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,a:_ rPTa,r s�.x+i r i 2,.; � a�+s•:'Er.4" ! '3.¥ �.:.F s � ? _ -¢%P gic '.��.T; _ _ +� � _ � ##-k ��r :f �'� ��`�.SPL� � �`��'`..2'�',/��..yr��i,� Ii5rt- ii [t1 GIt: OI, t) It; IC Ri: tit) I' ItCl: ti , 3 SOIL BORINGS AND HYDROGEOLOGI 0 s On 27 and 28 September 1989,six soil borings(B-10 through B-IS)were drilled by Exploration Geoservices Inc.of San Jose,California,using a Mobile B•56 hollow stem auger drill rig and 12-inch and 8-inch diameter flight augers,under the supervision of WGR geologist Richard Baldwin. Boring -- locations,shown in Figure 3,were selected based on previous analytical results for soil samples and site RTd access. Soil samples were collected at 1.5 ft to 5 ft intervals. Boring B-10 is labeled on Figure 3 as MW-4, power lints along Navy Drive prevented drilling closer than 6 ft to the southern property line. The soil cult-rags were placed adjacent to the soil stockpile on-site and covered with plastic sheeting. Thirty-three soil samples were sent under chain-of-custody to Central Coast Analytical Services(CCAS) of San Luis Obispo, California. Eighteen of these soil samples were selected for znalysis by EPA .- Method 8015 for TPPH and aromatic hydrocarbons. WGR standard operating procedure for soil y_ sampling is inchided as Appendix A. Boring logs are included as Appendix B. Soil encountered in the unsaturated zone during drilling is characterized by low- to moderate-estimated permeability clay, silt, and silty sand with discontinuous lenses of moderate- to , high-estimated permeability silty gravel and high-estimated permeability,fine to medium sand. Borings B-11 through B-15 were terminated at 26 ft below grade in the unsaturated lone. Hydrocarbon odors were detected in boring B-11 from 24.5 ft to 26 k below grade,in borings B-14 and B-LS from 14.5 ft to 26 It below grade. Figums 4 and 5 show generalized hydrogeologic cross-sections A-A'and B-B',along and across the hydraulic gradient, respectively. The cross-section lines are referenced on the map on Figure 3. Boring loip obtained from WA for monitor welts MW-1,MW-2,and MW-3 were used to construct the cross-sections. Both cross-scetions intersect boring B•10,labeled as MW-4 on Figures 4 and 5. The shallow water-bearing zone was encountered in boring B-10 at 26.8 ft below grade and is about 7.5 ft thick. Boring 13.10 was terminated at 39 ft below grade after confirming 5 ft of low-estimated permeability clay. The water-bearing zone in boring B-10 is characterized by high-estimated permeability fine to medium,poorlygraded sand,and low-to moderate-estimated permeability silt and clay. The water rose very slowly in boring B-10 during drilling,indicating either that the groundwater _ is under a slight confined condition or that the wafer-bearing material is of low permeability and recovered slowly. Hydrocarbon odor was detected in the Geld in boring B-10 from 22.8 It to 31 ft below grade,which is 4 ft below first water,and in borings B-11,B-14,and B-15 at 25 ft below grade. w- _� i a 0T5Rtfl .9.WP a++