Final Report for Targeted Investigations at Murdock, Nebraska, in 2004. Page: 35 of 253
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Targeted Investigation at Murdock, Nebraska
Version 00, 09/03/04 3-3
fill at about 1 ft below ground level (BGL) and (2) either topsoil or clay with graded humic
staining at about 3 ft BGL.
The near-surface soil samples were placed in jars, sealed, preserved on dry ice, and
shipped to the Applied Geosciences and Environmental Management (AGEM) Laboratory at
Argonne National Laboratory for analysis. The samples were analyzed (Argonne 2002,
Section 6.3.1) by (1) a headspace method with a gas chromatograph and electron capture detector
(GC-ECD; modified EPA Method 5021) and (2) a purge-and-trap sample preparation method
with analysis on a GC-MS system (EPA Methods 5030B and 8260B).
The headspace analysis was used to achieve the low detection limits required to evaluate
possible contaminant distribution patterns, for use in guiding subsurface soil sampling. The
results of the headspace analyses for shallow (1 ft BGL) and deeper (3 ft BGL) near-surface soils
are mapped in Figures 3.2 and 3.3, respectively, and presented in Appendix B, Table B.1. These
results are discussed in Section 4.4.1. Low concentrations of carbon tetrachloride were detected
by headspace analysis in soils from both depth intervals across much of the site, most commonly
in association with the locations of the former grain storage bins and with pavements.
The purge-and-trap data were used to support risk assessment calculations for the near-
surface soils (Section 4.4.3). The results of these purge-and-trap analyses are in Appendix B,
Table B.1. Neither carbon tetrachloride nor chloroform was detected above a quantitation limit
of 10 g/kg in any of the near-surface soils prepared by the purge-and-trap method and analyzed
with the GC-MS system.
3.2.2 Contaminant Data for Subsurface Soils
Subsurface soil samples collected during this investigation were analyzed to provide a
preliminary indication of carbon tetrachloride and chloroform levels remaining in the deep
vadose zone beneath the northern portion of the former CCC/USDA facility.
The deeper soil sampling locations were selected on the basis of the distribution of
relatively higher carbon tetrachloride levels observed in the headspace analyses of the near-
surface soils. Three sampling locations were proposed in a letter report (Argonne 2004)
submitted to the CCC/USDA and the EPA on June 18, 2004. Vertical-profile soil sampling was
performed at two proposed locations (SB85 and SB86, Figure 3.1) on June 28-29, 2004.
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LaFreniere, L. M. Final Report for Targeted Investigations at Murdock, Nebraska, in 2004., report, August 1, 2005; Argonne, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc786872/m1/35/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.