28 



individuals, and elevated OSI values. Overall, the lower average OSI value for the reference 

 area stations (+3.8) compared to the borrow pit (+5.6) suggests that the ambient bottom in 

 Morris Cove was more highly disturbed at the time of the survey. 



3.3 Tovi'ed Video Survey 



The towed video survey was conducted to document the apparent composition of the 

 surface sediments within the borrow pit. A series of seven transects (three longitudinal and 

 four transverse) were occupied in and around the Morris Cove borrow pit. Individual 

 transects are displayed in Figures 3-10 through 3-14 with both an aerial perspective and a 

 profile view presented. The corrected bathymetric profiles were used to compare depth and 

 slope to apparent surface sediment composition. A summary graphic displaying the 

 composite results of all seven transects is presented in Figure 3-15. 



3.3.1 Sediment Composition 



In general, fme sand, silt, and shell fragments were detected in patches throughout the 

 entire borrow pit. As expected, a correlation between bottom slope and sediment 

 composition was observed, with silt accumulating in the deeper, low relief areas of seafloor 

 and fine, silty sand/shell fragments detected along the walls of the borrow pit. Distinctions 

 between ambient sediment and recently deposited dredged material were difficult to detect 

 on the surface due to the age of the deposit, similar lithology (fine sand and silt), and the high 

 optical reflectance of the well-oxygenated surface layer. 



Transect A was a longitudinal pass within the boundaries of the borrow pit, 

 concentrating on the western margin of the bottom feature (Figure 3-10). The starting point 

 for this line was placed approximately 450 m north of the MCDA buoy position. Soft 

 material was observed for the majority of this transect with silty sand and shell fragments 

 observed as the video sled encountered the sloping walls of the pit. Silt was predominant in 

 areas of low relief and tended to be found at water depths below 5 m. A few patches of 

 pebble and cobble sized rock were also observed on the bottom, as the video sled was towed 

 south and east through the pit. The seafloor within a 30 m radius of the MCDA buoy 

 position was characterized as a silty sand, but showed no obvious differences from the 

 surface sediments in the northern portion of the borrow pit. 



Transect B represents the first transverse route occupied over the Morris Cove borrow 

 pit. The video sled passed approximately 60 m southeast of the disposal buoy position 

 (Figure 3-11). Fine, silty sand was observed in the shallow areas on either end of the 

 transect, and patches of silt were found at depth. Once again, a correlation with bottom slope 

 was detected as the margins of the pit were composed of fine sand or fine sand with shell. 



Monitoring Cruise at the Morris Cove Borrow Pit 



