Entergy Corp. v. Riverkeeper, Inc.

To reduce heat produced during power generation, large power plants relied on cooling water-intake structures that drew water from nearby water sources. Nationwide, these kinds of intake structures killed billions of aquatic organisms every year. To reduce these destructive effects, Clean Water Act (CWA) § 316(b) instructed the Environmental Protection Agency (EPA) (defendant) to set national standards for cooling water-intake structures reflecting “the best technology available for minimizing adverse environmental impact.” This section of the CWA did not list any factors that the EPA should use to set these standards. The EPA issued “Phase I” rules that governed only new power plants, requiring them to use advanced cooling water systems that reduced aquatic life mortality by 98 percent. However, for existing power plants, changing to these advanced systems would be expensive and would potentially reduce their power output. Several alternative technologies reduced mortality by 80 to 95 percent but were cheaper and less likely to reduce power output. The EPA balanced the systems’ costs and benefits and determined that these alternative technologies provided enough benefit that imposing the higher-cost technology on existing plants was unnecessary. Thus, the EPA issued “Phase II” rules that allowed existing plants to use these cheaper but slightly less effective alternative technologies. Entergy Corporation, a company that operated large power plants; Riverkeeper, Inc., an environmental organization; and multiple other entities (plaintiffs) filed three petitions in the United States Court of Appeals for the Second Circuit, challenging different aspects of the EPA’s rules. The Second Circuit ruled that the CWA did not allow the EPA to perform a true cost-benefit analysis in determining the cooling-facility-intake rules; rather, the EPA was required to choose the technology that reduced adverse environmental impacts the most at a cost that the industry could reasonably bear. The United States Supreme Court granted certiorari.