Toxicity monitoring uses U.S. Environmental Protection Agency (EPA) approved methods with Ceriodaphnia dubia and fathead minnows to provide systematic information that is used to verify biological water quality of EFPC at intervals throughout the year. Ceriodaphnia tests are conducted quarterly for two sites near Y-12 (EFK 23.8 and EFK 24.1). In addition, quarterly toxicity tests with fathead minnows and Ceriodaphnia are conducted at Outfall 201 as required by the Y-12 Plant's National Pollutant Discharge Elimination System (NPDES) permit.
|Recent results (Figure 1) show no evidence for toxicity in any of the 1998 Ceriodaphnia or fathead minnow tests of Outfall 201.|
|These results are consistent with other Ceriodaphnia and fathead minnow test results since flow management was instigated in the latter half of 1996.|
|Figure 1. No-observed-effect-concentration (NOEC, %) for toxicity tests of water from Outfall 201 using fathead minnows (FHM) and Ceriodaphnia (CD), before and after flow management.|