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<br /> EXECUTIVE SUMMARY
<br />' The subject property is at 1645 Cherokee Lane, Stockton, California, north of the intersection of
<br /> Cherokee Lane and Waterloo Road The subject property is in an area of mixed light-industrial and
<br /> commercial buildings, it is part of a property used by the Central Calitointa Traction Company to repair
<br /> ' railroad engines In January 1999, Thorpe Oil Company excavated and removed one 6,000-gallon
<br /> gasoline undergiound storage tank (UST) and one 1,000-gallon diesel UST from the subject property
<br /> One soil sample, collected from below the excavated diesel tank at 9 feet below surface grade (bsg), had
<br /> 8,000 milligrams per kilogram (mg/kg) total petroleum hydrocarbons (TPH) as diesel, 0 33 mg/kg
<br /> toluene, 0 740 mg/kg ethylbenzene, and 1,800 mg/kg total xylenes, benzene was below method detection
<br /> limits
<br /> ' Hydro-Environmental Technologies, Incoiporated (HETI) reviewed the September 1999 URS Greiner
<br /> Woodward Clyde (URSGWC) final report UST Investigation, 1645 Cherokee Lune, Stockton, CA In
<br /> August 1999, URSGWC conducted a soil boring/ground water investigation Five borings were drilled
<br /> using direct push (DP) and hollow stem auger The highest TPH as diesel concentrations (at 22 000
<br /> mg/kg) in soil were detected in samples collected from boring B-1 at the 10-foot depth interval
<br /> However, TPH as diesel was detected in soil samples collected from the entire soil boring to ground
<br /> ' water Concentrations ranged from 6,000 mg/kg (at 15-feet bsg) to 2,000 mg/kg (at 40-feet bsg)
<br /> Ethylbenzene and total xylenes were also detected ranging to 0 011 mg/kg and 0 061 mg/kg, respectively,
<br /> at 10 feet bsg
<br /> ' In their November 4, 1999 letter, the San Joaquin County Public Health Services, Environmental Health
<br /> Division (PHSIEHD) requested a further investigation to determine the lateral and vertical extent of the
<br /> petroleum contamination at the subject property On June 15, 2000, Ms Lori Duncan, Senior REHS with
<br /> the PHS/EHD, approved the work plan prepared by HETI HETI then installed three ground water
<br /> monitoring wells to sample ground water and to determine ground water flow direction and gradient
<br /> TPH as diesel was detected in all three ground water monitoring wells No detectable concentrations of
<br /> ' TPH as gasoline, benzene, toluene, ethylbenLene and total xylenes (BTEX), the five fuel oxygenates, 1,2-
<br /> dichloroethane (1,2-DCA), or 1,2-dibiomoethane (EDB) were found in the ground water samples
<br /> submitted for analysis
<br /> In September 2000, HETI began quarterly ground water monitoring at the subject site During the first
<br /> quarter of ground water monitoring, TPH as diesel was detected in MW-1 and MW-3 No detectable
<br /> concentration of TPH as diesel was found in MW-2 No detectable concentrations of TPH as gasoline,
<br /> BTEX, the five fuel oxygenates, 1,2-DCA, or EDB were found in the ground water samples submitted for
<br /> analysis During the August 2001 sampling round, MW-2 and MW-3 were dry and no samples were
<br /> ' collected A sample was collected from MW-1, however, the laboratory's quality control failed to
<br /> produce results within acceptable detection ranges On June 8, 2001, the PHS/EHD requested one
<br /> additional ground water monitoring well in the area of the former diesel excavation On August 10, 2001,
<br /> ' one additional groundwater monitoring well (MW-4) was installed All of the ground water monitoring
<br /> wells were dry (MW-1 to MW-4) during the November 2001 sampling sound
<br /> ' On April 2, 2004, the San Joaquin County PHS/EHD approved HETI's work plan that included the
<br /> installation of direct push (DP) borings to investigate the extent of soil and ground water contamination in
<br /> the area of the former USTs In June 2004, five DP borings were installed on-site Grab ground water
<br /> ' samples were collected from each boring No detectable concentrations of TPH as gasoline or BTEX
<br /> compounds were found in the soil of ground water samples submitted for analysis TPH as diesel was
<br /> detected in concentiations up to 4,300 pacts pei million (ppm) in soil and 2,900 parts per billion (ppb) in
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