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k%J KI_EINFELDER
<br /> 1 EXECUTIVE SUMMARY
<br /> This is a report presenting the Third Quarter 2005 groundwater monitoring for the
<br /> former Disco Facility located at 110 North Filbert Street in Stockton, California.
<br /> MONITORING EVENT RESULTS
<br /> On August 29, 2005, nineteen (19) monitoring wells and three (3) piezometers were
<br /> sounded for depth to groundwater. MW-DIS-4 was unable to be sounded due to an
<br /> obstruction over the well. Kleinfelder sampled thirteen (13) monitoring wells and
<br /> piezometers on August 29, 30 and 31, 2005. The wells sampled were MW-DIS-1, MW-
<br /> DIS-2, MW-DIS-9, MW-DIS-11s, MW-DIS-11d, MW-DIS-12, MW-DES-13, MW-DIS-14s,
<br /> i MW-DIS-14d, MW-DIS-15, NPI-70, NP1-80, and NP1-90. The monitoring wells were
<br /> sampled in accordance with the "Groundwater Monitoring Frequency Decision Tree"
<br /> developed by CH2M Hill for this project.
<br /> The depth to groundwater ranged from 44.46 feet below the top of the well casing (MW-
<br /> DIS-11s) to 53.67 feet below the top of the well casing (MW-DIS-14d). Groundwater
<br /> elevations in the monitoring wells ranged from —33.56 feet (MW-DIS-6) referenced to
<br /> Mean Sea Level (MSL) to —34.12 feet MSL (MW-DIS-13). A slight groundwater mound
<br /> was noted near MW-DES-11s. We estimate the remediation activities are the likely
<br /> cause of the mound. During the Third Quarter 2005 the groundwater gradient was
<br /> calculated to be towards the east/southeast at 0.0004 feet/foot. The groundwater
<br /> elevations recorded have shown the groundwater elevations to fluctuate over time from
<br /> season to season with a general increasing trend recorded from 1991 to 2000 followed
<br /> by a general decreasing trend from 2000 to present. Over the past year the
<br /> groundwater elevations at the site have increased.
<br /> The 13 groundwater samples were analyzed for the following: Total Petroleum
<br /> Hydrocarbon as gasoline (TPH-g), benzene, toluene, ethylbenzene, and total xylenes
<br /> (BTEX), Tert-Butyl Alcohol (TBA), 1,2-Dichloroethane (1,2-DCA), 1,2-Dibromoethane
<br /> (EDB). MW-DIS-15 was additionally analyzed for Di-isopropyl Ether (DIPE), Ethyl t-
<br /> Butyl Ether (ETBE), Methyl tert-Butyl Ether (MTBE), and tert-Amyl Methyl Ether
<br /> (TAME).
<br /> Decreases in the concentrations of benzene, toluene, ethylbenzene, xylenes, TPH-g,
<br /> 1,2 DCA, and EDB (EDB analyzed in MW-DIS-1 only) were noted in MW-DIS-1 and
<br /> MW-DIS-2. EDB was also detected at 4.4 ugll for the second consecutive quarter since
<br /> October 2001 in MW-DIS-1.
<br /> The seven downgradient well samples (MW-DIS-11s, MW-DIS-11d, MW-DIS-12, MW-
<br /> DIS-13, MW-DIS-14s, MW-DIS-14d and MW-DIS-15) all showed non-detectable
<br /> concentrations of TPH-g, BTEX, TBA, and EDB.
<br /> 12280.M0N/5T05R1424/CD:Iv Page 1 of 14
<br /> 0 2005, Kleinfelder, Inc. November 15,2005
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