586 



toward developing biological systems or marine sludges capable of 

 degrading industrial and domestic wastes discharged into marine 

 waters. 



Dredging and spoU 



The pollution effects resulting from dredging operations are part 

 of the problem of control of undesirable bottom deposits. Conceivably, 

 dredging may be offered as the method of choice for removing objec- 

 tionable bottom deposits ; thus, the disposal of such dredgings is a mat- 

 ter of importance and additional research on its handling and disposi- 

 tion should be pursued. Much of the spoil from commercial and navi- 

 gational dredging operations is deposited in the low-lying marsh 

 areas. As the value of wetlands increases, other areas for spoil dis- 

 posal must be developed. 



One possibility is the use of spoil for reclaiming certain areas. If 

 this is possible, the structural properties of the spoil must be improved 

 so that it will stabilize when placed in these areas. Methods, proce- 

 dures, and additives which would help to stabilize these materials 

 should be investigated. 



Ojf shore and near-shore dumping 



Much material is dumped offshore. Offshore dumping is a method 

 of disposal for both solid and liquid materials in the open sea. It in- 

 cludes discharge to coastal waters, both within and outside the terri- 

 torial waters of the United States. In shallow areas, much of this 

 material is subject to complicated energy forces which varjr from day 

 to day. Wind forces appear to exert stronger influences in shallow 

 areas than are generally encountered in deeper waters, perhaps fur- 

 ther inshore. Because of this, much more information is needed on 

 wind, tide current, and other offshore or onshore hydraulic effects be- 

 fore the fate of dumped materials can be accurately predicted and a 

 program of disposal wisely managed. 



Sources and rates of sedimentation 



We need to develop new and improved ways of measuring sedi- 

 mentatation rates, including model studies to evaluate methods of cur- 

 tailing sediment deposition and more effective and beneficial means of 

 sediment removal and disposal. We need to know what levels of sedi- 

 mentation rates are tolerated by organisms, and what levels are dam- 

 aging to desirable organisms. Since organisms are affected differen- 

 tially by sedimentation processes, rates of change would have to be 

 studied specifically for key individual species. Another source of sedi- 

 mentation is the flocculation of colloidal suspensions of materials en- 

 tering sea water with resulting deposition at the salt water interface. 

 In order to avoid the problems of silting and deposition of sediments 

 within lagoons or in channels, we must know more about rates of fill- 

 ing, mechanisms of clay and silt deposition, and concentration of 

 organic debris and pollutants in sediments and in marsh vegetation. 



STRUCTURES AND PHYSICAL MODIFICATIONS 



It is well known that structures and physical modifications within 

 the estuary may change the hydraulic, biological, sedimentological, 

 and many of the other characteristics of the area. While it is desirable 



