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Damaged Unexploded Ordnances Leach Explosive Residues

Researchers evaluate the movement of explosives through soil with the goal of preventing explosive chemicals from entering water supplies.

 

MADISON, WI, JANUARY 4, 2010 -- Unexploded ordnance (UXO) is a common by-product of military training and is found on military training areas around the world. Aside from the serious safety issues associated with explosive munitions, the explosive chemicals they contain can contribute to groundwater contamination. Explosives used in military munitions have been identified as potential carcinogens by the Environmental Protection Agency, and if they leach into an aquifer, they may be carried far outside the boundaries of a military training area to contaminate civilian drinking water supplies. With urban sprawl bringing previously remote military bases nearer to population centers, this issue has taken on increased importance in the past decade.
 
Scientists at the Defence Research and Development Canada (DRDC) and hydrogeologists at l’Institut national de la recherche scientifique (INRS) in Quebec City have teamed up to study how explosives can move through soil. The ultimate goal of this research is to prevent explosive chemicals from entering water supplies and to protect the environment on military training areas for future generations. This study, which was jointly funded by the Strategic Environmental Research and Development Program (SERDP) and by the Director - Land Environment (DLE) of the Canadian Forces, measured the amount of explosive residue that could be released by a single UXO after it had been damaged by a nearby explosion.  Results of this study appear in the November-December 2009 issue of the Journal of Environmental Quality.
 
The first aspect of this study was to see how 81-mm mortar shells could be damaged by other 81-mm mortar shells that exploded nearby. It was hypothesized that since many military impact areas are quite small and have been used for decades, it was reasonable to assume that a UXO could eventually be hit by another munition that explodes nearby. Prior to this work, it was unclear how explosives could escape from UXOs into the environment, since most UXOs have thick steel casings up to 2 cm thick that act as substantial barriers.  It was previously speculated that incomplete detonations or corrosion of the casings over many years could eventually release the explosives inside. This research provides another potential mechanism for the movement of explosives from UXOs into the environment: The researchers demonstrated that UXOs damaged by nearby detonations released up to a million times more residue into the environment than munitions that detonated properly.
 
These cracked UXOs and the explosives scattered nearby were collected and placed on columns of soil in a laboratory. Simulated rainwater was sprayed on the munitions and leached through the soil before being collected and analyzed. Up to 10% of the explosives were found to leach through the soil column during the first year, enough to contaminate over a million liters of groundwater to concentrations at or above USEPA lifetime exposure limits. 
 
Jeff Lewis, who conducted the study as part of his Ph.D. research, noted, “Groundwater quality issues are going to become increasingly important in the coming years. According to the USEPA, half the U.S. population relies on groundwater for their domestic needs. If an aquifer gets contaminated, it doesn’t just affect one or two people. It can affect a whole town.”
 
Research is ongoing at both DRDC and INRS to increase our understanding of how military activities can impact the environment, with a view to mitigating them before they happen.
 

Journal of Environmental Quality publishes original research, reviews and analyses, and environmental issue articles that address anthropogenic impacts on water, soil, and the atmosphere and pertain to some aspect of environmental quality in natural and agricultural ecosystems.

The ACSESS is an international scientific and professional society with its headquarters in Madison, WI.