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

Annual Site Environmental Report
concentration data for iron exhibiting a statistically significant increasing trend. It is likely that these
metals are sorbed onto suspended solids in the samples contributing to the exceedance of the reference
standards. Other metals were detected at low concentrations in groundwater samples collected from
Northwestern Discharge Area in 2009 and results are provided in the 2009 Environmental Monitoring
Results (DOE 2009). Detection limits for several undetected semi-volatile organic compounds (atrazine,
benzo(a)pyrene, hexachlorobenzene, and pentachlorophenol) exceeded reference standards. Diethyl
phthalate was detected at a low, estimated concentration in a sample collected from well 535. Plastic well
casing materials used in the construction of the well may explain the presence of the phthalate in the
sample. Toluene was also detected at low, estimated concentrations in samples collected from well 535 in
2009.
Southern Discharge Area Exit Pathway Results
Monitoring point S-01 was sampled by UT-Battelle in March 2009, but no samples were collected
during the dry season sampling event (August 2009) because the monitoring point was dry. Monitoring
point S-02 was sampled in March and August 2009.
No radiological parameters exceeded reference standards at either monitoring point; however, low
concentrations of 214 Bi and 214 Pb were detected in the sample collected from S-01, and gross alpha and
beta were detected in samples collected from S-02.
Concentrations reported for iron, aluminum, manganese, and lead concentrations exceeded reference
standards at S-02 during 2009. It is likely that these metals are sorbed onto suspended solids in the
groundwater samples collected contributing to the exceedance of the reference standards. Other metals
were detected at low concentrations in groundwater samples collected from Southern Discharge Area in
2009; these results can be viewed in the 2009 Environmental Monitoring Results (DOE 2009).
Detection limits for several undetected semi-volatile organic compounds (atrazine, benzo(a)pyrene,
hexachlorobenzene, and pentachlorophenol) exceeded reference standards. Acetone was detected in a
blank sample associated with samples collected from S-02. Subsequent to collection of the 2009
groundwater samples, acetone was found to be present in the deionized water used in preparing blank
samples. This source of deionized water is no longer used for blank samples or for decontamination of
sampling equipment.
5.6.2.2 Active Sites Monitoring
5.6.2.2.1 Active Sites Monitoring—HFIR
Surveillance monitoring of the HFIR site detected a subsurface release of 3 H from a process waste
drain in the autumn of 2000. At that time, reactor systems were shut down so that the release site could be
identified and repaired. The process waste drain was found to be the source of the release and was
repaired, ending the release of the 3 H to the subsurface. From 2000–2007, monitoring of HFIR-site wells
and subsurface drains was conducted to determine the size and scope of the 3 H plume that was created by
the release. This groundwater monitoring approach was conducted by the UT-Battelle Research Reactor
Division (RRD). The main mass of the 3 H plume was observed to move from the release area to the
south-southeast toward a tributary to Melton Branch and Melton Branch, itself. RRD discontinued routine
monitoring in 2007 based on a history of zero detectable subsurface releases of 3 H from the process waste
drain and observations of steep downward trends in 3 H concentration reductions in samples collected
from monitoring sites down gradient of the release site. The expectation is that 3 H concentrations should
continue to decrease with the possibility of additional precipitation-driven concentration spikes or
drought-induced 3 H concentration stagnation. Although RRD has ceased monitoring the 3 H plume, 3 H
monitoring at HFIR has continued under the auspices of the ORNL Radiological Monitoring Plan. Please
refer to Sect. 5.5 for results of 2009 3 H monitoring at HFIR. All wells used in the RRD groundwater
monitoring program are being maintained for future use as needed.
Oak Ridge National Laboratory 5-79