A compilation of useful soil vapor fate and transport models

Vapor Transport (Free)

Johnson and Ettinger Model – Excel/Web based one-dimensional model that quantifies the potential for vapor intrusion and health risks associated with groundwater and soil contamination.  Primarily used as a screening tool prior to gathering site specific information.  The USEPA has recently released a Vapor Intrusion Screening Level calculator that can be used to determine applicable criteria prior to modeling.  New versions are released regularly with updated toxicity and chemical property information.

VLeach – VLEACH is a one-dimensional, finite-difference screenign level model for simulating the leaching of volatile, sorbed contaminants through the vadose zone into groundwater. The program simulates: liquid-phase advection, solid-phase sorption, vapor-phase diffusion, and three-phase equilibration. In an individual run, VLEACH can simulate leaching in a number of distinct polygons, which may differ in terms of soil properties, recharge rates, depth of water, or initial conditions. Modeling results in an overall, area-weighted assessment of ground-water impact.

VS2DI – VS2DT is a finite-difference model for solute transport in the vadose zone. The model can analyze problems in one or two dimensions.  Solute transport processes include advection, dispersion, first- order decay, adsorption, and ion exchange. A modified version of VS2DI is VS2DH, which simulates energy transport instead of solute transport.

Vapor Transport (Commercial)

Air3D – Fortran based three-dimension airflow modeling originally derived from Modflow.   The program can simulates three-dimensional transport in a heterogeneous, anisotropic, unsaturated domain where air flow is induced through dry wells or trenches. The program can also be used to simulate natural air flow in the unsaturated zone caused by atmospheric-pressure variations.  The program is relatively old and therefore memory limitations exist and exporting results to windows can be problematic.

RUnsat – This two-dimension model simulates reactive, multispecies transport for heterogeneous porous media. R-UNSAT’s original purpose was for simulating vadose zone transport of volatile organic compounds, but can also be applied to other unsaturated-zone transport problems involving gas diffusion (radon and atmospheric depostion).

SeSoil –  A one-dimensional vertical transport model . It simulates fate and transport of chemicals based on diffusion, adsorption, volatilization, biodegradation, and hydrolysis.  Uses a national database of climate conditions to estimate infiltration based upon ground use patterns.  Temporal simulations allow the use of single release simulations like underground storage tanks.

Modflow Surfact – A modification of MODFLOW that does a much better job of handling desaturation of cells and also allows the simulation of vapor flow in the vadose zone grid cells.  Can correct redistribute total flow from a well if an intersecting layer goes dry.

FeFlow – Powerful finite element model for simulating both groundwater and soil vapor flow.

UnSat Suite – A one-dimensional vertical transport model.  This one dimensional model simulates the downward vertical flow of groundwater and migration of dissolved contaminants in the groundwater through a thin column of soil.

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