essential link from land to sea. The 

 northeastern United States is particularly 

 blessed with abundant natural harbors and 

 sheltered waterways. However, few of 

 these harbors or channels are naturally 

 deep, and they require frequent 

 maintenance dredging to permit use by 

 modern vessels. Unfortunately, these 

 same harbors are the storage areas for the 

 effluent of modern, industrialized cities. 



Most effluent contaminants tend to be 

 absorbed onto sediments; therefore, the 

 concentration of these contaminants tends 

 to be higher in sediments than in water. 

 During dredging, these sediments are 

 disturbed, creating a plume of suspended 

 sediments around the dredging operation. 

 It is unknown if or how much contaminant 

 material is released to the water column 

 through desorption from the particulate 

 matter and release of the interstitial water. 

 Different dredging methods appear to be 

 more appropriate for different contaminant 

 classes (Cullinane et al. 1989). 



Techniques for the safe disposal of 

 these dredged sediments are the focus of 

 this monograph. Management of dredged 

 material disposal in the United States has 

 adapted to the passage of major 

 environmental legislation, including the 

 Federal Water Pollution Control Act 

 Amendments of 1972, also known as the 

 Clean Water Act, and the Marine 

 Protection, Research and Sanctuaries Act 

 of 1972, also known as the Ocean 

 Dumping Act. These laws, in combination 

 with international regulations sanctioned at 

 the London Dumping Convention (IMCO 

 1975), established the regulatory authority 



for designation of disposal sites and 

 specified responsibilities for the oversight 

 and control of both dredging and disposal 

 operations (Park and O'Connor 1981). 

 This legislation has led to increased 

 regulations and tighter guidelines for ocean 

 disposal of dredged material. At the same 

 time, the Resource Conservation and 

 Recovery Act of 1976 imposed strict 

 regulations for land-based disposal of 

 hazardous solid waste. 



In New England, implementation of 

 these regulations significantly reduced the 

 number of coastal and land-based sites 

 deemed suitable for disposal of 

 contaminated dredged material. Sediments 

 showing unacceptable mortality to biota or 

 ecologically significant potential for 

 bioaccumulation must receive additional 

 treatment to satisfy the London Dumping 

 Convention. Ocean disposal of these 

 sediments is permitted only if the material 

 is "rapidly rendered harmless" by physical, 

 chemical, or biological processes in the 

 sea (EPA/USACE 1977, 1991). 



The increased need for disposal of 

 material dredged from numerous 

 industrialized harbors in New England led 

 to experiments in capping contaminated 

 material deposited on a level seafloor with 

 cleaner dredged material. The assumption 

 behind these experiments was that a 

 sufficiently thick layer of sediment would 

 isolate sediment-bound contaminants and 

 render them harmless. If contaminated 

 harbor and channel sediments could be 

 isolated in this way, the dredging 

 operations would achieve two important 

 goals: first, maintaining navigable waters 



Sediment Capping of Subaqueous Dredged Material Disposal Mounds 



