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i 22 February 1999 AGE-NC Project No 96-0263 Page 4of8 I surveyed relative to a bench mark at the southern portion of the Highway 205 off ramp to Grant Line ' Road On 30 December 1999, a California state-licensed survey engineer from Baumbach& Piazza, Inc surveyed a reference point on the top of each ground water monitoring well at the site to the I nearest 0 01-foot relative to the City of Tracy Bench Marks and Description at 35 00 feet above mean sea level (msl) The results of the monitoring well survey are contained in Table 1 The surveying report(Baumbach& Piazza) is presented in Appendix D I 3.0. FINDINGS ' Ground water flow direction was determined during two sampling event and gradient was inferred from data collected in the field, ground water levels were detected within the screen interval of the wells on the site, the hydrocarbon impact to ground water was quantified by the laboratory data obtained from the ground water samples 31 STRATIGRAPHY • Silty clay was generally encountered from surface grade to approximately 12 feet bsg A silty sand layer was encountered from 12 to 17 feet bsg IFrom 17 feet to 21 feet and 27 feet to 30 feet bsg the lithology was poorly graded sand, ranging in grain size from fine to coarse A sandy clay was discovered from 21 feet to 27 feet and 30 feet to 32 feet bsg The boring logs are included as Appendix A Cross section lines are illustrated on Figure 3 Stratigraphic cross sections are depicted in Figures 4 and 5 Organic vapor was detected in MW2, MW4, MW5, MW6, MW7 at concentrations as high as 627 ppmv(MW6 at 10 feet bsg) Organic vapor was not detected in soil samples collected from borings MW 1, MW3 or MW8 PID data is included on the boring logs (Appendix A) 3 2 GROUND WATER GRADIENT AND FLOW DIRECTION The elevation of ground water in each well was calculated by subtracting the depth to ground water from the surveyed well casing elevations (Table 1) For the December 1999 sampling event, depths to ground water ranged from 6 61 feet to 7 90 feet below the tops of the well casings Ground water elevations at the site ranged from 29 23 feet in well MW-8 to 29 71 in well MW 1 • Advanced GeoEnviron mental,Inc I