Open-water disposal : Ecological damage may occur when dredge spoil 

 is dumped directly overboard to spread through estuarine waters. Short- 

 term effects may include increased turbidity, sediment buildup, oxygen 

 depletion, and the release of nutrients and possibly toxic pollutants. 

 Long-term effects include changes in water circulation, accumulation of 

 deposits on estuarine bottoms that may prevent recolonization by benthic 

 species, and subsequent resuspension of polluting substances by boats, 

 wind, and currents. 



Altered by long uninterrupted spoil banks, large portions of estuarine 

 areas can become isolated or removed as productive units from the total 

 system [32]. Extensive damage to fish and wildlife resources can occur 

 when dredge spoil is deposited on vital habitats such as wetlands, tide- 

 lands, or shellfish beds. Before disposal sites are chosen, an inventory 

 should be taken of all vital habitat areas, and these areas should be 

 excluded from consideration as disposal sites. 



When the dredge spoil is coarse and clean--consisting of sand or 

 gravel--overboard disposal may be acceptable, provided that the spoils do 

 not contain toxic pollutants and are not deposited in ridges that 

 significantly impede water flow. 



Ocean disposal : A disposal alternative that may be used to protect 

 estuarine ecosystems involves transport of spoil to the ocean by hopper 

 dredge barge, or possibly pipeline. There are important differences in 

 opinion as to the environmental impact of deepwater ocean disposal of 

 various types of waste. In regard to dredged materials, it appears that 

 ocean disposal is acceptable for all but the most polluted spoil, if the 

 site is sufficiently far offshore to ensure against currents carrying the 

 spoil back onto the beaches or into the estuaries. Ocean disposal is 

 presently limited by the scarcity of hopper dredges as well as the high 

 cost of transport. 



Land disposal : Spoil disposal on land offers the possibility of 

 preventing many of the adverse environmental impacts that occur with open- 

 water disposal. Disposal areas are located inland, as far away from the 

 water's edge as possible and in places where their presence will not 

 interfere with vital habitat areas (e.g., in no instance should wetlands 

 be used). Upland disposal areas are usually limited to within one mile 

 of the water's edge. Upland disposal is not without concern. Items of 

 evaluation include (1) the quality of the water effluent separated from 

 the spoil, (2) the potential loss of wildlife habitat used as a disposal 

 site, and (3) possible alterations to the natural drainage pattern of 

 wetland or upland areas used for disposal and (4) pollution of ground- 

 water aquifers. Dredge spoil may be '<jery loose material and may require 



91 



