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U.S. Department of Defense (DoD) installations, especially demilitarization facilities and Army Ammunition Plants, have long used Open Burning/Open Detonation (OB/OD) as a safe, effective, and economic means to dispose of propellants, explosives, and waste military munitions. DoD installations are required to comply with the Resource Conservation and Recovery Act (RCRA) to operate OB/OD facilities. RCRA permits provide annual limits on the amount of energetic materials that can be disposed of at OB/OD facilities. The permit limitations are based on human health risk assessments that include evaluation of risks from airborne exposure to emissions generated from OB/OD. Air emissions from OB/OD operations have been very difficult to characterize because of rapid plume dispersion, the short duration of the event, the heterogeneous emission concentrations, large plume lift, soil entrainment, and explosive safety restrictions.
The main objectives of this project were to:
Secondary objectives were to measure emissions of CO2, CO, PM10, PM2.5, total PM, metals, and VOCs from open burning of propellants containing ammonium perchlorate.
Emissions from OB/OD of military ordnance were sampled using a novel aerostat-lofted instrument (termed the “Flyer”). A 16 ft (4.9 m) helium-filled aerostat/Flyer was maneuvered into the plumes by two tethers connected to two remotely controlled winches mounted on all-terrain vehicles. With a criterion of CO2 elevated above ambient concentration, 71% of the 109 detonations were successfully sampled over a three week period from June 11 to June 27, 2012 at Tooele Army Depot, Utah. Bulk energetics and cased munitions, including Comp B, V453, and V548 munitions, were variously detonated on the surface or at soil cover depths of 3 ft (1 m) and 6 ft (2 m). Emissions were characterized for determination of PM by size, CO2, VOCs, energetics, and metals.
A total of 13 open burns were conducted on two ammonium perchlorate-based propellants for measurement of hydrochloric acid (HCl), perchlorate, and chlorate species. Simultaneous measurements of CO2 concentration and aerostat/Flyer position were made to compare against predictions from the Open Burn/Open Detonation Dispersion Model (OBODM).
Energetic emissions were typically less than 1/100,000 of that in the original munition by mass. Limited evidence suggests that soil-covered detonations have higher energetics release than do surface detonations. Emissions, however, seem to be munition-specific as V548 released about 30 times that of the other munitions. Continuous particle size measurements show that 59% of the PM mass in the plume is less than PM2.5 and the total PM mass is much greater than that from the ordnance alone, as the plume contains large quantities of soil particles. The fate of metals in the emissions is metal- and ordnance-type-specific. Less than 1% of zirconium and 22% of hafnium, metals found in the munition and not typically in the soil, were found in the plume.
Results from this project combined with results from previous efforts have:
Repeat detonations under identical conditions resulted in large variation in the appearance of the resulting plumes. This visual evidence reinforces the need for collecting composite plume samples across multiple trials and for continuing this level of sampling in future testing. This study conducted only limited numbers of trials using developmental sampling methods. Although a great deal was achieved during this work, additional tests should be conducted in order to validate the sampling methods and develop well-substantiated and representative emission factors for OD.