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' 04 April 1997 <br /> AGE-NC-95-0112 <br />' page 4 of 5 <br />' submitted The laboratory report is included in Appendix C <br /> 3 4 PETROLEUM HYDROCARBON MASS CALCULATIONS <br /> 3 41 PRE-REMEDIATION <br /> Prior to remediation, high concentrations of petroleum hydrocarbons were detected in soil samples <br /> collected from the entire depth of borings MW-1 and RW-1, located near the former UST location <br /> Low hydrocarbon concentrations were detected in samples collected from depths of 40 to 50 feet bsg <br /> in borings SW-1 and SW-2 Hydrocarbons were not detected in samples collected from borings MW- <br /> 2,MW-4 or MW-5 Analytical results of soil samples indicated a relatively uniform lateral spreading <br /> of contaminants, forming a bell-shaped plume <br />' Approximately 3,138 cubic yard of soil were estimated to have been impacted with a volume of <br /> 1,463 gallons of gasoline from the former operation of the UST at the site Petroleum hydrocarbon <br /> concentrations were assumed to vary consistently radially from the former UST location The extent <br /> of impacted soil prior to remediation is illustrated on Figure 3 Mass calculations are included in <br /> Appendix D <br /> 3 4 2 POST-REMEDIATION <br />' Soil samples from borings B-9, B-10 and probings P1 through P5 were used to estimate the mass <br /> of hydrocarbons remaining at the site Analytical results indicated significant decreases in the extent <br /> and concentrations of hydrocarbons beneath the former UST location Approximately 547 c.iibic <br />' yards of soil were estimated to remain impacted with a volume of 240 gallons of gasoline <br /> Approximately 90 gallons are located between 5 and 27 feet bsg, approximately 150 gallons are <br /> located between 33 and 54 feet bsg, with the highest concentrations centered near 40 feet bsg A <br /> cross-sectional view of hydrocarbons remaining at the site is illustrated on Figure 4 Mass <br /> calculations are included in Appendix D <br /> 4.0. CONCLUSIONS AND RECOMMENDATIONS <br /> _ �4 1 - CONCLUSIONS ' - - - -- - y _ _x_ _ <br />' Based upon data collected from the site, the following conclusions are presented <br /> iField observations and analytical results of soil samples collected at the site indicate a <br /> significant reduction of petroleum hydrocarbon concentrations <br />