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WI: STI: R ` GEOLOGIC € FSOURCKS , INC . 3 SUBSURFACE INVESTIGATION f� - 3.1 SOIL BORINGS AND HYDROGEOLOGY On 28 August through 1 September 1989 and 5 September 1989,soil borings B-?and B-2 were drilled under the supervision of WGR geologists Nevan Kane aad Richard Baid�+riin by PC Exploration ® of Roseville,California,using a Mobile B-80 hollow-stem auger drill rig. On 25 through 27 September 1989,soil borings B-3 and B-4 were drilled under the supervision of WGR geologist Richard Baldwin by Exploration Geoservices,Inc.of San Jose,California using a Mobile B-56 hollow-stem auger drill rias ,. Boring Ioeations,shown in Figure 3,were selected based on the location of the former underground storage tank,estimated groundwater flow direction, underground utilities locations and site access. i� Where passible,soil samples were collected at approximately 5 ft intervals for lithoiogia and hydrogeolagic description and possible chemical analyses. The WGR standard operating procedure for SOU sampling is included as Appendix A. Boring logs are included as Appendix B. Fifty-seven soil samples were collected and sent under chain-of-custody to Central Coast Analytical Services(CCAS) of Napa,California or CCAS of San Luis Obispo,California. Figure 4 is a generalized hydrogeologic cross-section across the north part of the site(Figure 3). Materials encountered in the unsaturated zone during the drilling of borings B-1,B-3 and B-4 were characterizedbylow-estimated permeability clay and silt,moderate-estimated permeability silty sand and high-estimated permeability sand. The unsaturated zone of boring B-2 was dominated by low-estimated r permeability silt and clay with a few moderate estimated permeability silty-sand layers. Groundwater was first encountered at approximately 63 ft below grade and appears to be in an unconfined condition in 311 of the boreholes. Materials encountered in the saturated zone is borings B-2 and 0-4 were mostly low- to moderate-estimated permeability sandy silt and silty sand. The saturated zone in borings B-1 and B-3 was dominated by high-estimated permeability sand. During drilling, the soil samples from borings B-2 through B4 were screened with a photoionization detector(P.D),which indicated the presence of volatile organic compounds(VOCs)in D readings are included on the boring logs. Hydrocarbon odors samples from borings B-3 and B-4. 'PI were present in boring B-1 between the depths of approximately 20 ft below grade to 65 R below grade. 3.2 MONITORING WELL INSTALLATION AND DEVELOPMENT.....:. .. , .... .. .... ; The WGR standard operating procedure for monitor well installation and development is ►� included as Appendix C. Boring B-St and B-2 were converted to 4-inch monitor wells MW-1 and MW- 3 sad D66RIN09 d. - - - -