Aerial radiological survey of the La Salle County Station and surrounding area, Seneca, Illinois. Date of survey: July 1981

An aerial radiological survey was performed from 14 to 31 July 1981 over a 270-square-kilometer area centered on the La Salle County Station near Seneca, Illinois. The survey was conducted by EG and G for the US Nuclear Regulatory Commission. All gamma ray data were collected by flying lines spaced 152 meters (500 ft) apart at an altitude of 91 meters (300 ft) above ground level. Processed data showed that all gamma rays detected within the survey area were those expected from naturally occurring background emitters. Count rates obtained from the aerial platform were converted to exposure rates at 1 meter above the ground and are presented in the form of an isoradiation contour map. The observed exposure rates for the survey area were between 5 and 14 microroentgens per hour (μR/h), with most of the area ranging from 8 to 14 μR/h. The exposure rate obtained from soil samples taken from within the survey site displayed positive agreement with the aerial data