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i wells (MW-10 through MW-12) and drilled two soil borings (AB-1 and AB-2) in April 1992, and Environmental Assessors, Inc (EA) installed six monitoring wells (MW-13, MW-14, MW-16, MW-19, MW-20 and MW-24) and drilled four soil borings (SB-15, SB-17, SB-18 and SB-22) in October 1993 In September 1995, Geocon installed vapor extraction well VW-I Geocon also installed two vapor extraction monitoring wells (VM-1 and VM-2), two additional groundwater monitoring wells (MW-25 and MW-26) and one replacement groundwater monitoring well (MW- 11) in August 1996 to complete characterization of site conditions FIELD ACTIVITIES Groundwater Level Measurements and Flow Direction ' Representatives of Geocon measured the depths to groundwater in twelve groundwater monitoring wells on October 23, 1996 Depth to groundwater measurements were obtained using a battery operated water level meter with measurements obtained from the top of each well casing Groundwater was encountered at depths between 59 and 61 feet below the top of the well casings A summary of the top of well casing elevations, groundwater level measurements and groundwater elevations is presented on Table 1 Based on the October 23, 1996 groundwater elevation data, the groundwater flow is directed to the east at an approximate gradient of 0 002 ft/ft Groundwater elevation contours and gradient for the October 1996 monitoring event are depicted on the ' Groundwater Elevation Map, Figure 2 Well Purging and Sampling Prior to groundwater collection, approximately three well volumes of groundwater were extracted from wells MW-9, MW-11, MW-12, MW-13, MW-14, MW-16, MW-19, MW-20, MW-24, VW-1, MW-25 and MW-26 utilizing a 2-inch diameter submersible pump Groundwater extraction was ' performed to allow fresh formation water to infiltrate the wells During well purging activities the groundwater was monitored for pH, electrical conductivity and temperature Groundwater recovery was monitored in order to ensure 80 percent well recovery prior to well sampling Monitoring well sampling data sheets are presented in Appendix A Purged groundwater was discharged into a water trailer and DOT 17-H 55-gallon drums pending discharge to the City of Stockton (City) sanitary sewer system A new wastewater discharge permit for the disposal of purge water to the sanitary sewer is currently being processed by the City Following well recovery, a water sample was collected from each well using polyethylene disposable bailers and decanted into 40-m1 volatile organic analyses vials and one-liter amber bottles The samples were sealed, labeled and placed in an ice chest containing ice and were transported to Geocon's Sacramento Office for cold storage at 4 degrees celsius pending shipment to the analytical laboratory The samples were subsequently transported to Advanced Technology Laboratory (ATL) using standard cham-of-custody protocol ANALYTICAL METHODS AND RESULTS Laboratory Analysis I The groundwater samples were delivered to ATL for the analyses of TFHg and total petroleum hydrocarbons as diesel (TPHd) following EPA Test Method 8015 modified, and benzene, toluene, ethylbenzene and total xylenes (BTEX) and methyl tert-butyl ether (MTBE) following EPA Test ' Project No 58104-06-62 -2- November 27, 1996