PART IV: OTHER APPLICATIONS OF SIDE-SCAN SONAR 

 INSPECTIONS OF COASTAL RELATED STRUCTURES 



59. There is a wide variety of other applications where side-scan sonar 

 was used to evaluate coastal related structures described in the literature. 

 While this section is not meant to be a complete list of all coastal struc- 

 tures surveyed with side-scan sonar, it is intended to give the reader an 

 appreciation for the wide range of side-scan sonar applications. This section 

 is divided into three parts: (a) a description of harbor structure inspec- 

 tions, (b) a description of dredged material disposal site inspections, and 

 (c) a discussion of several other applications. 



Vertical Wall Harbor Structures 



60. Although inspections of several vertical harbor structures have 

 already been described, there have been several unique applications of side- 

 scan sonar capabilities to inspect these types of structures at other loca- 

 tions. Reduced wave energy and operational requirements often allow or 

 require vertical wall structures in harbors. Because of the orientation of 

 these structures, innovative techniques have been required to obtain useful 

 images. The applications discussed are inspections of concrete caissons in 

 Quebec Harbor and inspection of Navy piers in Norfolk, Virginia. 



61. Hydromar, Inc. (1982), a private Canadian Company, used a Klein 

 500-kHz side-scan sonar with a microprocessor signal processing accessory box 

 to inspect a variety of vertical structures in Quebec Harbor. The absence of 

 waves and the desire to inspect fine details led Hydromar to use a radical 

 departure from conventional inspection techniques. Rather than towing the 

 towfish on a cable, they constructed a steel frame to which the towfish was 

 attached (Figure 33). Limiting towfish movement to only a few centimeters 

 through use of the frame and very slow tow speeds (0.5 knots or less), allowed 

 very small features to be identified. The St. Lawrence Seaway's large tidal 

 range at Quebec also allowed visual confirmation of the features seen on the 

 side-scan sonar images. For example, one of the caissons inspected in Quebec 

 was made with tapered forms. The offset between the forms, approximately 



2 in. (Figure 34), was visible in the side-scan sonar records as was a ladder 

 and drain hole. Mazel (1984) describes the procedures used in Quebec in 

 detail . 



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