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I <br /> Site Conceptual Model <br /> Frontier Transportation <br /> June 30, 2003 <br />' Page S <br /> �.45�f rk <br /> Based on the groundwater sample results, it is estimated that 835,816 gallons of impacted <br />' groundwater exist in the subsurface (See Appendix E for extent of impacted groundwater) The <br /> impacted groundwater region starts at approximately 10'bg and ends at approximately 15' bg <br /> (assumption based on LNAPL characteristics such as density and miscibility) The estimated <br />' area of impacted groundwater was defined by existing groundwater sample results The <br /> estimated mass of dissolved petroleum hydrocarbons were calculated as follows <br />' Mass of Impacted Groundwater= a x 75 feet x 95 feet x 5 feet (thickness of groundwater) <br /> Mass of Impacted Groundwater= 111,919 W x 7 481 gallons/ft3 = 837,268 gallons <br />' Estimated Impacted Groundwater Removed from Well Purging = 1,452 gallons <br /> Mass of Impacted Groundwater in Place = 837,268 gallons - 1,452 gallons = 835,816 gallons <br />' Although a significant mass of impacted groundwater was calculated to exist beneath the <br /> site, historically the dissolved petroleum hydrocarbons have been confined to the site due to the <br /> discontinuous sandy clay lenses and the relatively flat hydraulic gradient Since the dissolved <br />' plumes have remained confined to the site, no impact to nearby receptors is anticipated (See <br /> Appendix E for map of nearby receptors) <br />' * 6.0) CONCLUSIONS <br /> Based on soil sample results, the shallow impacted soil extends from 4' to 9' bg was <br />' exclusively limited to borings B-1 through B-4end MW-13 Furthermore, elevated TPH-g, <br /> BTEX, and MTBE concentrations from the capillary fringe and saturated zone (9 5' to-I V bg) <br /> indicate that petroleum hydrocarbons have migrated through the soil and impacted the shallow <br />' groundwater The lateral extent of the deep impacted soil (9 5' to 14' bg) was spread by impacted <br /> groundwater As the source of TPH-g, BTEX, and MTBE identified in soil collected from B-1, B- <br /> 2, B-3, B-40MW-IRA, MW-IRB, MW-2RA, MW-2, MW-3`and MW-13 <br /> Based on groundwater sample analysis results, most of the mass of the dissolved TPH-g, <br /> BTEX, and MTBE plumes appear to be localized near the former gasoline UST locations--'No <br />' detectable to low level concentrations (below Maximum Contaminant Levels) of dissolved TPH- <br /> d, TPH-g, BTEX, and MTBE were identified historically in eleven of the thirteen monitoring <br />' wells dedicated to the site <br /> 1 <br /> 1 <br />