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Phase II Field <br /> ARCADIS Investigation and LNAPL <br /> ' Mobility Evaluation Report <br /> Union Pacific Railroad Company <br /> Former Maintenance Facility <br /> Tracy,California <br /> Sn, — residual LNAPL saturation, dimensionless <br /> Selg = effective total liquid saturation, dimensionless <br /> Relative permeability is the ratio of effective LNAPL permeability(that is the <br /> permeability of a soil to LNAPL at a particular LNAPL saturation)to absolute <br /> permeability of LNAPL at 100 percent saturation.The spreadsheet calculates LNAPL <br /> relative permeability as a function of water and LNAPL saturation using Equation 5 for <br /> the Mualem relationship and Equation 6 for the Burdine relationship. Mualem is <br /> typically more representative in cohesive soils,while Burdine is more representative in <br /> coarser materials. c <br /> km(`Sw,SJ=(S,)'x((1—Selwl —/1 Selrh/M l (Equation 5) <br /> ' <br /> km(Sw,s„)= S„ X((1—SelWl1/1 _(1_S.elrl7/Mr\I2 (Equation 6) <br /> Where, <br /> k,,, = relative permeability, dimensionless <br /> M = van Genuchten fitting parameter for the water-LNAPL,two-phase <br /> system, dimensionless <br /> The parameter M in Equations 5 and 6 is a fitting parameter used in the Mualem and <br /> Burdine relative permeability expressions. The van Genuchten saturation-capillary <br /> pressure prediction curves are calculated using fitting parameters alpha(a)and beta <br /> (N),which are dependent upon soil texture characteristics.Alpha and beta are derived <br /> via laboratory testing of air-water drainage. The relative permeability fitting parameter <br /> M can be directly related to the soil capillarity fitting parameter N through the following <br /> equations: M=1-11N for Mualem and M=1-2/N for Burdine.The Mualem and Burdine <br /> relationships were derived for air-water two-phase systems.Therefore, adjustments <br /> ' are made for the system being three-phase with air,water, and LNAPL by taking into <br /> account water and LNAPL physical properties, including density, viscosity, and, <br /> especially, interfacial tensions. <br /> The LNAPL conductivity is determined from the hydraulic conductivity, by taking into <br /> account modifications for the fluid property differences between water and LNAPL. The <br /> ' relationship between conductivities, density, and viscosity is given in Equation 7. <br /> Muo�+�r+�.q mmraHnzszo,o�eoc <br /> 21 <br />