Environmental Modeling Community of Practice

EPA On-line Tools for Site Assessment Calculation

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Source Conditions

Solution of the ground water flow and transport equation require specification of boundary conditions.

For petroleum hydrocarbon releases the boundary condition that we most often must specify relates to the release of mass from the source. From the point of view of contaminant transport in the aquifer, fuel floating on the water supplies a boundary condtion.

The simpliest way to treat fuel as a boundary condition is to assume that the water concentration remains constant at the boundary. The effective solubility calculator estimates the solubility of petroleum hydrocarbon constituents in contact with fresh gasoline. These solubilities are invariably lower than tabulated chemical solubilities as the "effective" solubility depends on the composition of the mixture. Thus in the calculator the fuel must be chosen.

An effective solubility can be used as the boundary condition for a transport simulation. The pulse source calculator provides a means to perform this simulation in one dimension. The fuel source simulation starts with a release of fresh fuel and allows the boundary concentration to change with time during the simulation.

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