18 



between the December 1991 and May 1992 bathymetric surveys showed that 0.5 m of 

 material accumulated at the B buoy location (Figure 3-8). 



To illustrate the full extent of any erosion of the material dredged from the 

 Connecticut River bars, and any deposition during the disposal of fine-grained material, a 

 comparison was done of depths between the October survey (following completion of the 

 sand disposal) and the May survey (following completion of the fine-grained disposal). 

 Losses of material between October and May are in the same area and the same amount as 

 between October and December. Accumulations during that time are just south of 

 41° 12.75' N, and at the B disposal location (Figure 3-9). The accumulation south of 

 41° 12.75' N is the same amount of material that had accumulated between October and 

 December. 



3.2 Current Meter Data 



The mid-water and near-bottom current meters deployed at CSDS measured current 

 direction and velocity from August 1 to December 12, 1991. A data report by Bohlen et al. 

 (1992) contains a detailed discussion of these data. In both the mid- water and the near- 

 bottom data, the tidal/current direction was dominated by the semi-diurnal east- west 

 component. For the mid- water data, the vectors were 270° on the flood tide and 95° on the 

 ebb. Near-bottom current directions were similar to the mid- water ebb current but shifted 

 slightly to the northwest on the flood at BTM-B. There was more variability in the current 

 direction at near-bottom (Figure 3-10). The east- west directions for both mid- water and 

 bottom currents were parallel to the axis of Long Sand Shoal to the north (Figure 1-1). 



The current velocities at CSDS were maximum during the flood portion of the tidal 

 cycle. Over the long term (monthly time scale), maximum mid- water velocities were about 

 120 cm-s" 1 on the spring tide and 60 cm-s" 1 on the neap. At the near-bottom station, 

 maximum velocities were about 80 cm-s" 1 on the spring tide and 40 cm-s" 1 on the neap. In 

 all cases, these current velocities would be sufficient to erode fine to medium sands. For the 

 near-bottom current, the flood tide velocities were highest. This resulted in a net westward 

 trajectory for particles as they approached the bottom. 



With the tidal variability removed from the current meter data at the mid-water 

 station, current vectors trended north and west. The combined net drift for the mid- water 

 current was 305° true at 4.65 cm-s" 1 . For the near-bottom meters, removal of the tidal 

 variability resulted in a south and west component with a combined net drift of 256° true at 

 8.33 cm-s' 1 . 



During the current meter deployment at CSDS, two major storms passed over the 

 area. Hurricane Bob passed over Long Island Sound on August 19, 1991 and produced 

 maximum wind speeds of 45 knots. During the hurricane, the near-bottom current meter 



Synthesis of Monitoring Surveys at the Cornfield Shoals Disposal Site, July 1991 to May 1992 



