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Jib � <br /> 31 May 2002 <br /> AGE-NC Project No 97-0290 <br /> Page 3 of 7 <br /> I removed from each well Ground water temperature,pH and conductivity were measured at regular <br /> intervals during purging using an Oakton water analyzer Field sheets and data are included in <br /> Appendix A Purged water was stored on-site in labeled, 55-gallon, DOT-approved drums <br /> I <br /> 25 COLLECTION OF GROUND WATER SAMPLES <br />' Water samples were collected from the monitoring wells using the dedicated disposable plastic <br /> bailers after allowing the wells to achieve a minimum 80%recovery of the pre-purge water volume <br /> Each water sample was transferred into 40-ml volatile organic analysis (VOA) vials containing 0 5 <br /> ml 18% hydrochloric acid as a sample preservative The samples were properly labeled, placed in <br /> a chilled container and transported under chain-of-custody to CTEL for analysis for <br />' 0 TPH-g in accordance with EPA Methods 8015 Modified and <br />' 0 BTEX and MTBE in accordance with EPA Method 8021 <br /> 2 6 WELL HEAD SURVEY <br /> Because of road-construction activities at the location of wells MW-4 and MW-5, and extension of <br /> the well casing in MW-2,a California state-licensed survey engineer from Baumbach&Piazza,Inc <br /> resurveyed the elevation at the top of the well casing of wells MW-2,MW-4 and MW-5 on 09 May <br /> I 2002 to the nearest 0 01-foot relative to City of Lodi Bench Mark#296, surveyed at 46 76 feet above <br /> mean sea level (MSL) The results of the monitoring well survey are contained in Table 4 The <br /> surveying report (Baumbach &Piazza, Inc ) is presented in Appendix B <br /> I <br /> 3.0. FINDINGS <br /> From field data collected at the SVE remediation system between 10 December 2001 and 15 April <br /> 2002, AGE determined the average TPH-g concentration and the average flow rate, and calculated <br /> the approximate mass and volume of hydrocarbons removed Ground water flow direction and <br /> gradient was determined from the field data collected on 25 February 2002 The contaminant impact <br /> to ground water was assessed from laboratory data <br /> 3 1 IN-SITU AIR SPARGING <br /> Elevated concentrations of dissolved oxygen were detected in monitoring wells MW-4 and MW-5, <br /> which were used as observation wells outside the on-site IAS network, dissolved oxygen <br /> Advanced GeoEnwonmental,Inc <br />