Many coastal areas have been used over extended periods of time by the armed services for training using live ordnance. Cleanup of unexploded ordnance (UXO)-contaminated coastal land areas and their surrounding waters is necessary prior to use by the public. Locating and classifying these well-camouflaged and sometimes buried objects represents a significant challenge. In this project, geophysical sensing systems developed by the University of Hawaii Marine Mineral Technology Center (MMTC) were demonstrated on a test range to map and classify UXO in coastal waters.

Target placement example

Tools and techniques for quantitatively mapping seabed mineral deposits, known as placers, have been developed by the MMTC. Placers consist of concentrations of relatively dense minerals that are sorted naturally into shallow seabed accumulations. Placers are similar to ordnance because they are smaller than most geological structures and consist of anomalous concentrations of specific materials. These tools were demonstrated for mapping and classifying underwater UXO on a test range. The test range was designed and installed offshore of the Pacific Missile Range Facility in Barking Sands, Kauai, Hawaii. Inert ordnance and man-made targets were placed on and under the seafloor to demonstrate these technologies. The targets were recovered from the test range upon completion of the project.

The results of the ordnance mapping and classification demonstration were inconclusive due to system failures, navigation problems with the location of towed sensors relative to the survey vessel, and movement of the targets in the underwater environment during the course of testing. The question of whether side-scan sonar and seismic systems used for mineral exploration are acceptable for detecting underwater UXO cannot be confirmed or denied with the data gathered. The performance of magnetic and electromagnetic techniques for detecting underwater UXO in the high magnetic background environment could not be evaluated since the team was unable to operate the sensors on the test range.

The use of a multi-sensor approach to increase the probability of detection for UXO in the underwater environment has promise. Future testing should be conducted at a site with less severe wave and sediment transport conditions so that targets can be left in place longer without concern for their loss due to shifting sand. (Project Completed - 1997)