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4.0 DISCUSSION 



The New London Disposal Site (NLDS) was monitored over four time intervals 

 during the period 1995-1998 and received dredged material from five distinct episodes of 

 disposal associated with the U.S. Navy Seawolf Mound (Figure 1-3). The specific patterns 

 of disposal leave clear results on the seafloor; the monitoring surveys provide an indication 

 of the processes that produce those results and tests of explicit predictions of potential 

 outcomes of disposal. This report presents details of the placement, capping and monitoring 

 of the U.S. Navy Seawolf Mound. It is the second of a two-volume report devoted to 

 disposal and monitoring at NLDS from 1991-1998. The first volume presents monitoring 

 results for three disposal mounds on the NLDS seafloor (NL-91 and D/S, USCGA, and NL- 

 94), as well as the baseline survey activity over the Northern Region of NLDS (SAIC 2001). 

 The first volume also presents a detailed analysis of recorded changes in the disposal site 

 bathymetry over a ten-year period (1986-1997) and reviews physical and biological response 

 to disposal activity at NLDS based on sediment profile surveys. 



The results of the long-term monitoring efforts are important for evaluating the 

 context of individual disposal mounds. The following section summarizes findings discussed 

 in Volume I and provides some perspective on survey results (Section 4.1). The history and 

 monitoring results of the U.S. Navy Seawolf Mound are then discussed (Section 4.2). 



4.1 Historical Disposal and Biological Response at the NLDS 



The 1997 master bathymetric survey showed several key features important for the 

 future management of NLDS. First, the spatial distribution and topography of the dredged 

 material mounds coincided well with the known buoy locations and mound growth over time 

 (SAIC 2001). Most significantly, the NL-RELIC Mound has been a prominent and 

 unchanging feature at the site since DAMOS bathymetric surveys began in 1977 (NUSC 

 1979, SAI 1980). The presence of discrete disposal mounds with consistent heights and 

 shapes provides evidence that dredged material placed on the seafloor at the NLDS has been 

 stable for at least twenty years. The importance of these results should be emphasized. 

 Despite clear evidence of surface winnowing of fine-grained material across the disposal site 

 and a potential for active bedload transport, the consolidated mass of disposal mounds 

 measured in bathymetric depth-difference calculations has been stable over a period of at 

 least twenty years (Knebel et al. 1999, Waddell et al. 2001). 



The REMOTS® sediment profile data collected from reference areas and within the 

 disposal site from 1991-1998 provide an opportunity to compare and contrast the biological 

 response to disposal activity over a six year period (SAIC 2001). Throughout this period, 

 the fresh and recent (1-6 years old) dredged material showed a rapid recovery from a 

 disturbed surface to a healthy benthic assemblage. Areas of historical dredged material 



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



