Deep Ocean Disposal 



Deep ocean disposal is not commonly practiced (Hawaii and Puerto Rico are 

 exceptions) and is generally considered to be economically infeasible (Conner 

 et al . 1979). However, as nearshore environmental concerns increase and 

 available land becomes more scarce, deep ocean disposal may become a viable 

 disposal alternative. 



Because of the lack of historic deep ocean disposal, there is a dearth of 

 information on impacts. Most of the discussion in this section is taken from 

 An Assessment of the Potential Impacts of Dredged Material Disposal in the 

 Open Ocean (Pequegnat et al . 1978), which is primarily a theoretical discus- 

 sion of probable effects. Readers should review this comprehensive work 

 remembering its theoretical nature. The authors concluded that "deep ocean 

 disposal .. .is an environmentally sound alternative to presently unsatisfactory 

 disposal operations" (p. 151). They also stated that "although there are 

 multiple el^fects that dredged material can and will exert upon any region or 

 ecological system, it is concluded generally that these impacts will be less 

 severe in the deep ocean than elsewhere in the marine environment." This con- 

 clusion is supported by the following assertions: (a) there are large areas 

 of ocean bottom and great volumes of water to receive and dilute any except 

 the most hazardous wastes; (b) the deep ocean has a demonstrated assimilative 

 capacity to receive huge volumes of sediment without losing its capacity to 

 sustain normal life processes; (c) the capacity of the deep ocean to produce 

 food for man is very limited and insignificant compared to rich estuaries and 

 continental shelves; and (d) the lack of fishes on deep ocean bottom is at- 

 tributed, in part, to the lack of benthic invertebrates. "On a worldwide 

 basis, the average benthic biomass on the floor of the deep ocean is no more 

 than 0.01% that of the continental shelf" (Pequegnat et al . 1978: 44). 



The reader may refer to our sections about estuarine and continental 

 shelf disposal for general effects on the aquatic environment. However, the 

 applicability of this information to the deep ocean environment is unknown. 



Mater column impacts . We agree with Pequegnat et al . (1978) when they 

 state that there is less potential for dredged material harming the water col- 

 umn than the deep ocean bottom. Impacts to the water column should be similar, 

 in a very general way, to those impacts discussed in the sections on estuarine 

 and continental shelf disposal, except that the dilution factor is greater. 



There should be little concern for uncontaminated river sediments. River 

 sediments appear to stimulate ocean productivity, a prime example being the 

 rich fishery of the Gulf of Mexico down current from the mouth of the Missis- 

 sippi River. Concern should be concentrated on the disposal of contaminated 

 sediments. However, the present lack of experience in, and research about, 

 deep ocean dumping leaves its effects on the water column unknown. 



Bottom impacts . Pequegnat et al . (1978: 45) state that "the ultimate fate 

 of the dredged material disposed in the deep ocean is the bottom sediments. 

 Here, potentially toxic elements and compounds may be subjected to conditions 

 that greatly differ from those in the overlying water columns and thereby may 



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