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i ' 20 January 2005 . AGE-NC Project No 97-0343 Page 20 of 21 containing soil borings B1, B3,B5,MW 1, and MW2, in the area of the former USTs (Table 6) The greatest concentrations of hydrocarbons were detected beneath the former UST location Higher concentrations were also detected toward the south, with moderate detections primarily toward the northwest of the UST area The plume of impacted soil at the site has an estimated north-south diameter of approximately 45 feet, an west-east diameter of approximately 30 feet and appears to extend downward to approximately 55 feetbsg The calculated volume of hydrocarbon-impacted soil is approximately 1,600 cubic yards (Appendices B and C) The feasibility for soil excavation and natural attenuation to effectively address the impacted soil is I low to uncertain AGE recommends that SVE be used to remove the contaminated mass in soil Soil remediation alternatives, estimated durations and associated costs for the site are summarized on Table 9 11 2 REMEDIATION OF HYDROCARBON-IMPACTED GROUND WATER ' Petroleum hydrocarbon-impacted ound water associated with the unauthorized release appears to �' be limited to the area surrounding monitoring wells MW-1 through MW-3 Mass of dissolved CDCs cannot be calculated accurately at this time due to the retreating ground water at the site Currently only one well,MW-8 screened at 90 feet to 95 feet bsg, is continually producing water for quarterly sampling Ground water samples have not been obtained from MW-1 through MW-3 since second quarter 2002,with exception to first quarter 2004(MW-2 and MW-3 were sampled with out purging and indicated dissolved hydrocarbons remain at those two locations) Ground water samples have ' been obtained intermittently from wells MW-4 through MW-7 since second quarter 2002, with samples coming during the winter and spring quarters ' The feasibility for air sparging,ground water extraction and natural attenuation to effectively address the impacted ground water is low to uncertain due to the lack of information (dry wells) and lateral ground water contamination no longer being adequately defined Ground water remediation Ialternatives, estimated durations and associated costs for the site are summarized on Table 10 Therefore,AGE recommends that additional ground water monitoring wells be installed to sample ' first ground water One well should be installed at or near the former UST area to quantify contamination at the UST area,while additional wells need installed at locations which would once again help define the lateral extent of the ground water contamination Advanced CeoEnvironmental,Inc