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f Third Quarter 1997 Status Report - Former Discovery Chevrolet October 17, 1997 Quarterly monitoring and sampling of the monitoring wells begin in March 1995. Historically, depth to .groundwater has fluctuated. between 9.25 and 11.53 feet bgs. Groundwater appears to flow toward the north-northwest .at a gradient of approximately 0.003 to 0.005. FIoating product has not been observed in the monitoring wells. TPHg, BTEX, or Oil and Grease have not been detected in we1I MW-3. TPHg or benzene have never been detected in well MW-5. TPHg concentrations in wells MW-1 and MW-2 have ranged from 60 to 17,000 ppb, and benzene concentrations have ranged from 1.1 to 3,100 ppb. TPHg (415 'ppb) and benzene (1.1 ppb) were detected only once in well MW-4 '(April, 1997) Historical quarterly groundwater monitoring and.chemical analytical data are summarized in Table 1. PRESENT QUARTER FTELD ACTIVITIES Quarterly monitoring and sampling of the groundwater monitoring wells for the Third quarter 1997 was performed by GR on September 17, 1997. .Field monitoring and chemical analytical data from the current quarter are summarized.in Table 1. The GR groundwater' sampling procedures are summarized in Appendix A. Copies of the GR 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. :J Groundwater Monitoring-and Gradient Evaluation Depth-to-water (DTW) measurements were obtained by GR 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 10.12 and 11.06 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. 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. analyzedd for 'TPHg by Environmental Protection Agency (EPA) Method 5030/GC-FID, and for benzene, toluene, ethylbenzene, and total xylenes (BTEX) and methyl Cert. butyl ether (MTBE) by EPA Method 8020.' The samples were analyzed by American Environmental Network (ELAP #1172) located in PIeasant Hill, California. 8146.04-3 3