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locations All overhead utilities or other obstructions were noted and referred to the driller prior to rig setup on any boring location ' 3.2 MonitoringWell Installation a anon AGS installed three ground water monitoring wells to determine the lateral and vertical extent of ground water contamination caused by the release of petroleum hydrocarbons at the site The following sections describe the installation, sampling and analysis performed for each monitoring well ' 3.2.1 Monitoring Well Installation and Soil Sampling Each monitoring well borehole was advanced using a hollow stem drill rig with a ' minimum outside hole diameter of eight inches to a depth of not more than 10 feet below first encountered ground water, with the exception of monitoring well MW-9 The borehole for MW-9 was advanced to a total depth of 45 feet below grade to determine ' potential vertical migration of contaminants During drilling, soil samples were collected in a 2-inch diameter California modified ' split-spoon sampler at intervals of not more than five feet The sampler was driven in advance of the augers to collect relatively undisturbed soil samples for possible analysis The sampler was driven into the soil 18 inches at each selected sampling interval by allowing a 140 pound hammer to Fall approximately 30 inches Split spoon samples were collected in clean brass or stainless steel sampling tubes After r retrieval, the ends of the tubes were covered with Teflon tape and sealed with PVC end caps to inhibit the escape of volatile compounds Each sample was then placed into a ' cooler chilled to 4° Celsius for transport to the analytical laboratory All sample information was recorded on boring log forms contained in Appendix A ' Soil samples collected from the split spoon sampler were screened by the site geologist using a headspace analysis technique One brass sleeve was extruded into a clean plastic zip lock-type bag A photoionization detector (PID) was then used to analyze the headspace of the samples after they had been allowed to warm in the sun for at least fifteen minutes Each headspace reading was entered on the appropriate boring log The ' results of the screening were used for selection of one representative sample from each soil boring for laboratory analysis. All soil samples were described in the field by the site geologist Field observations noting sediment type, color, grain size, sorting, hardness, texture, clay content, moisture content, visible evidence of contamination, odor, or any other information important to f1 the investigation were recorded in the field on appropriate log form by the site geologist American Geological Services, Inc CA95DE-029 6