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Mr Jeff Wong r{� Page 2 of 4 2.2 Groundwater Monitoring and Sampling On November 20 and 21, 2001, a Ground Zero technician monitored water levels in wells NMI through MW913, and sampled monitoring wells MW2 through MW913 No sample was collected from well MW 1 due to the presence of free product Groundwater elevations were calculated by measuring the depth to groundwater in each well and subtracting the measured depth from the respective well head elevation The measured depth to groundwater beneath the site ranged from 61 84 to 62 71 feet below the tops of the well casings Groundwater elevations at the site ranged from 30 78 feet (NIW2) to 31 10 feet (MW4) below mean sea level (MSL) Groundwater levels in shallow monitoring wells MW1 through MW8 fell an average of 0 41 feet between August 2001 and November 2001 The groundwater elevation in well MW9B, which was completed in a deeper aquifer, fell 0 02 feet during the same period A potentiometric surface map generated using the November 20, 2001 monitoring data is presented on Figure 2 The map indicates an apparent groundwater depression exists near well MW4, which suggests that the shallow aquifer is being influenced by pumping in the water supply well or that some vertical leakage of the shallow aquifer is occurring through the water supply well Groundwater monitoring data are summarized in Table 2 and field data sheets are included in Attachment A • Monitoring wells MW2 through MW9B were purged of at least three well casing volumes prior to sampling Temperature, pH and electrical conductivity parameters were measured during the purging process Samples were collected after the parameters stabilized and water levels in the wells recovered to at least 80% of their pre-purged levels Purged groundwater was contained in appropriately labeled DOT- approved 55-gallon drums in accordance with 49 CFR part 172 and 40 CFR part 262 Purge logs are included in Attachment A 3 0 GROUNDWATER ANALYSES Groundwater samples were delivered under chain of custody protocol to Argon Laboratones (ELAP 92359) for analysis of TPHg by EPA method 8015M, BTEX by EPA method 8020, and oxygenated gasoline additives, EDB and 1,2-DCA, by EPA method 8260B No sample was collected from well MW 1 due to the presence of free product TPHg was detected in wells MW2, MW3, and MW4 at 2,600 parts per billion (ppb), 69 ppb, and 310 ppb, respectively Benzene was detected in wells MW2, MW3, MW4 and MW6 at 370 ppb, 4 2 ppb, 10 ppb and 1 5 ppb, respectively MTBE was detected in wells MW2, MW3, MW4, MW5, and MW6 at 5 2 ppb, 4,900 ppb, 12,000 ppb, 26 ppb and 3,700 ppb, respectively Groundwater analytical results are summarized in Table 3 Laboratory reports and chain-of-custody documentation are included in Attachment B The estimated extents of benzene and MTBE in the shallow aquifer are presented on Figures 3 and 4, respectively G 1Data\CrROUNDZ1r1TCTLEBURG\Reports\QIva\4QM2001 doc