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22 January 1996 <br /> • AGE-NC Project No. 95-0112 <br /> Page 4 of 5 <br /> As of 31 October 1995, the vacuum extraction unit has operated for a total of approximately 1,440 <br /> hours. This data, the analytical results of 12,000 ug/l of the vapor sample and an average flow rate <br /> of 60 cfrn were used to calculate the approximate mass of extracted gasoline during this period. The <br /> Imass calculations are attached in Appendix D. <br /> 4.0. FINDINGS <br /> 4.1. GROUND WATER ELEVATION AND FLOW DIRECTION <br /> Thererelative iround water elevation data is depicted in Table 1. Between July and October 1995, <br /> g <br /> ground water elevation dropped an average of 1.5 feet. During the October 1995 monitoring, the <br /> ground water table continued to slope to the southwest (Figure 3 - Relative Ground 9 ater <br /> Elevation). The overall gradient is similar to that during previous monitoring events. <br />' <br /> 4.2. LABORATORY ANALYSIS OF GROUND WATER SAMPLES <br /> TPH-g was detected in ground water samples collected from MW-I and MW-5 at concentrations of <br /> 12,000 and 420 µg/l (parts per billion: ppb), respectively. Elevated concentrations of BTE&X were <br /> detected in samples from MW-1 and.MW-5; sample collected in MW-I was found to contain benzene <br /> at 1,700 ppb. Petroleum hydrocarbons were not detected in samples collected from MW-4, MW-6, <br /> MW-7 or MW-8. The analytical results of all water samples are summarized in Table 2. The <br /> laboratory report(AAL, Batch No. 95-1024-008) and chain-of-custody samples collected during the <br /> October 1995 monitoring are included in Appendix B. <br />' 4.3. LABORATORY ANALYSIS OF VAPOR SAMPLES <br />' The vapor sample collected on 31 October 1995 indicated the detection of TPH-g at 12,000 ppb and <br /> of benzene at 100 ppb. The laboratory report (MAI, sample ID No. 58083) and chain-of-custody <br /> form are included in Appendix C. <br /> 4.4. HYDROCARBON-IlVIPACTED SOIL REMEDIATION <br /> The total cumulative mass volume of hydrocarbons that have been extracted from RW-1 was <br /> calculated to be approximately 1,761 kg or 3,884 lbs. A gallon of gasoline weighs approximately 6.25 <br /> lbs. The approximate volume of hydrocarbons as gasoline removed during this operational period is <br /> . 621 gallons. The mass calculations are attached in Appendix D. <br />