but large-scale facilities for treating 

 contaminated dredged material do not 

 currently exist in the United States and are 

 expensive to maintain. 



Capping is a subaqueous containment 

 method which uses natural material (i.e., 

 noncontaminated dredged material) to 

 isolate the contaminants from the 

 environment. Although capping is a 

 containment method, the environmental 

 considerations are much different than they 

 are for land-based containment (i.e., 

 landfills). Material disposed on land is 

 subject to leaching from ground water; 

 therefore, liners are used to prevent 

 contaminants from leaching out of the 

 sediments and entering the ground water 

 (and eventually drinking water sources). 

 Marine sediments are already submerged; 

 primary movement of pore water is due to 

 active consolidation in the initial stages of 

 sediment deposition. 



To consider capping as a viable 

 disposal alternative, several questions must 

 be answered: 



• Can disposal operations form a 

 defined mound and ensure complete 

 cap coverage? 



• Is the cap effective at a) containing 

 contaminants with no evidence of 

 leakage and b) isolating 

 contaminants from the aquatic 

 ecosystem? 



• Will the capped mound remain 

 physically stable? 



1.2 Objectives 



This monograph is a critical review of 

 the use of caps of clean sediment to isolate 

 contaminated dredged material in mounds 

 on the seafloor. The operations and 

 associated monitoring programs reviewed 

 here were conducted as part of the 

 Disposal Area Monitoring System 

 (DAMOS) Program. DAMOS is a 

 regional program initiated by the New 

 England Division (NED) of the US Army 

 Corps of Engineers (US ACE). 



Since its inception in 1977, DAMOS 

 has generated a substantial amount of data 

 contained in a series of published 

 contributions, unpublished reports, and 

 data files. Because the logistical 

 approaches to capping and monitoring 

 methods evolved over this time, valuable 

 information is scattered throughout the 

 DAMOS record. This monograph presents 

 a synthesis and review of the available 

 information, with annotated data tables and 

 figures developed to provide access to 

 hitherto obscure or inaccessible data. By 

 compiling this information into one 

 document, we hope to facilitate application 

 of the knowledge gained from 14 years of 

 DAMOS capping experience (1979 to 

 1993) to future capping and monitoring 

 activities. 



1.3 Introduction to Capping 



Navigable waterways are an important 

 component of our coastal resources. Used 

 extensively by commercial shipping, 

 recreational vessels, and naval fleets, 

 coastal waterways and harbors provide an 



Sediment Capping of Subaqueous Dredged Material Disposal Mounds 



