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PHASE VII SUBSURFACE INVESTIGATION San Joaquin County Montgomery Ward Auto Service Center Public Health Services Department 5400 Pacific Avenue Stockton, CA Site Code 2163 4.0 SUBSURFACE CONDITIONS The following is a generalized summary of the soil stratigraphy encountered during the drilling of well MW-7 Appendix C contains a copy of the boring log The surface of the area explored was covered with approximately four inches of asphalt pavement From the base of the asphalt to a depth of approximately two feet bgs a dark brown silty clay was observed Below the silty clay to a depth of approximately 63 feet bgs is a rust to olive, slightly clayey, sandy silt becoming very sandy below 54 feet Between 63 and 67 feet bgs a very silty olive sand was observed Between 67 and 71 feet bgs a very sandy olive silt was observed Ground water was encountered at approximately 49 feet bgs 5.0 ANALYTICAL TESTING 5.1 GROUND WATER SAMPLES The ground water samples collected from the hydropunches were analytically tested by TEG TEG is a state certified hazardous waste testing laboratory certified for all tests completed as part of this Investigation The four ground water samples were tested for TPH-G using modified EPA Method 8015, and BTEX using EPA Method 8020 The results of the testing are shown on table 7 The laboratory reports are contained in Appendix B 5.2 SOIL SAMPLES The three soil samples collected from boring MW-7 at 40, 45 and 50 feet bgs were delivered for analytical testing to BC Analytical BC Analytical is a state certified hazardous waste testing laboratory certified for all tests completed as part of the Investigation The soil samples were tested for TPH-G and BTEX The laboratory report is contained in Appendix B 6.0 DISCUSSION AND CONCLUSIONS 6.1 GROUND WATER No TPH-G were detected in any of the ground water samples collected from hydropunches HP-1 through HP-4 Benzene was detected in the ground water samples collected from hydropunches HP-1 (36 2 parts per billion [ppb]) and HP-2 (3 ppb) No benzene was detected in the ground water samples collected from hydropunches HP-3 and HP-4 Toluene (0 5 ppb) MA xxrleneS 1(1 7 nr,hl alcn uteri- Aeterteri in tha arniinri water camnlPc rnllPrtF-d frnm hydropunch HP-2 Figure 3 Is a vicinity map which shows the location of wells associated with the Montgomery Ward site and the former Unocal site located north of the Montgomery Ward site Figure 3 _ also includes the TPH-G and benzene data associated with ground water sampling completed at both sites In December 1995 Montgomery Ward and Unocal have been conducting quarterly monitoring on the same dates for the past several events IProject No 1232 - 7 - ENVIRONMENTAL AUDIT, INC