would allow industrial plants to dump their wastewater into groundwater without any oversight. Those pollutants could eventually seep into major waterways.

The environmental groups, represented by Earthjustice, originally sued Maui County in 2012. Their supporters say the county and the Trump administration are essentially asking the Supreme Court to redefine the scope of the landmark 1972 environmental legislation that many credit with cleaning up and restoring the integrity of America's waterways.

The Maui's mayor office, which represents the greater county, did not respond to a request for comment.

In a brief filed in May, the county admitted that their wastewater flowed into the Pacific Ocean, but maintained that the Clean Water Act did not apply because they were dumping their waste into groundwater — not protected waterways. They noted that the case represented a dangerous expansion of the federal government's powers to prohibit how they deal with waste water.

The 60 breweries have joined a group of former EPA administrators, 13 states, a Native American tribe and clean water advocates in filing briefs in support of Earthjustice's position.

“This case pits those who are committed to the protection of life-giving, clean water against the Trump administration and polluting industries that want free rein to use groundwater as a sewer to dump their waste and toxic discharges into our nation’s lakes, rivers and oceans,” said David Henkin, an attorney for Earthjustice, a nonprofit that works to enforce environmental laws.

If the court rules that the law does apply, critics say that would require the court to essentially rewrite key elements of it. That's some thing the Trump administration is already making some headway on.

The current EPA appears to have endorsed Maui County’s claim that the wastewater station should be allowed to continue doing what it's been doing. In April, it released a new interpretation that “concluded that releases of pollutants to groundwater are categorically excluded from the Act’s permitting requirements because Congress explicitly left regulation of discharges to groundwater to the states and to EPA under other statutory authorities.”

That undercuts the entire point of the legislation, said Mark Ryan, a leading expert on the Clean Water Act who worked for 24 years as a senior litigator for the EPA.

“EPA just flipped on 30-plus years of interpretation of that decision and is saying Maui is correct,” said Ryan, who left the agency in 2014. “EPA has never taken that position before.”

As of now, Ryan explained, wastewater and industrial plants have to get costly EPA permits when discharging waste into a body of water. The permits limit what the source of the waste can discharge, requires monitoring and reporting, and includes a number of other provisions that ensure the water quality won't diminish or hurt people's health.

The rule change posed by the EPA, or a favorable Supreme Court decision, would essentially allow groups to circumvent the need for the permits by just discharging their waste into groundwater.

“It blasts a gigantic hole into the Clean Water Act,” Ryan said.

And it could also blast a gigantic hole in the burgeoning craft brewing industry.

Breweries across the country employed more than 503,000 people in 2017 and produced more than $76 billion in economic impact and $24.6 billion in labor income, according to the Brewers Association.

"There are over 7,000 craft breweries today," said Steve Fechheimer, CEO of the New Belgium Brewing Company, the fourth largest craft brewer in the United States, based in Colorado and North Carolina. "They’re in every corner of the industry and pulling water from all kinds of different watersheds and you need all those protected for the health of the industry."

The alternative is that breweries would have to test their water with a regularity that Fechheimer believes would be prohibitively expensive and nearly impossible to maintain.

"We can’t change the way we brew our beer every day," Fechheimer said of his 689 employees. "We can’t afford to test the water every 25 minutes. Those kinds of things are real costs and difficulties, so starting clean and remaining consistent really matters to us."

The Supreme Court agreed take the case up on appeal after the Hawaii federal district court and the 9th Circuit Court of Appeals in San Francisco sided with the environmental groups. But advocates are worried how the two justices appointed by President Donald Trump — Neil Gorsuch and Brett Kavanaugh — will respond to the case when it is argued in November. Hopes are not high.

Nevertheless, Fechheimer and Sanford said they would continue to advocate for the protections.

"This is just really critical to ensuring that we have clean water," Sanborn said. "Not just for brewers, but for everyone going forward. We can't wind up in situations like we’re seeing in other parts of the country where water systems are irretrievably polluted. We have to stay ahead of this issue."