as well as isolated patches surrounding the center of the area. 

 Visual identification of dredged material from sediment grab 

 samples correlated well with the results of the side scan survey. 

 The distribution of intermediate acoustic reflectance (usually 

 signifying thin layers of dredged material) suggests that 

 disposal operations ranged out to more than 300 meters from the 

 buoy (which had a scope of up to 150 m) and did not create a 

 disposal mound detectable with bathymetric survey procedures. 

 The depth of the disposal location (70 m) also contributes to 

 wider distribution of disposed material by the entrainment of 

 water during descent and the subsequent reduction in the density 

 of the material. 



Results of chemical analysis of sediment samples 

 collected in September 1984 did not reveal any significant 

 elevations in chemical concentrations that could indicate the 

 presence of contaminated dredged material. In general, no trends 

 could be seen throughout the sampling area. Slightly higher 

 concentrations of oil and grease at some stations indicate the 

 potential for isolated patches of recently deposited dredged 

 material existing. 



The Rockland Disposal Area experiences its maximum (40 

 cm/s) tidal current velocities only at maximum flood tide 

 conditions in a N-NE direction. Because the flood tide is the 

 dominant feature in the current regime, it yields the greatest 

 potential for transport of suspended sediment introduced by 

 dredged material disposal operations. Although the data from the 

 bottom current meter was lost, bottom current velocities 

 sufficient to resuspend and transport large amounts of dredged 

 material out of the disposal site are not expected, based on data 

 collected by the meter at the 10 m depth. 



If disposal occurred only on maximum flood tide (a 

 worst case) , an estimate of the material transported out of the 

 disposal site would be approximately 6%. However, if disposal 

 occurred evenly at all stages of the tide, this estimate reduces 

 to 1%. Once this small percentage of material has settled 

 outside the disposal site, it would be so widely distributed as 

 to be undetectable. The fact that no significant accumulations 

 of sediment were detected in the N-NE direction from the disposal 

 buoy by either bathymetry or side scan sonar supports this 

 conclusion. Alternatively, if adverse levels of sediment 

 accumulation were detected outside the disposal site, disposal 

 operations could be scheduled to avoid peak flood tide. 



In summary, although the potential for the movement of 

 suspended sediment produced by disposal operations exists at the 

 Rockland Disposal Site, results of the plume tracking experiments 

 indicate that this potential is small. Analysis of current meter 

 data suggests that any transport would occur to the N-NE, 

 although no evidence of accumulation of dredged material in that 



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