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Former Unocal Service Station #0187 October 9, 1995 Three on-site groundwater monitoring wells (U-4 through U-6), one on-site vapor extraction well (UV-1), and one off-site groundwater monitoring well (U-7) were installed and two on-site soil borings (U-N and U-O) were drilled July 19 and 20, 1995 One additional off-site groundwater monitoring well (U-8) was installed July 28, 1995 Soil borings were drilled using a truck-mounted drill rig equipped with 8-inch diameter hollow- stem augers Vapor extraction well UV-1 was installed with 10-inch diameter hollow-stem augers Drilling was performed by Mitchell Drilling Environmental of Rancho Cordova, California (license #C57-672617) A GSI geologist observed the drilling of the borings, described the encountered soil, and prepared a log of each boring Logging and sampling procedures are presented in Appendix A Logs of the soil borings are presented in Appendix B Locations of the wells and borings are shown on the Site Plan (Figure 2) and the Extended Site Plan (Figure 3) Barings U-N, U-O, and U-P/UV-1 were drilled to 45 feet bgs, and borings U-4 through U-8 were drilled to 55 feet bgs A vapor extraction well was constructed in boring U-P/UV-1 and groundwater monitoring wells were constructed in borings U-4 through U-8, as discussed below Borings U-N and U-O were backfilled to ground surface with neat cement Mr Harlen Knoll of SJCEHD was present on July 20, 1995, and Ms Mary Meays of SJCEHD was present on July 28, 1995 to observe the placement of the boring iand well seals Soil cuttings generated during the drilling process were stockpiled on and covered with plastic sheeting at the subject site pending disposal Approximately three cubic yards of soil were generated Four sample tubes (SS-la,b,c,d, referred to as sample SS-1) were collected from the soil stockpile The samples were submitted to the laboratory to be composited and analyzed as one sample Stockpile sampling procedures are presented in Appendix A Water generated during the cleaning of the drilling equipment was placed in properly labelled drums and stored at the subject site pending disposal Well Installation Groundwater monitoring wells U-4 through U-8 were constructed using two-inch diameter Schedule 40 polyvinyl chloride (PVC) casing and 0 02-inch machine-slotted screen. In each of the wells, the screens extended from 35 to 55 feet bgs Vapor extraction well UV-1 was constructed using four-inch diameter Schedule 40 PVC casing and 0 02-inch machine-slotted screen The screen extended from 15 to 45 feet bgs Well construction details are presented with the Logs of Boring in Appendix B 4927 04-3 4