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1 <br /> 15 September 1995 <br /> AGE-NC Project No 95-0105 <br /> Page 5 of 7 <br /> ' 4.4. FINDINGS <br /> 41 GROUND WATER ELEVATION AND GRADIENT <br /> ' The elevation ofgr ound water in each well was calculated by subtracting the depth to ground water <br /> from the surveyed casing elevation (Table 1) Monitoring well casing elevations were surveyed by <br /> ' Kleinfelder, Inc relative to a City of Tracy bench mark Ground water dropped an average of 1 13 <br /> feet between February and July 1995 <br /> The ground water gradient for 14 February was calculated to be 0 0031 ft/ft directed N 5° E (Figure <br /> 5) The gradient for 13 July 1995 was calculated to be 0 0032 ft/ft directed N 27°E (Figure 6) The <br /> ' gradients and flow directions are consistent with regional flow directions and data collected in <br /> September 1988 (0 0033 ft/ft, due north) <br /> ' <br /> 4 2 LABORATORY REPO 0 <br /> RT F GROUND WATER MONITORING <br /> In the February 1995 sampling, benzene was detected only in the sample collected from MW-3, at <br /> a concentration of 13 µg/1 (parts per billion ppb) Analytical results from the July 1995 sampling <br /> event indicated the detection of TPH-g, benzene, ethylbenzene and xylenes in MW-3 at <br /> ' concentrations of 74, 22, 0 66 and 0 66 ppb, respectively The analytical results for both sampling <br /> periods are summarized on Table 2 The laboratory reports and chain-of-custody forms for the last <br /> two monitoring events are presented in Appendix F <br /> 43 STRATIGRAPHY <br /> ' Silty clays to clayey silts were encountered from the surface to total depth of 10 feet in both borings <br /> A lens of coarse sand was encountered in boring B 1 at a depth of 8 feet Boring logs are included in <br /> ' Appendix B <br /> ' 4 4 FIELD AND LABORATORY RESULTS OF SOIL BORING/GRAB WATER SAMPLES <br /> Organic vapors were detected with the PID in samples B 1-5, B 1-7 and 112-5 at concentrations of 154, <br /> 70 and 1 ppm, respectively No organic vapors were detected in sample 132-7 <br /> ' TPH-g and TPH-d were detected in sample B 1-5 at concentrations of 2,700 mg/kg (parts per million <br /> ppm)and 3 7 ppm, respectively This sample also contains BTE&X at concentrations ranging from <br /> 11 to 250 ppm <br />