S5 



5.0 CONCLUSIONS 



The completion of the CAD mound at CLIS represents the end of a ten-year 

 dredging cycle in the central Long Island Sound region. Major maintenance dredging of 

 New Haven Harbor must be performed approximately every ten years to provide adequate 

 water depths for conraiercial, military, and private vessels utilizing the harbor. Thoughtful 

 management of smaller volumes of dredged material over the last decade not only 

 facilitated the economic and environmentally sound disposal of over 1 . 1 million cubic 

 meters of dredged material, but also demonstrated a management strategy that will 

 maximize the site capacity of CLIS as well as other DAMOS disposal sites (Morris et al. 

 1996). 



The management strategy of containment cell formation followed by central 

 deposition proved to be a successful method of constructing a CAD mound and efficiently 

 isolating a large UDM deposit from the sediment- water interface. The NHAV 93 mound 

 is a wide, flat bottom feature that has seen little to no change in vertical topography or 

 overall width since the March 1994 survey. This suggests that the majority of 

 consolidation and lateral spread of the fine-grained sediments occurred during disposal and 

 capping operations. Over the long term, the NHAV 93 mound is expected to further 

 consolidate and settle due to compaction of the underlying ambient material. 



Bathymetric, subbottom, and geoteclmical core data analyses are in good agreement 

 and indicate that the entire NHAV 93 mound is covered with a layer of cap material at 

 least 0.5 m thick. However, the results of the REMOTS® benthic community assessment 

 did indicate three areas of concern in existence on the surface of the NHAV 93 mound. 

 The stations 200 m north, 400 m south, and at the center of the NHAV 93 mound 

 exhibited lower RPD depths, recolonization rates, and OSI values than expected. 



Toxicity testing was completed in September 1994 to determine the quality of the 

 cap material at Stations CTR and 400S. The results of the toxicity testing indicated no 

 significant difference in sediment toxicity between the project mound CDM and the historic 

 Southern Reference Site. In accordance with the DAMOS tiered monitoring protocols, no 

 immediate action (i.e., cap supplementation) was required. Continued monitoring of these 

 areas in September 1995 did indicate improvement in benthic habitat quality with the 

 development of a stable infaunal population and improving RPD and OSI values (Morris 

 1996). 



The sediment chemistry results pertaining to the sampling effort over the NHAV 93 

 mound indicate that TOC, HMW PAH, and metals values for the CDM were within the 

 ranges of expected concentrations, as derived from the sediment chemistry analysis 



Monitoring Cruise at the Central Long Island Sound Disposal Site, July 1994 



