90 



Quinnipiac Rivers, and Black Rock and 

 New Haven Harbors, were not conducted 

 in distinct phases of mound and cap 

 deposition. Also, recent coring data 

 suggest that the cap material at MQR was 

 mischaracterized. Both of these factors 

 may have affected the observed 

 recolonization rate at MQR. 



The recent coring investigation at CLIS 

 provided further evidence that caps are 

 effective at isolating contaminants. 

 Chemical and lithological data showed 

 clear boundaries between cap and mound 

 material in most of the recovered cores. 

 Coring results also indicated that the 

 dredging method used can affect the 

 resulting heterogeneity of both the cap and 

 mound deposits. Clamshell-dredged 

 deposits, in particular, retained the 

 sediment texture and chemical character of 

 the pre-dredged sediment. 



This historical review of the early 

 years of capping and subsequent 

 monitoring provides a checklist of 

 recommendations for a successful capping 

 project. 



Pre-Operational Planning: 



• Characterize the sediments which 

 are proposed for disposal (this may 

 include sediment chemistry and 

 bioassay and/or bioaccumulation 

 data); and classify the sediments 

 using the best available 

 information. 



• Conduct site surveys, and choose a 

 disposal area with lesser or no 

 vulnerability to natural or 

 anthropogenic (i.e., trawling) 

 erosion. 



• Schedule dredging and disposal 

 operations so that mound and cap 

 are completed well before the storm 

 season to allow for consolidation 

 and surface stabilization, to insure 

 that the cap material can be 

 disposed as soon as possible after 

 mound material. 



Disposal Operations: 



• Use both precise navigational 

 techniques and a taut-wired buoy 

 for disposal of both cap and mound 

 sediments. 



• Point-dump mound material by 

 directing the barge to unload as 

 near to the buoy as possible. 



• Dispose a portion of the cap 

 sediments along the radius of the 

 contaminated mound sediments. 



• Maintain the pre-operational plan 

 for mound deposition followed by 

 cap deposition. 



• Keep complete records of all 

 disposal operations. 



Estimate the volumes of material to 

 be disposed. 



Sediment Capping of Subaqueous Dredged Material Disposal Mounds 



