the initial survey as soon as possible after construction. Because the 

 initial side-scan sonar survey was not completed until after a severe storm, 

 it was impossible to determine if the suspected structural flaws were due to 

 the storm or the result of initial construction. 



Ocean City Inlet, Maryland, South Jetty 



33. In September 1984 CERC assisted the US Army Engineer District, 

 Baltimore (NAB), in inspecting a contractor's efforts to repair a scour hole 

 along the channel side of the Ocean City Inlet south jetty (Figure 16). The 

 integrity of the south jetty had been threatened by a tendency for tidal flow 

 to channelize along the north side of the outer jetty section causing a deep 

 scour hole. As part of a major rehabilitation of the entire south jetty, NAB 

 required the contractor to hydraulically place sand fill into the scour hole, 

 seal the top of the scour hole with a 24-in. stone blanket, and construct a 

 stone berm at the base of the existing jetty. The stone blanket was specified 

 as a 2,000-ft-long, 200-ft-wide rectangle. The purpose of the side-scan sonar 

 inspection conducted was to document the sand filling operation and the uni- 

 formity of the stone cover. 



34. The inspection was conducted from a 24-ft outboard. A vessel of 

 this size was needed to provide sufficient maneuvering control in the strong 

 tidal currents at the inlet. A Klein 500-kHz system was used with a 50-m 

 range, a towfish depth of 5 to 10 ft, and a tow speed averaging 2 knots. A 

 microwave positioning system was used for position and navigation control. 

 Wave and current conditions reduced the surveying window, making surveying 

 possible only during the 2 to 3 hr before high tide when the tidal current 

 through the entrance was relatively slack. During the slack period associated 

 with the low flooding tide, wave breaking on the jetties entrained air in the 

 water column, severely reducing record quality. On ebb tide flows, opposing 

 waves and currents created steep waves at the entrance, causing excessive 

 towfish motion. 



35. A series of side-scan sonar surveys spread over two days was con- 

 ducted to define the areas of stone cover. No single survey could cover the 

 entire area due to the contractor's derrick barge blocking access to the 

 control portion of the stone cover during the first day of surveying. Indivi- 

 dual surveys were manually corrected for slant range and target position and 



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