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1 ' • ' the begmning of the third quarter and remained fairly constant throughout the quarter Concentrations in the deep well reached a peak in March of this year and dropped steadilly during the second quarter ' to their lowest levels ever, where they remained during the third quarter Laboratory analysis of the vapor sample collected in August indicates that the gasoline concentration ' has decreased significantly, to 137 ppm Coupled with the very low PID readings from the deep well, this suggests that remediation is nearing completion 4.2 Weight of VOC's Destroyed The weight of VOC's extracted during the quarter can be gomputed from the mean vapor concentration in the shallow well and the cumulative volume of extracted vapors WEIGHT OF VOC'S =CF x {VAPOR) x 10-6 x 100 mol/wt ' 379 cflmole 1 =3 852 x 106 W x 680 x IV x 100 mol/wt ' 379 cflmole =2619 x 105lbs r3 79x 102 =691 lbs 5.0 GROUNDWATER MONITORING 5.1 Monitoring Procedures Groundwater monitoring took place on August 28, 1996 The depth to groundwater was measured in ' all six monitoring wells, but not in the deep vapor extraction well, which has been consistently anomalous Depth measurements were recorded on the Well Monitor Report (Appendix C) Prior to sampling, MW-5 was purged of approximately 3 well volumes(12 gallons) 1 Two 40-m1 sample vials were collected from MW-5 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 fall in the water table was observed during the quarter (Table 1) A decline of approximately 3 feet took place during the quarter ' 5.3 Groundwater Gradient and Flow Direction rTable 1 illustrates a major departure in groundwater conditions from the pattern of previous quarters 4 1