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Feature Article

Finding Underwater Munitions: Technologies and Applications
SkyDiver Towed Magnetometer Array Combines Various Sensors for Marine Munitions Detection

By Dr. Gregory M. Schultz
Director of Science and Technology
Dr. John Foley
Chief Technologist and Vice President
Dr. Stephen Billings
Vice President of International Development
Sky Research Inc.
Hanover, New Hampshire

The rising number of encounters with marine military munitions during construction projects, cleanup efforts or recreational diving is a stark reminder of the ways nations train military personnel and the pervasive legacy of warfare in countless ports, harbors and along coastlines. During military conflicts and training before 1970, at-sea disposal of munitions was common. Some countries, despite international agreements, continue to discard munitions underwater.

Within the United States, it is estimated that nearly 10 million acres of marine and lacustrine environment are potentially contaminated with unexploded ordnance and discarded military munitions, which pose safety and environmental hazards, according to a Strategic Environmental Research and Development Program workshop report from 2007. A series of U.S. Department of Defense studies conducted in 2009 have identified 560 potential areas across 320 sites in the U.S. that are associated with underwater military munitions. Potential munitions and constituents at these sites have resulted from various live-fire testing and training, intentional or accidental dumping (e.g., disposal at locations such as piers, coastal bombing ranges and dredge spoil ponds) and active conflict or war.

Schematic showing the overlapping technologies used for marine munitions site characterization.

Investigation and remediation of underwater munitions is time-consuming and expensive, but federal and local stakeholders' interest in the process is growing due to concerns of underwater munitions affecting marine ecosystems and being present in waters used or desired for recreation, commercial transport and infrastructure and natural resources.

A major challenge for existing underwater munitions remediation is implementing methods to quickly characterize wide-area sites where munitions may reside. In an effort to overcome this, Sky Research Inc. (Hanover, New Hampshire) has developed a sequenced deployment of acoustic and nonacoustic geophysical sensors, followed by confirmation operations by ROVs and divers trained for explosive ordnance disposal (EOD).

Existing Methods for Munitions Detection
There is no silver bullet for investigating sites littered with munitions that settle on or in the seabed. Successful detection and characterization often requires the deployment of a suite of integrated technologies. These methods primarily include specially trained and equipped divers; various modes of side scan and multibeam sonar for 3D bathymetry; sub-bottom profiling for sediment characterization; ROVs for visual and acoustic searches; and AUVs for wide-area searches. To augment these methods, several technologies have been adapted from mature and extensively tested, land-based geophysical methods, such as those used in the oil and gas industry.

Historically, EOD-trained divers have been deployed to handle underwater munitions. Dive teams, often equipped with hand-held metal detectors and simple excavation tools, execute search-and-clearance operations, but these are highly restricted in duration, depth (under 30 meters) and by strict health and safety regulations. These limitations have created a need for technologies that can augment or replace the services provided by divers.

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Dr. Gregory M. Schultz is a research geophysicist and the director of science and technology at Sky Research in Hanover, New Hampshire. He specializes in the development and application of electromagnetic sensing systems from manned and unmanned platforms for characterizing underwater hazards.

Dr. John 'Jack' Foley is chief technologist and vice president of Sky Research. He has been entirely focused on munitions detection technology development since receiving his Ph.D. from the Massachusetts Institute of Technology in 1990. Foley has led numerous field applications of wide-area geophysical site assessment technology.

Dr. Stephen Billings is a senior geophysicist and vice president of international development for Sky Research in Brisbane, Australia. He is an expert in magnetic sensing and lead researcher in the development of innovative detection and classification methods for munitions and explosive hazards.

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