By a 6-3 vote, the high court handed a victory to the EPA, Entergy Corp, units of Public Service Enterprise Group Inc and the Utility Water Act Group, which consists of individual energy companies that operate power plants.
The justices overturned a ruling by a U.
S. appeals court in New York that the federal clean water law does not permit the EPA to consider the cost-benefit relationship in deciding the best technology available to minimize adverse environmental impact.
Electric power plants use billions of gallons of water each day from bays, rivers, lakes, oceans and other waterways for cooling of their facilities.
The court upheld a rule by the EPA in 2004 that set requirements for intake structures at large, existing facilities in an effort to protect fish, shellfish and other aquatic organisms from being harmed or killed.
The flow of water into the plants traps large aquatic organisms against grills or screens and draws smaller organisms into the cooling mechanism.
The technologies selected by the EPA include relocation of the intakes, fine-mesh screens, velocity caps, larger intakes to decrease the intake velocity and barrier nets.
The rule affected about 550 facilities that account for about 40 percent of the nation's energy production.
The EPA rejected stricter proposals, like requiring existing plants to use closed-cycle cooling technology, which reuses withdrawn water and which would have cost more than $3.5 billion a year nationwide.
The rule was challenged in court by environmental groups and by the states of Connecticut, Delaware, New Jersey, New York, Massachusetts and Rhode Island on the grounds it was not strict enough.
Writing for the court majority, Justice Antonin Scalia said the EPA permissibly relied on cost-benefit analysis in setting the national performance standards as part of the regulations.
Justice Stephen Breyer agreed with the majority that the law gives the EPA the authority to compare costs and benefits, but added he is not convinced the EPA has successfully explained the basis for the change.
Justices John Paul Stevens, David Souter and Ruth Bader Ginsburg dissented, saying the law prohibited the EPA's use of cost-benefit analysis when setting regulatory standards. "The court unsettles the scheme Congress established," Stevens wrote.