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S E C 0 R <br /> ZIECO Q <br /> 1 �y <br /> ti <br /> 5.0 PETROLEUM HYDROCARBON DISTRIBUTION AND CONCENTRATION <br /> TRENDS <br /> 5.1 Distribution of Petroleum Hydrocarbons in Soil <br /> 5.1.1 Lateral Distribution of Hydrocarbons in Shallow Soil. <br /> Concentrations of TPHg, benzene, ethylbenzene, xylenes, MtBE, TBA and the <br /> approximate extent of adsorbed hydrocarbons in soil are illustrated on Figures 4 and 5. <br /> ' Maximum adsorbed concentrations are located in the vicinity of the former underground <br /> storage tanks. The maximum adsorbed concentrations were reported in sample <br /> locations T-3-E @ 13' (5,800 ppb TPHg) from beneath the USTs and sample MW- <br /> 3@16' (6,800 ppb). <br /> The lateral distribution of hydrocarbons in shallow soil has been defined by the following <br />' <br /> borings.- <br /> Direction <br /> orings:Direction Delineation Boring/Well <br />' North (downgradient) GP-13, GP-14, and GP-16 Q <br /> South (upgradient) MW-8 <br /> lie East GP-4 and GP-5 <br /> West GP-2, GP-3, and GP-7 <br /> 5.1.2 Vertical Delineation of Hydrocarbons in Soil <br />' Vertical delineation of absorbed hydrocarbons y bons m sort was completed in February of <br /> 2005 by drilling two (DGP-1 and DGP-2) direct push soil borings (dual-hole) to depths of <br /> 70 to 75 feet bgs. The vertical extent of hydrocarbons was delineated onsite by DGP- °g <br /> 2@31' and offsite by DGP-1 @40'. <br />' 5.2 Petroleum Hydrocarbons in Groundwater <br /> Concentrations of TPHg, benzene, and MtBE dissolved in shallow groundwater in m <br /> January 2005, are illustrated in Figures 7 through 9. <br /> k� <br /> 5.2.1 Lateral Distribution of TPHg in Shallow Groundwater <br /> The lateral extent of TPHg in the shallow water bearing zone is delineated cross and <br /> upgradient of the site. Based on the isoconcentration map included as Figure 7, the N.. <br /> TPHg plume in shallow groundwater to the northeast (downgradient) is delineated to <br /> below 100 ppb by wells MW-17, MW-18 and MW-19. TPHg was observed in MW-17 at <br /> a concentration of 87 ppb based on the first sampling of the well. Historical maximum .' <br /> concentrations of TPHg was observed in well MW-5 at a concentration of 110,000 ppb. <br /> l .M <br /> 1205 SCM.doc � <br /> :ri <br />