PNNL-14702, Rev. 1 Vadose Zone Hydrogeology Data Package for Hanford Assessments G. V. Last G. W. Gee E. J. Freeman W. E. Nichols K. J. Cantrell B. N. Bjornstad M. J. Fayer D. G. Horton June 2006 Prepared for the U.S. Department of Energy under Contract DE-AC05-76RL01830 DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor Battelle Memorial Institute, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. 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Box 62, Oak Ridge, TN 37831-0062; ph: (865) 576-8401 fax: (865) 576-5728 email: [email protected] 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: [email protected] online ordering: http://www.ntis.gov/ordering.htm This document was printed on recycled paper. PNNL-14702, Rev. 1 Vadose Zone Hydrogeology Data Package for Hanford Assessments G. V. Last G. W. Gee E. J. Freeman W. E. Nichols K. J. Cantrell B. N. Bjornstad M. J. Fayer D. G. Horton June 2006 Prepared for the U.S. Department of Energy under Contract DE-AC05-76RL01830 Pacific Northwest National Laboratory Richland, Washington 99352 Preface This data package was originally prepared to support a 2004 composite analysis (CA) of low-level waste disposal at the Hanford Site. The Technical Scope and Approach for the 2004 Composite Analysis of Low-Level Waste Disposal at the Hanford Site (Kincaid et al. 2004) identified the requirements for that analysis and served as the basis for the data collection effort documented in this data package. Comple- tion of the 2004 CA was later deferred, and the 2004 Annual Status Report for the Composite Analysis of Low-Level Waste Disposal in the Central Plateau at the Hanford Site (DOE 2005) indicated that a comprehensive update to the CA was in preparation and would be submitted in 2006. However, the U.S. Department of Energy (DOE) has recently decided to further defer the CA update and will use the cumulative assessment currently under preparation for the environmental impact statement (EIS) being prepared for tank closure and other site decisions as the updated CA. Submittal of the draft EIS is currently planned for FY 2008. Acknowledgments The authors would like to acknowledge Thomas W. Fogwell and the Groundwater Remediation Project managed by Fluor Hanford, Inc. for supporting this work. We would like to thank Raziuddin Khaleel (Fluor Federal Services), and Charles T. Kincaid, Christopher J. Murray, Stephen P. Reidel, R. Jeffery Serne, and Robert W. Bryce for their technical reviews. The authors would also like to thank Anderson L. Ward for his technical support throughout the completion of this work, and Christopher A. Newbill for preparation of the site location map. We would also like to thank Launa F. Morasch for her technical editorial support, Kathy R. Neiderhiser, Shannon B. Neely, and the rest of the Publication Design team for their support in producing this document. iii Executive Summary This data package documents the technical basis for selecting physical and geochemical parameters and input values that will be used in vadose zone modeling for Hanford assessments. This work was originally conducted as part of the Characterization of Systems Task of the Groundwater Remediation Project managed by Fluor Hanford, Inc., Richland, Washington, and revised as part of the Characteri- zation of Systems Project managed by the Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy, Richland Operations Office (DOE-RL). This data package describes the geologic framework, the physical, hydrologic, and contaminant transport properties of the geologic materials, and deep drainage (i.e., recharge) estimates, and builds on the general framework developed for the initial assessment conducted using the System Assessment Capability (SAC) (Bryce et al. 2002). The general approach for this work was to update and provide incremental improvements over the previous SAC data package completed in 2001. As with the previous SAC data package, much of the data and interpreted information were extracted from existing documents and databases. Every attempt was made to provide traceability to the original source(s) of the data or interpretations. Kincaid et al. (2004) identified 1,052 waste sites from the Waste Information Data System (WIDS) sites and several existing and future storage sites for inclusion in Hanford assessments, with analyses to be conducted on a site-by-site basis whenever inventory and release data permit.1 The complexity of these assessments, together with the lack of detailed characterization data for some of the fine-scale fate and transport processes necessitates simplification of site features, release events, and contaminant fate and transport processes to those factors considered most dominant. The dominant factors affecting modeling of transport of contaminants through the vadose zone include: (1) waste inventory and release estimates, (2) estimates of deep drainage (recharge), (3) the hydrogeologic profiles and properties of the vadose zone affecting aqueous phase advection and dispersion, and (4) estimates of geochemical reactions (e.g., sorption and precipitation) affecting the retardation of contaminants. The last three of these data types are addressed by this data package. The first one, waste inventory and release estimates, is addressed in the inventory and release model data packages. Many large scale Hanford assessments will generally use a one-dimensional vadose zone model for computational efficiency (although the SAC framework is not inherently limited to a one-dimensional representation), configured to account for lateral spreading, and in selected cases, conditioned against multi-dimensional model results (Kincaid et al. 2004). In this report, and that of Kincaid et al. (2004), waste sites are grouped into a number of geographic areas assumed to have similar hydrogeologic structure and properties. Hydrogeologic units were identified and their thickness specified for each of these hydrogeologic provinces. To account for uncertainty in the model parameters, a stochastic distribution was developed for each process model parameter for each hydrogeologic unit. 1 Originally 974 of 2,730 Waste Information Data System (WIDS) sites were identified for inclusion in a large-scale Hanford assessment. Further work identified 48 more waste sites bringing the total to 1,022. Subsequent reviews identified an additional 30 sites that have been included, many of which account for offsite transfers of waste and nuclear material. This brings the total to 1,052. v The vadose zone hydrostratigraphic profiles and hydrogeochemical property distributions for Hanford assessments are represented by 30 generalized one-dimensional vertical columns representing 17 general geographic areas and 13 site-specific locations. Each hydrostratigraphic profile (template) is configured with the hydraulic and geochemical parameters necessary to simulate the flow and transport through the vadose zone using the Subsurface Transport Over Multiple Phases (STOMP) code (White and Oostrom 2000). As many as five variations of a single hydrostratigraphic template are incorporated for some geographic areas in order to more accurately represent the depth of waste release, the thickness of the vadose zone beneath the point of release, and variations in contaminant distribution coefficients (Kd values) associated with different waste chemistry designations. Each template represents the vadose zone using a few major hydrostratigraphic units that are treated as horizontal layers with constant thicknesses, and that are homogeneous and isotropic. Hydraulic and geochemical parameters for each hydrostrati- graphic unit are represented by stochastic distributions to facilitate sensitivity and uncertainty analyses. This data package is a compilation of the data available to support Hanford assessments. As site characterization is completed at waste sites, and as investigations into contaminant behavior are completed, the uncertainty in this information will be reduced and, as a result, the uncertainty in future assessments will be reduced. vi Contents Executive Summary............................................................................................................................... iii Preface ..................................................................................................................................................