6.0 SUMMARY OF DAMOS FIELD WORK 



A large part of the DAMOS Program since 1984 has been the continued monitoring 

 of nine offshore dredged material disposal sites located from Long Island Sound to the Gulf 

 of Maine. The sites have been monitored to assess the extent and stability of dredged 

 material deposits and the effect of dredged material disposal on the quality of the benthic 

 environment. At sites where dredged material formed mounds detectable by bathymetry, 

 repeated surveys showed that the mounds were stable. Hurricane Gloria moved over Long 

 Island Sound in September 1985 but showed no significant impact on mound stability. At all 

 sites, dredged material was found as a thin (<20 cm) layer of sediment beyond the base of 

 the mound flanks that were detected by bathymetry. The observed areal distribution of 

 dredged material was due to both the location of barge release points and the physical spread 

 of the sediment immediately following the bottom impact. Barge release points at most sites 

 ranged from 100 to 300 m from the specified disposal location. Variables controlling the 

 distribution of barge release points include the wide watch circle where conventionally 

 moored buoys are used, sites where buoys are not used for point control, and the influence 

 of weather and waves on operational control. 



The effect of dredged material disposal on the benthic environment was monitored 

 through REMOTS® surveys, sediment chemistry, and body burden analysis. Based on the 

 tiered approach to monitoring dredged material disposal sites (Germano, Rhoads, and Lunz 

 1994), all sites show the expected response in REMOTS® images for benthic recolonization 

 patterns (Tier 1). Sediment chemistry results at all sites showed decreasing concentrations of 

 contaminants going from fresh to relic dredged material and to ambient sediment. Any 

 contamination was low to moderate according to the guidelines of the New England River 

 Basins Commission (NERBC) and reflected the contamination levels expected of the dredged 

 material (Table 6-1). Studies of transects heading away from the dredged material showed 

 no far- field transport of the contaminated material. There were no trends reported in the 

 analysis of tissue concentration for any of the sites, suggesting that the organisms did not 

 take up significant levels of contaminants. 



Site-specific adjustments in management have been needed at NLDS since 1984. At 

 NLDS, a capping project required dredged material to be spread evenly over an existing 

 mound. Multiple points on the mound were chosen as target release points with the plan that 

 the randomness inherent in the disposal operation would result in an even distribution of the 

 sediment. The cap material formed discrete mounds with less spreading over the base 

 mound than expected. As a result of this finding, additional material was directed to this 

 location to augment the cap. 



DAMOS Summary Report, 1985-1990 



