ARCHIVED REPORTS_XR0004132- CASE 2

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Site Background Information Five Star Marina Page 8 of 8 15 feet bsg, at which point the contaminants encountered a more porous sandy unit and assumed ' a north-northeastern lateral migration in the dominant direction of ground water flow Lateral migration of petroleum hydrocarbon contaminants appears to terminate north of monitoring well MW-8 and east of boring P22 The vertical migration of soil contamination appears to be slowed ' by the silty and clayey layer encountered below the sand unit, starting at approximately 20 feet bsg ' Significant petroleum hydrocarbon-impact to soil in the smear zone was present in boring P22, advanced on 01 December 1997 east of the fan-ner eastern UST area TPH-g and MTBE were detected at concentrations of 2,100 mg/kg and 1,600 mg/kg, respectively, in a soil sample ' collected at 10 feet bsg Additionally, the grab ground water sample from boring P19 contained MTBE at 3,300 µg11 (EPA 8260) ' A grab ground water sample collected in February 2006 from boring B5 at a depth of 10 feet bsg did not contain detectable amounts of petroleum hydrocarbons However, a grab ground water sample collected at approximately 47 feet bsg from the same boring indicated an elevated amount of TPH-g and minor detections of ethylbenzene and xylenes TPH-g and BTEX have been detected in ground water samples from monitoring well MW-8, located 20 feet north of the former east UST area Well MW-5, located 75 feet north of MW-8, has typically remained 10 uncontaminated Graphs illustrating ground water contamination trends are included in Appendix I- R F S11)114 1 ~RFSI17fl4l CON TA IWIVA TION/I NI) 1/II6RATfON ' Most of 1_11c contamination in both the west and east 1JS`l areas apparently resides above 20 I cet bsg, in the Sandy and fine-grained layers comprising HU 1 and HU2 rhe highest residual contamination is present near the east UST, near bonng P22, at the former dispenser location ' t ateral hydrocarbon impact to soil and ground water is defined in all directions, cxcc,pt south of boring P19 at the east UST aiea, in both the west and cast tormcr UST areas (Higures 7 and 8) The vertical extent of soil contamination does not appear to exceed 25 feet bsg, with the ' exception of a minor dctcction of TPH-g to boring 131 at 30 feet bsg The vertical LXtLnt of ground tivatci contamination may not be defined vcrttcally in the area of the cast UST, as low concentrations of TPH-g, cthylbcnlcnL, and xylenes contamination arL, present in thu location of ' R5 at a depth of 47 feet bsg The vertical extent of ground water contamination is definers in the area cif the, we4 UST a5 Wntanlination was not. ptLs�,nt in i giah giound N�atLl sarnrle collccter_i at 40 feet bsg from boring 131 I I � 1 tdi m d( aiii sat:i iiiinii