EVALUATION OF THE RESIDENT-SPECIES PROCEDURE FOR DEVELOPING SITE-SPECIFIC WATER QUALITY CRITERIA FOR COPPER IN BLAINE CREEK, KENTUCKY

Abstract

Acute toxicity tests were performed on each of nine different organisms in Blaine Creek (Lawrence County, KY) water to determine 48-h LC50 values for copper (Cu). Blaine Creek is the receiving stream for Kentucky Power Company's Big Sandy Plant fly-ash pond discharge. Selection of the nine tested species and integration of the results were based on the U.S. Environmental Protection Agency's (EPA's) resident-species procedure. The following LC50 (μg Cu/L) values were obtained (hardness 100-120 mg/L as CaCO3): Daphnia pulex 37; Physella sp. 109; Isonychia bicolor 223; Pimephales promelas 284; Stenonema sp. 453; Eurycea bislineata 1,120; Chironomus riparius 1,170; Orconectes sp. 2,370; Lepomis macrochirus 4,300. A final acute value (FAV) of 10.1 μg Cu/L (hardness 50 mg/L as CaCO3) was derived using the Blaine Creek database, which is lower than the EPA's national FAV (18.5 μg/L). The differences in FAVs were due to the effect of database size, not differences in the relative sensitivity of test organisms. Our findings provide caution for dischargers who may choose to use the resident-species procedure for future site-specific water-quality-criteria demonstrations. The resident-species procedure, because of the inherent conservative bias of the calculation process, tends to produce more stringent criteria when used on a site-specific basis. A modified recalculation procedure, in conjunction with site-specific metal bioavailability data, was judged to be the most appropriate method for deriving site-specific Cu criteria for Blaine Creek.