TNX Soil Vapor Extraction Multiphase Model Summary
Multiphase numerical experiments were developed and run to better understand subsurface behavior at the TNX soil vapor extraction site. The model was built to match data from pilot-scale, vapor extraction tests conducted in 1997. The numerical model, T2VOC--developed at Lawrence Berkeley National Laboratory, used only the chemical properties of the known contaminants (literature values), measured geological and physical properties from SRS investigations and well installation, and the flow data from the test to match concentrations measured at the extraction well head during the test. Several contaminant source configurations assuming either residual DNAPL or an aqueous phase VOC source in the vadose zone were postulated for testing of the numerical model. The model was able to match the mass transfer limited or tailing portion of the characteristic behavior of the contaminant concentrations as measured at the wellhead during the soil vapor extraction test. The magnitude of the measured concentrations was not adequately matched in the DNAPL source simulations. This was probably due to slower effective diffusion resulting from either a longer actual distance between the effective well screen and the source or source below the water table. The magnitude of the measured concentrations and characteristic behavior were well matched using a postulated aqueous source within the lower clay of the system. Based on the model results and a simple exponential fit to the measured field data, the time for reducing gas concentrations to approximately 1 ppmv is between 1 and 5 years. Additional concentration monitoring is recommended and will help to refine the models and narrow the predicted window.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC09-96SR18500
- OSTI ID:
- 765608
- Report Number(s):
- WSRC-TR-2000-00291; TRN: US200430%%1849
- Resource Relation:
- Other Information: PBD: 17 Oct 2000
- Country of Publication:
- United States
- Language:
- English
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