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QUESTION: 



What are some of the greatest challenges that exist in the development of 

 alternative disposal methods for contaminated sediments? What are some 

 of the costs associated with this program? 



ANSWER: 



No method can be used to contain or treat contaminated sediment without 

 some disturbance and consequent release of contaminants, and a number of 

 challenges exist in the development of each alternative disposal method. 

 Development of alternative disposal methods will require research and 

 testing to address these challenges and problems. The use of confined 

 disposal facilities designed to retain dredged material is limited by problems 

 in acquiring land and permits, expenses in transporting dredged material, the 

 potential for contaminant migration into groundwater and surface runoff of 

 contaminated water, and plant and animal uptake of contaminants. 

 Subaqueous capping methods can be used only at sites where such factors 

 as current, water depth, and bottom material will not affect the placement 

 accuracy of the sediment as well as the integrity of the mound. 

 Furthermore, the success of capping operations is dependent upon the 

 development and availability of dredging equipment that can deposit material 

 on the bottom without resuspension. In addition, monitoring programs must 

 be undertaken to ensure that the integrity of the cap has not been 

 compromised by water body and other effects. 



Treatment options such as biodegradation, dechlorination methods, soil 

 washing, solvent extraction, solidification/stabilization treatment, 

 incineration, and thermal desorption are effective only on certain kinds of 

 contaminants, and are costly to implement on a large scale. The 

 effectiveness of each treatment method is also limited by the availability of 

 technology. While some treatments actually decontaminate the sediment 

 through chemical transformation, other treatments merely reduce the volume 

 of contaminated material which must be disposed of safely. Disposal costs 

 for reduced volumes of contaminated material, while lower, can still be 

 significant. Biological treatment can decontaminate a range of organic 

 contaminants but does not eliminate metals. Many factors, such as lack of 

 nutrients and temperature, also impede the degradation process. The cost 

 of excavating and constructing lined treatment beds required for biological 

 treatment can be quite high. Typical costs for biological treatment range 

 from $50-$80 per cubic yard of contaminated material. Processes 

 associated with dechlorination include: achieving adequate screening to 

 remove oversize debris, particle size separation, dewatering, and pH 



