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10 <br /> Site Background Information/SCM Former MBP - Mossdale <br /> AGE NC Project No 99-0570 <br /> Page 3 of 5 <br /> concentrations of 49 milligrams per kilogram(mg/kg), 180 mg/kg,0 36 mg/kg,and 78 micrograms <br /> per kilograms(µg/kg),respectively Laboratory analysis of grab groundwater samples indicated that <br /> the highest concentrations of TPH-g,TPH-d, BTEX, and MTBE were in the vicinity of the former <br /> dispenser islands Based on the data collected,the dispenser islands appear to be the primary source <br /> of the hydrocarbon release <br /> Soil from B-1,B-2,and B-7 at 15 feet bsg had low concentrations of hydrocarbons,while soil from <br /> B-1,B-6, and B-7 at 10 and 15 feet,as well as B-2 at 10, 15, and 20 feet bsg had low concentrations <br /> of fuel additives(MTBE) Hydrocarbon-impacted ground water .�s�je��,,V-I,B-6,B-7, and <br /> B-8 and MTBE was detected in grab ground water samples froii�.-6 and BE was detected <br /> by EPA Method 8260 in all grab ground water samples at a maximum of 150 pg/1(B-6) The results <br /> of the soil and ground water investigation are summarized in Tables 1 and 2 of this appendix <br /> Ground water monitoring wells MW-1 through MW-5 were installed on 27 and 28 September 2000 <br /> and monitored and sampled on 03 October 2000 TPH-g and TPH-d compounds were detected in <br /> only one of eleven soil samples, at similar concentrations of 170 mg/kg, in addition, BTEX and <br /> several additional volatile organic compounds were detected at concentrations up to 0 44 mg/kg The <br /> soil data is summarized in Table 3 of this appendix TPH-g,TPH-d,and BTEX were detected in two <br /> iground water samples collected on 03 October 2000 at maximum concentrations of 70µg/1, 2,000 <br /> pgd, and 160µg/1, respectively, in addition, MTBE was detected in three ground water samples at <br /> a maximum concentration of 170µ1 <br /> 1�� te' r ' ry 0 a . <br /> On 09 December 2003, three soil borings (CPT-1, CPT-2, and CPT-3) were advanced on-site <br /> utilizing cone penetrometer testing(CPT)technology to a total depth of approximately 110 feet bsg <br /> At each boring location, lithologic data was collected from the initial CPT boring, an immediately <br /> adjacent twin boring was then advanced to collect grab ground water samples CPT-1 was sampled <br />' between 55 feet and 60 feet bsg and between 80 feet and 84 feet bsg, CPT-2 was sampled between <br /> 55 feet and 60 feet bsg,between 89 feet and 94 feet bsg,and between 110 feet and 114 feet bsg, and <br /> CPT-3 was sampled between 55 feet and 60 feet bsg,between 85 feet and 90 feet bsg, and between <br />' 110 feet and 114 feet bsg The results of this investigation are summarized in Table 4 of this <br /> appendix <br /> HYDROGEOLOGIC MODEL <br />' Based on the CPT results,AGE has assigned names to four informal zones a vadose (unsaturated) <br /> zone and three hydrogeologic units <br />' Vadose Zone-This zone extends from surface grade to approximately 15 feet bsg,the depth to the <br /> water table The vadose zone is predominantly fine-grained material from surface grade to 15 feet <br /> . bsg The zone is characterized by low pore pressures �--- <br /> Advanced GeoEnvironmental,Inc <br /> I <br />