prospective site clean-up activities. As the first step in testing the X-star, it was 

 towed several times approximately 1 to 2 m above the inert ordnance test bed. 

 Targets were detected which may be interpreted as representing the ordnance located 

 on the bottom (Figure 9 ); however, nothing could be detected at the location of the 

 single buried piece or at the buried cluster. Since a return from the buried ordnance 

 could not be detected, we conclude that the scattering of the acoustical signal by the 

 sandy sediment prohibits the use of X-star to identify buried ordnance targets in 

 this setting. The X-star was towed along a number of lines in the survey area and 

 throughout the record there were target returns from the bottom surface similar to 

 those observed in the test bed at the Coast Guard Station. There were some 

 subsurface targets noted in the tows from the borrow area, but the nature of these 

 returns could not be used to verify if they were or were not ordnance. The acoustical 

 return from the X-star cannot be used to discriminate between objects of different 

 composition. Thus, the observed returns could be stones, wood, or ordnance. The 

 conclusion of the pilot study is that X-star would be of limited use during the 

 conduct of a full-scale survey. 



In summary, both acoustical systems did provide information on the bottom 

 texture and indicated the presence of hard target returns. However, interpretation of 

 these targets as ordnance is not appropriate without verification via ground-truthing 

 or the magnetometer. The X-star did not provide the additional information on 

 buried targets which was its primary aim. In addition, the footprint (i.e., width of 

 field of view) of the X-star is much more limited than that of a magnetometer. It is 

 not (under presently available operational configurations) appropriate to use the X- 

 star for conducting the broad survey operations. The side-scan sonar, however, is 

 appropriate as a reconnaissance tool to document bottom conditions and 

 obstructions prior to conducting a magnetometer survey/sweep of an area. 



Chapter 4 Acoustical Systems 1 9 



