A Site-Specific Field and Laboratory Evaluation of Fish and Asiatic Clam Population Responses to Coal Fired Power Plant Discharges

A combined effort of field receiving system monitoring and field located laboratory and formal laboratory bioassay testing was used to evaluate and compare responses of fish and the Asiatic clam (Corbicula fluminea) to cower plant discharges. Discharges and effluents evaluated during an 8-yr period included thermal and chlorinated discharges and pH excursions from fly ash effluent released into a lotic receiving system of the New River drainage in Glen Lyn, Virginia, USA. Constituents within the fly ash effluent studied included the effects of the particulate ash fraction, heavy metals, and pH (acidic and alkaline) excursions. The field laboratory was used for testing fish preference-avoidance behavioral and lethal temperature responses to elevated temperatures and in chlorinated, thermal plumes. Formal laboratory protocol included static, flow through, and artificial stream bioassays of fly ash, pH excursions, and selected heavy metals to fish and clams. Results of this study showed that fish populations preferred and avoided heated waters, depending on their seasonal acclimation requirements, both in the field laboratory and in the field receiving system of the New River. Fish populations avoided sublethal chlorinated discharges from laboratory intermittent chlorine bioassays after attraction into the laboratory and field thermal plumes. The interactions of fish populations with fly ash showed that responses were more difficult to predict in the laboratory and field systems employed. The complex variables of elevated temperature, ash particules, heavy metals, and pH excursions associated with fly ash require more research effort in order to predict the validity of data between laboratory and field systems for hazard evaluation. The Asiatic clam has invaded the New River at the rate of 9 miles a year from the Kanawha River near Charleston, West Virginia (~138 river miles) that enters downstream from the Glen Lyn coal-powered generating plant in Virginia at the West Virginia border. During the period of investigation, October 1976-September 1978, clams were more numerous in the vicinity of the thermal discharge of the plant than they were in unheated waters, and their population fell sharply during winter months when the water temperature dropped to approximately 2°C. The temperature (35°C) of the heated discharge water in late summer did not adversely affect the clam since in laboratory thermal tolerance studies mortality occurred at temperatures >36°C. The clam proved to be highly resistant to the conventional biocidal practice of intermittent chlorination and to exposure to heavy metals in both static and artificial stream bioassavs. Copper was more toxic than either zinc or a combination of zinc and copper. Potassium was not an effective biocidal (gaping) agent at low concentrations (<100 mg/l). Although only minor incidents of Corbicula. infestation have been observed in the cooling system of the power plant, such infestation has become a serious problem in other parts of the United States. The ability of the clam to use heated discharge areas as overwintering sites has allowed them to expand their range into frozen northern aquatic systems of the USA. “It is the mark of an instructed mind to rest satisfied with the degree of precision which the nature of the subject permits and not seek an exactness where only an approximation of the truth is possible.” Aristotle