The United States Supreme Court has voted five to four to weaken rules that govern how much pollution is discharged into the country’s water supply, undermining the 1972 Clean Water Act.

The case involved San Francisco suing the U.S. Environmental Protection Agency (EPA) after the city was found to have violated the terms of a permit required for the discharge of wastewater pollution into the Pacific Ocean, reported The Washington Post.

San Francisco officials argued that the EPA’s authority had been exceeded due to vague permit rules that made it impossible to tell when a line had been crossed.

The justices ruled that generic prohibitions against violations of water quality standards cannot be imposed by the EPA. The decision could impact businesses, as well as other cities like Boston, New York and Washington, DC that are adjacent to bodies of water.

The opinion by Justice Samuel Alito said the EPA would be blocked from issuing “end result” permits — those that put the permittee in charge of surface water quality, The Guardian reported.

“The agency has adequate tools to obtain needed information from permittees without resorting to end-result requirements,” Justice Alito wrote.

The city’s wastewater permit has 100 pages of detailed effluent limit rules. However, it was objecting to other, less specific standards holding officials responsible for polluting discharge, reported The Washington Post.

During the case’s oral arguments last October, the Biden administration pointed out that generic rules are important safety nets for specific water pollution limits. Officials also said they had been hampered by San Francisco’s lack of information about its discharge, but the city denied that assertion.

“This decision is going to make the job of EPA and other permitting agencies much harder, because the type of limits the court says have to be used are much harder to identify and calculate,” said Becky Hammer, Natural Resources Defense Council senior attorney.

Sam Sankar, Earthjustice’s senior vice president for programs, criticized the justices for increasing EPA’s workload while the Trump administration cuts agency staff and spending.

“The majority is saying EPA can still protect water quality if it invests more staff time in issuing each permit,” Sankar said. “I guess they haven’t heard that Trump is gutting the agency.”

San Francisco’s aging water treatment plant — which serves roughly 250,000 residents — combines sewage and stormwater. Heavy rains can cause it to overflow, sending fecal water and other household waste into the Pacific.

The case has split environmental groups that often agree with liberal cities like San Francisco, as well as the EPA.

“The city is wrong,” said Justice Amy Coney Barrett, who authored the dissenting opinion, as The Guardian reported. “The relevant provision of the Clean Water Act directs EPA to impose any more stringent limitation that is necessary to meet… or required to implement any applicable water quality standard.”

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