Department of Defense policy requires all military ranges to be operated in ways that ensure their long-term viability to meet the national defense mission while protecting human health and the environment. These policies further require DoD to prevent or respond to a release or substantial threat of a release of munitions constituents (MC) to off-range areas (DoD Directive 4715.11). Munitions constituents are explosives and propellants originating from military munitions and include nitro amines such as cyclotrimethylenetrinitramine (RDX), nitro aromatics such as trinitrotoluene (TNT), nitrate esters such as nitroglycerin (NG), and perchlorate. These constituents can accumulate in shallow soils as a result of to military activities on ranges. They also can migrate through surface and groundwater to off-range receptors.  

SERDP and ESTCP have supported a comprehensive long-term program that addresses all facets of characterizing, monitoring, and managing sites impacted by munitions constituents. Proven products and results are available to support DoD range management. In addition, innovative next generation technologies under development offer the potential for ranges to be managed in a fully sustainable manner.  

The release of munitions constituents is a process unique to the military. The sources and magnitude are distinctly different from the release of chemicals from industrial processes. Test and training ranges also present unique challenges for characterization, control and treatment technologies. These ranges in many cases encompass thousands of acres and have limited historical records. They also are subject to continued use, which may restrict access and introduce additional constraints.

SERDP and ESTCP hosted a Technical Exchange Meeting on DoD Operational Range Assessment and Management Approaches in 2007. The meeting provided a summary of the state of the science and identified technology needs of the range management and assessment community that could be addressed through research and development. Several critical research paths were identified, including the need for improved methods for estimating the source zone, optimized well placement on operational ranges, and forecasting models to predict the potential for off-site migration of munitions constituents.

Sources, Fate, and Transport

Investments in research and technologies to understand and predict the sources, fate, and transport of munitions constituents on ranges have led to a new paradigm on how contamination can occur, as well as its distribution, and its fate and transport. Munitions constituents can be found at impact areas (where detonations occur), at demolition ranges (where disposal occurs) and at firing points. Various impact areas, including grenade ranges, artillery ranges, rocket ranges, bombing ranges, as well as demolition ranges and firing points, show different and distinctive distributions of munitions constituents. Munitions constituents have found their way into groundwater aquifers underlying various DoD facilities. The overall objective of this work is to understand, quantify, and predict the transport of particulate and dissolved MC in realistic vadose-zone conditions.

Appropriate values of dissolution rates are essential because these rates control the source for MCs in the environment. To successfully model the fate of MCs on ranges, it is essential to understand three key factors: dissolution rate, degradation rate, and partitioning to soil. This knowledge improves the ability to predict whether off-site migration of residues of energetic chemicals will occur in specific range areas.

Recent results have improved the ability to predict the rate of dissolution of certain energetic chemicals from particles of these substances as a function of rainfall and particle size. In addition, in recent years, the understanding of the mass of energetic chemical residues present in surface soil source zones has improved. The incorporation of these formulations into fate and transport models may provide an improved predictive tool to estimate flux rates of energetic chemicals at various locations on operational ranges.

The concentration that reaches a biological receptor or a downgradient site will depend on the degradation rate of the compound and its sorption to the soil matrix. The overall objective of ongoing work is to develop models supported by appropriate data that can predict the dissolution, release rate and partitioning of military MC and mixtures of these MCs to soils of varying physical and chemical characteristics. Because MCs are highly polar compounds, high orders-of-magnitude errors result from trying to quantify sorption properties via the traditional methods applied to organic contaminants. Models supported by new data on dissolution and partitioning are available for more accurate prediction of MC fate and transport for scientifically sound risk assessments.

Sampling and Monitoring

SERDP and ESTCP projects have developed a significant body of knowledge regarding the types of munitions constituent residues present and their distribution at various types of operational ranges. At impact areas, the residues deposited from high-order detonations for a wide variety of munitions were found to be minor when compared to the large amounts of residues resulting from low-order detonations and ruptured rounds. At firing points, propellant residues are deposited by a variety of munitions, including large caliber artillery, mortars, shoulder-fired rockets, and small arms. The major deposition in both cases occurred as particles that varied in size from the micrometer to centimeter in diameter.

The distribution of MC residues on ranges is heterogeneous. As a result, the classical sampling approach using discrete samples is not effective at providing accurate and precise estimates of residue concentrations. A technique using multi-increment sampling (MIS) method has been developed to provide more accurate characterization. This technique has been validated and transitioned as EPA method 8330B.

Ongoing work seeks to develop cost effective methods for assessment of the munitions constituent source term on large, operational ranges where the use of MIS alone is impractical. 

Treatment  

Treatment and control technologies address the remediation or containment of range-related contaminants and residue such as metals, energetics (RDX, HMX, TNT, DNT, picric acid), propellants such as perchlorate, or mixtures containing these contaminants in soils. Of particular interest are remedial and control technologies that allow for continued range operation during technology implementation, can be deployed over large areas, or can serve to sustain areas subject to continued use.

Grenade ranges are among the most heavily used training areas in the military. These ranges consist of large sand pits, surrounded by cement walls. Troops practice throwing live grenades into these sand pits. If the grenades fail to fully explode, munitions constituents such as RDX may remain in the sand. Over time, large amounts of RDX can accumulate in the soil and potentially contaminate the groundwater on the military installation and in surrounding communities.

Recently, researchers have successfully demonstrated that tilling agricultural lime into the sandy soil of hand grenade ranges increases the pH level in the soil, which leads to the immobilization of heavy metals and the degradation of explosive compounds such as RDX. The application of lime on a regular basis can be incorporated into standard range maintenance procedures at minimal cost while having zero impact on the military's ability to continue to train soldiers.

In the future, major advances in the science of phytoremediation offer DoD a qualitatively different and exciting approach to managing and sustaining live fire ranges. Recent findings provide the insight and technology needed to apply radically new approaches for long term range sustainability. Military leaders can now envision a range that, through its own biology, prevents the migration of these chemicals and self remediates.