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' ARCADIS Phase II Field <br /> ' Investigation and LNAPL <br /> Mobility Evaluation Report <br /> Union Pacific Railroad Company <br /> ' Former Maintenance Facility <br /> Tracy, California <br /> 3.6 LNAPL Sampling <br /> LNAPL samples were collected from site wells on August 20, 2008 using a disposable <br /> bailer and submitted to Harris Laboratories, Inc., of Houston, Texas, for physical <br /> analysis. The LNAPL sample from well MW-6A was collected to assess the physical <br /> properties of the weathered LNAPL associated with historical releases. <br /> The LNAPL sample collected from well MW-6A was analyzed for LNAPL density, <br /> viscosity, and interfacial tension between air,water, and LNAPL.A brief background of <br /> each test and the pertinent information generated from the tests are below: <br /> ' LNAPL Density—ASTM D1481: This test provides basic information on the density <br /> of the LNAPL,which is compared to that of water and used when modeling the <br /> ' distribution and mobility of the LNAPL. The density test was run at 77 degrees <br /> Fahrenheit(°F). <br /> • LNAPL Viscosity—ASTM D445: This test assesses fluid viscosity at a controlled <br /> temperature representative of groundwater temperature. LNAPL is typically more <br /> viscous than groundwater, and LNAPL viscosity is used to translate hydraulic <br /> conductivity to LNAPL conductivity. The viscosity test was run at 65°F. <br /> ' Interfacial Tension—ASTM D971: Interfacial tension between air-water, air- <br /> LNAPL, and water-LNAPL fluids is assessed with this test. This information is used <br /> ' as input for the LNAPL modeling to determine the distribution and mobility of the <br /> LNAPL in the subsurface.Air-water interfacial tension was not run on MW-6A. The <br /> water-LNAPL interfacial test was run at 77°F. <br /> ' 4. Phase II Field Investigation Results and Discussion <br /> The following sections summarize analytical data and results obtained during the <br /> investigation activities outlined above. <br /> ' 4.1 LNAPL Characterization <br /> 4.1.1 LNAPL in Wells <br /> ' Currently, there are 21 A-Zone monitoring wells, 10 piezometers, and four temporary <br /> monitoring wells located in the vicinity of the Engine House. LNAPL accumulation has <br /> ' been observed consistently in several monitoring wells in this area since 1995. <br /> �.Mo �W MWIM1,.zazo,o) <br /> ' 11 <br />