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APPENDIX C <br /> ALTERNATIVE ANALYSIS: <br /> ASSUMPTIONS, CONDITIONS, AND CALCULATIONS <br /> Alternative 1: Excavation/Off-Site Disposal <br /> Assumptions/Conditions <br /> 1 Lateral extent of petroleum hydrocarbon impact is approximately 2,400 square <br /> feet <br /> 2 The plume thickness ranges in depth from 35 feet to 50 feet Excavated volume of <br /> soil is approximately 4,000 cubic yards <br /> • 3 An attenuation factor was developed utilizing historical groundwater monitoring <br /> data from Monitoring Well MW-11 (Figure C-1) This attenuation factor was <br /> applied to the most heavily impacted well on the site, Well MW-13, for the <br /> purpose of determining the total time for the groundwater monitoring effort <br /> Therefore, utilizing the attenuation factor obtained from Monitoring Well MW-11, <br /> the total time for groundwater monitoring at the site until water quality goals can <br /> be attained at Well MW-13 was calculated to be 3 years <br /> 4 A 6-foot diameter bucket auger foundation ng will be utilized to excavate soils to <br /> a depth of 50 feet <br /> 5 Assume 90 days to complete excavation <br /> 6 Excavated soils will be manifested and transported to a Class II landfill <br /> 7 Assume backfill will be composed of lean grout <br /> 8 Assume landfill requirement of 1-4 point composite sample for each 100 cubic <br /> yards and regulatory requirement of 1 sample for every 10-foot gnd from the <br /> 3201337BI1918REV C - l August 31, 1995 <br />