Evaluation of Improved Airborne Techniques for Detection of UXO

Recent development of helicopter boom-mounted magnetic detection systems (Gamey and Mahler, 1999) have made it possible to detect much smaller objects than could be detected with conventional towed systems. Data acquired with the HM3TM system in June 1999 at the Badlands Bombing Range (BBR) in South Dakota indicate sensitivity to ordnance and buried metals that have a mass of less than 1Okg. This is significantly better than was observed in an earlier test with the HM3TM system at Edwards Air Force Base (EAFB) in California (Doll et. al., 1999). This paper presents an overview of the project and initial results. Data were acquired in six areas at BBR. These included two trench areas, two bombing targets, a controlled test site, and an undiscovered bombing target. The first two bombing targets had previously been surveyed with the MTADS system (McDonald and Robertson, 1996). The third bombing target was discovered in the course of a blind survey of a “clean” part of the range. The controlled test site consisted of 24 holes in which deactivated ordnance, fragments of ordnance, simulants, plumbing pipes, and known metallic objects (e.g. segments of reinforcing rods and I-beams) were placed at depths ranging from 0 to lm. The smallest objects at the test site were approximately 5kg. The improved sensitivity at BBR is attributed to: 1) higher data sampling rates, 2) elimination of a low pass filter that was used at EAFB, 3) improved techniques for removal of geologic noise, 4) lower instrument altitude in flatter terrain, and 5) more favorable geologic background conditions. These results indicate that airborne magnetic methods are an appropriate tool for detection of ordnance, and for screening or characterizing large areas of suspected contamination. This is particularly true at sites where low survey altitudes are possible, background geologic response is low, and expected target size is within range.