11 



CLIS received approximately 1,175,000 m 3 of dredged material from 1985 to 1990 

 (Figure 6-3). Distinct disposal mounds were formed during each disposal season. A 

 common objective within the DAMOS monitoring program has been to assess the extent and 

 stability of dredged material. The areal extent of dredged material, including deposits less 

 than 15 cm (the limit detected by bathymetry), was mapped by REMOTS® photographs 

 (Figure 6-4). The larger footprint of dredged material detected by REMOTS® as compared 

 to that detectable by bathymetry was due partly to the distance of the release points from the 

 buoy location (Figure 6-5). Continued monitoring has shown that the disposal mounds 

 remain stable over time (Figure 6-6). During Hurricane Gloria in 1985, only disposal 

 mound CS-1, capped with silt rather than sand, experienced a loss of surface sediment (SAIC 

 1989a). Reductions in mound height over time are due to consolidation of dredged material 

 and ambient sediment. Consolidation will be more pronounced where mounds are capped 

 with permeable sediment, as was shown at STNH-N where a sand cap was used (Poindexter- 

 Rollings 1990). 



The convenient location and protected waters at CLIS resulted in the selection of this 

 site for several capping experiments from 1979 to 1983. Since 1984, capping projects have 

 been conducted at CLIS-86 (SAIC 1990c) and CS-90-1. Both sand and silt have been 

 employed as capping material. The scarcity of dredging projects with clean sand in Long 

 Island Sound probably restricts future capping operations to employ mainly clean silt. Data 

 show that both methods are effective in containing contaminants, but that sand caps provide 

 greater resistance to erosion during storm events (SAIC 1989a). 



Chemical and biological parameters at CLIS were investigated in 1986 and 1987. 

 Sediment samples were collected in 1986 at 10 disposal mounds, at eight stations around the 

 STNH-N mound, and at the reference area (Figure 6-7). Recent and relic areas of dredged 

 material showed higher levels of Cr, Cu, Fe, Zn, and oil and grease than off-mound and 

 reference areas (Figure 6-8). Concentrations of metals and oil and grease were either low or 

 moderate by NERBC limits; moderate levels of Cu, Pb, and Zn were present on the recent 

 dredged material (Table 6-1). 



Test organisms for body burden analysis in 1986 were collected from four of the 

 disposal mounds (STNH-N, FVP, MQR, and CLIS-86) and at the reference area (Figure 6- 

 7). Results indicated higher levels of Cd, Cr, Cu, and Pb at CLIS-86 as compared with the 

 reference area and relic areas (Figure 6-9). Comparing CLIS-86 Nephtys samples with 

 samples from other mounds showed sediment in the gut of the CLIS-86 samples. This could 

 account for the higher levels of metals as compared to other mounds (SAIC 1990a). PCBs 

 were not detected in any of the Nephtys samples analyzed. 



A transect study was conducted in 1987 along the axis of predominant current 

 movements to monitor possible contaminant resuspension and transport and provide 

 additional baseline data on contaminant body burden in the polychaete worm Nephtys. 



DAMOS Summary Report, 1985-1990 



