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Fourth Quarter 1998 Status Report - Former Discovery Chevrolet December 8, 1998 In August 7, 1998,Horizon Environmental Inc.over-excavated the former UST pit. Well MW-1 was destroyed to accommodate these activities. Analytical data from these activities have not been made available to GR. PRESENT QUARTER FIELD ACTIVITIES Quarterly monitoring and sampling of the groundwater monitoring wells for the fourth quarter 1998 was performed on December 7, 1998. 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. Groundwater Monitoring and Gradient Evaluation Depth-to-water(DTW)measurements were obtained from groundwater monitoring wells MW-2 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 10.18 and 10.99 feet below the top of the well casings. These 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. Laboratoly Analytical Data The groundwater samples were collected in sample containers supplied by the laboratory. Samples from wells MW-2 through MW-5 were analyzed for TPHg, for benzene, toluene, ethylbenzene, and total xylenes (BTEX), and for methyl tert-butyl ether (MTBE) by Environmental Protection Agency(EPA)Methods 8015 Mod./8020. The samples were analyzed by Sequoia Analytical (ELAP #1271) located in Walnut Creek, California. TPHg, BTEX, or MTBE were not detected in the groundwater samples collected from wells MW-3 or MW-5. The sample from well MW-2 contained benzene(8.2 ppb), ethylbenzene(1.3 ppb),xylenes(4.8 ppb)and MTBE(4.4 ppb). The sample from well MW-4 contained TPHg(59 ppb),benzene(0.89 ppb), ethylbenzene(1.2 ppb), and xylenes(6.2 ppb). These data have been used to construct a TPHg/Benzene/MTBE Concentration Map (Figure 4). 948146.05-8 3 r