Characterization of Vadose Zone Sediments from C Waste Management Area: Investigation of the C-152 Transfer Line Leak

Abstract

Executive SummaryThe 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 Hanford. To meet this goal, CH2M HILL Hanford Group, Inc., tasked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediments from within waste management area (WMA) C. Specifically, this report contains all the geologic, geochemical, and selected physiochemical characterization data compiled on vadose zone sediment recovered from direct-push samples collected around the site of an unplanned release (UPR), UPR-200-E-82, adjacent to the 241-C-152 Diversion Box located in WMA C.UPR 200-E-82 was a waste-loss event near the 241-C-152 Diversion Box that occurred in December 1969 and involved the loss of approximately 2,600 gallons of cesium-137 recovery process feed solution (Wood et al. 2003). The leak event created a temporary ground-surface puddle measuring 100 gallons in volume, which was quickly covered over with clean gravel. It is estimated that 11,300 Ci of cesium-137, 18.3 kg of uranium, and 5.01 Ci of technetium-99 were released to the subsurface.An initial geologic/geochemical investigation in the vicinity of UPR-200-E-82 was performed using pairs of direct-push probe holes. A total of 41 vertical direct pushes extending to approximately 60 ft below ground surface (bgs) were completed between July and September 2005 to characterize vadose zone moisture and the distribution of contaminants. Twenty vadose zone sediment sample sets, containing one or two core samples in stainless-steel liners and one grab sample, were delivered to the laboratory for characterization and analysis. The sediments were collected around the documented location of the C-152 pipeline leak (UPR-200-E-82) and created an approximately 120-ft-diameter circular pattern around the waste site.A second series of six probe holes were emplaced around the site of the pipeline leak between March and June 2006. Unlike their 2005 vertical counterparts, these probe holes were driven at angles of 30º, 45º, or 60º from horizontal, and extended to approximately 80 ft bgs. Up to three sets of samples (1.5 ft of core plus material recovered from the drive shoe) were retrieved from each slant probe hole. The goal of this operation was to collect a sample at depth from directly beneath the projected site of the pipeline leak.A core log was generated for both sets of samples and a visual geologic evaluation of all liner samples was performed at the time of sample processing. Aliquots of sediment from the liners were analyzed and characterized in the laboratory for the following parameters: moisture content, gammaemitting radionuclides, one-to-one sediment:water extractions (which provided soil pH, electrical conductivity, cation, trace metal, and anion data), total carbon and inorganic carbon content, and 8-M nitric acid leaches (which provided a measure of the total leachable contaminant content in the sediment). Two key ra...

Geochemical Characterization Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

“…Geochemical Characterization: Sediments Contaminated from the C-152 Transfer Line Leak Brown et al (2007a) presents the results of a geochemical investigation of sediment samples taken near the C-152 transfer-line leak. Specifically, their report contains all the geologic, geochemical, and selected physicochemical characterization data compiled on vadose zone sediment recovered from direct-push samples collected around the site of an unplanned release (UPR), UPR-200-E-82, adjacent to the 241-C-152 Diversion Box located in WMA C. Characterization probe holes locations are shown in Figure 3.12.…”

“…After evaluating all the characterization and analytical data, Brown et al (2007a) concluded that the vadose zone surrounding the C-152 pipeline leak site had been contaminated by tank-related waste. The two regions that contained the largest amount of contaminants, either in concentration or by occurrence of several key constituents/contaminants of concern, were located: 1) between the 241-C-151 and 241-C-152 Diversion Boxes, and 2) west of the C-153 Diversion Box.…”

“…The samples collected for study by Brown et al (2007a) were retrieved as close as possible to the cap overlying the pipeline leak site, as well as directly beneath the projected leak point. Collectively, the data indicate that the bulk of the activity associated with the leak event (i.e., 137 Cs) is constrained to the shallow vadose zone in close proximity to the discharge point.…”

“…Tier III testing is reserved for analyses and experiments that will provide detailed information on the type of contamination present (e.g., element oxidation state or its physical/ chemical state within the sample), as well as information on the transport properties of the contaminants. Detailed information about the specific tests performed during each tier of analysis is included in several reports (Lindenmeier et al 2002(Lindenmeier et al , 2003Serne et al , 2002e, 2004aBrown et al 2005Brown et al , 2006aBrown et al , 2007aBrown et al , 2007b and procedures (EPA 1984(EPA , 2000a(EPA , 2000b(EPA , 2000cASA 1996;ASTM 1998;USGS 2001). (Cantrell et al 2007) summarizes the most current and relevant information regarding geochemical processes that impact contaminant transport at the Hanford Site in general, but with a focus on vadose zone sediments beneath the SST waste management areas (WMAs) and the IDF at the Hanford Site.…”