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Gamma Survey Plan <br />The radiometric survey of the site will be conducted with an advanced <br />GPS -based gamma scanning system mounted to a backpack along <br />with a mini - tablet PC with special software for automated data <br />collection (Figure 1). Gamma detector instrumentation for the survey <br />will include a factory calibrated 2 "x2" Ludlum Model 44 -10 sodium <br />iodide (NaI) detector, connected to Ludlum Model 2350 rate meter. <br />Gamma readings (in pR/hr) and location coordinates from a GPS <br />receiver will be simultaneously recorded every 1 -2 seconds during a <br />walkover survey of the site. <br />The gamma detector height will be approximately 3 feet from the Figure 1: Automated <br />ground surface. Wherever possible, the maximum distance between _ backpack scanning <br />adjacent scan travel paths will be kept within 30 -50 feet of each other system. <br />to maintain adequate areal scan coverage. All areas of the site that are safely accessible by foot <br />will be surveyed. Following completion of the survey, raw gamma scan data will be kriged <br />(interpolated) in GIS to provide a continuous, color -coded map of the spatial distribution of <br />terrestrial gamma radiation across the site. Figure 2 shows an example of raw survey data (left) <br />along with a kriged rendering of the same data (right). <br />Figure 2: Example of raw gamma scan data (left) and corresponding kriged representation of the <br />distribution of terrestrial gamma radiation. <br />