[en] An aerial radiological survey was conducted over the Weldon Spring Chemical Plant, which is in St. Charles County, thirty miles from St. Louis, Missouri. The survey was performed in May 1976 using sodium iodide detectors mounted in a helicopter. Gamma gross count and thallium radiation isopleths were superposed on an aerial photograph of the Site. Several concentrations of uraium and thorium waste were located. All contaminants were on the Site or within 200m of the fence line. The survey was sponsored by the U.S. Department of the Army, authorized by the U.S. Energy Research and Development Administration, and conducted by EG and G, Incorporated of Las Vegas, Nevada