ARCHIVED REPORTS_QUARTERLY REPORT - THIRD QUARTER 2005

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Appendix A- Historical Background • River City Petroleum and Connell Motor Lift Truck Page 9 of 13 • Benzene, toluene, ethylbenzene and total xylenes were detected in the soil samples at maximum concentrations of 58 mg/kg, 230 mg/kg, 71 mg/kg and 360 mg/kg, respectively, in the sample from VW14-45 and 62 mg/kg, 330 mg/kg, 120 mg/kg and 550 mg/kg, respectively, in the sample from VW15-45. • TBA was detected in four soil samples with a maximum concentration of 160 micrograms per kilogram(µg/kg), in sample VW13-45; all other detections were above 50 µg/kg. • 1,2-DCA was detected in twelve soil samples at a maximum concentration of 810 pg/kg, in sample VW14-55. GROUND WATER DEPTH, FLOW DIRECTION AND GRADIENT According to the map titled Lines Of Equal Depth Of Water Wells-Fall 1996, published by the San Joaquin County Flood Control and Water Conservation District,the estimated depth to ground water at the property is approximately 50 to 60 feet below surface grade(bsg).The prevailing ground water flow direction in eastern Stockton is generally northeast,although flow directions may vary locally • and seasonably.According to current monitoring well information,the ground water table near the site occurs at approximately 50 feet bsg.The seasonal fluctuation of the ground water table has been between 35 feet and 60 feet bsg. The ground water flow direction at the site has been primarily northeast,however,variability in the flow direction has shown western and northwestern directions, with a typical gradient of 0.001 ft/ft or greater. One domestic ground water well is located on the property. This well is located approximately 350 feet north of the UST release area. The well is reportedly screened from approximately 150 feet bsg to the total depth of the water well. The well services two buildings on the property. Analytical analysis of the water samples collected directly from the well head have been no-detect for the chemicals of concern. HYDROGEOLOGICAL MODEL Hydrological units may be defined as significant vertical intervals of sediments having significant lateral extent and having similar hydrologic characteristics (i.e. hydraulic conductivity, transmissivity, etc.) over its vertical and horizontal extent. A `flow unit' may be defined as a hydrologic unit and is characterized by significantly greater hydraulic conductivity values than overlying and underlying units.A flow unit is capable of serving as a preferred migration route,and could potentially allow migration of large contaminant masses over great distances. Advanced GeoEnvironmental,Inc.