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i iSite Background Information • PREM DOR i433 West Scotts Street, Stockton, California STRATIGRAPHY ' Generally, gray, orange-brown to dark-brown, dry, silt with sand and gravel (fill matenal),was encountered from surface grade to approximately 6 feet bsg Light yellow-orange-brown to dark ibrown, damp to moist, clays, clayey silts and clayey sands were encountered from approximately 6 feet bsg to 21 feet bsg Brown,blue-gray to dark-gray, saturated, fine to coarse sand and silty sand was encountered from approximately 21 feet to 29 feet bsg, but to almost 35 feet bsg in the area of iMW2 Gray to blue-gray, moist to saturated clay with medium to high toughness and plasticity was encountered from approximately 29 feet bsg to 36 feet bsg Blue-gray to green-gray, saturated, silt ' was encountered from approximately 36 feet bsg to 49 feet bsg in soil boring B4 Green-grey saturated, fine sand was encountered from approximately 49 feet bsg to the extent of the boring in soil boring 134 PREVIOUS SITE ASSESSMENTS ' On 15 and 16 October 2002, three soil bonngs B 1 though B3 were advanced to a depth of 35 feet below surface grade (bsg), utilizing a van-mounted Geoprobe 5400 direct-push probing unit ' equipped with 1 25-inch probing rods,for the collection and analysis of soil and `grab' groundwater samples After probing to a depth of 25 feet bsg, ground water was found to be at approximately 22 feet bsg Soil boring B 1 was advanced in the northwest corner of the former UST excavation Soil boring B2 was advanced approximately five feet cast of the former UST excavation and soil boring B3 was ' advanced approximately ten feet southwest of the former UST excavation A total of six soil samples were analyzed for the petroleum hydrocarbon products TPH-g was detected in soil samples collected from all three borings at a maximum concentration of 22,000 milligrams per kilogram (mg/kg), in sample B2-15 TPH-d was detected in soil samples collected from borings B1 and B2 at a maximum concentration of 7,500 mg/kg in sample B2-15 BTEX ' compounds were detected in soil samples collected from all three borings at maximum concentrations of 1 I mg/kg,460 mg/kg,320 mg/kg and 1830 mg/kg,respectively,in sample B2-15 ' Lead was detected by EPA Method 6010B in one soil sample collected in boring B2 at a concentration of 59 mg/kg,in sample B2-15 No additional target analytes were detected at or above laboratory detection limits in the soil samples analyzed A grab ground water sample was collected from each of the three borings on 15 and 16 October 2002 and were analyzed for the petroleum hydrocarbon products TPH-g was detected in ground water samples collected from each boring at a maximum concentration of 170,000 p.g/l in boring B2 TPH- d was detected in ground water samples collected from borings B1 and B2 at a maximum concentration o f 23,000 gg/1 in bonng B2 BTEX compounds were detected in groundwater samples Advanced GeoEnvironmental,Inc