EPA On-line Tools for Site Assessment Calculation

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Arrival of MTBE at Receptors

While this may be good news for concerns about potential vapor impact to residents, it does not help us account for the missing MTBE. Another approach is to estimate the arrival time for MTBE at receptor locations. We will begin by estimating the seepage velocity in the aquifer.

We will need to collect some additional data before we can complete this calculation:

Hydraulic Conductivity
Porosity
Bulk Soil Density
Fraction of Organic Carbon

The hydraulic conductivity can be estimated from aquifer testing (pumping tests, slug tests). The porosity, bulk density and fraction organic carbon f_oc can be obtained from laboratory analysis of soil samples or approximated by using values consistent with the soil type.

In our case, hydraulic conductivity was estimated during a pumping test, which was conducted during the design phase of the pump & treat IRM. Porosity and the fraction of organic carbon in the soil, were provided by a laboratory.

Try plugging in the following site specific values along with the gradient previously calculated to the Seepage Velocity Calculator:

Input Values

Parameter	Value
Hydraulic Conductivity (from pump test)	216 ft/day
Porosity (lab value)	0.30
Fraction of Organic Carbon (lab value)	0.0001

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Contact Jim Weaver to ask a technical question on this material.