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Depth measurements were recorded on the field monitoring data sheet (Appendix C) The depth to the ' bottom of each well was also measured, and used to calculate the volume of water in each well prior to purging The volume of water purged from each well was recorded on the field monitonng sheet The purged water was stored in a 55-gallon drum near the vapor extraction unit for later disposal During ' purging, a Corning Checkmate meter was used to measure pK conductivity, and temperature to insure that these parameters stabilized before water samples were collected ' After purging, the deep vapor extraction well did not recharge, and could therefore not be sampled Two 40-m1 sample vials were collected from each of the other wells and were labelled 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 December 14, it had risen approximately 2 feet from its September level and had reached an average depth of ' 61 5 feet 5.3 Groundwater Gradient and Flow Direction ' Dunn the first two quarters of 1995 depth-to-groundwater mesurements identified a central trough During q 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 the gradient had steepened slightly to 0 0015 ft/ft(Figure 6) ' 5.4 Groundwater Contamination As in the previous three quarters, contaminants were detected in MW-5 (Table 2)` The benzene and ' TPH-g concentrations were slightly lower than in previous quarters, and toluene was not detected above the reporting limit of 0 50 ppb 6.0 CONCLUSIONS AND RECOMMENDATIONS ' Approximately 4,262,940 cu ft of vapors were withdrawn and combusted between October 1 and December 31, 1995 VOC concentrations (as measured by PID) in the two-well vapor stream ranged ' from 100 ppm to 2,380 ppm during this period, and an overall decrease in concentrations appears to have occurred This trend is most apparent in the deep well, but this may be partially due to rising groundwater, which by quarter's end was at or above the bottom of the well As groundwater rises, it ' fills the pore spaces between the soil particles and restricts or prevents air flow to the well In the Third Quarter Report, Upgradient noted that the rate of change in hydrocarbon concentrations in the vapor stream had decreased markedly since early 1995, and recommended that vapor monitoring 5 r