SITE INFORMATION AND CORRESPONDENCE

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CJe0109& f?ecknicsInc. Page 2 Former Moresco Property Project No. 251.3 April 8, 1998 I Chronology of Events A chronology of events for the operation of the SVES is enclosed in the attached documents. II Amendment to Reports - Review of Calculations Note: This section amends the report dated October 11, 1997. The January 26, and February 7, 1998 correspondence, along with the Remedial Action Report dated February 6, 1998, need no amendments, they already contain the current, corrected calculations. Equations It is recognized that contaminant mass estimate calculations can .be performed in various manners, but each approach should include the following parameters: • volume of impacted media(i.e., air, soil water) • contaminant concentrations in various media • density • unit conversions Contaminant mass estimate calculations divide the zone of contaminated soil into a series of layers according to geology. A cylinder shape area was then used to figure out the volume of soil that has been impacted in each layer. Due to differences in contaminant levels, an inner core and an outer ring were used on several of the layers. The mass of contaminant in each cylinder is determined by squaring the radius of the cylinder and multiplying by Pi to determine the area. The area is then multiplied by the thickness of the layer to get the volume. .The volume is multiplied by the density of the soil (lbs'/ft) then by 0.4536 to convert from pounds of soil to kilograms of soil. The contaminant load is then multiplied by this number to give the mass of contaminant in milligrams. The contaminant mass in milligrams is then converted to kilograms which is the contaminant mass value. The soil gas value is calculated much the same, except that the soil gas contaminant load is multiplied by the volume of air in the pore space of the soil. The volume of air is determined by multiplying the porosity of the soil times the volume of soil. I Estimated Volumes The estimated contaminant mass is approximately 185 gallons of gasoline. JThe calculations are presented in Table 2. While Table 3 shows the equations as they are in the working spread sheet. These calculations are based on TPH-G lab data which includes BTEX concentrations. The estimate of mass of MTBE can be made by referring to information provided by the Material Safety Data Sheet (MSDS) for gasoline which shows that it contains 10 to 20 % MTBE by volume. Thus, in approximately 185 gallons of gasoline, there would be '19 to 37 gallons of