47_ 



the New Haven Capping Project. Dredged material generated by those smaller projects is 

 now used to develop containment rings that concentrate deposition of large volumes of 

 UDM and facilitate efficient capping. By continuing to build rings of closely spaced 

 disposal mounds over the 6.85 km 2 area of CLIS, a network of containment cells, similar 

 to honeycombs, will be produced (Figure 5-1). Over time, this network of cells will 

 minimize the surface area occupied by each dredged material deposit and therefore 

 maximize the overall capacity of the site. 



In the past, the management strategy at CLIS and other DAMOS disposal sites was 

 to build many independent mounds over the given area of the disposal site. Each mound 

 could be monitored individually, assessing mound stability, cap thickness, recolonization 

 status, etc. Although this practice was highly successful, the overall capacity of the 

 disposal site was reduced due to the unusable area between the discrete sediment mounds. 

 This strategy changed at CLIS in 1983 with the placement of the SP mound to the 

 northeast of the historic NORWALK mound (SAIC 1984). As dredging and disposal 

 practices continued to improve, advancements in precision navigation and point deposition 

 helped concentrate sediment mounds in smaller areas. By repositioning a taut- wire moored 

 disposal buoy at the start of each disposal season, a ring of disposal mounds was formed 

 and eventually completed in 1992 with the development of the CLIS 91 mound. At this 

 time project plans for the large-scale New Haven Capping Project were being finalized. 



The reported volumes provided by the DAMOS Disposal Barge Logs state that 

 approximately 590,000 m 3 of UDM was deposited at the NHAV buoy, followed by an 

 estimated volume of 569,000 m 3 of CDM. The wealth of data collected over the NHAV 

 93 project area suggests that the resulting mound is broad, stable, adequately capped, and 

 exhibiting a CDM to UDM ratio of 0.96 to 1.0 (Morris 1994). In the past, CDM to UDM 

 ratios varied from 2:1 to 6:1 when initiating a capping operation on a flat or gently sloping 

 area of seafloor without natural (i.e., rock outcrops, glacial troughs) or artificial (i.e., 

 disposal mound ring, geotextile fabrics) means of restricting the lateral dispersion of a 

 UDM deposit (SAIC 1995). Lacking means of containment, the apron of UDM is free to 

 spread into a wide, thin layer of material, increasing the amount of CDM required to 

 completely cover the flanks of the mound. 



The NHAV 93 capping project was the first in the New England region to utilize an 

 artificial containment cell to control the spread of UDM. The use of the disposal mound 

 ring at CLIS significantly reduced the outward migration of the UDM mound apron. As a 

 result, cap material was distributed over a much smaller area, decreasing the total volume 

 of CDM required to cap the inner harbor sediments. Dredging operations in urbanized 

 areas may not produce an abundance of CDM for use in capping operations. However, the 



Monitoring Surveys of the New Haven Capping Project, 1993-1994 



