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1 ' TABLE 1 RELATIVE GROUNDWATER ELEVATIONS Top Filling Station ' 101 S. Wilson Way, Stockton, California Relative Depth to Groundwater Relative Groundwater ' Well No. Casing Elevation Elevation 1/17/95 1/17/95 ' MW-1 10000 5995 4005 MW-2 10078 6088 3990 ' MW-3 10094 6098 3986 Measurements m leet Jl • ' 4.0 FINDINGS ' 41 Stratigraphy The borings penetrated soil units consisting of various mixtures of clay, silt and sand from surface grade to depths of 80 feet below surface grade (bsg) In all borings, backfill material was encountered from surface grade to depths of approximately 5 feet Clayey silt or silty clay was encountered to depths of approximately 40 feet Sand was encountered at approximately 40 feet to boring teimination Clay and silt lenses interfingei deeper sand units These soil characteristics suggest fluvial channel deposits, which is a typical deposit in the area Two cross sections of the soil stratigraphy at the site are illustrated in Figure 2 Cross section A-A' includes bonngs MW-1, B-1, B-2, B-5 and MW-3 (Figure 3) Cross section B-B' includes borings B-1, B-3, B-4 and MW-2 (Figure 4) Boring logs are included in Appendix A 4.2 Field Screening of Soil Samples and Auger Returns Hydrocarbon odors were detected in soil samples throughout borings B-2 and B-5 In boring B-4, hydrocarbon odors were detected at depths of 15 and 20 feet, and at depths of 35 feet to boring termination at 65 feet In B-6, a small concentration of organic vapors were detected in samples from depths of 30 feet to boring termination of 65 feet In borings MW- 1, MW-2 and MW-3, hydrocarbon odors were detected in samples from depths of approximately 25 feet to depths of 65 feet No hydrocarbon odors were detected in B-1 and B-3 No organic vapors were detected below depths of 70 feet in bonngs B-1, B-2 and B-3 OmIoSal A*&S.—k W A Tap F464P1HRr QWJ&F 19➢5 `'F I