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' 27 February 1997 <br /> AGE-NC-95-0112 <br /> Page 3 of 5 <br /> ' Between 30 October and 26 November 1996, the vacuum extraction unit operated a total of 641 9 <br /> hours, between 26 November and 20 December 1996, the extraction unit operated a total of 576 2 <br /> hours This data, the analytical results of the vapor samples and an average flow rate of 70 cfm were <br /> 1 used to calculate the approximate mass of extracted gasoline during these periods The mass <br /> calculations are attached in Appendix D <br /> 1 30 FINDINGS <br /> 3 1 GROUND WATER ELEVATION AND FLOW DIRECTION <br /> Between October 1996 and January 1997, ground water elevation increased an average of 2 01 feet <br /> ' Ground water continues to remain below the tops of the screened intervals in all monitoring wells <br /> at the site The relative ground water elevation data is given in Table 1 As in previous monitoring <br /> ' events, ground water mounding was observed during the January monitoring event The ground <br /> water flow direction remained southerly Relative ground water elevations for January 1997 are <br /> depicted in Figure 3 <br /> li <br /> 3 2 LABORATORY ANALYSIS OF GROUND WATER SAMPLES <br /> MTBE was detected in the ground water sample collected from MW-7 at a concentration of 4 1 parts <br /> per billion(ppb, reported as micrograms per liter) Other petroleum hydrocarbons were not detected <br /> ' in samples collected from the site during the January 1997 monitor ing event MTBE had not <br /> previously been detected at the site The analytical results of current and previous water sarnples are <br /> summarized in Table 2 The laboratory report (AAL, Batch No 97-0110-018) and chain-of-custody <br /> ' form are included in Appendix B <br /> ' 3 3 LABORATORY ANALYSIS OF VAPOR SAMPLES <br />' TPH-g was detected in the vapor samples collected on 26 November 20 December 1996 at <br /> concentrations of 1,000 µg/l and 390 µg/1, respectively Both samples were collected during <br /> extraction from RW-1 The concentration of extracted hydrocarbons has generally decreased since <br /> ` the previous quarter Field data is included on Table 3 Analytical resultsof vapor samples are <br /> summarized in Table 4 The laboratory reports(MAI, sample ID Nos 71609, and 72343) and chain- <br /> of-custody forms are included in Appendix C <br /> 1 <br /> i <br /> 1 <br /> 1 <br />