27 



disposal mounds were stable and no significant sediment erosion occurred (SAIC 1990e; 

 Figure 6-13). Increased water depth over "B" mound from 1988 to 1990 was attributed 

 partly to compaction of sediments on the mound and partly to an artifact of the data analysis 

 (Germano, Parker, and Williams 1993). The October 1985 survey, when mound height was 

 determined to be unaffected by the passage of Hurricane Gloria, further confirmed mound 

 stability (SAIC 1988b). Based on bathymetric and REMOTS® surveys, thin layers (<20 cm) 

 of dredged material extended beyond the base of the disposal mounds detectable by 

 bathymetry (Figure 6-14). The two factors contributing most to this distribution are the 

 physics of the disposal process and the release of dredged material away from the center of 

 the mound (Figure 6-15). 



In August 1986, REMOTS® photography at WLIS revealed a stressed biological 

 community in conjunction with the extremely low near-bottom DO levels which were 

 recorded throughout Long Island Sound (SAIC 1987a, 1987b). This regionwide low DO 

 phenomenon, unrelated to disposal activities, is believed to be due to eutrophication effects 

 during the strong temperature gradient present in the water column during the summer 

 months in the Sound (SAIC 1987b). DO measurements recorded since that time have been 

 above hypoxic levels (i.e., greater than 3 mg-1 1 ). In addition, REMOTS® analyses have 

 shown an overall continued improvement in the benthic habitat at WLIS with no significant 

 difference between the on-site and reference station communities in 1987 and 1988 surveys. 

 The disturbance resulting from dredged material disposal has been primarily physical in 

 nature, with rapid recolonization of the seafloor by the resident benthic fauna. 



Sediment chemistry samples were collected in 1985, 1986, and 1987 to monitor 

 contaminant levels within the disposal site and check for indications of contaminant 

 resuspension and transport. Samples were obtained from the center of each of the three 

 disposal mounds ("A", "B", and "C") and the WLIS reference area in 1985; the "A" mound 

 and WLIS reference area in 1986; and along an east- west transect in the direction of the 

 dominant current regime in 1987 (Figure 6-16). Body burden samples were obtained in 1986 

 and 1987 at locations identical to the sediment chemistry sampling stations. 



Results of sediment chemistry analyses in 1985 indicated that the sediment at the 

 reference area had lower concentrations of Cu, Cr, and Pb, while the recent dredged 

 material, in general, showed higher concentrations of most metals in comparison to relic 

 dredged material and the reference area (Figure 6-17). Statistical analyses of sediments 

 collected in 1986 indicated that the concentrations of Pb, Ni, Cu, and oil and grease were 

 significantly higher in the relic dredged material than in the reference area (Figure 6-17). 

 The levels of Hg, Ni, Pb, Zn, and PCBs at the "A" mound were moderate according to the 

 NERBC limits (Table 6-1). 



The objective of the 1987 sediment chemical study was to assess whether 

 contaminants deposited at the WLIS site were subject to resuspension and transport, possibly 



DAMOS Summary Report, 1985-1990 



