1J3_ 



4.0 DISCUSSION 



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

 during the period 1991-1998 and received dredged material from twelve distinct episodes 

 of disposal (Figure 1-3). The patterns of disposal and monitoring provide an overview of 

 the processes affecting the environment within the disposal site. This report includes 

 specific details regarding individual disposal mounds, their history and monitoring results. 

 This report is the first of two-volume report that covers D/S, NL-91, USCGA, NL-94, and 

 the Northern Region. Volume 2 of this report covers the results of monitoring the U. S. 

 Navy Seawolf mound in 1997 and 1998. Before discussing each mound complex and the 

 baseline study of the northern region, it is helpful to review the evidence of physical and 

 biological response to disposal activity at this site. 



The master bathymetric survey conducted in 1997 over the revised DAMOS NLDS 

 site boundaries provided data for an analysis of the topographic signature of the disposal 

 site over a ten year period since the prior master survey in 1986 (Section 4. 1). The 

 REMOTS® sediment profile photography results from the disposal sites are compared in a 

 general way with the results from the three surrounding reference areas (NLON-REF, NE- 

 REF, and WEST-REF) in Section 4.2. The history and monitoring results of each disposal 

 mound (D/S & NL-91, USCGA, NL-94) are then discussed (Sections 4.3, 4.4, 4.5). 

 Finally, a discussion of the baseline characterization results for the Northern Region is 

 provided in Section 4.6. 



4.1 Topography and Evidence of Historical Disposal at the NLDS 



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

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

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

 over time as recorded in previous surveys (NUSC 1979, SAI 1980, Parker and Revelas 

 1989, SAIC 1990a, b, c; 1995a, b; Germano et al. 1995). Coherent disposal mounds can 

 be seen associated with the historical placement of dredged material at the following 

 locations: NL-I (1978), NL-II (1979-80), NL-III (1980-81), Seawolf, NL-85, NL-88, 

 Dow/Stonington & NL-91, USCGA/NL-TR, NL-95, and NL-94/96 (Figure 1-2). 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 washing of fine-grained material across the disposal site and a potential for active 

 bedload transport (Knebel et al. 1999, Waddell et al. 1999), the consolidated mass of 



Monitoring Cruise at the New London Disposal Site, 1992 - 1998 



