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f <br /> FIELD PROCEDURES <br /> Alton Geoscience monitored and sampled ground water Monitoring Wells AW-1 through <br /> AW-9 on October 21, 1992. Alton Geoscience ground water monitoring and sampling <br /> protocol is presented in Appendix A. Ground water field survey forms including field <br /> i measurements and observations are presented in Appendix B. <br /> Ground water samples were analyzed for total petroleum hydrocarbons as diesel and <br /> gasoline (TPH-D and TPH-G) and BTEX at Sequoia Analytical Laboratory, Concord, <br /> California. Official laboratory reports and chain of custody records are included in <br /> Appendix C. <br /> DISCUSSION OF RESULTS <br /> Laboratory results for this and previous ground water monitoring and sampling events are <br /> summarized in Table 1. A ground water elevation contour map for the July 1992 event is <br /> shown in Figure 3. Results of this event are summarized as follows: <br /> 0 Average depth to ground water was 10.97 feet, with an average hydraulic gradient <br /> of 0.01 foot per foot. The ground water gradient direction and magnitude have <br /> remained relatively consistent to the northeast since 1990. <br /> • TPH-G and BTEX were not detected at or above reported detection limits in any <br /> of the wells except TPH-G in AW-3 (65 ppb) and benzene in AW-9 (1.2 ppb). <br /> • TPH-D was present only in AW-3 and AW-5 (880 and 96 ppb). The presence of <br /> detectable concentrations of TPH-D in AW-5 is inconsistent with past data and <br /> appears anomalous. <br /> ALTON GEOSCIENCE <br /> S ep an Rosen lobert E. Logan R.G. 5088 <br /> Senior Geologist Manager,Northern California Operations <br /> 2 <br />