ph: (865) 576-8401 fax: (865) 576-5728 email: reports@adonis.osti.gov Available to the public from the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, VA 22161 ph: (800) 553-6847 fax: (703) 605-6900 email: orders@ntis.fedworld.gov online ordering: http://www.ntis.gov/ordering.htm Executive Summary 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 at the Hanford Site. To meet this goal, CH2M HILL Hanford Group, Inc. tasked scientists from Pacific Northwest National Laboratory (PNNL) to perform detailed analyses on vadose zone sediments from within Waste Management Area (WMA) C. This report is the first of two reports written to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physiochemical characterization data collected on vadose zone sediment recovered from borehole C4297, installed adjacent to tank C-105, and from borehole 299-E27-22, installed directly north of the C Tank Farm. This report also presents the interpretation of data in the context of sediment types, the vertical extent of contamination, the migration potential of the contaminants, and the likely source of the contamination in the vadose zone below the C Tank Farm. The information presented in this report supports the WMA A-AX, C, and U field investigation report in preparation by CH2M HILL Hanford Group, Inc. Sediments from borehole 299-E27-22 were characterized for their potential to be used as background (i.e., uncontaminated) sediments against which to compare contaminated sediments during the C Tank Farm characterization effort. Upon analysis of sediment samples from borehole 299-E27-22, elevated concentrations of chloride, nitrate, sulfate, phosphate, magnesium, calcium, strontium, and sodium were encountered at various depths within the borehole. Although no known spills have been recorded at the location where borehole 299-E27-22 was emplaced, the data strongly suggest the sediment has been contacted by a non-radiological waste stream. While the data from borehole 299-E27-22 are presented within this report, it is not recommended that the data be used holistically as background or baseline values for uncontaminated sediment. Instead, data from a companion report (Lindenmeier et al. 2002), which was an investigation of samples from borehole 299-E33-338, should be used for baseline comparisons. A core log was generated for both boreholes and a geologic evaluation of all core samples was performed at the time of opening. Aliquots of sediment from the borehole core samples were analyzed and characterized in the laboratory for the following parameters: moisture content, gamma-emitting radionuclides, one-to-one sediment:water extracts (which provide soil pH, electrical conductivity, cation, trace metal, and anion data), total carbon and inorganic carbon content, and 8 M nitric acid extracts (which provide a...