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1 <br />' 2 SITE CONDITIONS <br />' 2.1 ARCO SERVICE STATION No. 2168 <br />' 2.1.1 Background <br />' The ARCO Service Station No 2168 is located at 441 West Charter Way on the northeast <br /> corner of Charter Way and Lincoln Street in Stockton, California (see Figure 1) <br /> Information provided by ARCO indicates that there are four underground gasoline tanks <br />' in use at the site These tanks currently store super unleaded, mud-grade unleaded, and <br /> regular unleaded gasoline Currently, one waste-oil tank is located at the site but is not in <br /> use It is EMCON's understanding from ARCO personnel that no other tanks have <br />' occupied the gasoline storage tank cavity, and the gasoline tanks have not stored other <br /> fluids <br />�} <br /> 2.1.2 Site Assessment <br />' To evaluate and delineate residual hydrocarbons in soil and groundwater, 19 soli borings <br /> were drilled on site and 2 soil borings were drilled off site, 5 on-site groundwater <br /> monitoring wells and 2 off-site monitoring wells were installed, and 7 vapor extraction <br />' wells were installed on site (RESNA Industries, June 10, 1994) <br /> Site Geology and Site Hydrogeology Sediments beneath the site consist primarily <br />' of silt to clayey suit with clay lenses from surface grade to approximately 33 feet below <br /> ground surface (bgs) and silty sand and sand from 33 to 57 feet bgs Three generalized <br /> cross-sections (A-A', B-B', and C-C' [see Figures 2 through 4}) were constructed using <br />' the logs of borings from ARCO investigations (RESNA Industries, June 10, 1994) and <br /> cross-sections from the adjacent property (Groundwater Technology, Inc [GTI], <br /> September 16, 1992, GTI, December 16, 1992, Science and Engineering Analyses <br />' Corporation [SEACOR], September 29, 1994) <br /> Groundwater was encountered at approximately 41 to 43 feet bgs during drilling Since <br />' monitoring began, the depth to water beneath the site has fluctuated from approximately <br /> 37 to 44 feet bgs Based on information provided by SJCPHS, seasonal high for static <br /> groundwater has historically reached approximately 25 feet bgs',/The direction of <br /> SACW TJ"805\08051460 2AS-94\pas i Rev 0 515/95 <br /> 0805-14602 2-1 <br />