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' Atlantic Richfield Company 5 <br /> _ARCO 595 6100 North Highway 99,Stockton CA December 12 2001 <br /> . Stockpiled Soil <br />' Approximately 10 cubic yards of soil generated during the installation of the wells was <br /> stockpiled onsite One composite sample (4 sleeves to 1 sample) was collected from the <br />' stockpiled soil and analyzed for TPHg, BTEX, MtBE, and total lead No compounds <br /> were detected Soil was disposed of at Forward Landfill in Manteca, California <br /> Stockpiled soil analytical data Is presented in Table 7, and a soil disposal confirmation is <br />' Included as Attachment H <br /> SUMMARY OF FINDINGS <br /> • TPHg, MtBE, and fuel oxygenates were reported as nondetectable in <br /> all soil samples Only trace detections of benzene, toluene, and <br />' xylenes were reported In soil samples from MW-5 <br /> • MtBE and 1,2-DCA were reported in depth discrete water samples <br />' from PSB-1 at depths of 75 feet bgs and 90 feet bgs MtBE and 1,2- <br /> DCA concentrations In the sample collected at 90 feet bgs were 39 ppb <br /> and 10 ppb, respectively MtBE and 1,2-DCA were reported In depth <br />' discrete water samples from PSB-2 at depths of 64 feet bgs and 95 feet <br /> bgs MtBE and 1,2-DCA concentrations In the sample collected at 95 <br /> feet bgs were 2 7 ppb and 4 2 ppb, respectively Additionally, the <br /> groundwater sample from PSB-2 at 95 feet bgs contained minor <br /> detections of toluene (1 0 ppb), ethyl-benzene (0 54 ppb), and xylenes <br />' (3 0 ppb) <br /> • MtBE was reported at concentrations of 2 6 ppb (MW-5) and 94 ppb <br /> (MW-7) In the newly Installed wells 1,2-DCA was reported at <br />' concentrations of 3 2 ppb (MW-5) and 23 ppb (MW-7) Other <br /> analytes in the new wells were reported as nondetectable The highest <br />' hydrocarbon concentrations in the existing wells were generally <br /> reported in well MW-4 <br /> • Groundwater flow was to the northwest at a gradient of 0 002 ft/ft <br />' • Two previously unknown domestic wells, and one additional <br /> previously unknown well were located during a 500-foot radius door- <br /> to-door well survey <br /> • Approximately 10 cubic yards of stockpiled soil generated during <br />' drilling activities was disposed of at Forward Landfill In Manteca, <br /> California <br />' CONCLUSIONS AND RECOMMENDATIONS <br /> Based on the data collected during this assessment, petroleum hydrocarbons in soil have <br />' been delineated both laterally and vertically Vertical and lateral delineation of fuel <br />' 077 43029 3301well insta112 doc <br />