EPA On-line Tools for Site Assessment Calculation
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We set the distance to match the last groundwater sampling transect which was completed on 6/23/98. This will allow us to "calibrate" the concentration portion of the model by adjusting the contaminant halflife until we get a reasonably lose match to our field data. The highest concentration detected in this transect was 650 ug/L. Now adjust the halflife until the advective concentration approaches this value. Once we have the model calibrated we are ready to advance the model into the future to evaluate the concentrations and arrival time at the receptor. In our example the receptor is a boat channel which is approximately 4,200 feet from the source area so we'll change the distance x to 4,200.
The calculator tells us that advective transport to the channel will take 3,027 days from the initial release date for arrival on 6/12/00 at a concentration of 270 ug/l. We can now enter our own travel time in days to evaluate the peak concentration and the duration above the 50 ug/L regulatory limit and the maximum concentration which we can expect.
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