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. underground tanks have been upgraded The former USTs had been located on the <br /> subject property since the early 1970's The present improvements located on the <br /> subject property include new double walled plexisteel underground tanks for auto <br /> refueling, and large above ground diesel tanks located in the rear of the subject <br /> property intended for truck refueling <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 <br /> area of concern was noted in a boring placed in the area of the underground tanks <br /> (10,000 gallon unleaded, 8,000 gallon diesel, and a 6,000 gallon diesel) located in the <br /> northern portion of the subject property Levels of 22,000 ppb diesel were <br /> encountered in the groundwater Minor levels of gasoline, 2,700 ppb, are described <br /> in Advanced's report to be the volatile end of diesel <br /> I 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 <br /> situated in the northern portion of the property were removed in October of 1998 <br /> Elevated levels of contamination, 240,000 ppb diesel, were encountered in the <br /> I0 southern diesel tank area Elevated levels of hydrocarbons were also found in the soil <br /> and groundwater in the northern tank pit area The results were as follows 100,000 <br /> ppb TPH gasoline, 31,000 ppb MTBE, 4,600 ppb Benzene, 16,000 ppb Toluene, 3,000 <br /> ppb Ethyl Benzene, and 170,000 ppb Xylenes As groundwater is at approximately <br /> 9 feet below ground surface (bgs), the groundwater samples were collected directly <br /> from the tank pit excavations <br /> In November of 1998, Avalon Environmental Consultants performed soil and <br /> 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 <br /> define and identify potential contamination from two former underground tank areas <br /> A total of four borings were drilled to a depth of 20 feet below ground surface (bgs) and <br /> 11 borings were drilled to a depth of twelve feet bgs Avalon concluded that the site <br /> had been impacted by gasoline, diesel and MTBE Due to the elevated levels of MTBE <br /> in the northern tank area, Avalon recommended that further characterization be <br /> conducted at the subject property <br /> I <br /> Avalon Environmental Consultants 9627-001-2 <br /> foes Truck Plaza 15600 South Harlan Road <br /> March 20, 2000 2 Lathrop, California <br /> I <br />