Usefulness of TOUGH to determine mixed strata permeabilities
Totally newbie to this software package, SOOOOO-
1) We are wondering if there is a 3D simulation package that could simulate permeability rates, both vertical and lateral, of underlying soils with mixed-strata soil types by hydrocarbons (principally gasoline). We're trying to determine how quickly gasoline could reach the water table, which can vary from 10's of feet to more than 200 ft. Soil layers can be a mix of any or all-- sandy, rocky, loam, caliche, etc.
2) Also, if TOUGH or another might be useful, any suggestions on the make-up of a team of experts to assemble/run/interpret the simulations- e.g. hydrologists, geologists, etc?
3) Is this an effort that a team of graduate students could handle?
Thanks for your thoughts.
J. Trego, President Tanque Verde Valley Association
4 replies
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Welcome, James — great questions.
Short answer: TOUGH can model this type of problem, but it does not *determine* permeability from soil descriptions by itself. Permeability/hydraulic properties must come from site data (borings, grain-size, slug/pumping tests, lab tests, etc.), then the model predicts flow and contaminant migration.
For a gasoline release to groundwater, the technically relevant process is multiphase flow in the vadose zone (air/water/LNAPL) plus dissolution to groundwater. In the TOUGH family, TMVOC/T2VOC are typically used for volatile hydrocarbon mixtures.
A practical workflow is:
1) Build a hydrostratigraphic conceptual model (layering, water table, heterogeneity).
2) Assign initial property ranges for each unit (k, porosity, capillary/relative-perm parameters).
3) Calibrate against observations (water levels, soil-gas, groundwater concentrations).
4) Run uncertainty/sensitivity cases to bound travel time (best/likely/worst).
Team composition that works well:
- Hydrogeologist (conceptual model + field data)
- Contaminant transport/modeling specialist (multiphase calibration + uncertainty)
- Environmental chemist/geochemist (if degradation/partitioning is important)
- Field engineer/geologist (sampling design + QA/QC)
Could graduate students do this? Yes, with strong supervision and enough site data. The hardest part is usually not software operation, but building/defending a realistic conceptual model and uncertainty bounds.
If useful, I can suggest a minimum data package and a staged modeling plan before full 3D simulation.
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Thanks for the info! Would it be reasonable to utilize logs taken by water well drillings in various areas?
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That is, would it be reasonable to utilize well drilling logs as sources of data? Or would specific core drillings have to be conducted? (Looking at costs to do significant field work.)