Underwater military munitions (UWMM) may pose a risk to aquatic environments because they typically contain munitions constituents (MC) such as 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). If UWMM become corroded or breaches, the fill material may leak or dissolve into the surrounding environment, which could potentially adversely affecting affect the exposed biota. In large part, because of the high cost and complexity associated with sampling MC at UWMM sites, detailed and reliable information about MC in water, sediment, and biota is available for only a few sites, and therefore temporal and spatial uncertainties persist. Examination of available data indicates that concentrations of MC in water and sediment were largely below detection or were relatively low (e.g., parts per billion), with higher concentrations being highly localized and typically near a point source. These findings were in accordance with predictive modeling and with fate studies. Available toxicity data derived for a variety of freshwater and marine species were compiled and used to derive interim water quality criteria and protective values derived from species sensitivity distributions. Toxicity varied widely across a diversity of MC and species. For most aquatic sites, MC contamination in sediment and in the watercolumn presents low risk to the resident biota.

Military munitions are present in waters around the world, including those waters located at current and former Department of Defense sites. This report provides a review of the aquatic ecotoxicology of munitions constituents (MC), including nitroaromatics (2,4,6-trinitrotoluene (TNT), dinitrotoluenes (DNTs), 1,3,5-trinitrobenzene (TNB), 2,4,6-trinitrophenylmethylnitramine (tetryl) and 2,4,6-trinitrophenol (picric acid)); nitrate esters (nitrocellulose (NC), pentaerythritoltetranitrate (PETN), nitroglycerine (NG)); and nitramines (hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)). The major focus of this report is on the fate and effects of MC in the marine environment. Most MC observed in this study rapidly degraded in aqueous exposure systems and nitroaromatics showed a significant binding affinity with organic matter. To support the assessment of risk from MC in aquatic environments, laboratory-based toxicity data have been derived for a variety of aquatic species for both lethal and sublethal exposure endpoints using spiked water or sediment. Frequently, unrealistically high concentrations were used to derive toxicity benchmarks. In general, nitramines were less toxic than nitroaromatics, with a wide range of sensitivity among species. MC are weakly hydrophobic and bioaccumulative potential was low, as expected. High elimination rates for MC resulted in a virtually complete loss of body residue within hours to days following transfer to clean water. Uptake of TNT resulted in the substantial formation of bound residues. For fish, aqueous exposure was the dominant route of exposure to explosive compounds, with dietary uptake providing only minimal contribution. More realistic exposures using Composition B and multiple species found the presence of munitions in aquatic environments unlikely to result in biological effects. Verification of this conclusion should be pursued by determining site-specific exposure risk.

Sea disposal of wastes from industry and government was accepted internationally as a safe and efficient practice until the 1970s. Options available for addressing excess, obsolete, and unserviceable munitions prior to the 1970s were limited to salvage, destruction by open detonation or open burning, or burial on land or at sea. Sea disposal of conventional and chemical munitions and other waste material was considered appropriate until the enactment of the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter in 1972 and its 1996 Protocol prohibiting sea disposal of chemical and biological agents. The 1993 Chemical Weapons Convention contains a similar ban. Sea-disposed munitions pose two types of risk. These are acute—injury or death caused by either detonation or direct exposure to chemical agents—and chronic—adverse health impacts resulting from prolonged exposure to munition constituents. The type and configuration of sea-disposed munitions, disposal location, water body properties (e.g., depth, current), and its usage (e.g., commercial fishing, recreation, pipeline construction) are factors in determining the relative risk posed by munitions. The collection, analysis, and sharing of historical information allow more efficient investigation and management of risks from sea-disposed munitions.

Munitions and explosives of concern (MEC) in U.S. waters can present a risk to the development and operation of offshore wind energy resources. Therefore, the U.S. Bureau of Ocean Energy Management requires offshore wind energy developers to evaluate the risk MEC poses to the development, operation, and maintenance of offshore wind energy generation and transmission systems. This article describes an MEC risk management framework consisting of the following steps: (1) MEC hazard assessment, (2) MEC risk assessment, (3) MEC risk validation, and (4) MEC risk mitigation. The MEC hazard assessment involves historical research to identify MEC potentially present in the development area. The MEC risk assessment evaluates the development activities and provides a relative MEC risk ranking for those activities. The developer determines the acceptability of these risks, and any potentially unacceptable MEC risks undergo risk validation through field surveys. The developer then considers the tolerability of the validated risks and develops and implements an appropriate MEC risk mitigation strategy based on actual site conditions. A risk framework provides a structured method to plan and operationalize the identification, evaluation, and mitigation of MEC risk throughout the development, operation, and maintenance life cycle of an offshore wind energy generation and transmission project.

Development of methods and technologies to characterize sites with underwater military munitions (UWMM) and respond to UWMM where the risks posed to human health or the environment or explosive hazards are unacceptable is underway. Department of Defense Military Munitions Sea Disposal Site Hawaii (HI-06), referred to locally as Ordnance Reef, is off Oahu’s leeward coast. This site has become the focal point for research on UWMM. Past studies found that the site presents no immediate danger to public safety. The location and water depth at this site present advantages for UWMM research and development.Promising technologies demonstrated at Ordnance Reef (HI-06) include those for munitions recovery, at-sea demilitarization, nondestructive testing, and explosives detection. Studies on fate and transport of munitions-related compounds and corrosion are ongoing.Among these technologies are the Remotely Operated Underwater Munitions Recovery System (ROUMRS) and the Explosive Hazard Demilitarization System (EHDS). Both are assemblages of commercial off-the-shelf components, and each is housed in a standard 6-m International Organization for Standardization (ISO) shipping container and can be operated on a barge.ROUMRS consists of a remotely operated vehicle, manipulators, an interface between a precision GPS, and underwater navigation equipment used during recovery of UWMM. The system also transports recovered UWMM for treatment. The EHDS consists of a portable X-ray unit to allow positive identification of recovered munitions, remotely operated wet band saws to cut recovered munitions to expose their explosive fill, and low-temperature ovens to treat the exposed explosives, making the remaining material safe for recycling.