133 



yards :o . Somehow, although scow logs showed 1.2 million cubic yards having 

 been deposited at the site to serve as a cap, 400.000 cubic yards were not to be 

 found. The authors attributed this finding to a loss due to poor disposal 

 operations. 



ii. Capping does not necessarily prevent bioaccumulation 



A mussel bioaccumulation study was performed at the Mud Dump Site 21 to 

 determine if mussels exposed to disposed dredged materials accumulated any of 

 the known contaminants greater than those accumulated at "control" sites. The 

 study claimed that the accumulation of mercury and cadmium by mussels exposed 

 to uncapped dregded materials was greater than those exposed to capped dredged 

 materials. Differences in PCB accumulations were not statistically significant. 

 Unfortunately, the experiment's results are limited by the design of the 

 experiments. Mussels exposed to the capped site were exposed during the winter 

 months, a period in which mussels are inactive metabolically and feed at low 

 rates. In addition, the platform at the capped site was lost after only several 

 months. Mussels were deployed to other sites during the summer, when mussels 

 are more actively filter feeding. Also, water, sediment and mussel food data 

 were not collected to help correlate mussel bioaccumulation to dredged material 

 disposal. 



iii. PCBs were found to be have moved into the sand cap 



Cores were taken from the EMD to determine the effectiveness of the cap 

 in isolating contaminants from the dredged material". The cores revealed that 

 metals were an order of magnitude lower in the cap than below the cap and that 

 no vertical gradient of concentrations existed between the upper portion of the 

 cap and the interface region with the dredged materials. However, the same 

 could not be said for PCBs. In the case of PCBs, the vertical gradient from the 

 cap down through to the dredged material was gradual and the PCB 

 concentrations in the cap were only a factor of 2 lower than the dredged material 



:o Ibid at 13 



:i Stephen J. Koepp et al. March 1982. Bioaccumulation Monitoring in the 

 New York Bight Using the Blue Mussel . Final Report to Corps of Engineers, 

 New York District. New Jersey Marine Sciences Consortium. 



:: J.M. O'Connor and M. Moese. March 1984. Distribution of Contaminants 

 in Experimentally Capped Dredged Material Deposits . New York, New York. 



