40 



3.3.2.2 Benthic Community Assessment 



Replicate-averaged RPDs were fairly deep, ranging from 1.37 cm at 200N to 

 2.77 cm at CTR (Figure 3-20). Neither methane nor low dissolved oxygen was noted in 

 any photograph. 



Station 200N showed no evidence of Stage III activity, while the remainder of the 

 NHAV 93 stations were classified as Stage I on Stage III. In response to the deep RPDs 

 and strong presence of Stage III individuals, OSI values over the center of the mound were 

 quite high. Median OSIs ranged from 3.0 at Stations 200N (no Stage III) and 200S (Stage 

 III in one replicate) to 9.0 at CTR (Figure 3-20). 



In comparison to the results of the September 1995 REMOTS® survey, improving 

 benthic conditions were detected at four of the five stations sampled in July 1996 (Morris 

 1997). A degradation in the benthic environment was observed at Station 200N relative to 

 September 1995 with shallower RPD depths and lack of Stage III individuals (Figures 3-21 

 A and B). Overall, REMOTS® sediment-profile photography results indicate that the 

 NHAV 93 mound is still recovering from the impact of dredged material disposal as 

 predicted (Germano et al. 1994). 



3.4 MQR Mound 



The July 1996 CLIS survey collected bathymetric data over approximately 75 

 percent of the historic MQR mound, lying in the southwest corner of the 4.41 km^ survey 

 area. Detailed analysis of these data was achieved by scaling down the area of interest to a 

 700 m X 500 m region centered on the apex of the MQR mound. A bathymetric chart of 

 the July 1996 data depicts a discrete, stable, and capped sediment mound with a minimum 

 depth of 17.25 m at MLLW. The MQR mound is approximately 400 m wide as the 

 western flank continues beyond the margin of the survey grid (Figure 3-22). 



During the 1993-94 disposal season, approximately 65,000 m^ of supplemental 

 CDM was placed over MQR, creating a new apex 100 m northeast of the mound center 

 (Morris and Tufts 1997). Depth difference calculations based on the July 1994 survey 

 indicate small to moderate pockets of consolidation (0.25 m to 0.75 m) near the apex as 

 well as the southwestern margins of the MQR mound (Figures 3-23 and 3-24). A 

 significant percentage of the supplemental cap material released over the western MQR 

 mound consisted of coarse sand with some larger grains (Morris and Tufts 1997). The 

 deposition of this denser material is likely the basis for sediment de-watering and 

 subsequent consolidation of the underlying silts and clays deposited in 1982 and 1983. 



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



