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community. Thirteen sampling stations were occupied in August 2000; these are the same 

 stations sampled in three previous REMOTS® surveys over this bottom feature. At least 

 three replicate images were obtained and analyzed at each station, except station SOON (only 

 two replicates obtained/analyzed). A complete set of REMOTS® image analysis results is 

 provided in Appendix B 1 ; these results are summarized in Table 3 - 1 . 



The images showed that sediments comprising the surface of the NL-91 and D/S 

 Mound Complex were predominantly silt/clay (grain size major mode of >4 phi). This 

 silt/clay appeared to contain a significant fraction of very fine to fine sand at each station, 

 such that surface sediments across the site are best described as "sandy mud." Sandy mud 

 was also the predominant sediment type at the three reference areas. 



All of the sediment observed in the REMOTS® images at each of the thirteen stations 

 was identified as capping dredged material. This CDM generally extended fi-om the 

 sediment surface to below the imaging depth of the REMOTS® camera prism at each station 

 (see dredged material thickness measurement indicated with a "greater than" sign in Table 3- 

 1). The CDM observed in the images at the majority of stations in August 2000 appeared to 

 be placed recently (i.e., within the past year or two) and was therefore categorized as the 

 newer, supplemental CDM (Figures 3-4 and 3-5 A). At stations 200S, 300E, 400E, and 500E, 

 the CDM displayed characteristics similar to those observed in previous surveys (1995, 1997, 

 and 1998) and was therefore categorized as "old" CDM (Figure 3-5B). The contour line in 

 Figure 3-4 indicates that the distribution of supplemental CDM as detected in the REMOTS® 

 images correlates very well with the bathymetric depth difference results. The deposit of 

 supplemental CDM completely covers the original main deposit of UDM placed at the D/S 

 buoy in 1991. 



The apparent RPD measured in each REMOTS® image provides an indication of the 

 degree of oxygen penetration into the sediment. A well-developed RPD depth (defined as 

 greater than 3 cm) generally indicates good or healthy sediment aeration as a result of active 

 bioturbation by benthic organisms. The replicate-averaged apparent RPD depths fi-om the 

 mound complex ranged fi-om 1.8 to 4.9 cm, with an overall average of 3.4 cm (Figure 3-6; 

 Table 3-1). This average value was greater than the average RPD depth of 2.6 cm measured 

 at the reference stations (Table 3-2) and is considered indicative of healthy aeration of the 

 surface sediments. 



The successional status was advanced, with Stage II or Stage II on HI communities 

 inhabiting the surface sediments of the mound complex (Figure 3-7). Stage III organisms 

 were present at 12 of 13 stations. In addition, tubes of the amphipod Ampelisca sp. were 

 observed at the sediment- water interface at 12 of the 13 stations. At numerous stations, the 

 tubes appeared to be mature or in a state of decay (Figure 3-8 A). However, patches of 



Monitoring Cruise at the New London Disposal Site, August 2000 



