Preliminary results of a helicopter electromagnetic and magnetic survey of the Oak Ridge Reservation, Tennessee for environmental and geologic site characterization
The 35,252 -acre Oak Ridge Reservation (ORR), in the western portion of the Appalachian Valley and Ridge province in Tennessee, has been a nuclear production and development facility for 50 years. Contaminants in the many waste sites on the ORR include heavy radioactive isotopes as well as many organic and inorganic compounds. The locations, geometry, and contents of many of these waste sites are reasonably well known, while others are poorly known, and some may be unknown. To better characterize the known sites and locate and characterize additional environmentally hazardous sites, a two-phase aerial survey of the ORR was begun in April, 1992. Phase I, which began in April, 1992, consisted of aerial radiation, multispectral scanner, and photographic surveys. Phase II, which began in November, 1992 and is described in this presentation, consisted of a helicopter electromagnetic (HEM), magnetic, and radiation survey. Targets of the survey were both man-made (drums, trench boundaries, burn pits, well heads) and geologic (fractures, faults, karst features, geologic contacts). The Phase II survey has three components: testing, reconnaissance, and high-resolution data acquisition. To date, the testing and reconnaissance data acquisition have been completed, and part of the data have been processed. They indicate that: 1) magnetic and HEM data are complementary, and do not always highlight the same anomaly; 2) under favorable circumstances, helicopter magnetometer systems are capable of detecting groups of 4 or more 55-gallon drums at detector altitudes of 15 m or less, 3) HEM data provide data which compare favorably with surface data collected over burial trenches, 4) well casings seem to be related to magnetic monopole anomalies, as would be expected, 5) Changes in EM and magnetic anomaly character are related to lithologic changes and might be used to track contacts between known outcrops.