ARCHIVED REPORTS_XR0005657 - Laserfiche WebLink

Home Browse Search

5 Mr Jeff Wong Page 2 of 4 • summarizes product thickness measurements and volumes removed Field notes are included in Attachment A 2.2 Groundwater Monitoring and Sampling A Ground Zero technician monitored water levels in all site wells and collected samples from monitoring wells MW2 through MW9B on June 12 and 13, 2002 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 below the tops of the well casings ranged from 64 79 feet in well MW1 (corrected for the presence of free product) to 65 71 feet in well MW5 (completed at approximately 2 25 feet above ground surface) Groundwater elevations at the site ranged from 32 86 feet to 33 35 feet below mean sea level Groundwater levels in shallow monitoring wells MW1 through MW8 fell an average of 3 73 feet between June 12, 2002 and September 12, 2002 Groundwater levels in well MW9B, which was completed in a deeper aquifer, fell 3 38 feet during the same period Groundwater flowed in a northeasterly direction with an average gradient of 0 002 (approximately 10 5 feet per mile) The apparent groundwater depression previously observed in the vicinity of well MW4 has not been present since the destruction of the old water supply well in March 2002 A potentiometric surface map generated using the September 12, 2002 monitoring data is presented on Figure 2 Groundwater monitoring data are summarized in Table 2 An experienced Ground Zero technician purged at least three well casing volumes of water from monitoring wells MW2 through MW9B prior to sampling the wells The technican measured the water's temperature, pH and electrical conductivity during the purging process and collected samples after the physical 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 Groundwater samples collected from the monitoring wells were delivered under chain of custody protocol to Argon Laboratories (FLAP #12359) for analysis Field data sheets and purge logs are included in Attachment A 3.0 GROUNDWATER ANALYTICAL RESULTS Argon Laboratories analyzed the groundwater samples 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 report is included in Attachment B TPHg was detected in wells MW2, MW3, and MW4 at concentrations of 1,100 parts per billion (ppb), 110 ppb, and 210 ppb, respectively No TPHg was detected in wells MW5 through MW9B G1Data1GROUNDZLITULEBURG\Reports\QMR\3QM2002 doc