CONSEQUENCES OF PROPOSED CHANGES TO CLEAN-WATER-ACT THERMAL DISCHARGEREQUIREMENTS

This paper summarizes three studies that examined the economic and env ironmental impact on the power industry of: a) limiting thermal mixing zones to 1,000 feet (similar to 305 m), and b) eliminating the Clean Water Act (CWA) 316(a) variance. Both of these proposed changes were i ncluded in S. 1081, a 1991 Senate bill to reauthorize the CWA. The bil l would not have provided for grandfathering plants already using the variance or mixing zones larger than 305 m. Each of the two changes to the existing thermal discharge requirements were independently evalua ted. Power companies were asked what they would do if these two change s were imposed. Most plants affected by the proposed changes would ret rofit cooling towers and some would retrofit diffusers. Assuming that all affected plants would proportionally follow the same options as th e surveyed plants, the estimated capital cost of retrofitting cooling towers or diffusers at all affected plants ranges from $21.4 to 24.4 b illion. Both cooling towers and diffusers exert a 1%-5.8% energy penal ty on a plant's output. Consequently, the power companies must generat e additional power if they install those technologies. The estimated c ost of the additional power ranges from $10 to 18.4 billion over 20 ye ars. Generation of the extra power would emit over 7.3 billion kg per year of additional carbon dioxide. Operation of the new cooling towers would cause more than 94.5 m(3) per second of additional evaporation. Neither the restricted mixing zone size nor the elimination of the 31 6(a) variance was adopted into law. More recent proposed changes to th e Clean Water Act have not included either of these provisions, but in the future, other Congresses might attempt to reintroduce these types of changes.