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• URS Corporation February 10, 2005 ' Page 3 ' along these same traverses, resulting in a total of 3,710 EM measurement points. The limits of the VMG/EM surveys are shown on Plate 1. ' Preliminary data analysis was performed in the field to monitor data quality and field survey parameters. Final analysis and data presentation were completed in our office. We transferred the EM and VMG data to a computer and contoured the data sets to produce EM and VMG contour maps. The ' contour maps were then analyzed to determine potential locations that may represent buried metallic and/or nonmetallic landfill material. ' Electrical Resistivity Survey Following the EM and VMG surveys,we conducted an ER survey over the landfill area. The specific location of this survey was based on the approximate boundaries of the landfill debris as determined by our interpretation of the EM and VMG survey results. ' Electrical resistivity dipole data were obtained along two profiles,referred to as Lines 1 and 2 on Plate 1. Lines 1 and 2 are 631 feet long and oriented in southwest to northeast and northwest to southeast ' directions, respectively. Both lines were positioned over interpreted zones of landfill debris. Upon completion of the ER survey,we downloaded the apparent resistivity data to a computer. These data were used to produce 2-D models showing the variation of the electrical resistivity values with depth. ' RESULTS AND INTERPRETATION ' The results of the geophysical investigation are presented on Plates 2 through 5. These plates are the respective Vertical Magnetic Gradient, EM Terrain Conductivity, and EM In-phase Component Contour Maps (Plates 2 through 4), and the ER Profiles, Lines 1 and 2 (Plate 5). Vertical Magnetic Gradient ' The results of the VMG survey are shown on the Vertical Magnetic Gradient Contour Map,Plate 2. This map defines VMG anomalies throughout the site. VMG anomalies are shaded red and blue and ' represent effects from buried ferrous metal objects. The distribution of most of these anomalies suggests accumulations of scattered metal debris throughout the site, including relatively large areas along the north boundary and in the southwest and southeast quadrants. There is a group of closely ' spaced VMG anomalies that form a south to north linear trending alignment in the northwest corner. Unlike the scattered nature of most of the debris, this group is characteristic of metal debris that has been deposited in a landfill trench. It measures approximately 100 feet long by 15 to 25 feet wide. In t addition, there are also large areas of the site, primarily along the perimeter and in the center, that exhibit an absence of VMG anomalies. The lack of anomalies indicates areas that are probably free of buried ferrous metal or contain minimal amounts.