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1 <br /> 1 <br /> ARCADIS Phase II Field <br /> ' Investigation and LNAPL <br /> Mobility Evaluation Report <br /> Union Pacific Railroad Company <br /> t Former Maintenance Facility <br /> Tracy,California <br /> LNAPL relative permeability,calculated using the Mualem model and the Burdine <br /> ' model and provided by the laboratory, by formation intrinsic permeability, results in <br /> permeability to LNAPL in the presence of water(i.e., LNAPL permeability) in square <br /> centimeters. The laboratory and modeled LNAPL permeability for LIF-02 are presented <br /> on Figure 9.Analysis of the data indicates that the van Genuchten-Burdine model is <br /> more appropriate than the van Genuchten-Mualem model for modeling LNAPL mobility <br /> at the Site. The van Genuchten-Burdine model provides a conservative estimate of <br /> ' LNAPL mobility as illustrated by the separation between the laboratory-reported and <br /> modeled LNAPL permeability curves(Figure 9). The LNAPL permeability calculated <br /> using the van Genuchten-Burdine model was two orders of magnitude greater than the <br /> laboratory results for LIF-02. <br /> 4.2 Groundwater <br /> ' 4.2.1 TEPH-d and VOC Concentrations <br /> Analytical results from groundwater samples collected at the 23 HP locations are <br /> summarized in Table 3. Groundwater monitoring results from March and June 2010 <br /> are presented in Table 1. Figure 8 includes TEPH contours based on both HP samples <br /> ' and groundwater monitoring results. The observations of LNAPL noted in Figure 8 only <br /> represent observed LNAPL in wells and do not represent LIF results. Results from HP <br /> samples confirm our understanding of the extent and distribution of impacted <br /> groundwater based on groundwater monitoring well data. <br /> TEPH-d in Grab Groundwater Samples <br /> ' The highest TEPH-d concentration in grab groundwater samples(8,900,000 pg/I; Table <br /> 3)was detected in a sample collected in the TPCA pond (HP-11).TEPH-d was not <br /> ' detected above detection limits in most HP samples outside of the TPCA pond, with <br /> the exception of HP-12 located west of the Engine House and HP-6 located northeast <br /> of the Engine House. The TEPH-d concentration was 220 pg/I at HP-12 and 180 pg/I at <br /> ' HP-6. Groundwater impacts are contained on the property and currently extend from <br /> the TPCA pond 900 feet north-northeast to MW-24A and 700 feet north to MW-27A. <br /> 1 <br /> mwpm r+ lmoW"I1-2a2oiu).eoc <br /> t 15 <br />