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d-Od-1997 d:d7Pf,1 FRU-1 AGE NC 209 956 0700 P- 5 <br /> 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 /> 3.4.1. PRE-REMEDIATION <br /> Pzior to remediation,high concentrations of petroleum hydrocarbons were detected in soil samples <br /> collected from the entire depth of borings MW-I 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 3,135 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 PI 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 cubic <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 <br /> Based upon data collected from the site, the following conclusions are presented: <br /> • Field observations and analytical results of soil samples collected at the site indicate a <br /> significant reduction of petroleum hydrocarbon concentrations. <br />