EXECUTIVE SUMMARY 



As part of the Disposal Area Monitoring System (DAMOS) Program, Science 

 Applications International Corporation (SAIC) conducted monitoring surveys of the U.S. 

 Navy Seawolf Mound within the New London Disposal Site (NLDS) in September 1997 and 

 July 1998. Field operations in each survey year included data collection of one or more of 

 the following: precision bathymetric surveys, Remote Ecological Monitoring of the Seafloor 

 (REMOTS®) sediment-profile surveys, grab sampling of benthic invertebrates, and sediment 

 coring. This report summarizes the disposal and monitoring activities at the U.S. Navy 

 Seawolf Disposal Mound from 1995-1998. This information is presented as a single report 

 to provide a clear, concise picture of the use of the Seawolf Mound during this time frame 

 and to synthesize important monitoring information related to this dredged material mound. 

 A companion report, Volume I, covers monitoring conducted at other mounds in the site 

 from 1992-1998. 



Since its inception in 1977, the DAMOS Program has investigated dredging and 

 dredged material disposal practices in an effort to minimize adverse physical, chemical, and 

 biological impacts. DAMOS utilizes a flexible, tiered management approach centered on 

 comprehensive environmental monitoring to oversee the placement of sediments at nine 

 open water disposal sites along the coast of New England. Active disposal sites are surveyed 

 on a regular basis to ensure the environmental effects of dredged material deposition on the 

 benthic habitat are localized and temporary. 



There has been an active dredged material disposal site near New London since at 

 least 1955. DAMOS monitoring of the New London Disposal Site started in 1977 when the 

 program was established. The New London disposal site has been used for on-going 

 disposal throughout the 1990's, including unconfined disposal of suitable sediments, and 

 capped disposal of unsuitable sediments. During the 1995-1996 disposal season, the NLDS 

 received a total barge volume of 877,500 m 3 of dredged material generated from three 

 separate projects in the eastern Long Island Sound region (Seawolf, Venetian Harbor, Mystic 

 River). Disposal resulted in creation of one disposal mound, the U.S. Navy Seawolf Mound, 

 consisting of unsuitable dredged material (channel, berthing areas and Mystic River) and 

 suitable cap material (Thames River channel, Venetian Harbor and Mystic River). 



Bathymetric surveys, REMOTS® data and sediment core data confirmed that the 

 Seawolf Mound was capped with at least 50 cm of suitable dredged material. The Seawolf 

 Mound formed a flat, nearly circular deposit with a diameter of approximately 600 m. After 

 an initial period of consolidation of the fresh dredged material (9 months to 1 year), the 

 mound settled to an average height of 2 m with a small oval apex of 3 m. Across the surface 

 of this mound, a thick layer (0.5-3 m) of suitable material formed a cap consisting of sandy 

 sediments and gray glacial clays from improvement dredging in the Thames River channel. 

 Based on visual analysis and direct sampling of animals in this surface layer, recolonization 

 of the fresh dredged material by marine invertebrates proceeded as expected. The stiff clay 



