Although it can generally be concluded from the literature that dilution 

 occurring with open-water disposal will render most contaminants harmless over 

 the short term, bioaccumulation and biomagnification of some contaminants is 

 known to occur. The following account is not from a dredging operation, but 

 illustrates the point. In 1965, in the Netherlands, copper sulfate released 

 in coastal waters killed large numbers of fishes and mussels. Dilution levels 

 should have been safe, however, the chemical accumulated at high levels in 

 certain links of the food chain. Korringa, as quoted in Merlini (1971: 465) 

 commented that "...this case clearly demonstrates how erroneous it is to make 

 a decision to discharge a pollutant into the sea on the basis of calculations 

 of the eventual concentration of the pollutant following disposal and dilu- 

 tion." Another example is the accumulation of PCBs to levels of about 5 mg/g 

 in certain fishes of the Great Lakes even though monitoring of Great Lakes 

 water consistently indicated concentrations of 0.01 mg/1 or less (U.S. Envi- 

 ronmental Protection Agency 1976). 



The work by Plumb (1976) indicates that stimulatory or inhibitory materi- 

 als released from dredged sediments do not have a significant effect on algae 

 when the rate of dilution at deep ocean sites (such as on the continental 

 shelf) is considered. Dilution will prevent low levels of dissolved oxygen at 

 the point of discharge from becoming a problem. Likewise, continental shelf 

 disposal should pose no problems to concentrations or migrations of fishes. 

 The literature does not document any instances of short-term impacts of dredg- 

 ed material to the water column in well -mixed waters. 



Bottom impacts . The possibility of impacts to the bottom appears much 

 greater than for the water column. Potential bottom impacts include smother- 

 ing and burial of organisms, contaminant uptake, and physical changes in 

 topography which could alter nearbottom currents. 



Pratt (1979) discussed the monitoring of 10 dredged material disposal 

 areas in New England waters. He noted that the greatest deleterious effects 

 of dumping have been obstruction of trawling for shrimp and finfish and burial 

 of ocean quahogs. On the positive side, throughout the region disposal sites 

 became productive lobster grounds 1 to 3 yr after dumping ended. First (1969) 

 and Valenti and Peters (1977) noted significantly greater assemblages of de- 

 mersal fish and lobsters in the historic Eatons Neck, Long Island Sound, 

 disposal area than outside the disposal area. 



Although information is lacking, concerns over contaminant uptake are 

 probably similar to those expressed earlier in the estuarine disposal section. 



Disposal of dredged material on the continental shelf should have little 

 impact on water movements except possibly for unusually deep accumulations of 

 material such as in the New York Bight disposal areas. 



First (1969) recommended deepwater disposal because bottom effects of 

 waves and tidal currents decrease as depth increases, resulting in greater 

 sediment stability with increasing depth, Oertel (1976) studied a disposal 

 site off the Savannah River mouth. Six months after disposal the dredged 

 material still occupied the disposal site but there was some redistribution of 

 grain sizes forming sand ridges and some sediment movement due to storms. 



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