13_ 



3.0 RESULTS 



3.1 Side-scan Sonar 



The side-scan sonar data were used to create an acoustic map of the seafloor 

 surrounding the borrow pit and potentially differentiate between ambient sediment and 

 dredged material placed within the pit. Three lanes of swath data were overlaid to create a 

 mosaic of the survey area (Figure 3-1). Data collection was curtailed somewhat by shallow 

 water to the east and an active mooring field in the southern portion of the borrow pit. 



The western and northeastern margins of the borrow pit provided a strong sonar 

 return to the transducer (represented by a thick, dark line) and were readily apparent in the 

 mosaic (Figure 3-1). Soft sediment (weaker return) appears to have accumulated within both 

 the northern and southern portions of the borrow pit. Approximately 14,200 m^ of sediment 

 dredged from the USCG basin were deposited in the southern portion of the pit. Given the 

 relatively small volume of dredged material disposed and position of the disposal point 

 (southern portion), most of the fine-grained material detected within the confines of the pit is 

 likely the result of natural deposition. This fine-grained material could be emanating from 

 the Mill and Quinnipiac Rivers, advected from other areas of New Haven Harbor, or the 

 product of multiple sources. The side-scan image shows a gradual strengthening of signal in 

 close proximity to the margins of the pit, suggesting a coarsening of the sediments, relative 

 to the center. This change in texture is probably related to an increase in the sand or shell 

 content of the sediments located near the walls of the borrow pit. 



Slight differences in surface texture detected in close proximity to the MCDA buoy 

 position, relative to the remainder of the sediments in the pit, provide subtle distinctions 

 between the recently deposited dredged material and the ambient sediments (Figure 3-2). 

 Multiple bottom features with vertical relief and increased surface roughness were detected 

 within a 50 m radius of the central disposal point. The larger bottom features, approximately 

 30 m in diameter, were concentrated to the east of the MCDA disposal buoy. Based on their 

 position relative to the disposal buoy and size, these features are attributed to dredged 

 material deposition. 



3.2 REMOTS® Sediment-Profile Imaging 



The complete set of REMOTS® image analysis results for both the borrow pit and 

 reference area stations is presented in Appendix B; these results are summarized in Tables 3- 

 1 and 3-2. 



Monitoring Cruise at the Morris Cove Borrow Pit 



