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

Oak Ridge Reservation
Fig. 5.19. ORNL surface water, National Pollutant Discharge Elimination System,
and reference sampling locations.
Expressing radioactivity concentrations as percentage of the DOE DCG values is used in this section
as a means of comparing effluent points with different radioisotope signatures. Annual average
concentrations were compared with DCG concentrations where applicable (there are no DCGs for gross
alpha and gross beta activities) and when at least one individual measurement indicated detectable activity
(i.e., at least one individual measurement had a concentration greater than or equal to the measurement’s
minimum detectable activity [MDA]). For analyses that cannot differentiate between two radioisotopes
(e.g., 89/90 Sr), and for radioisotopes that have more than one DCG for different gastrointestinal tract
absorption factors, the most restrictive (lowest) DCG was used in the comparisons. DCGs are not
intended to be thresholds for instream values as they are for effluents, but are nonetheless useful as a
frame of reference. Effluents and instream concentrations are compared to DCGs that were calculated for
exposures to humans by ingesting water, but their use in this section does not imply that ORNL effluents
or ambient waters are sources of drinking water.
In 2009, there were no measured annual average concentrations of radioactivity that exceeded 100%
of DCG concentrations. The annual average concentration of at least one radionuclide exceeded 4% of the
relevant DCG concentration in dry-weather discharges from eight NPDES outfalls (080, 085,204, 241,
302, 304, X01, and X12) and at instream sampling locations X13, X14, and X15. Four percent of the
DCG is roughly equivalent to the 4-mrem dose limit on which the EPA radionuclide drinking water
standards are based (4% of a DCG is a convenient comparison point, but it should not be concluded that
ORNL effluents or ambient waters are direct sources of drinking water) (Fig. 5.20).
The total annual discharges (or amounts) of radioactivity measured in stream water at WOD, the final
monitoring point on WOC before the stream flow leaves ORNL, were calculated from concentration and
flow. Results of those calculations for each of the past 5 years are shown in Figs. 5.21 through 5.25.
CY 2009 discharges at White Oak Dam continue to be generally decreased in comparison to years
5-52 Oak Ridge National Laboratory