ARCHIVED REPORTS_GROUNDWATER MONITORING AND REMEDIATION REPORT - 3RD AND 4TH QUARTERS 2010

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respectively: total petroleum hydrocarbons as gasoline (TPHg), total petroleum hydrocarbons as diesel (TPHd), benzene, methyl tertiary-butyl ether (MTBE), and tertiary-butyl alcohol (TBA). 3.4.1 TPHG ISOCONCENTRATION MAP As shown on Figure 4, maximum TPHg concentrations occurred in wells MW-37, located near the truck loading rack, and well MW-10, located near Tank 14. TPHg concentrations in wells MW-37 and MW-10 were 31,000 and 28,000 micrograms per liter (gg/L), respectively. With the exceptions of wells MW-18 and MW-33, the TPHg plume attenuates to less than 100 gg/L in all perimeter wells. TPHg concentrations in wells MW-18 and MW-33 were 860 and 5,600 gg/L, respectively. Well DW-2 defines the vertical extent of the TPHg plume. The laboratory noted that there was analyte present in the associated method blank for several wells,including MW-10 and MW-37. 3.4.2 TPHD ISOCONCENTRATION MAP As shown on Figure 5, maximum TPHd concentrations occur in wells MW-10 and MW-15. TPHd concentrations in these wells were 5,400 gg/L (MW-10) and 4,200 gg/L (MW-15). The TPHd plume attenuates to 100 gg/L in perimeter wells, with the exceptions of wells MW-18 (620 gg/L) and MW-33 (1,100 gg/L). The laboratory noted that the TPHd reported in well MW-33 did not match the chromatographic pattern of the diesel standard and that while the TPHd reported in well MW-18 did match the diesel standard pattern, lighter hydrocarbons were also present. Well DW-2 contained 130 gg/L TPHd, although the laboratory noted that the TPHd reported did not match the chromatographic pattern of the diesel standard. 3.4.3 BENZENE ISOCONCENTRATION MAP As shown on Figure 6, maximum benzene concentrations occur in well MW-10 (12,000 gg/L). With the exception of well MW-33 (170 gg/L), the benzene plume attenuates to 1.0 gg/L in perimeter wells, and well DW-2 defines the vertical extent of the benzene plume. 241729(28) 4 CONESTOGA-ROVERS&ASSOCIATES