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S URS Ms.Lori Duncan Page 3 San Joaquin County Environmental Health Department July 5, 2002 Permitting San Joaquin County Public Health Services (SJCEHD)requires that permits be obtained prior to drilling and installation of the monitoring wells. URS will submit the appropriate permit application with fees to the SJCEHD prior to conducting field activities. Drilling and Soil Sample Collection To monitor groundwater contamination associated with the former product lines, URS proposes to install three groundwater monitoring wells at the locations shown on Figure 1 in Attachment I. Underground Service Alert (USA) will be notified a minimum of 48-hours prior to commencement of field activities. The borings will be drilled using a hollow stem auger (HSA) drill rig. The borings will be drilled with 8.25-inch-outside-diameter (OD) augers to accommodate installation of a 2-inch diameter groundwater monitoring well. The total depth of each boring will be approximately 25 feet bgs. Groundwater is located at approximately 11 feet bgs. During drilling, soil samples will be collected at 5-foot intervals with a modified California split-spoon sampler for possible laboratory analysis. The soils will be logged by a geologist according to the Unified Soil Classification System. One soil sample from each boring will be selected for laboratory analysis using a photoionization detector (PID) and visual observations. If elevated PID readings are not reported, or there is no visible sign of contamination, then, the soil sample collected from the capillary fringe will be submitted for analysis. Soil samples will be analyzed for TPHg by EPA Method 801518020, and for BTEX, MTBE, tertiary amyl methyl ether (TAME), diisopropyl ether(DIPE), ethyl tertiary butyl ether (ETBE), tertiary butyl alcohol (TBA), ethylene dibromide (EDB), and 1,2- dichloroethane(1,2-DCA)by EPA Method 8260B. All downhole equipment will be thoroughly decontaminated between drilling locations by steam cleaning. Rinseate water will be collected and stored on the ARCO property until disposal. The monitoring wells will be constructed using 2-inch-inside-diameter(ID). Schedule 40,flush-threaded polyvinyl chloride (PVC)well casing. Twenty feet of 0.020-inch machine-slotted well screen will be set from 15 feet below to 5-feet above first water. A Monterey No. 3 silica sand filter pack will be installed from the bottom of the boring to 6 inches above the well screen. A 2-foot bentonite seal will be placed above the sand pack, and neat cement will be used to seal the remaining annular space to the surface. Surface completions will consist of 12-inch flush-mounted well boxes. A locking, water tight well cap will be placed on the well. The actual well completion details will be based upon groundwater conditions encountered in the field. V_A0545MWorkP1m&c