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3.0 RESULTS 



3.1 Seawolf Mound 



3.1.1 Bathymetry 



The Seawolf Disposal Mound is a flat, nearly circular capped sediment mound 

 complex composed of an estimated barge volume of 877,500 m 3 of dredged material. This 

 complex was formed from 862,000 m 3 of dredged material (305,200 m 3 UDM and 

 556,000 m 3 CDM from the Seawolf Project and 803 m 3 UDM from Mystic Seaport) 

 deposited at the U.S. Navy buoy from 21 October 1995 through 31 January 1996. In 

 addition, a total of 15,490 m 3 of CDM from Mystic River and Venetian Harbor were 

 deposited at the NDA 95 buoy, which also contributed to the Seawolf Mound. In September 

 1997, a 1000 x 1000 m survey was performed over the Seawolf Mound, replicating the size 

 and orientation of the surveys used to track the development of the sediment deposit. This 

 survey was used to monitor the long-term stability of the disposal mound as well as to 

 measure the amount of dredged material consolidation in the underlying layers since 

 February 1996. Bathymetric results of the entire NLDS for this period are presented in 

 Volume I of this report (SAIC 2001). 



In October 1995, Gahagan and Bryant, Inc. conducted a 1500 x 1500 m survey over 

 the northwest corner of NLDS to serve as the baseline against which all future Seawolf 

 Mound surveys would be compared (Figure 3-1). Depths within the 1000 x 1000 m analysis 

 area ranged from 13.5 m over the NL-RELIC Mound to 22.5 m along the southwest margin. 

 Dredging operations around Seawolf Piers 8 and 10 and sections of the main channel 

 commenced on 21 October and continued through 7 December 1995, producing large 

 volumes of UDM (Appendix A). Upon the deposition of the final barge load of UDM at the 

 U.S. Navy buoy on 7 December, a precapping survey was completed to determine the 

 thickness and lateral extent of the UDM deposit. A distinct elevation in bottom topography 

 was found near the center of the survey grid, between the U.S. Navy and NDA 95 buoys 

 (Figure 3-2). Depth difference calculations based on comparisons with the baseline 

 bathymetric dataset indicated the disposal operations had formed a discrete UDM deposit 

 approximately 400 m wide and with a maximum height of 3.5 m (Figure 3-3). The apex of 

 the mound was developed 75 m southwest of the Navy buoy position, and the development of 

 the mound seemed to be strongly affected by a consistent disposal pattern (tow boat and 

 barge approach) and the slope of the NLDS seafloor. The deposit also included 2,310 m 3 of 

 CDM from the Venetian Harbor and Mystic River dredging projects disposed at the NDA 95 

 buoy prior to the precap survey (Figure 3-3). 



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



