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Two 40-m1 sample vials were collected from MW-5 and VE-I and were labeled and placed in a cooled ice chest for later delivery to Sequoia Analytical in Sacramento The laboratory report and chain-of- custody form are included in Appendix B 5.2 Depth to Groundwater The normal seasonal rise in the water table was observed during the quarter (Table 1) As of February 20, it had risen approximately 3 feet from its December level and had reached an average depth of 58 5 feet 5.3 Groundwater Gradient and Flow Direction ' During the first two quarters of 1995, depth-to-groundwater measurements identified a central trough in the groundwater gradient centered in the vicinity of MW-5 In September, this trough disappeared ' and the gradient assumed a more planar form, with flow almost due east By December, the trough had returned, and was well developed when water depths were measured in February(Figure 6) 5.4 Groundwater Contamination As in the previous four quarters, contaminants were detected in MW-5 (Table 2) The benzene and ' TPH-g concentrations were virtually identical to those in December For the first time, a water sample from VE-1 was analyzed All BTEX compounds were detected and a relatively high gasoline concentration was reported As directed by PHSIEHD, the laboratory also analyzed the samples for the octane booster methyl-butyl-tertiary ether(MTBE), but none was present ' in the samples The values are suspect, however, because the sample was very turbid and had a"milky" appearance This suggests that degraded hydrocarbons may be preferentially concentrated near the extraction well, and the values might have been somewhat lower if it were possible to purge before ' sampling 6.0 CONCLUSIONS AND RECOMMENDATIONS Approximately 4,608,404 cu ft of vapors were withdrawn and combusted between January 1 and ' March 31, 1996 VOC concentrations(as measured by PID) in the two-well vapor stream ranged from 355 ppm to 2,200 ppm during this period, and an overall increase in concentrations appears to have occurred The mean VOC concentration measured during the 12 monitoring events was 970 ppm, ' however, comparison of the PID and laboratory measurements on January 2 suggests that the measured PID concentrations may be too low Using the mean value, calculations indicate that 1179 pounds of hydrocarbons were destroyed Efforts to volatilize contaminants from the groundwater and improve the efficiency of the extraction system during the quarter have evidently been successful, and vapor concentrations measured with field equipment showed a sharp reversal from the previous downward trend We therefore recommend that 5 r