Table 2.1. Stratigraphy of the Vadose Zone Beneath the SX Tank Farm. Stratigraphic Symbol (a) Formation Facies/Subunit Description Genesis Holocene/Fill NA Backfill Poorly sorted gravel to medium sands and silt derived from the Hanford formation (Price and Fecht, 1976a) Anthropogenic Unit H1a-gravelly sand Upper coarse-grained sequence equilvalent to Johnson et al.'s (1999) "Hanford Gravel Unit B" and Sobczyk's (2000) "Hanford Unit B" H1a Unit H1a-slightly silty sand Upper fine sand and silt sequence. Equivalent to "Hanford silty sand" of Sobcyzk (2000) H1 Unit H1 Lower coarse-grained sequence equivalent to "Gravel Unit A" described by Johnson et al. (1999) and "Hanford Unit A" described by Sobcyzk (2000).

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This revision of PNNL-13895 is an updated version of the original document. The changes in this document include the addition of K d data for iodide and uranium that became available during fiscal year 2003. Supplementary data are also included regarding the sediment and solution characteristic used in the studies. This document compiles in a single source the K d values measured with Hanford sediment for radionuclides and toxic compounds that have the greatest potential for driving risk to human health and safety in the vadose zone and groundwater at the Hanford Site. A small number of available K d values that had limited documentation and could not be readily evaluated were excluded from this compilation. In addition to the actual K d values, all significant experimental parameters and solution and sediment characterization data associated with these K d values have been compiled and documented as part of this task. These data will be compiled and made available on a site wide database. This database will be periodically updated as new data become available.

This report was revised in September 2008 to remove acid-extractable sodium data from Tables 4.14, 4.16, 5.20, 5.22, 5.43, and 5.45. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in February 2002. The overall goal of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc. asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediment from within the S-SX Waste Management Area. This report is one in a series of four reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from Resource Conservation and Recovery Act (RCRA) borehole bore samples and composite samples.

Executive SummaryThis report was revised in September 2008 to remove acid-extractable sodium data from Table 4.22. The data was removed due to potential contamination introduced during the acid extraction process. The remaining text is unchanged from the original report issued in 2002.The overall goal of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc., asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediments from within Waste Management Area B-BX-BY. This report is the first in a series of four reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from borehole 299-E33-45 installed northeast of tank BX-102.This report also presents interpretation of the data in the context of the sediment lithologies, the vertical extent of contamination, the migration potential of the contaminants, and the likely source of the contamination in the vadose zone, perched water and groundwater east of the BX tank farm. The information presented in this report supports the Waste Management Area B-BX-BY field investigation report prepared by CH2M HILL Hanford Group, Inc. (a) Overall, the analyses identified common ion exchange and heterogeneous (solid phase-liquid solute) precipitation reactions as two mechanisms that influence the distribution of contaminants within that portion of the vadose zone affected by tank liquor. Significant indications of caustic alteration of the sediment mineralogy or porosity were not observed, but slightly elevated pH values between the depths of 79 to 141 ft below ground surface (bgs) were observed. X-ray diffraction measurements indicate no evidence of mineral alteration or precipitation resulting from the interaction of the tank liquor with the sediment. However, no samples were studied by scanning electron microscopy, a more sensitive technique for searching for faint evidence of caustic attack.The analyses do not firmly suggest that the source of the contamination in the groundwater east of the BX tank farm is the 1951 overfill event at tank BX-102. However, evidence is convincing that the fluids from the overfill event are present in the vadose zone sediments at borehole 299-E33-45 to a depth of 170 ft bgs.The near horizontally bedded, northeasterly dipping sediment likely caused horizontal flow of the migrating contaminants. At borehole 299-E33-45, there are several fine-grained lenses within the Hanford H2 unit at 74.5, 120, and 167 ft bgs that likely cause some horizontal spreading of percolating fluids. The 21-ft thick Plio-Pleistocene fine-grained silt/clay unit is also an important horizontal flow conduit as evidenced by the perched water zone between 227 and 232 ft bgs.The following are the key findings of the detailed characterization o...