NATIONAL BRIEFING / WASHINGTON, D.C.

The U.S. Supreme Court said the Environmental Protection Agency may consider whether protecting fish and other aquatic creatures is worth the cost of the most advanced upgrades for older power plants, a defeat for environmentalists who had challenged the Bush administration.

The court ruled 6 to 3 that such cost-benefit decisions are allowed under the Clean Water Act as the agency moves to require more than 500 older power plants to upgrade how they draw water to cool machinery. Water-intake systems kill 3.4 billion fish and shellfish each year, the EPA estimated. But the technology to upgrade the older plants would cost about $3.5 billion annually, the EPA said. It is unclear whether the Obama administration will maintain the Bush administration’s position.