34 



During the 1990 survey, dredged material was detected at several REMOTS® stations 

 up to 300 m from the buoy locations (Figure 3-9). This seems to indicate that some 

 sediments were released more than 200 m from the buoy. Cross-checking release locations 

 recorded in the barge logs for the 1988/89 and 1989/90 disposal seasons confirm this (Figure 

 4-3). However, most release points did fall within 200 m of the buoy location. 



The disposal of Harbor Village dredged material at the CS-90-1 buoy between 

 October 1989 and January 1990 was followed by a capping operation using Branford 

 River/Harbor sediments that were to be released at eight designated LORAN-C coordinates. 

 The objective was that the material would be released around these eight points and spread 

 relatively evenly over the seafloor. Comparing the pre- and postcap bathymetry showed the 

 greatest accumulations of cap material at three discrete locations within the radius of the 

 dredged material deposit. The thinner cap at the remaining LORAN-C locations (Figure 4-2) 

 seemed to indicate that the material was not released evenly at all intended locations. 

 Comparing bathymetric values to obtain cap thickness has two inherent limitations which may 

 partially explain the apparent cap thinness. The bathymetric survey has a resolution of 

 between 20 and 25 cm, and sediment thicknesses less than the resolution will not be detected 

 in a bathymetric survey. The bathymetry also only measures the depth to the seafloor. As 

 material (the ambient bottom and the dredged material under the weight of the cap) is 

 compressed, the cap will appear thiimer than it actually is. 



The significantly shallower RPD depths at disposal site stations versus the reference 

 stations probably were due to the recent disturbance (disposal events) and the presence of 

 dredged material with its increased sediment oxygen demand compared to the ambient 

 sediment at the reference areas. Lx)calized areas of oxidized sediment layers greater than 

 3 cm were near CS-90-1, CLIS-87, and in the northwest comer of the survey area. The 

 increased RPD depths in these areas were due to greater bioturbational activity by the local 

 infaunal assemblages. With the exception of the area around CS-90-1, most of the greater 

 RPD depths correspond to areas with fewer dredged material release points (Figure 4-3). 



Prevalence of Stage I organisms is characteristic of newly recolonized mounds, 

 whereas dominance by Stage III organisms typifies an undismrbed climax community. The 

 predicted recolonization at CLIS was Stage I on the CLIS-89 and CS-90-1 mounds, 

 progressing to Stage III on CLIS-87 and CLIS-88. Only Stage I organisms were found at the 

 six stations around the CLIS-89 mound and at two stations adjacent to CS-90-1. Stage III or 

 I/III was identified at CLIS-87 and CLIS-88, and at most of the REMOTS® stations away 

 from the active disposal mounds and at the reference areas (Figure 3-14). The exceptions 

 were isolated occurrences of Stage I assemblages at reference stations 2500W and CLIS-REF 

 and at station Dl in CLIS. None of these locations had any obvious benthic disturbance. 



Monitoring Cruise at the Central Long Island Sound Disposal Site, July 1990 



