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5.0 CONCLUSIONS AND RECOMMENDATIONS 



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

 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. 

 We include general conclusions for the site as a whole in this report for convenience; the 

 results for some of these conclusions were presented and discussed in Volume I (SAIC 

 2001). The current report (Volume II) presented and discussed results from surveys 

 conducted at the U.S. Navy Seawolf Mound from 1995-1998. This section provides 

 conclusions both for the site and the Seawolf Mound (and recommendations for site 

 management). 



5.1 Overview of NLDS 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. 



The stability of historic disposal mounds at the NLDS has remained the same over at 

 least the last twenty years, indicating a stabilization 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, -HI 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 during spring and summer promoted 

 deposition of fine-grained sediment on the surface of NLDS. Senescence or migration 

 of these organisms during the fall and winter 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 



Monitoring Cruise at the New London Disposal Site, Seawolf Mound 1995 - 1998 



