51 



so that there is evidence of 

 contaminants migrating through the 

 cap, this leads to Box 3.22 and an 

 immediate replacement of the cap 

 with more suitable material. If there 

 is no evidence of contaminants 

 migrating through the cap, the only 

 reasonable concusion is that the 

 negative impacts seen to this point are 

 from regional phenomena or an errant 

 disposal event, and not due to failure 

 of the cap to isolate underlying 

 contaminants. This would lead to Box 

 3.15 and back up to Tier 1, where the 

 situation would be reassessed the 

 following year. 



Sources of Uncertainty: The main 

 source of uncertainty is that one has 

 arrived at Box 3.21 by never having 

 done a laboratory sediment bioassay 

 test. By relying on just 

 bioaccumulation or bulk chemical 

 analyses alone, we assume we can 

 identify the contaminant of concern; 

 given the limitations discussed under 

 Boxes 1.4 and 1.7 in Section 2, we are 

 relying on infaunal recolonization 

 patterns to be the field analog of a 

 laboratory bioassay. 



As stated earlier, the decision to cap 

 necessarily commits one to a long-term 

 monitoring program. If one never 

 progresses beyond Tier 1, then 

 monitoring should occur on an annual 

 basis for at least 4 or 5 years, on a bi- 

 annual basis until 10 years post- 

 capping, and then every 5 years on an 

 indefinite basis. 



An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites 



