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' irreducible water saturation, oil can flow, but water will be held by capillary forces <br /> Likewise, at an oil content less than the residual oil saturation, water can flow, but oil <br /> cannot, at least as a separate phase Oil droplets dispersed in the water can stall migrate <br /> In order for hydrocarbons (oil) to become entrapped in soil in this way, the hydrocarbons must <br /> first pass through the soil As previously stated, the water table elevation began to rise and at the <br /> present time the screened intervals of some wells are submerged It appears from soil samples <br /> collected below the current water table, that when the groundwater rose, the residual <br />' hydrocarbons were left within the saturated zone This is also demonstrated by the fact that well <br /> WB-MW1 has contained detectable amounts of LPH (0 02 feet on 21 June 2001) <br />' Figure S 22c (presented in Appendix K) (Fetter 1993) illustrates the aftermath of the rise in <br /> groundwater These residual hydrocarbons exist in a water-saturated environment where the <br /> water content is much greater than the irreducible water saturation In this case, as the reference <br /> above states, water can flow at a much lower rate but the residual hydrocarbons (oil) will not <br /> flow The residual hydrocarbons will instead achieve equilibrium by conserving surface area and <br /> adhering to the soil The transfer of submerged residual hydrocarbons into groundwater is a very <br /> slow diffusion limited process that does not generally produce large concentrations in <br /> groundwater Based on this, groundwater extraction would not effectively remediate this site <br />' under current hydrogeologic conditions <br /> • No remedial action. Based on a review of the site conditions and past performances of <br /> remedial systems, active remediation is not proposed Current hydrogeologic conditions <br /> limit dissolution and transport of hydrocarbons in the saturated zone This has allowed <br /> natural attenuation processes to effectively limit the migration of hydrocarbons The primary <br /> process limiting hydrocarbon transport downgradient is biodegradation It has been shown <br /> that this process can limit migration as hydrocarbon concentrations at the source decrease <br /> Natural attenuation is the proposed remedial alternative for the site <br /> 1 <br />' 0 IPioJeLts173942,MASTERNWP1RaOSOIker(2 doc 9 <br />