3 Pilot Study Overview 



Background 



Previous to this investigation, the ordnance contamination characteristics of the 

 offshore borrow area were unknown. Data were lacking on the ordnance density 

 per sector and ordnance distribution, and it was not known if the ordnance were 

 proud (i.e. located on the surface), shallow-buried, or situated deep in the 

 sediments. In order to investigate the possibility that more efficient dredging can 

 be conducted in certain areas or if the ordnance fields may be suitable for efficient 

 clean-up operations, it is necessary to characterize the degree of contamination. 

 The challenges of mapping an underwater ordnance contamination field are 

 significant and have received recent attention at other US ACE projects (Pope, 

 Lewis, and Welp 1996; Welp et al. 1994) and within the Military Research and 

 Development Program. A review of available and emerging technologies was 

 made and a pilot offshore geophysical survey designed with the intent of testing 

 geophysical and oceanographic techniques which might be suitable for use at Sea 

 Bright. The results of this pilot study would be used to determine the potential for 

 application as part of a large-scale survey and to identify the appropriate 

 development and equipment integration needed for an efficient operational-scale 

 survey. The ultimate goal of the pilot study was to develop a recommendation 

 and reasonable cost estimate for a full-scale study. 



Equipment adapted and mobilized to the project site included a research vessel 

 with GPS positioning, two underwater video cameras, two acoustical systems, and 

 a magnetic gradiometer. In addition, a number of inert pieces of ordnance were 

 used on site calibration testing of the equipment. The underwater video system 

 and two acoustical systems were "off-the-shelf' items which required no further 

 development for their use at this site. The two acoustical systems included a high- 

 frequency side-scan sonar and sweep frequency subbottom profiler (i.e., X-star). 

 Some field experimentation was conducted to improve system deployment and 

 evaluate the performance of each system in detecting ordnance-like objects. Most 

 of the effort during this pilot study was expended in adapting a state-of-the- 

 technology cesium-vapor magnetic gradiometer for underwater deployment and 

 towing. This involved the design and fabrication of a water-tight tow containing 

 two magnetometers, integration with an altimeter for controlling elevation, and 

 adaptation of data processing software. A sea trial of the fabricated system was 

 conducted in California prior to shipment to Sandy Hook. 



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Chapter 3 Pilot Study Overview 



