Ecological Effects of Contaminants in the Upper Three Runs Integrator Operable Unit

摘要

For risk assessment purposes, the 780 km2 Savannah River Site (SRS) has been partitioned spatially into Integrator Operable Units (IOUs) that correspond to the watersheds of the Savannah River tributaries that drain the SRS. The streams within each watershed are integrators because they receive contaminants transported by surface or subsurface flow from all sources within their watersheds. Ecological receptors within the streams are exposed to these contaminants, and their health reflects the severity of contamination within the watershed. The Upper Three Runs (UTR) drainage is one of the six IOUs on the SRS. The UTR IOU includes five IOU subunits that correspond to the upper (UTR-upper), middle (UTR-middle), and lower (UTR-lower) reaches of UTR; Tinker Creek; and Tims Branch. Also included in the UTR IOU are three relatively small tributary streams: Mill Creek, McQueen Branch, and Crouch Branch. Tinker Creek, Mill Creek, and UTR-upper are largely undisturbed by SRS operations. UTR-middle, UTRlower, Tims Branch, Crouch Branch, and McQueen Branch are potentially impacted by SRS waste sites or industrial operations. Assessment of the ecological effects of contaminants in the SRS IOUs involves (1) the measurement of contaminant levels in sediment, fish, crayfish, and surface water; (2) the use of contaminant exposure models that estimate potential contaminant doses to ecological receptors; and (3) field bioassessments of the fish and invertebrate assemblages inhabiting SRS streams. The data generated by these studies provide a broad basis for a weight-of-evidence characterization of the extent and severity of contaminant related ecological impacts on SRS aquatic ecosystems.