Environmental Modeling Community of Practice

EPA On-line Tools for Site Assessment Calculation

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Release Date

Now that we have completely defined the extent of the dissolved components, we can revise the estimated start date of the release by back-calculating using the distance the plume has traveled and the advective velocity of the contaminant. Since MTBE is typically recalcitrant with respect to biodegradation, it will give us a better estimate of the travel time. 3,200 feet/1.4 feet per day x retardation of 1.01 = 2,308 days or 6.3 years. This is approximately 3.3 years earlier than the release date as estimated from the file search.

Using the day-date conversion, we can calculate the approximate release date of the spill, based on the date that the toe of the plume (6/23/98) was delineated and the total travel time (2,308 days).

The calculator gives us a starting release date of February 27, 1992.

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