ASSESSMENT OF IMPACTS OF DISPOSAL ALTERNATIVES 



Dredged rraterial is disposed: on terrestrial sites; on islands, fast- 

 lands, and beaches; on wetlands; in estuaries; on the continental shelf; and 

 in the deep ocean. The terms "deep ocean" and "continental shelf" are used 

 similar to that of Pequegnat et al. (1978). The continental shelf includes 

 the area seaward of land and estuaries out to the "shelf break." The shelf 

 break varies considerably around the coast of the U.S. but generally occurs at 

 depths of 60 to 200 m (200 to 650 ft). Deep ocean disposal includes the area 

 seaward from the shelf break and thus includes the continental slope and the 

 deep ocean basin or abyss. 



Terrestrial Disposal 



For this discussion, "terrestrial" refers to land masses above mean high 

 tide or nonwetlands. Also included are confined disposal areas situated in 

 shallow waters that become emergent as they are filled. 



During the 1970's, confined disposal in shallow waters became a popular 

 alternative to disposal in deeper waters and was extensively used for polluted 

 material. However, available land for disposal of dredged material is becom- 

 ing increasingly difficult to find, particularly in the northeast (Boyd et al. 

 1972). Wetlands, once considered suitable for disposal of dredged material, 

 are now considered more valuable for fish and wildlife. In addition, owners 

 of well drained useable land, or land already suited for developm.ent, gener- 

 ally are opposed to the placing of dredged material that nay present problems 

 from the enoineerina or aesthetic point of view and lower the economic value 

 of the land (Boyd et al. 1972). 



Most containment areas are surrounded by earthern dikes. Only large or 

 more permanent containment areas are protected by riprap or stone facing. 

 Nearly e^ery containment area is equipped with a spillway or overflow weir and 

 some also have settling basins (Figure 2). To accommodate varying filling 

 rates and varying ponding time requirements, most weirs are of the stoplog or 

 otherwise height-adjustable variety (Boyd et al. 1972). 



Diked containment areas have often been considered a panacea for the dis- 

 posal of contaminated dredge material. However, impacts to fish and wildlife 

 associated with these sites may be positive or negative. Habitats resulting 

 from disposal may or may not be more valuable or productive than the habitat 

 that existed before. Often confined disposal areas become industrial sites 

 and have no value to wildlife. 



Confinement area levees may provide valuable habitat to wildlife. The 

 raised land increases habitat diversity, provides habitat for birds, raccoons 

 ( Procyon lotor ), mink ( Mustela vison ), deer ( Odocoileus sp.), and other spe- 

 cies. During periods of high water and especially during hurricanes, levees 

 offer refuge for large numbers of animals (Glasgow and Enswinger 1957). The 

 interiors of disposal areas may provide wetland habitat. On the negative side, 

 local conditions may cause undesirable animal and plant species to proliferate 

 in confinement areas. If not well located, confinement areas can seriously 

 alter runoff patterns, thus adversely affecting the biological populations 

 (Schroeder et al. 1977). 



19 



