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l <br /> A Preliminary Site Assessment Report, conducted by Advanced GeoEnvironmental Inc <br /> (Advanced), identified two areas of concern at the subject property One concern <br /> consisted of elevated levels of diesel fuel in the groundwater near a 12,000 gallon <br /> underground diesel tank located in the southern portion of the subject property The <br /> highest levels of diesel encountered was 320,000 parts per billion (ppb) The other area <br /> of concern was noted in a boring placed in the area of the underground tanks (10,000 <br /> gallon unleaded, 8,000 gallon diesel, and a 6,000 gallon diesel) located in the northern <br />' portion of the subject property Levels of 22,000 ppb diesel were encountered in the <br /> groundwater Minor levels of gasoline, 2,700 ppb, are described in Advanced's report to <br /> be the volatile end of diesel <br /> The tanks, which were the focus of the Advanced's, investigation, were removed in <br /> February and October of 1998 The diesel tank located in the southern portion of the <br /> property was removed in February of 1998, and the tanks located in the tank farm situated <br /> in the northern portion of the property were removed in October of 1998 Elevated levels <br /> of contamination, 240,000 ppb diesel, were encountered in the southern diesel tank area <br /> As groundwater is at approximately 9 feet below ground surface (bgs), the groundwater <br /> sample was collected directly from the tank pit excavation Elevated levels of <br /> hydrocarbons were also found in the soil and groundwater in the northern tank pit area <br /> Water samples were collected directly from the tank pit and the results were as follows <br /> 100,000 ppb TPH gasoline, 31,000 ppb MTBE, 4,600 ppb Benzene, 16,000 ppb Toluene, <br /> 3,000 ppb Ethyl Benzene, and 170,000 ppb Xylenes Additionally, a small hole was <br /> discovered in the unleaded tank during the removal <br /> In November of 1998, Avalon Environmental Consultants were contracted to perform soil <br /> and groundwater testing in order to help define the limits of contamination at the site A <br /> total of 15 geoprobe borings were placed in two separate areas of the property to define <br /> and Identify potential contamination from two former underground tank areas A total of <br /> four borings were drilled to a depth of 20 feet below ground surface (bgs) and 11 borings <br /> were drilled to a depth of twelve feet bgs <br /> 2.1 Purpose <br /> The purpose of this Investigation was to determine the lateral and vertical extent <br /> of the hydrocarbon impact identified by Advanced GeoEnviron mental Inc , in a <br /> subsurface investigation dated January 1997, and during two underground tank <br /> removal operations conducted in February 1998, and in October of 1998 <br /> 2.2 Methodology <br /> All work was performed in accordance with the "Scope of Work," prepared and <br />' submitted to the client and to the San Joaquin County Environmental Health <br /> Avalon Environmental Consultants Kashmir&Dalwidner Dhoot <br /> 20 Corporate plaza 9627-001-1 <br /> Newport Beach,Califomia 2 1.5600S Hadan Road <br />