Electromagnetic conductivity and magnetic surveys for characterization of an abandoned nuclear reactor facility

Electromagnetic conductivity and total field magnetic surveys were conducted over a 14 acre portion of a site used during the Manhattan Project for nuclear research and plutonium production. While the facility was decommissioned and abandoned in 1953, there is presently some concern related to the potential for movement of radioactively contaminated ground water and sediments through high permeability underground features, such as tunnels or pipes. In addition, a number of underground storage tanks were left in place when the site was abandoned. The objectives of the surveys were to enhance the available data base related to the locations of underground features. The electromagnetic results clearly defined the presence of steam lines, water mains, electrical utility lines, building foundations, underground storage tanks, and a tunnel. The magnetic results were ineffective in detecting elongated subsurface features and provided relatively poor definition of building foundations. However, the magnetic results did detect disposal areas and reactor remains that were poorly defined by the electromagnetic data. The differences in the two data sets demonstrate the need for both electromagnetic and magnetic surveys in site characterization studies. Thirteen of the excavated anomalies were associated with buried utility features that could serve as high permeability conduits for ground water or sediment movement. The deepest of these was a 6 inch water main at a depth of 6 feet. The remainder of the utilities were at depths of 4 feet or less. Three of the anomalies resulted from underground storage tanks that ranged in size from 1000 gallons to 5000 gallons. Seven of the anomalies resulted from general waste disposal areas. The use of historical documentation combined with electromagnetic and magnetic surveys provided a cost effective method for baseline characterization of the complex underground features associated with a nuclear reactor facility