17_ 



5.0 CONCLUSIONS 



CSDS, a high energy, dispersive dredged material disposal site, has traditionally 

 been used for the disposal of both fine-grained and sandy dredged material. When sandy 

 dredged material has been released at the center of the disposal site, it has been transported 

 out of the site without forming a disposal mound. The detection of sand ripples and waves 

 in the July 1994 subbottom survey indicates active bed transport at the site after disposal 

 activity. Despite the presence of active bed transport, much of the fine-grained dredged 

 material from North Cove that was released at the site during disposal season operations in 

 1991 and 1992 did form a persistent mound. 



The formation of a dredged material mound at a dispersive disposal site allows the 

 site to be managed in two ways. If close control or management of dredged material is 

 desired, material should be released at a taut-wire moored buoy. This is likely to result in 

 the accumulation of material, but it may also reduce the long-term site capacity. If close 

 management is not desired, relatively small volumes of fine-grained material may be 

 released at numerous discrete locations. This management approach would serve to 

 prevent mound formation, enhance dispersal, and retain site capacity. 



Bathymetric and Subbottom Survey at the Cornfield Shoals Disposal Site, July 8, 1994 



