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kn KLEINFELDER 1 EXECUTIVE SUMMARY } This is a report of Kleinfelder's second quarter 2002 groundwater monitoring for the former Disco Facility located at 110 Filbert Street in Stockton, California. On May 13, 2002, six (6) monitoring wells were sampled by Del-Tech Geotechnical Support Services. The monitoring wells (MW-DIS-11s, MW-DIS-1 id, MW-DIS-12, MW-DIS-13, MW- DIS-14s, and MW-DIS-14d) were sounded for depth to groundwater and sampled. . The monitoring wells were sampled in accordance with the "Groundwater Monitoring Frequency Decision Tree"by CH2M Hill. The depth to groundwater ranged from 41.10 feet below the to of the well casing (MW-DIS- 11s) g ( 11s) to 50.27 feet below the top of the well casing (MW-DIS-14d). Groundwater elevations for the monitoring wells ranged from —29.93 feet (MW-DIS-5) to —30.74 feet (MW-DIS-12). Groundwater flow direction at the site is estimated to be towards the southeast at approximately 0.0004.ft./ft'. The 6 groundwater samples were analyzed for the following analysis: benzene, toluene, ethylbenzene, xylene, Total Petroleum Hydrocarbon as gasoline (TPH-g), 1,2-Dichloroethane (1,2-DCA), 1,2-Dibromoethane (EDB), tert-Butyl Alcohol (TBA), and the oxygenates Di- isopropyl Ether (DIPE), Ethyl t-Butyl Ether (ETBE), Methyl tert-Butyl Ether (MTBE), and tert- Amyl Methyl Ether(TAME). TPH-g was detected in one groundwater sample collected. The concentration of TPH-g detected was 76 ug/1 (found in MW-DIS-11 s). No other concentrations of TPH-g were detected. Benzene was also detected in one groundwater sample, collected from MW-DIS-lls, with a concentration of 0.42 ug/l. The remaining five groundwater samples showed non-detect concentrations of benzene above the laboratory reporting limit (ND < 0.3 ug/1). The Primary Maximum Contaminant Level (PMCL) for benzene is 1 ug/l. The detected concentration of benzene is below the PMCL for benzene in water in monitoring well MW-DIS-11s. Toluene was not detected in any of the six groundwater samples collected for laboratory analysis.. Similarly,.ethylbenzene or xylene was not detected in any of the groundwater samples. 1,2-DCA was detected in two of the six groundwater samples analyzed with concentrations of i 180 ug/l (MW-DIS-11s) and 7.2 ug/1 (MW-DIS-14s). The remaining four groundwater samples showed non-detect concentrations of 1,2-DCA above the laboratory reporting limit (ND < 5.0 ug/1). The PMCL for 1,2-DCA is 5 ug/l. The detected concentrations of 1,2-DCA exceeded the PMCL for 1,2-DCA in groundwater in MW-DIS-1 is and MW-DIS-14s. 12280.MON/STO2R134 Page 1 of 14 ©2002,Kleinfelder,Inc July 26,2002