Second report on the Oak Ridge Y-12 Plant fish kill for Upper East Fork Poplar Creek

This report summarizes the monitoring of fish kills in upper East Fork Poplar Creek (EFPC) from July 1990 to June 1993. Since the opening of Lake Reality (LR) in 1988, total numbers of fish inhabiting upper EFPC have increased. However, species diversity has remained poor. Water quality data have been collected in upper EFPC during the time period covered in this report. Total residual chlorine (TRC) levels have exceeded federal and state water quality criteria over the years. However, with the installation of two dechlorination systems in late 1992, TRC levels have been substantially lowered in most portions of upper EFPC. By June 1993, concentrations of TRC were 0.04 to 0.06 mg/L at the north-south pipes (NSP) and below detection limits at sampling station AS-8 and were 0 to 0.01 mg/L at the inlet and outlet of LR. The daily chronic fish mortality in upper EFPC has been attributed to background stress resulting from the continuous discharge of chlorine into upper EFPC. Mean daily mortality rates for 22 acute fish kills were three fold or more above background and usually exceeded ten fish per day. Total number of dead fish collected per acute kill event ranged from 30 to over 1,000 fish; predominant species killed were central stonerollers (Campostoma anomalum) and striped shiners (Luxilus chrysocephalus). Spills or elevated releases of toxic chemicals, such as acids, organophosphates, aluminum nitrate, ammonia, or chlorine, were identified as possible causative agents; however, a definitive cause-effect relationship was rarely established for any acute kills. Ambient toxicity testing, in situ chemical monitoring, and streamside experiments were used to examine TRC dynamics and ambient toxicity in EFPC