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Ground Penetrating Radar , <br /> A high frequency radio signal is transmitted into the ground via the <br /> antenna As radio waves propagate into the ground, these signals <br /> are reflected off structures with differing electrical properties <br /> These reflected signals are then captured by the receiver and are ' <br /> presented as vertical profiles on the GPk unit <br /> GPR traverses were collected over areas identified in the <br /> magnetics data The GPR data were collected along bi-directional <br /> traverses These data were reviewed in the field and used to better <br /> characterize the source of magnetic anomalies ' <br /> Results There were a number of surficial metallic objects which caused ' <br /> significant magnetic anomalies that were characterized by high <br /> amplitude negative monopoles in the total field data (Figure 2) ' <br /> These features included the fenced vapor extraction system <br /> (surrounded by metallic parking barriers and a dumpster), a parked <br /> car, the building, and the overhead sign/mailbox ' <br /> This site also contains a number of metallic objects located below <br /> ground, or at the surface, which produced moderate to high ' <br /> amplitude positive monopoles in the magnetic data <br /> A 12-inch diameter metallic well casing was the source of one <br /> significant anomaly centered at Line 43, Station 41 which produces <br /> a magnetics anomaly 5000 gammas above background Metallic <br /> monitoring well covers, a PG & E vault cover, and conduits also ' <br /> _ - <br />