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technique. Capping of contaminated dredged material in pre- 

 existing deep, subaqueous borrow pits is a potentially viable but 

 untried management option. 



Depending upon the physical and chemical nature of the 

 contaminated material, control of material during placement of 

 caps may be needed. Other potentially significant factors, such 

 as the location of placement sites and engineering design and 

 monitoring costs have to be considered and may be significant. 



Construction of Confined Disposal Facilities . Confined 

 disposal facilities are engineered structures that may be located 

 entirely upland above the water table, partially in-water 

 adjacent to the shore, or completely surrounded by water. The 

 principal design criterion of confined disposal facilities has 

 been to retain as high a percentage of the fine-grained sediment 

 particles as practical. It has been demonstrated that most 

 chemical contaminants associated with sediments can be 

 effectively retained through efficient solids containment. 

 Current costs for confinement of moderately contaminated dredged 

 material ranges from $10 to $30 per cubic yard of site capacity. 

 Significant quantities of sediment have been disposed of in this 

 manner. 



Building Wetlands with Marginally Contaminated Dredged 

 Material . Wetlands have been and continue to be created with 

 relatively uncontaminated dredged material. Sediments unsuitable 

 for aquatic disposal because of toxicity and contaminant 

 bioavailability would have to be effectively capped within the 

 constructed wetland to minimize risk. However, wetlands may be 

 created with marginally contaminated dredged material such that 

 contaminants do not pose an unacceptable risk. This technique 

 has not been field evaluated with marginally contaminated dredged 

 material. However, extensive testing of two San Francisco 

 projects has been completed for aquatic, wetland and upland 

 environments. The data from investigations of these projects are 

 currently being evaluated to develop guidance on the suitability 

 of dredged material for wetland creation. Costs of creating 

 wetlands with marginally contaminated sediments may range widely. 

 Capping or containing contaminated sediment in a wetland would 

 also increase costs. 



In Situ Vitrification . In situ vitrification can be used to 

 treat contaminated soils and sludges where the process 

 electrically melts the waste media, creating an extremely stable 

 glass-like solid. In situ vitrification has been demonstrated on 

 a field scale for a number of contaminated soil sites. In situ 

 vitrification has not been demonstrated for high water content 

 contaminated sediments. A laboratory evaluation of vitrification 

 performed on dewatered New Bedford Harbor sediment demonstrated 

 99.94 percent reduction in PCB concentration. Application of in 

 situ vitrification to in-water treatment of contaminated 



