As a result of past military training and weapons testing activities, munitions are present on thousands of current and former Department of Defense sites, encompassing millions of acres. On many of these sites, munitions exist in underwater environments. In some cases, ranges and training areas are located on land adjacent to water environments, such as ponds, lakes, rivers, estuaries, and coastal ocean areas. In other cases, training and testing on or in water was required, and therefore, targets were deliberately located in water environments. In addition, disposal and accidents have generated significant munitions contamination in the coastal and inland waters in the United States. In all, the U.S. Army Corps of Engineers and the Navy have identified more than 400 underwater sites potentially contaminated with munitions.

Unlike on the land, the risks from munitions in the underwater environment are driven by two different effects:  the explosive hazard associated with encounter and the environmental hazard associated with the release of the constituents contained in the round. In many underwater sites, particularly in deeper water not often accessed by divers, the likelihood of direct exposure is remote. In such cases, the main concern that drives management decisions is likely to be the environmental impact.

In either case, the first step in deciding how to manage an underwater munitions site is understanding the location and quantity of munitions present. On dry land, modern geophysical surveying techniques can be used to characterize sites with potential for munitions contamination. The underwater environment, however, both restricts access to, and may have a significant impact on, the performance of established and emerging characterization technologies.

Site characterization requires a suite of technologies to provide the range of data needed to make decisions under a wide variety of site conditions. At present, acoustic, optical and geophysical technologies are in research and demonstration phases. Deployment of such sensors on platforms from tow bodies to autonomous underwater vehicles is expected to provide a tool box of capabilities.

For underwater locations where munitions contamination is suspected but uncertain, technologies are needed to conduct rapid assessment. Such technologies will enable site managers to identify areas with concentrations of munitions, as well as areas free of munitions. In contaminated areas, data are needed to define the nature and extent of munitions contamination to support either site management or the initial steps of a response program.

Detailed surveys of contaminated areas are conducted where the remediation of individual munitions is required. Individual items must be detected with high probability and sufficient location accuracy that they may be unambiguously identified and retrieved. A number of technologies meant for conducting detailed surveys of munitions response sites in the underwater environment have been demonstrated. To date, all such technologies have been found to be limited by factors such as water depth, water turbidity, and sea state. These methods have achieved neither reliable detection of small munitions nor discrimination of munitions from other clutter not of interest. Addressing these shortcomings is an ongoing subject of research.

Direct encounters of munitions occur when they wash up during storm events or when they are transferred to beaches as an unintended result of dredging operations. Munitions may migrate in the fluid underwater environment. Work is underway to develop tools to assess and predict the potential mobility of munitions as a function of site conditions. Information on munitions mobility will help managers assess site management approaches and timelines for reacquisition or for remediation of suspected items.

SERDP and ESTCP are working to improve the understanding of the environmental impacts associated with munitions in the marine environment. Of particular importance is developing effective methods to assess impacts at environmentally relevant concentrations and to understand dominant fate and transport mechanisms. The munitions compounds of interest include, but are not limited to, military explosive compounds such as trinitrotoluene (TNT), pentaerythriol tetranitrate (PETN), cyclotrimethylenetrinitramine (RDX), and cyclotetramethylenetetranitramine (HMX) as they occur in munitions, as well as any breakdown products.

Managing the risk due to military munitions in the marine environment requires knowledge of the potential impact of materials used in munitions. Developing scientific information on the potential sources, transport, fate, and effects of these materials is essential. Such information will provide a more complete assessment of the potential for environmental impacts and exposure at current and former military ranges and disposal sites. SERDP and ESTCP researchers are working to achieve the following:

• Determine what constitutes environmentally relevant concentrations of munitions constituents (i.e., concentrations typically found in the environment in and around water ranges) under various hydrodynamic and geochemical conditions in both the water column and the aquatic sediments
• Assess the predominant fate and transport mechanisms and the kinetics of such reactions at environmentally relevant concentrations in both the water column and the aquatic sediments
• Assess the impacts of munitions constituents to relevant ecological receptors in the marine environment, including the potential for biomagnification
• Provide predictive ability to assess the potential environmental impacts in the marine environment and the uncertainty in these assessments
• Develop, where needed, improved techniques for sampling of munitions constituents in relevant biological samples

The knowledge of the potential environmental impact of munitions compounds and their breakdown products in marine environments will support decisions regarding past DoD activities. Such knowledge also could be applied to ensure the sustainable management of military ranges, improve management of marine environmental resources, and facilitate compliance with current and proposed regulations.