Experiences with unexploded ordnance discrimination using magnetometry at a live-site in Montana

Advanced discrimination methods and careful optimization of operational procedures are critical for efficient remediation of unexploded ordnance (UXO) contaminated sites. In this paper, we report on our experiences with a 200 acre magnetic survey that was collected and processed under production survey conditions at Chevallier Ranch, Montana. All anomalies with fitted moments above 0.05 Am were excavated. During the survey the magnetic remanence metric was predicted but not used to guide the discrimination. The retrospective analysis presented here reveals that discrimination using remanence would have significantly reduced the total number of anomalies (with good dipolar fits) that needed to be excavated, from 524 to 290 while still recovering all 69 UXO. The false alarm rate (FAR = number of non-UXOs excavated divided / number of UXO found) was reduced from 6.3 to 2.9. At a cut-off of 75% remanence, 77% of anomalies due to shrapnel and metallic debris and 64% of geological anomalies were rejected. 1 Phone: 604 827 3220; Fax: 604 827 3221; Email: [email protected] 2 Phone: 406 324 3085; Email: [email protected]