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MM <br /> i - <br /> I~ � <br /> 3 SUBSURFACE iWVEMGATION <br /> 3.1 SOIL BORINGS AND HYDROGEOLOGY <br /> On 31 May and i June 1990, soil boring B-6 was drilled by Bayland Drilling of Foster City, <br /> California using a Central Mining Equipment (CME)55 hollow-stem auger drill rig. On 8 and <br /> 12 June 1990,soil boring B-5 was drilled by B&F Drilling of Rancho Cordova,California using a <br /> CME 55 hollow-stem auger drill rig,and soil boring B-7 was drilled on 9 June 1990 by B&F Drilling <br /> using a Mobile B-61 hollow-stem auger drill rig. All drilling operations were supervised by WGR <br /> geologist Michael Edmonson. Soil boring locations were selected based upon estimated <br /> groundwater flow direction, overhead and underground utilities and structures, and site access. <br /> Boring B-5 was located south of the former location of the underground storage tank and within <br /> the central portion of the API building. Boring B-6 was located along the central portion of the <br /> 4± eastern property boundary and boring B-7 was located west of B-5,on the eastern boundary of the <br /> Port Stockton Food Distributors property. <br /> Soil samples were collected at 5 ft intervals from borings B-6 and B-7. Collection of set samples . <br /> r from boring B-5 was Iess frequent because drilling inside the building restricted normal drilling <br /> activities. Soil was classified in accordance with the Unified Soil Classification System (USCS). <br /> Field estimates of permeability are based on grain size,sorting,sedimentary fabric and cementation. <br /> The WGR standard operating procedure for soil sampling is included in Appendix A. Boring logs <br /> n <br /> p are included as Appendix B. Figures 4 and 5 are generalized hydrogeologic cross-sections A-A'and y <br /> B-B',respectively. The cross-section reference lines are indicated on Figure 3. Soils encountered <br /> during the drilling of borings B-5,B-6 and B-7 can be generalized as follows: <br /> Soils encountered during the drilling of borings B-5,"and B-7 include low estimated permeability ' <br /> fine grained material beneath the asphalt,concrete or baserock(fill)to between 14.5 ft and 35 ft <br /> below ground surface. Lenses of coarser grained material are interbedded with lower estimated <br /> permeability fine grained soils to a depth of between 66 ft and 703 ft below ground surface. These <br /> 066RLTIA,va 9 <br /> �J <br />