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i 28 April 1998 - - "' AGE-NC-95-0103 ' Page 2 of 9 { w 1 well Purged water was stored in 55-gallon drums on property Field measurements of the ground water purging parameters are included tlni Appendix A t2 2 GROUND WATER SAMPLE COLLECTION ' Water samples were retrieved from each purged well using new disposable bailers The samples were transferred into 40-m1 EPA-approved VOA vials containing 0 5 ml of 18% hydrochloric acid as a preservative and were transported in a chilled container under chain-of-custody to McCainpbell ' Analytical, Inc (MAI), in Pacheco, California, for laboratory analysis Samples were analyzed for total petroleum hydrocarbons quantified as gasoline (TPH-g), volatile ' aromatic compounds (benzene,toluene,ethyl-benzene and total xylenes BTE&X) and methyl-tert- butyl ether(MTBE) and the oxygenating fuel additives tertiary butyl alcohol (TBA), di-isopropyl ' ether (DIPE), ethyl tertiary butyl ether (ETBE) and tertiary amyl methyl ether (TAME) in accordance with EPA methods 80151n and 8020 and 8260m 23 SPARGING/EXTRACTION SYSTEM OPERATION AND MONITORING , f' ' The IAS system operated continually ddnng the quarter The sparging flow rate was adjusted to approximately 10 scfin or to"a minimum,pressure of 15 psi During each molutonng event,the depth to ground water and per cent dissolved oxygen were measured for each monitoring well (Table 3) ' General system maintenance and'adjustments were performed to January and March 1998 `f f Due to low performance the SVE unit a one-month hiatus was conducted from 15 December 1997 to 15'January 1998 The one-month hiatus was used to consult with Mr-Chapin and representatives , of the San Joaquin County Health Department, to'consider reconfiguring the system, and to check ' for a'rebound effect on extracted soil gas vapor concentrations At the time of the temporary-shut- dovnl,and^until the end of March the'SVE collection system extracted vapor from all six extraction wells on the site Since 31 March 1998, vapor has been extracted only from,VW-1°and VE-1 S The,flow rate,{of extracted vapor was measured using a Dwyer differential pressure flow meter ` Organlcvapor concentrations in the extracted soil 'gas stream were measured before entenng the ' blower(ninfluent stream)and after exiting the Catalytic Oxidizer(effluent stream) using an organic,vapor meter(OVA) equipped with a photo-iomzation detector(PIDThermo Environmental 580A,, 10 OeV, calibrated to isobutylene) One soil vapor sample was collected after 24-hours of SVE unit operation and one was collected 5- ; days of operation Then monthly sampling was conducted In Febru ry and'March Advanced GcoEnviroamental,Inc. r