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sf � Fourth Quarter 1997 Status Report - Former Discovery Chevrolet January 15, 1998 (April, 1997), and have never been detected in well MW-5. Historical quarterly groundwater monitoring and chemical analytical data are summarized in Table 1. PRESENT QUARTER FIELD ACTIVITIES Quarterly monitoring and sampling of the groundwater monitoring wells for the fourth quarter 1997 was performed on December 18, 1997. Field monitoring and chemical analytical data from the current quarter are summarized in Table 1. Groundwater sampling procedures are summarized in Appendix A. Copies of the field data sheets are presented in Appendix B. Copies of the laboratory analytical report and completed chain-of-custody form are presented in Appendix C. Well MW-3 is scheduled for annual sampling during the first quarter of each calendar year only.. Groundwater Monitoring and Gradient Evaluation Depth-to-water (DTW) measurements were obtained from groundwater monitoring wells MW-1 through MW-5 prior to well purging and sample collection. Static groundwater levels were measured from the north edge of the top of each well casing and recorded to the nearest ±0.01 foot. Groundwater was measured between 9.81 and 10.72 feet bgs. These water-level data were used to construct a Potentiometric Map (Figure 3). Based on these data, the shallow groundwater beneath the subject site appears to flow toward the north at a gradient of approximately 0.004 ft/ft. Each well was inspected for the presence of floating product. Floating product or a product sheen was not observed in any of the groundwater monitoring wells this quarter. Laboratory Analytical Data The groundwater samples were collected in sample containers supplied by the laboratory. Samples from wells MW-1, MW-2, MW-4, and MW-5 were analyzed for TPHg by Environmental Protection Agency (EPA) Method 50301GC-FID, and for benzene, toluene, ethylbenzene, and total xylenes (BTEX) and methyl tert-butyl ether (MTBE) by EPA Method 8020. MTBE was confirmed by EPA Method 8260. The samples were analyzed by American Environmental Network (FLAP #1172) located in Pleasant Hill, California. TPHg, benzene, or MTBE were not detected in the groundwater samples collected from wells MW-4 or MW-5. TPHg were detected in samples from wells MW-1 (230 ppb) and MW-2 (980 ppb). Benzene was also detected in these samples at 83 and 173 ppb, respectively. The EPA Method 8020 analysis detected MTBE in the samples from well MW-1 (8.0 ppb) and MW-2 (12 ppb). However, the presence of MTBE in either well was not confirmed by EPA Method 8260 (C 5 ppb). In addition, none of the,other gasoline oxygenate compounds [t-butanol(TBA), di-'isopropyl (DIPE), ethyl t-butyl ether (ETBE), or 8146,04-4 3 i i i i