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Site Background Information <br /> • Former FISCO WAREHOUSE (Howard Lenz Property) <br /> I1648 Shaw Road, Stockton, California <br />' the site): <br /> Vadose Zone - This zone extends from the surface to 54 feet below surface grade (bsg), the depth <br />' to the water table.The vadose zone consists of predominantly fine-grained material from the surface <br /> to 54 feet bsg, with a coarse-grained sand unit occurring between 20 feet and 25 feet bsg across a <br /> portion of the site. This zone is characterized by low pore pressure. <br />' Hydrological Unit 1 (HU1) - Starting at the top of the current saturated zone, HU1 extends from <br /> 54 feet to 80 feet bsg and is comprised of silty sand to sandy silt. This zone is characterized by <br />' predominantly high pore pressure. <br /> Hydrological Unit 2 (HU2) - HU2 extends from 80 feet to 96 feet bsg; it is comprised of an upper <br />' 10-foot layer of fine-grained soil underlain by a 5-foot sand and gravelly sand interval. This zone is <br /> characterized by low pore pressure. <br />' Hydrological Unit 3 (HU3) - HU3 extends from 96 feet bsg to, and possibly beyond, 134 feet bsg. <br /> Silt and clay are the dominant soil type in this interval_ HU3 is characterized by pore pressure <br /> variations from moderate to high pressures. <br />' UNDERGROUND STORAGE TANK REMOVAL <br /> Two 550-gallon underground storage tanks (USTs)were removed from the site on 03 October 1986 <br />' by Stockton Service Station Equipment Company. According to correspondence from the San <br /> Joaquin County-Environmental Health Department(EHD),both USTs were reportedly used to store <br /> gasoline.Upon removal of the USTs,one soil sample was collected from the floor of the excavation. <br />' The sample was analyzed by California Water Labs, Inc., a state-certified analytical laboratory, for <br /> total petroleum hydrocarbons quantified as diesel (TPH-d), benzene, toluene and xylenes. <br />' TPH-d and xylenes were detected in the soil sample at concentrations of 3,000 milligrams per <br /> kilogram(mg/kg) and 0.188 mg/kg,respectively. Benzene and toluene were not detected above the <br /> analytical method reporting limit of 0.010 mg/kg.Based upon results of the soil sample analysis,the <br />' <br /> EBD required assessment of the lateral and vertical extent of hydrocarbon-impacted soil and/or <br /> ground water in the area of the former UST. <br />' PREVIOUS SUBSURFACE INVESTIGATION <br />' On 18 September 1997,five soil probe borings(B-1 through B-5)were advanced at the site to assess <br /> • the lateral and vertical extent of petroleum-impacted soil. Total petroleum hydrocarbons quantified <br />' Advanced GeoE,nvironmentat,Inc <br />