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15 October 2000 <br /> AGE-NC Project No 96-0232 <br /> Page 5ofII _ <br /> and Water Conservation District(FCD&WCD)dating back to 1971 suggests that ground water depth <br /> near the site has fluctuated between approximately 5 and 15 feet bsg <br /> Based on ten ground water monitoring events recorded at the site between July 1996 and March <br /> 2000, depth to ground water measurements have fluctuated between 3 and 15 feet bsg <br /> 22 Ground Water Flow Direction And Gradient ' <br /> Review of regional ground water elevation maps dating back to 1971 and published by the <br /> FCD&WCD suggest a southeast to south ground water flow direction <br /> Based on ten ground water monitoring events recorded at the site between July 1996 and March <br /> 2000, gradient has been relatively horizontal at the site ranging between 0 001 ft/ft and 0 01 ft/ft <br /> Ground water flow direction has been inferred to be towards the north on four occasions (May 97, <br /> February 98, November 98 and March 2000), towards the west on one occasion (July 1998), towards <br /> the cast on one occasion (February 2000), towards the south on two occasions (July and August <br /> 1996), locally varying between northeast and southwest on one occasion(February 1999) and locally <br /> varying between northwest and southeast on one occasion (June 1999) ' <br /> 23 Vertical And Lateral Extent Of Pollution' <br /> Grab ground water samples were collected from twenty-six soil borings at the site (PI through P5, <br /> PI through P32, P34 and P35) Laboratory analysis of grab ground water samples site indicated that <br /> ground water at the site has been impacted by MTBE,TPH-d and TPH-g, laboratory analysis of grab <br /> ground water samples also detected low concentrations of dissolved BTEX, 1,2-DCA, TBA, ethanol <br /> and methanol <br /> The highest concentration of dissolved MTBE in shallow ground water was detected at a <br /> concentration of 11,000 jcg/l in the sample from soil boring P32 near the southwest fuel dispenser, <br /> moderate to high concentrations of dissolved MTBE were detected in samples from P19, P22 , P30, <br /> P31 and P34 at concentrations ranging from 1,000µg/1 to 4,300,ug/l The highest concentration of <br /> dissolved TPH-g detected was from the grab sample from soil'boring P30 near the middle-west fuel <br /> dispenser, at a concentration of 11,000 ug/l, low concentrations of dissolved TPH-g were detected <br /> in samples P22, P24, P31 and P34 at concentrations ranging between 110 µg/1 and 210 ,ug/1 The <br /> highest concentration of dissolved TPH-d was from the sample collected soil boring P30 at a` <br /> concentration of 1,900µg/l, moderate to low concentrations of dissolved TPH-d were detected from <br /> soil borings P18,. P19, P20, P23, P24, P25,' P27, P28, P31, P32, P34 and'P35 at concentrations <br /> ranging from 60µg/1 to 250µg/l The above results suggest the dispenser area, the southwest comer <br /> of the UST pit and the storm water drain line area as potential source area(s) <br /> Adv"ced Geo F.nYIT0nmentai,inc <br />