Vadose Zone Transport Field Study FY 2003 Test Plan
Conceptual models have been identified as one of the sources of uncertainty in the interpretation and prediction of contaminant migration through the vadose zone at Hanford. Current conceptual models are limited partly because they often do not account for the random heterogeneity that occurs under the extremes of very nonlinear flow behavior typical of the Hanford vadose zone. Over the last two years significant progress has been made in characterizing physical heterogeneity and in the development of techniques for incorporating this heterogeneity into predictive and inverse models for field-scale subsurface flow. One of the remaining pieces of the puzzle is the impact of heterogeneity on the distribution of reactive contaminants. Reactive transport occurs over a wide range of spatial and temporal scales. However, the manner in which the various subsurface physical and chemical processes interact to influence transport is not very well understood. Hydrogeologic characterization and model analysis, however, have traditionally focused on measurement of physical properties and predicting the effects of variability in these properties on flow and transport. As a result, the role of geochemical heterogeneity on solute transport has remained largely unexplored. This project will use a combination of geophysical and soil physics techniques to investigate the infiltration and redistribution of water and reactive tracers in a controlled field experiment at the Army loop Road clastic dike site. In the FY2003 tests, surface deployed ground penetrating radar will be used to identify the discrete three-dimensional pattern of horizonation and small-scale heterogeneities that characterize the test site and to develop a lithofacies map. The transect will be instrumented to allow water to be applied along its length from a line source. Local-scale water content, matric potential, and tracer concentrations will be monitored as a function of spatial scale by multipurpose TDR probes and suction lysimeters. The tension infiltrometer will be used to measure mobile-immobile parameters. The resulting data will used characterize fine-scale heterogeneity as well as correlation lengths of hydraulic and transport parameters. Tracer breakthrough data will be used to determine longitudinal and transverse dispersivities and their scale dependence. Parameters will be analyzed to identify a suitable averaging (upscaling) procedure for field-scale infiltration predictions. A combination of in situ permeability, water content and resistivity measurements will be combined with the granulometry and core analysis to quantify hydraulic geochemical properties in the laboratory. These data will be coupled with the field-measured hydraulic and transport parameters and the 3-D lithofacies map to generate a 3-D hydrofacies map of the site that includes the distribution geochemical properties controlling sorption. This map, along with measured distributions of water and solute, will be used to validate a numerical model for forward predictions and the applicability of upscaled parameters to reactive transport processes that typically occur under transient flow and at large spatial and temporal scales. The results of this study will help to bridge the gap between local-scale transport observations and field-scale transport behavior. It will allow validation of recently developed inverse procedures for predicting field-scale parameters and will improve our prediction capability fort reactive transport in heterogeneous sediments at Hanford. The improved conceptualizations will permit the DOE to make defensible corrective and remedial action decisions at Hanford and other waste sites.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 15010200
- Report Number(s):
- PNNL-14240; EY3542301; TRN: US200502%%596
- Resource Relation:
- Other Information: PBD: 15 Apr 2003
- Country of Publication:
- United States
- Language:
- English
Similar Records
Multi-Scale Mass Transfer Processes Controlling Natural Attenuation and Engineered Remediation: An IFRC Focused on Hanford’s 300 Area Uranium Plume
70193-Influence of Clastic Dikes on Vertical Migration of Contaminants in the Vadose Zonde at Hanford