DOE/ORO/2327 Oak Ridge Reservation Annual Site Environmental ...

Oak Ridge Reservation
Fig. 3.48. Major storm water outfalls and biological monitoring locations on Mitchell Branch.
Clams from the Mitchell Branch watershed were
analyzed for mercury (both total mercury and methyl
mercury) in 2009 for the first time in many years
(Table 3.39). Although mercury was detected in all
clams, the highest levels of mercury were found in the
clams from SD-190 (62.6 ng/g total mercury) and
below SD- 170 at MIK 0.5(56.9 ng/g total mercury).
Mercury levels decreased downstream from SD-190.
Methyl mercury concentrations in clams from
Mitchell Branch ranged from 20%-40% of the total
mercury concentration with the highest levels of
methyl mercury being found in the clams from MIK
Fig. 3.49. Water flea Ceriodaphnia dubia.
0.5 (15.0 ng/g) and MIK 0.4 (14.4 ng/g)
Fish were collected from K-1007-P1 Pond
(Fig. 3.51) in February 2009. The fish were collected earlier than usual because of the remediation
activities planned for the pond. Fish were also collected from Mitchell Branch and K-901-A Pond in May
2009 (Table 3.39). Largemouth bass were collected from the pond sites, and redbreast sunfish (Fig. 3.52)
were collected from Mitchell Branch. Game fish of a size typically caught by sports fishermen were
selected both to provide more accurate data of potential human health concerns, and to reduce the amount
of variation in contamination levels in the individual fish due to age and size differences. Fillets were
taken from each game fish and analyzed for PCBs. Results from all three monitoring locations were lower
than last year’s results, but the relative spatial results were similar to those of historical results. The fish
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