12 



Sediment chemistry results indicated levels of metals and oil and grease to be low (Table 6-1) 

 at reference, mound, and off-mound locations. No major trends were noted. Concentrations 

 of organochlorine pesticides and polychlorinated biphenyls (PCBs) in sediments were below 

 the analytical detection limits at almost all of the reference and on-site stations. The 

 concentration of PCBs was greatest in the recent dredged material, but was also below the 

 1.0 ppm considered to be a high level of contamination according to the NERBC guidelines 

 (Table 6-1). 



Body burden results for 1987 indicated that the concentrations of Cd, Pb, and Hg in 

 Nephtys were below the analytical detection limits at both the reference and on-site stations 

 (Figure 6-9). Reflecting the general pattern of sediment contaminants, Nephtys body burdens 

 showed no distinct trend (SAIC 1990a). 



Dissolved oxygen (DO) measurements were made in 1987, 1988, and 1990 (SAIC 

 1990b, 1990c, Germano et al. 1994). Hypoxic water (DO concentration less than 3 mg-1 1 ) 

 was present throughout the water column in all of Long Island Sound in the summer of 1987. 

 The similarity of DO measurements at the disposal mounds and reference stations led to the 

 conclusion that hypoxic conditions were unrelated to disposal activity (SAIC 1990b). In 

 1988 and 1990, the thermocline was well developed at 5-10 m, and there continued to be no 

 significant difference in DO values between the mound and reference stations. 



6.1.2 CLIS: 1990 Monitoring Results 



Field operations at CLIS were conducted in July 1990 to delineate the extent and 

 topography of the recently deposited dredged material, to measure near-bottom and near- 

 surface DO concentrations and vertical profiles of temperature and salinity at select disposal 

 site and reference stations, and to collect additional baseline sediment grain size and 

 chemistry samples from the reference areas. The data included precision bathymetry, 

 REMOTS® sediment-profile photography, conductivity, temperature, depth (CTD) and DO 

 information, and sediment grab samples. 



The precision bathymetric survey detected disposal mounds CLIS-88, CLIS-89, and 

 CS-90-1, formed since the 1988 survey. Dredged material was detected at all REMOTS® 

 stations in the survey. In many cases, REMOTS® photographic evidence of off-mound 

 deposits of dredged material was supported by small (0.20 to 0.40 m) decreases in water 

 depth detected in a comparison of 1988/1990 bathymetric data. 



Benthic recolonization was determined from the analysis of REMOTS® photographs 

 obtained at CLIS-89, with Stage I taxa (initial stages of recolonization) predominating and at 

 CS-90-1, with Stage I taxa occurring 200 m southwest of the buoy location. Most of the 

 remaining stations and the reference stations had Stage III (mature successional stage) 

 assemblages. 



DAMOS Summary Report, 1985-1990 



