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i r� Former Discovery Chevrolet '? ? January 10, 1996 Quarterly monitoring and sampling of the monitoring wells begin in March 1995. Historically, depth to groundwater has fluctuated between 9.95 and 11.53 feet bgs. Groundwater appears to flow toward the north-northwest at a gradient of approximately 0.003. Floating product has not been observed in the monitoring wells. Petroleum hydrocarbons have not been detected in well MW-3. TPHg concentrations in wells MW-1 and MW-2 have ranged from 60 to 7,600 ppb, and benzene concentrations have ranged from 10 to 730 ppb. Historical quarterly groundwater monitoring and sampling data are summarized in Table 1. PRESENT QUARTER FIELD ACTIVITIES Quarterly monitoring and sampling of the groundwater monitoring wells for the fourth quarter 1995 was performed by G-R on December 20, 1995. Field monitoring and chemical analytical data from the current quarter are summarized in Table 1. The G-R groundwater sampling procedures are summarized in Appendix A. Copies of the G-R 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 Ll Depth-to-water (DTW) measurements were obtained by G-R from groundwater monitoring wells MW-1 through MW-3 prior to well purging and sample collection. Static groundwater, levels were measurer] from the north edge of the top of each well casing and recorded to the nearest ±0.01 foot. Groundwater was measured between 9.86 and 10.49 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- northwest at a gradient of approximately 0.005. 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. The samples from well MW-1 through MW-3 were analyzed for TPHg by Environmental Protection Agency (EPA) Method 50301GC-FID, and for benzene, toluene, ethylbenzene, and total xylenes (BTEX) by EPA Method 8020. The sample from well MW-3 was also analyzed for TPHd by EPA Method 50301GC-FID, Oil and Grease (O&G) by Standard Method 552013F, and chlorinated hydrocarbons (Cl-HCs) by EPA Method 8010. The samples were analyzed by American Environmental. Network (FLAP #1172) located in Pleasant Hill, California. i 8146.024 3 I