418 
oxic conditions free the metals where their environmental activity is in- 
creased. 
A possible solution to this problem which has more than one environmental 
advantage is to employ sea-going barges for transport. In many instances 
the hopper dredge is not only the dredger but the transporter of the ma- 
terial to the dumpsite. During this period of transport it is out of ac- 
tion, thus prolonging the dredging operation. A possible solution, which 
has been used successfully, would be to pump the hopper material directly 
into a sea-going barge without the overfill. The small decrease in sedi- 
ment carried per load would very likely be compensated for by virtue of 
keeping the dredger on the dredging job 24 hours a day. 
Moreover, these barges could be equipped to either shunt material below the 
zone of maximum phytoplankton production or to pump very polluted material 
into pits on artificial islands. 
CONCLUSIONS AND RECOMMENDATIONS 
CONCLUSIONS 
1) The need for dredging of ports and harbors both for enlargement and 
maintenance of existing channels is expected to increase in the 1980s 
and beyond. 
2) A certain percentage of this dredged material, particularly that deriv- 
ed from maintenance dredging, can be expected to be polluted with Annex 
I substances. 
3) This material must be disposed in such manner as to cause the receiving 
environment as little degradation as is reasonably possible. 
4) By the same token, it is becoming increasingly difficult to find and 
use disposal sites on the land that can be considered safe and within 
reasonable distances from ports and harbors. 
