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- I r rr Third Quarter 1996 Status Report-Former Discovery Chevrolet September 23, 1996 Quarterly monitoring and sampling of the monitoring wells begin in March 1995. Historically, depth to groundwater has fluctuated between 9.86 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. TPHg, BTEX, or Oil and Grease have not been detected in well MW-3. TPHg concentrations in wells MW-1 and MW-2 have ranged from 60 to 17,000 ppb, and benzene concentrations have ranged from 10 to 3,100 ppb. 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 third quarter 1996 was performed by G-R on August 13, 1996. 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 'J 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 measured from the north edge of the top of each well casing and recorded to the nearest +0.01 foot. Groundwater was measured between 10.83 and 11.48 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.northwest at agradient 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. Laboratory Analytical Data The groundwater samples were collected in sample containers supplied by the laboratory. The samples from wells MW-1 and MW-2 were analyzed for TPHg by Environmental Protection Agency (EPA) Method 5030/GC-FED, and for benzene, toluene, ethylbenzene, and total xylenes (BTEX) and Methyl Tertiary Butyl Ether (MTBE) by EPA Method 8020. The sample from well MW-3 was analyzed for TPHd by EPA Method 5030/GC-FID; and chlorinated hydrocarbons (Cl-HCs) by EPA Method 8010. The samples were analyzed by American Environmental Network (FLAP.#1172) located in Pleasant Hill, California. TPHg and benzene were detected in the groundwater sample from well MW-.1 at concentrations of 100 ppb and 20 ppb, respectively. The groundwater sample from well 8146.03-3 3