ARCHIVED REPORTS_MONITORING WELL INSTALLATION REPORT - SITE ASSESSMENT WORK PLAN

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' Historical Background: • gr River City Petroleum and Connell Motor Lift Truck ' Page 9 of 13 September 2004 - Installation of Deep Ground Water Monitoring Well ' Between 22 and 26 September 2004, the pilot boring for monitoring well MW-35 was advanced using a 50 Km Sonic drill rig, equipped with 6.0-inch and 8.0-inch diameter drive drill stems; the ' 8.0-inch diameter drive drill stems were advanced to 180 feet bsg, and the 6.0-inch drive drill stems were utilized to advance to a total depth of 250 feet, after the 8-inch stems encountered refusal at ' 185 feet bsg. Pilot boring MW-35 was completed as a deep, ground water well using two-inch diameter PVC casing with 0.020-inch slotted screen installed from approximately 243 to 248 feet bsg,with blank casing extended to the surface.The filter pack was installed from approximately 240 ' feet to 248 feet bsg. ' 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. 1 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. Based on field and laboratory analytical data, the screened intervals of these wells were set within Advanced GeoEnvironmental,Inc.