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Mr Jeff Wong Page 2 of 4 2.2 Groundwater Monitoring and Sampling On June 12 and 13, 2002, a Ground Zero technician monitored water levels in all site wells and collected samples from monitoring wells MW2 through MW9B 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 at the site ranged from 61 14 feet(MWl)to 62 02 feet(MW5)below the tops of the well casings Groundwater elevations at the site ranged from 29 19 feet (MW2) to 30 10 feet (MW9B) below mean sea level (MSL) Groundwater levels in shallow monitoring wells MW1 through MW8 fell an average of 0 52 feet between March 2002 and June 2002 Groundwater levels in well MW9B, which was completed in a deeper aquifer, fell 1 14 feet during the same period Groundwater flowed in a northeasterly direction with an average gradient of 0 002 ft/ft (approximately 11 feet per mile) A groundwater depression previously observed in the vicinity of well MW4 has not been apparent since the destruction of the old water supply well in March 2002 A potentiometric surface map generated using the June 12, 2002 monitoring data is presented on Figure 2 Groundwater monitoring data are summarized in Table 2 Morutoring 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 physical parameters stabilized and water levels in the wells recovered to at least 80% of then' 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 Groundwater samples collected from the monitoring wells were delivered under chain of custody protocol to Argon Laboratories (FLAP #2359) for analysis Field data sheets and purge logs are included in Attachment A 3.0 GROUNDWATER ANALYTICAL RESULTS Groundwater samples collected from the site were analyzed for total petroleum hydrocarbons as gasoline (TPHg) using EPA 8015M, benzene, toluene, ethylbenzene, and total xylenes (BTEX) using EPA 8020, and oxygenated gasoline additives, ethylene dibromide (EDB) and 1,2-dichloroethane (1,2- DCA)using EPA 8260B A copy of the laboratory reports are included in Attachment B TPHg was detected in wells MW2, MW3, and MW4 at concentrations of 3,200 parts per billion (ppb), 1,100 ppb, and 2,100 ppb, respectively, although the laboratory noted for wells MW3 and MW4 that gasoline is primarily composed of MTBE Benzene was detected in wells MW2, MW3 and MW4 at 74 ppb, 5 2 ppb and 35 ppb, respectively MTBE was detected in wells MW2, MW3, MW4, MW5, and MW6 at 16 ppb, 4,100 ppb, 42,000 ppb, 4 5 ppb and 46 ppb, respectively Toluene, ethylbenzene, and xylenes were also found at relatively low concentrations in well MW2 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 1Data1GROUNDZEIT ULEBURG\Reports\QMR�2QM2002 doc