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4.0 DISCUSSION 



The July 1996 survey operation represents the first monitoring effort conducted at 

 WLIS, since the 1993 REMOTS® sediment-profile photography survey. Within this three- 

 year period, two new disposal mounds were developed on the WLIS seafloor and a third 

 mound received a considerable volume of supplemental dredged material. Depth 

 difference comparisons with the 1992 and 1990 bathymetric surveys display the new 

 sediment mounds as discrete bottom features connected by a ridge of material 0.25 m 

 thick, formed by overlapping mound aprons (Figure 3-4). 



In accordance with the successful management strategy demonstrated at CLIS, the 

 recent disposal activity at WLIS has been tightly controlled in order to construct rings of 

 disposal mounds. Upon completion, these rings of mounds will provide large cells of 

 lateral containment and maximize the available space within the 5.29 km^ area of the 

 disposal site. As of July 1996, the first cell nears completion as the WLIS D, E, F, G, and 

 H mounds begin to form an artificial containment ridge. The development of small 

 dredged material disposal mounds between D-E; E-H; and H-F will close the ring in the 

 near future (Figure 4-1). 



Supplementary lateral containment measures could be achieved by utilizing the 

 natural containment ridge provided by the steep slopes of the terminal moraine margin. 

 Large volumes of dredged material could be confined by strategically constructing 

 sediment mounds in a semi-circle pattern north of the terminal moraine margin. The 

 placement of one additional mound approximately 150 m southwest of WLIS G would 

 complete such a structure (Figure 4-2). The resulting cell could facilitate the deposition of 

 a large volume of fine-grained dredged material and minimize the development of a wide, 

 thin apron. 



Records pertaining to dredging and sediment deposition in the Long Island Sound 

 region between 1954 and 1976 indicate sediments excavated from the channels and harbors 

 that border Long Island Sound were transported to as many as 19 open water disposal sites. 

 In most cases, dredging operations within each harbor utilized a distinct area of seafloor 

 for the disposal of sediments (Fredette et al. 1992). A total of eight disposal sites 

 (Bridgeport, Eaton's Neck, Norwalk, Port Jefferson, Smithtown, South Norwalk, 

 Southport, and Stamford) were established between the East River and Stratford Shoal 

 from 1954 to 1972 (Figure 1-1). The nearly two decades of disposal activity over these 

 sites led to relatively broad distribution of dredged material within western Long Island 

 Sound prior to the instimtion of the DAMOS Program (estimated total of 22 million cubic 

 yards, with close to 60% released at Eaton's Neck). 



Monitoring Cruise at the Western Long Island Sound Disposal Site, July 1996 



