Spatial Analysis of Contaminants in 200 West Area Groundwater in Support of the 200-ZP-1 Operable Unit Pre-Conceptual Remedy Design

Abstract

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 ...

Revised Geostatistical Analysis of the Inventory of Carbon Tetrachloride in the Unconfined Aquifer in the 200 West Area of the Hanford Site

“…The stochastic simulations of CTET and chloroform used to generate the revised inventory estimates were generated for the mapping project, and details of the data and spatial and geostatistical analysis that form the basis for those simulations are described in a separate report (Murray and Bott 2008). For completeness, a brief summary of the methodology and results of the mapping project are presented here.…”

“…A Microsoft Access database developed for the mapping project includes all relevant depth-discrete data on the distribution of CTET and chloroform, as well as other COIs, in the study area (Murray and Bott 2008). Data sets from several sources were included in the database: the 200-ZP-1 Remedial Investigation data set; the 200-ZP-1 Feasibility Study data set; depth-discrete CTET and chloroform data sets evaluated by V. J. Rohay at CHPRC; and a retrieval of the most recent data available in the Hanford Environmental Information System.…”

“…Murray and Bott (2008) describe the procedures and assumptions used to establish the well and sample elevations, the elevation of the water table, and the DBWT for each sample.…”

“…Section 3 of Murray and Bott (2008) provides a detailed description of the univariate and spatial distribution of the depth-discrete CTET and chloroform data. Both CTET and chloroform are strongly skewed, with mean concentration values much higher than the median concentrations.…”

“…Fluor Hanford, Inc. (FH) (the previous site contractor) requested that PNNL update that inventory estimate using as input a set of geostatistical realizations of CTET and chloroform recently created for a related but separate project (Murray and Bott 2008) In this report, Section 2 describes the approach used for generation of the inventory estimates. The results of the estimation process are presented in Section 3.…”