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t Site Background Informatlon/SCM Former MBP - Moss dale AGE NC Project No 99-0570 Page 3 of 5 concentrations of 49 milligrams per kilogram(mg/kg), 180 mg/kg,0 36 mg/kg, and 78 micrograms per kilograms (pg/kg), respectively Laboratory analysis of grab ground water samples indicated that the highest concentrations of TPH-g, TPH-d, BTEX, and MTBE were in the vicinity of the former ' dispenser islands Based on the data collected,the dispenser islands appear to be the primary source of the hydrocarbon release ' Soil from B-1,B-2,and B-7 at 15 feet bsg had low concentrations of hydrocarbons,while soil from 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 of fuel additives (MTBE) Hydrocarbon-impacted ground watera 'a ¢ete at B-i B-6 B-7 and ' B-8 and MTBE was detected in grab ground water samples fro al al MTBE was detected by EPA Method 8260 in all grab ground water samples at a maximum of 150 µg/l(B-6) The results of the soil and ground water investigation are summarized in Tables 1 and 2 of this appendix ' Ground water monitoring wells MW-1 through MW-5 were Installed on 27 and 28 September 2000 ' and monitored and sampled on 03 October 2000 TPH-g and TPH-d compounds were detected in only one of eleven soil samples, at similar concentrations of 170 mg/kg, in addition, BTEX and several additional volatile organic compounds were detected at concentrations up to 0 44 mg/kg The soil data is summarized In Table 3 of this appendix TPH-g,TPH-d,and BTEX were dete� ed Intwo o U groundwater samples collected on 03 October 2000 at maximum concentrations oflg/1, 2; - µg/l, and 160µg/1, respectively, in addition, MTBE was detected in three ground water samples at ' a maximum concentration of 170 µg/1 On 09 December 2003, three soil borings (CPT-1, CPT-2, and CPT-3) were advanced on-site ' utilizing cone penetrometer testing(CPT)technology to a total depth of approximately 110 feet bsg At each boring location, hthologic data was collected from the initial CPT boring, an immediately adjacent twin boring was then advanced to collect grab ground water samples CPT-1 was sampled between 55 feet and 60 feet bsg and between 80 feet and 84 feet bsg, CPT-2 was sampled between 55 feet and 60 feet bsg,between 89 feet and 94 feet bsg,and between 110 feet and 114 feet bsg, and CPT-3 was sampled between 55 feet and 60 feet bsg, between 85 feet and 90 feet bsg, and between ' 110 feet and 114 feet bsg The results of this Investigation are summarized In Table 4 of this appendix ' HYDROGEOLOGIC MODEL ' Based on the CPT results, AGE has assigned names to four Informal zones a vadose(unsaturated) zone and three hydrogeologic units Vadose Zone- This zone extends from surface grade to approximately 15 feet bsg, the depth to the water table The vadose zone Is predominantly fine-grained material from surface grade to 15 feet r is bsg with a coarse-grained sand unit occurring between 20 feet and 25 feet bsg at CPT-2 The zone kejH Advanced GeoEnviron mental,Inc V ryL