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County Environmental Health Division (SJCEHD) . Alton Geoscience <br /> ground water monitoring and sampling protocol is presented in <br /> Appendix B. The ground water sampling field survey forms <br /> presenting field measurements and observations are presented in <br /> Appendix C. <br /> Ground water samples were analyzed for total petroleum <br /> hydrocarbons as gasoline (TPH-G) , total petroleum hydrocarbons as <br /> diesel (TPH-D) , and BTEX constituents at Sequoia Analytical of <br /> Concord, California. The official laboratory reports and chain <br /> of custody record are included in Appendix D. <br /> DISCUSSION OF RESULTS <br /> The laboratory results for this and previous quarterly ground <br /> water monitoring and sampling events are summarized in Table 1. <br /> A ground water elevation contour map, based on the depth to <br /> ground water measurements collected on February 21, 1992, is <br /> presented in Figure 3 . The analytical results of ground water <br /> sampling are presented in Figure 4. <br /> Results of this ground water monitoring and sampling event and <br /> laboratory analysis indicate the following: <br /> • The average depth to ground water is 10.70 feet with an <br /> average hydraulic gradient of 0. 009 foot/foot to the <br /> northeast. This is consistent with past data. <br /> • With the exception of the lack of hydrocarbons in AW-3, <br /> the analytical data from this event for all other wells <br /> is consistent with historical data prior to <br /> November 1991. <br /> • Current analytical data appears to confirm the <br /> presumption that the November 1991 data was anomalous <br /> with respect to diesel reportedly detected in all <br /> monitoring wells (as discussed in the Alton Geoscience <br /> report dated March 6, 1992) . <br /> ALTON GEOSCIENCE <br /> Stephan Rosen /Peter Lang R.G. 5089 <br /> Senior Geologist Associate, Northern California Operations <br /> 2 <br />