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Previous work on the CT plume in the Hanford Site 200 West Area indicates that 65% of approximately 750,000 kg of CT that was delivered to the ground as a result of plutonium processing remains unaccounted for. In addition, the results of groundwater monitoring have been used to suggest that persistent sources of CT may be feeding the contaminant plume in the aquifer. Report Scope This report documents two separate geostatistical studies performed by researchers from Pacific Northwest National Laboratory (PNNL) to evaluate the CT plume in the groundwater. The first chapter of the report examines and evaluates a number of potential continuing source locations within the unconfined aquifer that had been identified in the 200 West Area by Fluor Hanford, Inc. (FH), based on locally elevated carbon tetrachloride groundwater concentrations. FH requested that PNNL perform a geostatistical study of the persistence of CT groundwater concentration values over time in those areas. This work was completed in 2005, and a letter report describing the work was sent to FH. The first chapter of this report is a reformatted version of that letter report, with no update of the analysis. The second chapter of this report followed from a request by FH that PNNL re-evaluate the inventory of CT in the unconfined aquifer in the 200 West Area and perform a 3D geostatistical study of the deep CT groundwater concentration values available in the area. An initial study was completed as a letter report to FH in January 2006, based on depth-discrete data collected during the drilling process. The second chapter of this report documents an updated version of that study, incorporating additional data available through November 2006 and also incorporating 3D concentration data from existing wells collected using packers to attempt to isolate and sample restricted depth intervals in the wells.

Chum salmon Oncorhynchus keta and fall Chinook salmon O. tshawytscha segregate spatially during spawning in the Ives Island side channel of the lower Columbia River downstream from Bonneville Dam. Previous research during one spawning season (2000) suggested that these species selected spawning habitats based on differences in hyporheic temperature and vertical hydraulic gradient (VHG). In this study we confirmed the spatial segregation of spawning based on hyporheic characteristics over 4 years (2001)(2002)(2003)(2004) and examined the effects of load-following operations (power generation to meet short-term electrical demand) at Bonneville Dam on hyporheic function and characteristics. We found that during the study period hyporheic temperature and VHG in chum salmon spawning areas were highly variable during periods of loadfollowing operation, when river levels fluctuated. In contrast, hyporheic water temperature and VHG within chum salmon spawning areas fluctuated less when river levels were not changing owing to load-following operation. Variable temperature and VHG could affect chum and fall Chinook salmon spawning segregation and incubation success by altering the cues each species uses to select redd sites. Additional research will be required to fully assess the effects of load-following operations on the hyporheic environment, spawning site selection, and incubation success of chum and fall Chinook salmon downstream from Bonneville Dam.

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SummaryThis report documents a preliminary spatial and geostatistical analysis of the distribution of several contaminants of interest (COIs) in groundwater within the unconfined aquifer beneath the 200 West Area of the Hanford Site. The contaminant plumes of interest extend within the 200-ZP-1 and 200-UP-1 groundwater operable units. CH2M HILL Plateau Remediation Company (CHPRC) currently is preparing a plan that identifies locations for groundwater extraction wells, injection wells, transfer stations, and one or more treatment facilities to address the contaminants of concern identified in the 200-ZP-1 CERCLA Record of Decision. To accomplish this, Fluor Hanford, Inc. (the previous site contractor) requested that Pacific Northwest National Laboratory (PNNL) provide numerical models of the three-dimensional distribution of selected COIs throughout the 200 West Area groundwater. The COIs included in the PNNL study were carbon tetrachloride (CTET), technetium-99 (Tc-99), iodine-129 (I-129), chloroform, plutonium, uranium, trichloroethylene (TCE), and nitrate.The project included three tasks. Task 1 involved the development of a database that includes all relevant depth-discrete data on the distribution of COIs in the study area. The database includes well construction information, well sample data for the COIs named above, fields describing the sources of the data, and data quality flags. The database includes all forms of the COIs identified above-for example, all plutonium and uranium isotopes included in the Hanford Environmental Information System, as well as total uranium and all forms of nitrate and chromium. The concentration and activity values summarized in the resulting tables of the Microsoft Access database are considered final for carbon tetrachloride, chloroform, and Tc-99 and were used in the subsequent analysis and mapping (Tasks 2 and 3). However, further work will be needed to transform and select concentrations for some of the other COIs when multiple forms of a COI are present in the database (e.g., chromium, nitrate, and uranium are present in multiple forms). In addition, some uranium and uranium-238 data in the database are measured in picocuries per liter and will need to be converted to micrograms per liter. The appendix to this report contains several electronic files that document in detail the data sources, transformations, and selections that were performed in assembling the database, as well as a copy of the database itself.The second task involved a spatial analysis of the three-dimensional (3D) distribution of data for the COIs in the study area. The main focus of the task was to determine if sufficient data are available for geostatistical mapping of the COIs in 3D. The results of that study indicate that sufficient data are available for 3D mapping of CTET, chloroform, and Tc-99 using geostatistical methods. Although the conclusions are preliminary, the number of data that appear to be available for the other COIs is much lower; geostatistical mapping of those COIs in 3D may not ...