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. medium-grarned sand (SP) from approximately 14 to 20 feet below grade. The soil encountered within the former tank excavation consisted of fill material comprised of fine -to medium -grained sand. Drilling logs are contained in Appendix II. 4.0 DRILLING SUMMARY On May 25, 1991 WaterWork supervised the drilling of three monitoring wells and two soil borings to assess possible hydrocarbon contamination from the former underground storage tanks. Drilling was conducted by Exceltech Corporation of Fremont California, using a hollow -stem auger drill rig_ A total of five soil borings were drilled to characterize subsurface conditions at the site (Figure 4). Two, seven -foot soil borings were drilled, one an each former tank pit. Three soil borings were drilled to provide for the installation of the groundwater monitoring wells for groundwater characterization. These wells were completed at a depth of 25 to 27 feet below grade. 4.1 Sampling Procedures Drill cuttings were logged continuously for characterization of soil type using the Unified Soil Classification System. Samples were collected from each boring at five-foot depth intervals for lithologic classification. Descriptions of soils encountered and monitoring well construction details are recorded on boring/well logs included in Appendix II. Laboratory samples were collected at 10.5 feet below grade (the soil/groundwater interface), during drilling of the monitoring wells. Samples were collected in two- inch brass sleeves using a modified California split -spoon sampler. Laboratory samples were sealed with aluminum foil, a plastic cap, and duct tape. The samples were then placed in an air -tight bag, placed on blue ice and transported under strict chain -of -custody to state -certified Applied Analytical Environmental Laboratories in Fremont, California. 4.2 Monitoring Well Construction Borings CPMW1, CPMW2, and CPMW3 were advanced 15 feet beyond first encountered groundwater and converted to groundwater monitoring wells. The wells were constructed of 2 -inch diameter, flush - threaded PVC screen and casing. Wells were filter packed with 2/12 Monterey silica sand from 2.5 to 3.5 feet above the top of the screen, sealed with bentonite, then neat cement to grade. The wells were completed at grade in water -tight, street -rated well protectors. Each well was fitted with a locking cap for security purposes. A San Joaquin County representative was present during is Corrigan Property - 381 2 R0691 TLP