UXO Site selected: HELENA ARMY NAT GUARD SITE, MT |
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General Area: Helena, MT Site Type/Program: Army Guard - MMRP Location: Helena Valley, Montana Brief History: Once open fields, portions of the Helena Valley were used in the 1950s for military training by the Montana Army National Guard (MT ARNG). Years later, many of these open areas were sold and subdivided. Because the property was never under federal ownership or federal lease, it was not eligible for remediation under either Formerly Used Defense Site (FUDS) or Defense Environmental Restoration Program (DERP) funding. The remediation project was funded by the National Guard Bureau with O&M funds. |
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Range / Site Description: Associated Munitions: Activities Completed: MT ARNG has completed two phases of a project to locate and remove UXO from nearly 500 acres of ranch and residential property in the Helena Valley, Montana. The project incorporated an aggressive remediation effort that sought to both inform the public through timely news releases and public forums and increase UXO detection efficiency by using appropriate, proven technologies. The UXO project was divided into Phase I and II and focused on two discrete impact areas Diamond Springs (Phase I, 1997) and Guthrie Road (Phase II, 1998). These areas were delineated after a comprehensive archival search was conducted. Phase I UXO remediation focused on 220 acres of residential property adjacent to a former artillery impact area. The geophysical survey work used dual sensor, man-portable cesium vapor magnetometers. The geophysical survey resulted in the identification of 370 anomalies that were then dug by members of the 120th FW Explosive Ordnance Disposal (EOD) team of the Montana Army National Guard. Thirty-seven intact ordnance items were recovered. Phase II was initiated in the Guthrie Road area in the summer of 1998. A sophisticated cart system was used to conduct a geophysical survey of the area. The cart system, developed and operated by Geophysical Technology Limited (GTL) of Armidale, Australia, was equipped with real time GPS and eight cesium vapor sensors connected to two TM-4 data loggers. This cart system was used during the Phase II investigation because the area differed significantly from the Phase I area. Used as a direct target area for mortar and tank training, the Guthrie Road area had much more surface shrapnel than the Phase I area. Sensors on the cart were configured close to the ground, providing GTL with the ability to filter out small pieces of surface clutter. GPS allowed the anomalies to be positioned within about 20 centimeters, greatly assisting in the validation effort. GTL found 840 anomalies that were tagged as potential UXO. As a result of this investigation, three fully fuzed 81-mm high explosive (HE) UXO rounds were found and removed. In addition, two 81mm white phosphorus (WP) rounds, one 76mm WP burster (fuze with charge), 61 81mm practice mortars, and 11 76-mm practice tank rounds were found. Nearly 30 additional 76 mm WP rounds were recovered that were large enough to resemble a piece of military ordnance, but not fully intact. The Montana results are notable because the work was done quickly (under 36 months from UXO discovery to completion) at a cost well below the average (under $1,000/acre) at a very high detection efficiency (over 95%). Issues: Public Awareness. The MT ARNG has a very active UXO awareness program for elementary school kids. The public has been very supportive of this aggressive effort. Other Information: The MT ARNGs clearance strategy was to develop a systematic approach that incorporated the best available technology and to execute the approach in a time-critical fashion with full accountability and full transparency. |
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