1 - paducah environmental information center

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Paducah Site
4. SIGNIFICANiT REVISIONS TO
PREVIOUS PLUME MAPS
source of both TCE and INTc;
The site-wide PGDP plume maps were
last revised in 1998. More recent investigations
provide information in the area of the known and
suspected sources of groundwater contamination
and along the PGDP security fence line. Data sets
added to the OREIS database since the last
revision include the WAG 27 RI (DOE 1999b),
the WAG 28 RI (DOE 2000a), the Sitewide
Evaluation for Source Areas Contributing to Off­
Site Groundwater Contamination (DOE 2000b),
and the WAG 8 Site Evaluation (DOE 2000c).
These additional data have permitted
confirmation and enhanced definition of the
Southwest PluW~ as well as refinements to the
distribution of contaminants on-site and
identification of five new potential source areas.
The soil borings of the Sitewide Evaluation for
Source Areas Contributing to Off-Site
Groundwater Contamination (DOE 2000b), in
particular, provided contaminant profiles with
depth in the area of a main effluent ditch in the
north-central area of the PGDP, the North/South
Diversion Ditch, and filled gaps in a transect
around the east, north, and west sides of the
plant. These analyses appear to define a distinct
plume of both TCE and 99Tc that is sourced in the
north-central area of the plant, near the C-616
effluent clarifier, and migrates to the northeast.
The following list highlights the significant
revisions to the previous plume maps:
• New potential source area - C-746~
C area (Sitewide Evaluation)
interpreted to contribute to Northeast
Plume,
maximum concentrations measured -
2200 Ilg/L TCE and 1500 pCiIL 9\1Tc;
• New potential source area - C-310
Building area (WAG 28)
interpreted to contribute to Southwest
Plume,
maximum concentrations measured
330 Ilg/L TeE and 1390 pCiIL 99Tc;
o New potential source area - C-410
Building area (Data reinterpretation)
interpreted to contribute to Northeast
Plume;
• New potential source area - Kellogg
Building Pad (SWMU 99) (WAG 28)
MW256 adjacent to pad indicates
increase in 99Tc levels in RGA;
soils data from WAG 28 suggest that
equipment stored on pad may be source;
. • Confirmation and definition of
Southwest Plume (WAG 27 RI I Sitewide
Evaluation)
confirmed suspected existence of
separate Southwest Plume,
defined extent of plume,
maximum concentrations measured -
to,OOO Ilg/L TCE and 3710 pCiIL 99Tc;
• New potential source area -
northeast of Oil Landfarm [Solid Waste
Management Unit (SWMU) 1] (Sitewide
Evaluation)
primary source for Southwest Plume,
• "Depleting source" for Northeast
Plume - northwest comer of C-333
(WAG 28)
TCE concentrations in PZ118 declined
from 6700 to toOOIlg/L since Phase IV
investigation;
TCE concentrations in MW255 and
MW258 dropped by approximately 50%
over same period.
The following subsections describe the
main revisions to the groundwater plume maps
and contaminant trends.
0-4
Appendix 0