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4.0 DISCUSSION 



The current 1994 survey was the largest conducted at CLIS since the 1986 master 

 survey which encompassed the entire disposal site, an area of 8.375 km^ (SAIC 1990). 

 The large July 1994 survey allowed SAIC and NED to reconstruct the history of CLIS, 

 assess the stams of the NHAV 93 and MQR mounds, and establish a new baseline for 

 fiimre bathymetric data comparisons. 



The NHAV 93 mound is an example of a new type of CAD mound, utilizing seven 

 historic disposal mounds (CLIS 87, CLIS 88, CLIS 89, CLIS 90, CLIS 91, SP, and 

 Norwalk) as an artificial lateral containment structure. These seven mounds were 

 systematically placed on the bottom by changing the position of the CDA taut-wire moored 

 buoy annually and employing precision disposal operations (Figure 4-1). The formation of 

 a ring of small to moderate dredged material disposal mounds developed a containment cell 

 on the CLIS seafloor capable of receiving a large volume of UDM and facilitating quick 

 and efficient capping operations (Morris et al. 1996). 



During the 1993/94 disposal season, 590,000 m' of UDM was deposited at the 

 NHAV buoy located over the center of the cell. Due to this added containment measure, 

 the lateral spread of the UDM deposit did not exceed 500 m. The capping process was 

 completed within 75 days due to the restricted shape and size of the disposal mound. A 

 total of 569,000 m^ of cap material was required to cap the entire NHAV 93 mound to a 

 thickness of 0.5 m to 1.0 m. The end result was a wide, flat, and stable central mound 

 that yielded a historically low CDM to UDM ratio of 0.96:1.0 (SAIC 1995). 



In contrast to the New Haven Harbor Capping Project at CLIS, a recent capping 

 project conducted at the New York Mud Dump Site required significantly more cap 

 material to cover a lesser volume of contaminated dredged material. In June and July of 

 1993 approximately 445,000 m^ of dioxin contaminated material was dredged from the 

 Port of Newark/Elizabeth (SAIC 1994). This material was deposited on the bottom of the 

 New York Mud Dump Site without the use of a containment cell to restrict the size of the 

 deposit. An additional requirement of the project was to limit the height of the mound by 

 creating a broad flat mound. To achieve this, disposal operations were conducted along 

 predetermined lanes rather than at a single buoy. The apron of the dioxin-contaminated 

 mound that was formed by this disposal covered an area with a diameter of approximately 

 1.25 km. Capping operations at the New York Mud Dump Site were conducted from July 

 1993 through February 1994. The final volume of sand required to cap the dredged 

 material mound to a uniform thickness of 1 m was 1,862,000 m^ resulting in a cap to 

 mound ratio of 4. 18: 1 .0 (SAIC 1994). The final volume of material required to cap the 



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



