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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 to repair railroad engines by the Central California
<br /> Traction Company In January 1999, Thorpe Oil Company excavated and removed one 6,000-gallon
<br /> gasoline underground 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, Incorporated (HETI) reviewed the September 1999 URS Greiner
<br /> Woodward Clyde (URSGWC) final report UST Investigation, 1645 Cherokee Lane, Stockton, CA In
<br /> August 1999, URS Greiner Woodward Clyde (URSGWC) conducted a soil boring/ground water
<br /> investigation Five borings were drilled using direct push (DP) and hollow stem auger The highest TPH
<br /> as diesel concentrations (at 22,000 mg/kg) in soil were detected in samples collected from boring B-1 at
<br />' the 10-foot depth interval However, TPH as diesel was detected in soil samples collected from the entire
<br /> soil boring to ground water Concentrations ranged from 6,000 mg/kg (at 15-feet bsg) to 2,000 mg/kg (at
<br /> 40-feet bsg) Ethylbenzene and total xylenes were also detected ranging to 0 011 mg/kg and 0 061 mg/kg,
<br /> respectively at 10 feet bsg
<br /> In their November 4, 1999 letter, the San Joaquin County Public Health Services, Environmental Health
<br /> Division (PHS/EHD) 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 Lon Duncan, Senior REHS with
<br /> the PHS/EHD, approved the work plan prepared by HETI HETI then installed six DP borings
<br />' throughout the subject property Grab ground water samples were obtained from each boring No
<br /> detectable concentrations of TPH as gasoline, TPH as diesel, benzene, toluene, ethylbenzene and total
<br /> xylenes (BTEX), or the five fuel oxygenates were found in the 46 soil samples and six grab ground water
<br /> samples submitted for analysis
<br /> HETI then installed three ground water monitoring wells to sample ground water and to determine ground
<br />' water flow direction and gradient TPH as diesel was detected at 100 parts per billion (ppb) in MW-1 and
<br /> MW-3 and at 87 ppb in MW-2 No detectable concentrations of TPH as gasoline, BTEX, or the five fuel
<br /> oxygenates, 1,2-dichloroethane (1,2-DCA) and 1,2-dibromo ethane (EDB) were found in the ground water
<br />' samples submitted for analysis
<br /> HETI then began quarterly ground water monitoring at the subject site TPH as diesel was detected at 60
<br />' ppb in MW-1 and at 89 ppb in MW-3 No detectable concentrations of TPH as diesel was found in MW-
<br /> 2 No detectable concentrations of TPH as gasoline, BTEX, or the five fuel oxygenates, 1,2-DCA and
<br /> EDB were found in the ground water samples submitted for analysis
<br />' Ground water monitoring will continue for three additional quarters HETI recommends that no- or non-
<br /> purge ground water sampling methods be instituted at this site Because no TPH as gasoline has been
<br />' detected in the initial and first quarter ground water monitoring event, HETI recommends that the five
<br /> fuel oxygenates be removed from the subsequent ground water monitoring rounds
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