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• ' URS Corporation February 10, 2005 ' Page 4 ' EM Terrain Conductivity The results of the TC survey are shown on the Terrain Conductivity Contour Map,Plate 3. This map indicates a general decrease in terrain conductivity values from the perimeter towards the center of the survey area. The highest TC values (shaded yellow to red) are evident along the perimeter and in a small circular area in the center. The lowest TC values (shaded gray to blue) define a large broad ' circular zone that covers most of the central portion of the site. It has been our experience that low conductivities are indicative of buried landfill debris. Therefore, it is our interpretation that most of ' the survey area consists of buried landfill debris. The VMG anomalies located throughout portions of this low conductivity zone indicate that the landfill material contains both metallic and nonmetallic debris. ' EM In-phase Component ' The results of the IPC survey are shown on the EM In-phase Component Contour Map,Plate 4. This map defines several anomalous areas that are indicative of above or below ground metal objects. They are manifested by closely spaced linear and circular contours that are shaded gray to green. The linear contours are located around the perimeter and represent effects from the wire fence. The circular contours are generally located along the west and east sides of the survey area. These anomalies correspond with the VMG anomalies previously described and probably represent effects from the ' same subsurface sources. It should be noted,that the IPC map does not define all of the buried metal objects detected by the VMG. Therefore,we believe that some of the objects detected by the VMG are probably too small or too deep to be detected by the IPC. ' Electrical Resistivity Profiles The results of the resistivity survey are shown on the 2-D model resistivity sections, Plate 5. These models illustrate general electrical resistivity variations along each section to depths of about 120 feet. The resistivity sections show that most of the subsurface consists primarily of low resistivity materials ' of less than 40 ohm-m. This material is indicated as green to blue on Plate 5 and generally covers the lower regions of each profile. We interpret this zone as representing native materials(interbedded silt, ' clay, and sand). Above this material is a layer of higher resistivity material (indicated as yellow to red) that occurs throughout both profiles. It is our interpretation that this high resistivity material represents buried landfill debris. Along Line 1, the landfill material comprises one relatively large zone that is approximately 450 feet long and 20 to 30 feet thick. Along Line 2,this material occurs in four discrete ' zones. One is relatively large, measuring approximately 150 feet long and 20 to 35 feet thick. The others are smaller,each measuring approximately 30 to 50 feet long and 15 to 20 feet thick. The depth to these zones ranges from 5 to 10 feet below ground surface.