A Simplified Comparison of Once-Through and Closed-Cycle Cooling Systems

Power Plants Kill Fish - Animation

Power plants that draw in cooling water from the nation’s rivers, lakes and estuaries kill fish.  Older plants in particular kill them in enormous numbers.

Whether it’s American shad in the Hudson River, perch in the Great Lakes, or anchovies along the California coast, aging power plants can kill and injure anything living in the massive volumes of water that they withdraw.

Power plants that date as far back as the 1940s are responsible for the indiscriminate destruction of fish, shellfish and other aquatic species at all life stages. A fleet of hundreds of power plants that rely on outdated “once-through” cooling systems can withdraw 370 billion gallons of water every day from the nation’s rivers, lakes and estuaries. A single plant with a once-through cooling system can take in several billion gallons of water per day, and in the process, devour eggs, larvae and young hatched fish as they are sucked into the intake pipes.  Larger fish and other aquatic species are injured or killed when they are trapped by screens intended to keep them out of the cooling systems.

This aquatic destruction has a simple solution: by modernizing existing power plants to recirculate cooling water, rather than continually take in more water, the harm to fish and other waterborne life is dramatically reduced. Closed-cycle cooling is a proven technology that reduces power plant water intake by 93 to 98 percent, thereby reducing the damage to aquatic life by 93 to 98 percent.

In March 2011, the U.S. Environmental Protection Agency released a draft rule intended to minimize the impact that power plant cooling water intake structures have on aquatic life. Several organizations concerned with the impacts of power plants on aquatic life, however, have declared that the draft rule is unacceptably weak, and does little to stem the tide of this aquatic destruction.