A soil vapor extraction pilot study in a deep arid vadose zone Part 2: simulations in support of decision making processes
- Mail Stop T-003, Los Alamos National Laboratory, Los Alamos NM (United States)
- Mail Stop M-992, Los Alamos National Laboratory, Los Alamos NM (United States)
- Apogen Technologies, Los Alamos NM (United States)
Soil vapor extraction (SVE) is a vital tool for remediating subsurface volatile organic plumes at waste sites with deep unsaturated zones. Plumes in the vadose zone are affected by many factors including vapor advection and diffusion, liquid movement, and source release processes. Leakage from buried drums may occur at different rates over the lifetime of a waste site, requiring modeling tools that can adequately address uncertain future scenarios. To demonstrate this concept, we present a numerical model of an SVE pilot test on a volatile organic compound (VOC) plume in the subsurface at Material Disposal Area L, Los Alamos National Laboratory. A site-scale numerical model was previously developed to evaluate the impact of subsurface processes on subsurface contaminants associated with waste disposed at the site. One important goal of model development is to support future corrective measures assessment activities. The model has been extensively tested and used to confirm our conceptual model for transport within the very dry mesa-top setting. In this study we present results of simulations of the SVE test. A 2-D radial model is used to test our conceptual model of flow and transport at this site. The 2-D model is calibrated to the SVE pilot test concentration and pressure data using field measured values for in situ permeability, porosity, saturation and site specific details such as asphalt coverage. A dual porosity formulation, including both matrix and fracture nodes, is necessary to fit the test data. Fracture flow at this site is necessary because the data show large drops in concentration from wells around the extraction hole that cannot be modeled as flow through a high porosity matrix. Matrix transport via diffusion into lower permeability storage provides a source term source that can replicate concentration rebound spike seen in data from the extraction borehole and other nearby boreholes. Simulations having matrix only are shown to fit the data at times greater than 3 weeks, suggesting that the matrix is strongly coupled to the fracture network and that dual porosity simulations may not be necessary for capturing long term behavior. Next we present a new high resolution, 3-D, site scale model that we plan to calibrated to the SVE pilot test concentration and pressure data using guidance from the 2-D radial model. We conclude by discussing how the 3-D model will be used to guide future decisions. (authors)
- Research Organization:
- WM Symposia, 1628 E. Southern Avenue, Suite 9 - 332, Tempe, AZ 85282 (United States)
- OSTI ID:
- 21290798
- Report Number(s):
- INIS-US-09-WM-07185; TRN: US10V0123038209
- Resource Relation:
- Conference: WM'07: 2007 Waste Management Symposium - Global Accomplishments in Environmental and Radioactive Waste Management: Education and Opportunity for the Next Generation of Waste Management Professionals, Tucson, AZ (United States), 25 Feb - 1 Mar 2007; Other Information: Country of input: France; 34 refs
- Country of Publication:
- United States
- Language:
- English
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