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1 12 June 1996 AGE-NC Project No 95-0112 Page 6 of 7 ' MW-1 at concentrations of 5 ppb, 2 9 ppb, 7 4 ppb and 7 ppb, respectively Petroleum hydrocarbons were not detected in samples collected from MW-3, MW-4, MW-5 or MW-7 Samples were not collected from MW-2, MW-6 or MW-8 during the current quarter The analytical results of all water samples are summanzed in Table 3 The laboratory report(AAL, Batch No 96-0410-009) and chain- of-custody form are included in Appendix D 45 LABORATORY ANALYSIS OF VAPOR SAMPLES ' TPH-g was detected in the vapor samples collected on 22 March and 25 April 1996 at concentrations of 4,400 ppb and 2,100 ppb, respectively The March sample was collected from RW-1, the April sample was collected from MW-1 Concentrations of extracted hydrocarbons continue to show a decrease over time Higher concentrations of hydrocarbons were extracted from VW-1 versus MW-1 Field data is included on Table 4 Analytical results of air samples are summarized in Table 5 The 1 laboratory reports (MAI, sample ID Nos 62704 and 64508)and chain-of-custody forms are included in Appendix E 4 6 HYDROCARBON-IMPACTED SOIL REMEDIATION The mass of hydrocarbons extracted from RW-1 between 29 February and 26 March 1996 was calculated to be approximately 354 kg or 780 lbs A gallon of gasoline weighs approximately 6 25 lbs The approximate volume of hydrocarbons as gasoline removed during this operational period is 125 gallons The mass of hydrocarbons extracted from MW-1 between 26 March and 30 April 1996 was calculated to be approximately 70 gallons This brings the total volume of hydrocarbons removed from the soil since initiation of the SVE system up to approximately 1,361 gallons The mass calculations for the current quarter are attached in Appendix F 5.0. CONCLUSIONS & RECOMMENDATIONS 1 Petroleum hydrocarbons were encountered at depths of 45 to 50 feet in both borings drilled during the current quarter This corresponds to a smear zone due to fluctuations in ground water elevation, confirming a very limited lateral extent of impacted soil in the vadose zone Concentrations of organic vapors detected in soil samples have decreased since the installation of sparging wells SW-1 and SW- 2 No petroleum hydrocarbons were encountered above the smear zone The air sparging/extraction system appears to have promoted a decrease in hydrocarbon concentrations in the smear zone Soil 1 vapor samples will continue to be collected monthly to further monitor the mass of hydrocarbons removed Bonngs installed dunng the next quarter will be placed near MW-1 and the former UST location