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1 INTRODUCTION This report presents data collected during the fourth quarter 1995 monitoring period at the Pacific Gas and Electric Company (PG&E) Tracy Service Center, 502 East Grantline Road, in Tracy, California(see Figure 1). 2 GROUNDWATER GRADIENT AND DIRECTION Fourth quarter groundwater levels were measured at the PG&E Tracy Service Center on November 21, 1995, using an electronic sounding device, and recorded on the monitoring well data form included in Appendix A. The groundwater elevations are summarized in the table. The November data were used in constructing a groundwater contour map (see Figure 2). November water levels ranged from a low of 0.98 feet above mean sea level (MSL) in well OW-4 to a high of 1.50 feet above MSL in well OW-3. The estimated groundwater gradient is approximately 0.001 foot per foot(ft/ft) to the north. 3 SAMPLING, ANALYSIS, AND MONITORING PROGRAM RESULTS Groundwater samples were collected from well OW-2 on November 21, 1995, consistent with the protocol presented in Figure 3. The samples collected from well OW-2 were analyzed for gasoline by the U. S. Environmental Protection Agency (USEPA) Method 8015 Modified; and benzene, toluene, ethylbenzene, and xylenes (BTEX) by USEPA Method 8020. Field readings from the fourth quarter 1995 monitoring event are recorded on the water sample field data sheets (see Appendix A) and summarized in the table. The analytical results are discussed below. Fourth quarter 1995 and historical analytical data are summarized in the table. Certified analytical reports and chain-of-custody records are included in Appendix B. The samples taken from well OW-2 did not contain any detectable constituents. Toluene and total xylenes were detected in the trip blank at concentrations of 0.7 micrograms per liter (gg/L) and 0.8 gg/L, respectively. 4 FIELD AND LABORATORY QUALITY CONTROL RESULTS Analytical data were evaluated for accuracy and precision based on field and laboratory quality control (QC) sample performance. The field QC consisted of collecting one trip blank and analyzing it for gasoline and BTEX. The trip blank was collected to assess the effect of the sample bottles on the analytical results and to identify false positives. Toluene at 0.7 gg/L and total xylenes at 0.8 gg/L were detected above their respective method report limits in the trip blank, indicating some adverse effects from the bottles used in the sampling procedures. SACIN:1PJ010143101431150.1AS-961wpt:4 1 Rev.0,114/96 0143-115.01