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SOIL VAPOR EXTRACTION PILOT STUDY REPORT San Joaquin County Montgomery Ward Auto Service Center Public Health Services Department 5400 Pacific Avenue Stockton, CA Site Code 2163 ' obtained The maximum distance at which such changes can be observed is an Indication of the radius of influence of the spargmg system ' 8 2 1 Dissolved Oxygen in Ground Water ' Figure 30 shows the dissolved oxygen levels in ground water samples from various wells before and after the spargmg test as determined by testing the samples at a analytical laboratory Results show an increase in oxygen level in all wells except MW-6 This suggest that the radius of influence of the spargmg zone ranges from 30 ft to 60 ft at the elevation of ' the ground water table Laboratory reports for ground water analyses are included in Appendix J ' Figure 31 shows the dissolved oxygen in ground water as determined using a field instrument (GT-302) Again, the results suggest an Increase in oxygen level in most of the monitoring points, particularly in VEW-3, VEW-4 and VEW-5 ' 8 2 2 Vapor Concentrations Before and After As part of the air-sparging test, concentration were measured in soil vapor probes using a field ' instrument before and after the air spargmg test Results are shown in Figure 32 The concentrations are somewhat erratic and do not suggest any particular pattern The high initial values are probably due to "rebound" overnight As the day proceeded with active vapor extraction, these values appeared to reduce There is somewhat of an indication that the concentration values show an increase towards the end of the day This may be the result of the air spargmg activities that started at approximately 12 30 PM 8.3 VES Unit Performance Results ' As part of the pilot test, EAI monitored the performance of the VES unit The information obtained will help design the appropriate VES unit for the final remediation system, if so required ' 8 3 1 Vacuum versus Flow Rate Figure 33 shows vacuum vs flow rate measured at the VES unit during the pilot test The ' first two columns (vacuum of 20 and 30 in WC) were measured with ambient air only The next five columns (vacuum of 80, 81, 95, 100 and 110 in WC) are measured with only one well (VEW-1A) connected to the VES unit Finally, the last six columns are when two wells (VEW-IA and VEW-1B) were connected to the VES Note that the measured flow rate is a combination of vapor from the well and dilution air By reducing the dilution air, the unit can be forced to extract vapors from wells at higher vacuum rate However, as the data shows, this decreases the total air flow into the unit When the vacuum is low (by opening the dilution valve), more dilution air is drawn into the VES but when the vacuum increases (by closing the dilution valve), more vapors are being drawn from the wells Throughout the test, EAI could not completely close off all dilution air because It caused the vacuum to increase beyond the capacity of the pump From this observation, it appears that ' Project No 1232 - 14 - ENVIRONMENTAL AUDIT, INC