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i KLEINFELDER 1 EXECUTIVE SUMMARY S This is a report of Kleinfelder's Second Quarter 2005 groundwater monitoring for the 4 former Disco Facility located at 110 North Filbert Street in Stockton, California. i MONITORING EVENT RESULTS On June 20, 2005, twenty (20) monitoring wells and three (3) piezometers were sounded for depth to groundwater. On June 20 and 21, 2005, eight (8) monitoring wells were sampled by Kleinfelder. The wells included MW-DIS-9, MW-DIS-11 s, MW-DIS- 11d, MW-DIS-12, MW-DIS-13, MW-DIS-14s, MW-DIS-14d and MW-DIS-15. The t 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 43.40 feet below the top of the well casing (MW- DIS-11s) to 52.64 feet below the top of the well casing (MW-DIS-15). Groundwater elevations in the monitoring wells ranged from —32.09 feet (MW-DIS-5 and MW-DIS-6) i referenced to Mean Sea Level (MSL) to —33.16 feet MSL (MW-DIS-13). A slight groundwater mound was noted near MW-DIS-11s. We estimate the remediation activities are the cause of the mound. During the Second Quarter 2005 the i groundwater gradient was calculated to be towards the southeast with a relatively flat gradient ranging from 0.0006 feet/foot between MW-DIS-6, MW-DIS-10, and MW-DIS-4 to 0.0008 feet/foot between MW-DIS-10, MW-DIS-12, and MW-DIS-13. The groundwater elevations recorded have shown the groundwater elevations to fluctuate over time from season to season with a general increasing trend recorded from 1991 to 2000 followed by a general decreasing trend from 2000 to 2005. Over the past year the f groundwater elevations at the site have increased. The eight groundwater samples were analyzed for the following: Total Petroleum Hydrocarbon as gasoline (TPH-g), benzene, toluene, ethylbenzene, and total xylenes (BTEX), Tert-Butyl Alcohol (TBA), 1,2-Dichloroethane (1,2-DCA), 1,2-Dibromoethane (EDB). MW-DIS-15 was additionally analyzed for Di-isopropyl Ether (DIPE), Ethyl t- Butyl Ether (ETBE), Methyl tert-Butyl Ether (MTBE), and tent-Amyl Methyl Ether (TAME). 1,2-DCA was detected in MW-DIS-11s, MW-DIS-12, MW-DIS-14s, and MW-DIS-15 at concentrations of 8 ug/L, 1.5 ug/L, 1.2 ug/L and 0.97 ug/L, respectively. A continued decreasing trend was noted from previous results in MW-DIS-12, MW-DIS-14s, and MW-DIS-15; while the concentration in MW-DIS-11s remained similar to the concentration detected last quarter (7.6 ug/L), and much less than the previously l detected concentration of 200 ug/L previously detected during the fourth quarter 2004. There were no other analytes detected in the remaining wells sampled this quarter. 12280.M0NIST05R8031JZ:IV Page 1 of 15 ©2005, Kleinfelder, Inc. July 25,2005 1