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KLEINFELDER 1 EXECUTIVE SUMMARY This is a report of Kleinfelder's Second Quarter 2004 groundwater monitoring for the former Disco Facility located at 110 North Filbert Street in Stockton, California. MONITORING EVENT RESULTS On June 1, 2004, twenty(20) monitoring wells and three (3) piezometers were sounded for depth to groundwater. On' June 1 and 2, 2004, seven (7) monitoring wells were sampled by Kleinfelder. The wells included MW-DIS-I ls, MW-DIS-ltd, MW-DIS-12, MW-DIS-13, MW- DIS-14s, MW-DIS-14d and MW-DIS-15. All of the wells included during this monitoring event are considered downgradient monitoring wells. The monitoring wells were sampled in accordance with the "Groundwater Monitoring Frequency Decision Tree" developed by CH2M Hill for this project. The depth to groundwater ranged from.43.98 feet below the top of the well casing (MW-DIS- 11s) to 55.80 feet below the top of the well casing (MW-DIS-15). Groundwater elevations for the monitoring wells ranged from —32.85 feet. (MW-DIS-6) to —36.12 feet (MW-DIS-15). Groundwater flow direction at the site is estimated to be generally towards the southeast with a gradient of approximately 0.006 ft./fl. The seven groundwater samples were analyzed for the following: benzene, toluene, ethylbenzene, and total xylenes (BTEX), Total Petroleum Hydrocarbon as gasoline (TPH-g), 1,2- Dichloroethane (1,2-DCA), 1,2-Dibromoethane (EDB), and Tert-Butyl Alcohol (TBA). The groundwater samples collected from MW-DIS-14s, MW-DIS-14d, and MW-DIS-15 were additionally analyzed for the oxygenates Di-isopropyl Ether (DIPE), Ethyl t-Butyl Ether(ETBE), Methyl tert-Butyl Ether(MTBE), and tert-Amyl Methyl Ether(TAME). The seven downgradient well samples showed a decrease of TPH-g concentration in MW-1ls to a non-detectable result versus last quarter (61 ug/1).. There were no other detections of TPH-g in the other samples. There were no detected concentrations of any of the BTEX compounds in any of the downgradient wells this quarter. Additionally, there were no EDB concentrations detected at or above the laboratory reporting limit. TBA concentrations in each of the downgradient samples analyzed remained non-detectable concentrations for the second consecutive quarter. The concentrations of 1,2-DCA detected in the downgradient wells increased in 3 of the 7 samples (MW-11s, MW-12 and MW-15) from 130 ug/l, non-detect and 5.8 ug1I to 160 ug/l, 1.2 ug/l and 7.8 ug/l, respectively. The analyte 1,2-DCA decreased in one location (MW-14s) and remained non-detect in the remaining three samples. The samples collected from MW-14s , MW-14d, and MW-15 were analyzed for the fuel oxygenates MTBE, DIPS, ETBE, and TAME this quarter and showed non-detectable results. 12280.M0NIST04R1092 Page I of 12 Copyright 2004 Kleinfelder,Inc. September 2,2004