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5.0 CONCLUSIONS AND RECOMMENDATIONS 



The New London Disposal Site (NLDS) monitoring results from 1992-1998 form a 

 time-series of observations of individual mounds and the site as a whole including 

 reference areas. This time-series provides insights into physical and biological processes 

 and any potential environmental impacts from the disposal of dredged material at the site. 

 This section provides conclusions for the site and each individual mound or region 

 surveyed (and recommendations for site management). 



5.1 Overview of Monitoring 



• A dredged material management strategy has been successfully developed for NLDS 

 that takes into account regional influences over the site as well as site-specific 

 constraints on dredged material disposal. This strategy has incorporated the use of off- 

 site reference areas to determine regional effects on the site. It also uses preexisting 

 disposal mounds, and a planned placement of mounds to form a "ring of mounds," that 

 will both contain the spread of dredged material on the seafloor and allow 

 unacceptably contaminated dredged material (UDM) to be capped with a minimum 

 amount of capping dredged material (CDM). 



• The configuration of disposal mounds at the NLDS has remained stable over at least 

 the last twenty years between master surveys, indicating stability of the mass of 

 material at the disposal site, despite sorting and winnowing of surficial fine-grained 

 material. There is strong evidence of stability of deposits placed at NLDS as much as 

 twenty to thirty years ago (NL-RELIC, NL-I, -II, -III and -TR). 



• All areas surveyed during this period showed evidence of healthy, stable benthic 

 communities and rapid recolonization of dredged material following disposal 

 activities. 



• Biological activity had a strong seasonal impact on surface sediments. Widespread 

 settlement and growth of tube-building organisms promoted deposition of fine-grained 

 sediment on the surface of NLDS. Senescence or migration of these organisms 

 caused decomposition of tubes and removal of fines and tubes leaving coarser 

 sediment on the surface. 



• Physical and biological monitoring data from the NLDS were consistent with a model 

 of seasonal winnowing of surficial fine-grained material. This process serves to armor 

 the disposal mounds with a surficial scour lag deposit providing a mechanism for long- 

 term stabilization of the mounds. 



Monitoring Cruise at the New London Disposal Site, 1992 - 1998 



