Variables Influencing Fish Impingement at Five Alabama Power Steam Plants

Abstract

With increasing need for electricity, steam powered electric generating facilities are increasing across the nation. The cooling water intake structures at these plants are responsible for removing millions of fish and other aquatic organisms from U.S. waters annually. Due to recent rulings by the Environmental Protection Agency, steam powered electric generating facilities that meet certain criteria need to reevaluate Section 316(b) of the Clean Water Act of 1972. These steam plants are required to quantify fish mortality caused by impingement and determine the affects this mortality is having on local fish assemblages. Previous studies have noted numerous physical, chemical and biological variables (i.e. dissolved oxygen, water temperature, conductivity, pH, turbidity, intake velocity, intake flow, debris loading, river stage, number of screens in use, hydraulic zone of influence and river discharge) influencing impingement rates. The majority of studies found impingement rates to be most influenced by water temperature, with higher impingement rates corresponding to low water temperatures. The majority of these studies, however, were conducted in northern climates, where winter temperatures are often much lower than in Alabama. Additionally, most of the studies conducted on impingement rates were done in the 1970s. Therefore, the need to reevaluate the factors influencing impingement is great. In this study, impingement rates were determined for five steam plants (Barry, Gadsden, E. C. Gaston, Gorgas, and Greene County Steam Plants), seasonal and monthly patterns in impingement rates were investigated, and the potential influence of several physical, chemical and biological variables (i.e. dissolved oxygen, water temperature, conductivity, pH, turbidity, intake flow velocity, intake flow volume, debris loading, river stage and river discharge) on impingement rates were determined. From this, the majority (86%) of fish impinged were comprised of threadfin shad (Dorosoma petenense), blue catfish (Ictalurus furcatus), and freshwater drum (Aplodinotus grunniens). In addition, impingement rates were most affected by water temperature, dissolved oxygen, hydraulic zone of influence, river discharge, and time of year. Since the majority of fish impinged were from the smaller length classes, fluctuations of these variables may have had a more dramatic effect on these smaller more easily stressed individuals, ultimately causing higher impingement rates.