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disposal mounds with a surficial scour lag deposit providing a mechanism for long-term 

 stabilization of the mounds. 



• Reference areas reflected conditions throughout eastern Long Island Sound including: 

 seasonal responses to biological and physical processes and apparent impacts of low 

 dissolved oxygen or organic enrichment. All reference areas supported stable, healthy 

 benthic communities. 



5.2 U.S. Navy Seawolf Mound 



• The U.S. Navy Seawolf Mound was found to be a flat, circular deposit with a diameter 

 of approximately 600 m. Peak heights of a small central apex extended 1-2 m above a 

 large flat plateau and a relatively narrow apron. The Seawolf Mound (minimum 

 elevation 16 m) is a few meters lower than the NL-RELIC Mound (minimum elevation 

 13.5 m) that lies immediately to the east. 



• The Seawolf Mound was formed from five distinct disposal events resulting in a thick 

 sediment cap (CDM) over a discrete mound of unsuitable dredged material (UDM). 

 The CDM to UDM ratio was 1.82:1.0, providing a substantial volume of capping 

 material composed of improvement dredging material from the Thames River channel 

 (Gardiner's Clay) and sandy sediments from the outer channel. 



1997 



The survey conducted in 1997 achieved the following five objectives: 



• Assess the benthic recolonization status of the Seawolf Mound relative to the 

 three reference areas surrounding NLDS. 



Sediment profile images showed the widespread presence of improvement material 

 (gray Gardiner's clay) that was serving to cover and stabilize the mound surface. The 

 presence of this non-marine, glacially-derived plastic clay may have slowed somewhat the 

 normal rate of recolonization. The successional stage of the Seawolf Mound during the 

 1997 survey was predominantly Stage II, based on both REMOTS® and benthic taxonomic 

 data showing the numerical dominance of Nucula annulata and tubicolous polychaetes. 

 Although the OSI values were more variable than those at the reference areas (range +5.0 to 

 +10.0), the average OSI value for the Seawolf Mound (+6.1) was similar to the reference 

 area average (+6.7). The presence of non-marine, glacially-derived plastic clay at NLDS and 

 other disposal sites monitored under the DAMOS program (e.g., Massachusetts Bay 

 Disposal Site) requires minor adjustment of the normal recolonization paradigm because of 

 the lack of organic matter in such clays. As ambient sediments accumulate and are worked 

 into the clay, normal recolonization will proceed. 



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



