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1 <br /> 17 August 1998 <br /> AGE-NC Project No 95-0103 <br /> ' Page 3 of 7 <br /> 24 SPARGING/EXTRACTION SYSTEM OPERATION AND MONITORING <br /> The IAS system operated continually during the quarter The sparging flow rate was adjusted to <br /> approximately 10 scfm or to a minimum pressure of 20 psi During each monitoring event,the depth <br /> to ground water and percent dissolved oxygen were measured in each monitoring well (Table 3) <br /> General system maintenance and adjustments were performed in April and Aine 1998 <br /> ' The flow rate of extracted vapor was measured using a Dwyer differential pressure flow meter <br /> Organic vapor concentrations in the extracted soil gas stream were measured before entering the <br /> blower(influent stream) and after exiting the Catalytic Oxidizer (effluent stream) using an organic <br /> vapor meter(OVA)equipped with a photo-ionization detector(PID Then-no Environmental 5 80A, <br /> ' 10 OeV, calibrated to isobutylene) <br /> A soil vapor sample was collected on 04 June 1998 The vapor sample was collected in a Tedlar bag <br /> from the influent stream The sample was collected with a vacuum pump The sample was labeled, <br /> placed in a cool ice chest and transported under chain-of-custody to MAI The extracted so.] gas <br /> sample was analyzed for TPH-g and BTE&X <br /> A one-month hiatus was initiated on 14 June 1998 due to Iow performance the SVE unit The one- <br /> month hiatus was used to consult verbally with Mr Chapin and representatives of the San Joaquin <br /> ' County Health Department to consider reconfiguring the system and to check for a rebound effect <br /> on extracted soil gas vapor concentrations <br /> 3.0. FINDINGS <br /> ' 3 1 RELATIVE GROUND WATER ELEVATION <br /> ' Over the second quarter of 1998 ground water elevation remained high, relative to the initial ground <br /> water elevation observed at the site The ground water elevation increase was approximately 0 2 feet <br /> between March and June 1998 <br /> The relative ground water elevation at the site appears to be depressed on the northern portion of the <br /> property(Figure 3) The ground water on the site is inferred to be moving toward the ground water <br /> ' depression. <br /> ' 3 2 ANALYTICAL RESULTS OF GROUND WATER SAMPLES <br /> TPH-g was detected in samples from wells MW-1, MW-3, MW-4 and MW-5 at concentrations of <br /> Advanced GeoEnvironmental,fne <br />