100 



100SW, the remaining replicates indicated ambient sediment, while historic dredged 

 material from the NL-I mound was detected at 150SE (Figure 3-40 A&B). This resulted in 

 mean dredged material thickness of 2.9 to 5.5 cm for these stations. At 100E, all 

 replicates had dredged material over ambient sediment, for an average thickness of 5.3 cm. 

 Ambient sediment was found in all replicates at stations 100 m west, northwest, and 

 northeast of the center. 



The mean camera penetration depths for REMOTS® stations at the NL-94 mound 

 ranged from 7.9 cm to 15.6 cm and averaged 11.85 cm. These values are consistent with 

 the presence of fine-grained material at most of the stations (Figure 3-41). 



The major modal grain size was consistently classified as fine-grained silt-clay (>4 

 phi) at the stations within 50 m of the center station and at Station 100SE. The remaining 

 station replicates ranged from silt-clay (>4 phi) to very fine sand (3 to 4 phi; Table 3-6). 

 Sand-over-mud layering was observed at the majority of the stations outside a 50 m radius 

 from the center. 



Average boundary roughness values ranged from 0.6 cm to 2.9 cm. The 

 distribution of boundary roughness values showed no spatial pattern. With the exception 

 of three stations, boundary roughness over the NL-94 mound was attributed to biogenic 

 activity. One replicate from Station 100E exhibited evidence of a scour lag feature, one 

 replicate from Station 50NE showed a possible erosional boundary, and one replicate at 

 50NW displayed a shell lag feature. 



Average RPD values at NL-94 stations ranged from 0.7 cm to 5.1 cm, with an 

 average RPD value of 2.02 cm over the entire mound (Table 3-6). There was no apparent 

 geographic pattern to the distribution of deep and shallow RPD depths (Figure 3-42). The 

 shallowest RPD was measured at 50S (0.7 cm), and the deepest RPD was measured at 

 50SE (5.2 cm). 



Stage II and Stage II on III communities dominated the NL-94 mound. Stations 

 100NE and 50NW had Stage I present, as well as Stages II and III (Figure 3-43). Because 

 these are advanced successional stages for an area recently impacted by dredged material, 

 NL-94 appeared to have recovered rapidly relative to the normal progression of benthic 

 recovery (Germano et al. 1994). 



Median OSI values ranged from +6 to +11 over the NL-94 mound, with an overall 

 average of +7.4 (Table 3-6). In general, an OSI of less than +6 indicates areas of benthic 

 disturbance (Rhoads and Germano 1982). The highest OSI value of +11.0 was detected at 

 Station 50SE, where there was Stage II on III and a mean RPD thickness of 5. 1 cm 



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



