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

Oak Ridge Reservation
Fig. 5.34. Mean concentrations of mercury (µg/g, ± standard error, N = 6) in
muscle tissue of sunfish and bass from White Oak Creek (WCK 3.9, WCK 2.9) and
White Oak Lake (WCK 1.5), 1998–2009. WCK = White Oak Creek kilometer
sampled for the first time in 2007) averaged 0.38 µg/g in 2009, significantly lower than in previous years.
Mean PCB concentrations in redbreast sunfish at WCK 3.9 were also significantly lower in 2009
(0.30 µg/g ) than in 2008 (0.66 µg/g). This apparent decrease may be because the fish collected in 2009
were significantly (approximately 20% by weight) smaller than in 2008. In contrast, mean PCB
concentrations in fish from WCK 2.9 increased from 0.26 in 2008 to 0.43 µg/g in 2009 despite no
difference in the average size of the fish collected between the two years (Fig. 5.35).
Benthic Macroinvertebrate Communities. Monitoring of benthic macroinvertebrate communities in
WOC, First Creek, and Fifth Creek continued in 2009. Additionally, monitoring of the macroinvertebrate
community in lower Melton Branch continued under the Water Resources Restoration Program. Benthic
macroinvertebrate samples are collected at sites upstream and downstream of the influence of ORNL
operations; reference sites for WOC, First Creek, and Fifth Creek are used as references for the Melton
Branch site (Melton Branch kilometer [MEK] 0.6). The objectives of this activity are to (1) help assess
ORNL’s compliance with the current NPDES permit requirements and (2) evaluate and verify the
effectiveness of pollution abatement and remedial actions taken at ORNL.
The benthic macroinvertebrate communities in First Creek, Fifth Creek, and WOC downstream of
effluent discharges have recovered significantly since 1987, but community characteristics indicate that
ecological impairment remains (Figs. 5.36, 5.37, and 5.38). Relative to reference sites, the metrics total
taxonomic richness (i.e., the number of different species per sample) and richness of the pollutionintolerant
taxa (i.e., mayflies, stoneflies, and caddisflies or Ephemeroptera, Plectoptera, and Trichoptera
[EPT] richness) continue to be lower at sites adjacent to and downstream of the main ORNL campus.
Reductions in metric values observed at FFK 0.2 in 2008 persisted in 2009, providing stronger evidence
that an additional stress (or stresses) occurred after April 2007. In 2008, FCK 0.1 had exhibited reductions
in metric values comparable to those at FFK 0.2, but increases in metric values in 2009 indicate that the
change in 2008 was either a response to a limited but significant disturbance associated with facility
5-62 Oak Ridge National Laboratory