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' r r QUARTERLY REPORT APACHE PLASTICS L.P. ' 2050 East Fremoipt Street Stockton,CA ' THIRD QUARTER 1997 ' EXECUTIVE SUMMARY This report discusses groundwater and vapor extraction monntonng during the third quarter of 1997 ' at the Apache Plastics manufacturing facility in Stockton, California The report was prepared by Upgmdient Environmental Consiittants under contract no. 97004 ' The VR Systems vapor extraction unit operated for 54 days (1,071 hours) between July 1 and Septmber 30, 1997, withdrawing approximately 2,090,340 cubic feet of soil vapor In general, the unit operated sporadically, and was out of service for many days in August and September ' The unit's on-board computer monitored all essential parameters except vapor concentration, winch was manually monitored by Upgradient personnel dunng operating weeks, using a portable photo- ionization detector These data, along with laboratory analysis of three vapor samples collected in September, were used to assess the efficiency of the system Groundwater was monitored in September The depth to groundwater was measured in all six "monitoring wells, and samples were collected from each of these and from the out-of-use vapor extraction well (VE-1 "deep") Gasoline and BTEX were detected in two wells (MW5 and VE-1), ' and one or two gasoline oxygenates were detected in three wells (MW-2, MW-5, and VE-1) The ~ oxygenates methyl-tertiary-butyl ether and ternary butanol were detected at concentrations that are very close to the reporting limits, and gasoline and BTEX concentrations were also in the low range As in previous quarters, depth measurements indicate that the water table was not planar, but ' formed a trough trending across the site However, there has been a change in the trend of the axis of the trough Rather than southeast, it presently trends east-northeast at a slope of 0 002 ft/ft The depth to groundwater averaged 54 feet, three feet deeper than in the second quarter 1 1 1