Corps of Engineers, Charleston, South Carolina). Agitation dredging that 

 entails bringing sediments into suspension by mechanical agitation, such as 

 through the use of a dredge, and the subsequent removal by strong currents 

 may occasionally be employed as a disposal alternative. Sidecasting is also 

 an alternative technique in a dynamic environment. Sanderson (1976) describes 

 the use of sidecasting in North Carolina inlets. The reader should remember, 

 however, that if contaminants are present, agitation and suspension of soil 

 particles will maximize the potential for release of contaminants to the water 

 column. 



Each project utilizing currents to remove sediments must be evaluated on 

 its own merits. If sand must be removed from channels it appears to be more 

 desirable, from an environmental standpoint, to leave the sand in the littoral 

 zone rather than release it in deep water. Deep water disposal will lead to a 

 deficit sand budget in the littoral zone, which in turn will affect littoral 

 zone organisms and cause beach erosion. The scant available literature on im- 

 pacts of agitation dredging leads to the conclusion that careful site selec- 

 tion for this technique will impose few environmental hazards if the material 

 is unpolluted. 



Nutrient release: There is often a significant release of nutrients and 

 biostimulants during disposal operations, particularly ammonia, but also less- 

 er amounts of forms of ortho-phosphates (Blom et al . 1976, Brannon et al . 

 1976, Schroeder et al . 1977). The greatest potential for detrimental condi- 

 tions and accompanying blooms of unwanted algae from dredged material disposal 

 appears to be in poorly-mixed estuarine waters where nitrogen is often limit- 

 ing. In nutrient deficient waters, the addition of nutrients could actually 

 be beneficial . 



Dissolved oxygen: Short-term dissolved oxygen depletion due to dredging 

 is seldom a problem (Slotta et al . 1974, Smith et al . 1976). At the discharge 

 site, reduced oxygen levels are usually found near the bottom at the point of 

 discharge, but are of short duration (Stern and Stickel 1978). However, long- 

 term anoxia can occur when highly organic sediments are discharged. Adverse 

 impacts are most likely to occur in poorly-mixed waters receiving highly or- 

 ganic dredged material, such as sediments taken from inner harbor areas. 



Impacts on animal concentrations and migrations: The adverse impact of 

 turbidity on concentrations and migrations of aquatic organisms is well docu- 

 mented (^Darnell et al . 1976), but the role played by dredging is not well 

 known. Potential impacts are very site specific. Dredging and disposal of 

 dredged material could conceivably cause disorientation due to the confusion 

 of organic smells and alteration of normal behavior due to physical disturb- 

 ances such as noise of the operations and discharge of the solids. Suspended 

 solids from dredging and disposal could also cause abrasion of gills which 

 could result in chronic bacterial infections, coating of the gills (causing 

 anoxia), and decreases in catchability of fish. Apparently, levels of turbid- 

 ity created by natural occurrences (e.g., storms and floods) and levels from 

 dredging do not normally cause direct mortality. However, laboratory tests 

 have shown that concentrations of particulate matter greater than those nor- 

 mally occurring during dredging or natural events cause direct mortality 

 (Hubert and Richards 1963, Brannon et al . 1976). 



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