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QUARTERLY GROUNDWATER NIONffMNG F132CW 420 West Kettleman Lane Lodi California 4.0 GROUNDWATER MONITORING 4.1 Groundwater On January 21 and March 12, 1992, Emcon personnel collected measurements of the depths to groundwater in wells MW-1, MW-2, and MW-3 Over the past 5 months, since October 17, 1991, groundwater levels have risen in the three wells (Figure 3) The rise ranged from 3 43 to 3 52 feet (Table 1) On the basks of the January 21 and ' March 12, 1992, measurements, groundwater is estimated to flow to the southwest (Figures 4A and 413) at an average gradient of approximately 0 002 ft/ft Figures 4A and 4B are potentiometric surface maps of the shallow water-bearing zone on March 12 and January 21, 1992, respectively ' Previous groundwater levels are summarized in Table 1 All groundwater elevation measurements were made from the referenced wellhead elevations, measured to the nearest 0 01 foot, and conducted according to the Emcon standard procedures (SP) included in Appendix A 4 2 Water Sampling and Analysis On January 21 and March 12, 1992, Emcon personnel collected groundwater samples from wells MW-1 and MW-3 at the site One bailer blank and one trip blank sample was r collected during the March 12, 1992, monitoring event The samples were collected according to the Emcon SP included in Appendix A, and delivered under chain-of-custody to Sequoia Analytical of Redwood City, California, a state-certified analytical laboratory, and National Environmental Testing, Inc , of Santa Rosa, California, a state-certified analytical laboratory for the January 21 and March 12, 1992, samples, respectively The January samples were analyzed for concentrations of a) TPH, as low/medium boiling point hydrocarbons (gasoline) by EPA Method 8015, and b) BTEX by EPA Method 8020 The March samples were analyzed for concentrations of a)TPH, as gasoline, by GC/FID Method 5030, and b) BTEX by EPA Method 8020 The samples collected from wells 1 MW-1 and MW-3 were also analyzed for ethylene dibromide by EPA Method 504 1 The analytical results are summarized in Table 2 The analytical reports and chain-of-custody forms are included in Appendix B Concentrations of TPH, as gasoline, and benzene reported in Table 2 are also shown on Figure 5 The wells were resampled on March 12, 1992, for the first quarter based on the analytical results indicated for the water samples collected on January 21, 1992 The January 1992 results levels of TPH, as gasoline, and benzene not reported in previous sampling events However, the March 12, 1992, results verified that the January 1992 analytical results were anomalous 119.013A OM R 2 s