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This model was originally a three-dimensional finite difference model for multiphase flow, transport, and chemical flooding. The UTCHEM code has been modified to transform it into a general purpose NAPL simulator. Appropriate physical, chemical, and biological process models have been incorporated into the simulator to create a three-dimensional multiphase, multi-component model capable of simulating the fate and transport of nonaqueousphase liquids (NAPLs) in the saturated and unsaturated zones of aquifers. The model can be used to simulate the actual field operation of remediation activities, such as surfactant remediation or bioremediation as well as laboratory experiments with large-scale aquifer models.

UTCHEM is capable of modeling transient and steady-state, three-dimensional flow and mass transport in the groundwater (saturated) and vadose (unsaturated) zones of aquifers. Physical, chemical, and biological process models important in describing the fate and transport of NAPLs in contaminated aquifers have been incorporated into the simulator. These include multiple organic NAPL phases, the dissolution and/or mobilization of NAPLs by non dilute remedial fluids, chemical and microbiological transformations, and changes in fluid properties as a site is remediated. The model allows for non equilibrium inter-phase mass transfer, sorption, geochemical reactions, and the temperature-dependence of pertinent chemical and physical properties. It can simulate the flow and transport of remedial fluids whose density, temperature, and viscosity are variable, including surfactants, co-solvents and other enhancement agents. The biodegredation model includes inhibition, sequential use of electron acceptors, and co-metabolism, and can be used to model a very general class of bioremediation processes.

Biodegredation capabilities have been added to describe the transformation of organic contaminants from NAPL sources and can accommodate multiple substrates, electron acceptors and biological species. A new multiphase, capillary-pressure, relative-permeability function has been added to allow the use of either Brooks-Corey or Van Genuchten capillary pressure functions. New organic and tracer components have been added, as well as watertracer components and gas-phase tracers. The number of oil/water tracers has been expanded to allow any number of tracer components. The geochemical option has been extended to allow modeling of any solid or aqueous species. UTCHEM uses a solution scheme analogous to the Implicit Pressure Explicit Saturation routine where the pressure is solved for implicitly, but concentrations instead of saturations are solved for explicitly. Phase saturations and concentrations are solved in a flash routine. An energy balance equation includes heat flow between the reservoir and the over- and under-burden rocks.


Version 9.0
Release Date July 2000
Development Status general release
Development Information  
Operating System Windows
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UTCHEM UNIX version (GZIP)(595 Kb, About G-ZipExit EPA disclaimer)

UTCHEM PC version (EXE) (895 Kb) 

US EPA. (1999) "Three-Dimension NAPL Fate and Transport Model." Publication No. EPA/600/R-99/011.

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