30 



sediments 15 months after completion of the capped mound. Slightly coarser sediments (4 

 to 3 phi) were detected in one replicate of Station lOOS, but this finding was most likely 

 attributable to variability within the sediment deposit rather than loss of fine-grained 

 material due to winnowing. The replicate-averaged mean camera penetration was deepest 

 (18.12 cm) 100 m south of the center and was shallowest (14.71 cm) at CTR (Appendix A, 

 Table 3-2). 



Boundary roughness measurements showed no distinct pattern over the center of the 

 CLIS 94 mound. Replicate-averaged boundary roughness values ranged fi-om 0.35 cm at 

 lOOE to 1.15 cm at CTR. The primary cause for surface roughness was classified as 

 physical disturbance as anticipated over a relatively recent sediment deposit. As 

 consolidation and increased bioturbation affect the surface sediment layers in the fumre, 

 boundary roughness over the CLIS 94 mound is expected to become more biogenic in 

 namre. 



3.2.2.2 Benthic Commimity Assessment 



The replicate-averaged mean RPD values ranged from 1.09 at CTR to 3.38 cm at 

 lOON, deeper in comparison to the 1995 results (Figure 3-13). No methane was noted in 

 any photograph, but indications of low dissolved oxygen were detected in one replicate of 

 Station lOOS. 



The successional stage status for the center of the CLIS 94 mound can be 

 characterized as Stage I on III, widi the exception of Station lOOS (Stage I recolonization 

 stams). Stage III activity at four of the five stations and deep RPD depths were the factors 

 behind high OSI values. Median OSI values of the CLIS 94 replicates ranged from 3.0 at 

 CTR to 10.0 at lOOE (Figures 3-13 and 3-14 A and B). Low OSIs (<6) were calculated 

 for two of the five stations and were the result of shallow RPD values (CTR), or low DO 

 and lack of Stage III organisms (lOOS). 



3.3 NHAV 93 Mound 



3.3.1 Bathymetry 



A total of eight bathymetric surveys have now been conducted over the NHAV 93 

 mound since September 1993 to monitor the progress of the CAD mound construction, 

 stability, and consolidation over time. The latest bathymetric survey, 2.5 years after 

 capping operations were completed, displays a mound complex approximately 820 m wide 

 and composed of eight disposal mounds (CLIS 87, CLIS 88, CLIS 89, CLIS 90, CLIS 91, 

 SP, Norwalk, and NHAV 93) (Figure 3-15). 



Monitoring Cruise at the Central Long Island Sound Disposal Site, July 1996 



