Calculations using baildown test data from a monitoring well (MW-A) located near the downgradient extent of the LNAPL resulted in a hydrocarbon velocity range of zero to approximately 2.33 feet/year based on 2003 thickness measurements, and zero to 1.85 feet/year based on the 2004 thickness measurements. By comparison, the groundwater beneath the Site is estimated to flow at approximately 200 to 300 feet/year.

Using the thickness of free product measured at the furthest downgradient extent can give an indication of the potential movement of the leading edge of the LNAPL. Assuming the monitoring well located at the downgradient edge of the LNAPL release (MW-B) has a similar LNAPL saturation profile and hydrocarbon conductivity as MW-A, the measured free product thickness in MW-B resulted in an LNAPL velocity range of zero to approximately 0.67 feet/year, or a maximum of only about 8 inches/year. The mobility assessment was used to show that the two LNAPL plumes will not commingle based on current conditions, distance between the plumes, and no future releases of LNAPL to the subsurface.