avoiding creation of precipitous sides of deep pits would result in a better habitat. The 

 amount of sand that should be left to prevent damage would depend on requirements of 

 the species in the area and would vary. Spreading dredging activities to avoid opening new 

 or different interfaces and creating deep holes is practical with hopper-dredge operations. 



The maximum size of the offshore dredging operation could be based on a 

 proportionate removal of a deposit. Information is available from CERC of the sand survey 

 of the Inner Continental Shelf to estimate amounts to be removed. Unfortunately, the 

 quantitative effects of dredging on the fauna, quantitative substrate requirements of the 

 fauna, or the adaptability of the fauna (long- or short-term) to dredging and substrate 

 removal activities are unknown. Studies of minor or restricted dredging would provide an 

 initial basis for predicting the effects of larger scale operations. 



The amount of dredging and substrate removal required for beach-nourishment projects 

 probably would not be harmful in most situations. Situations could be readily identified as 

 potentially harmful before operations began. Commercial removals, on the other hand, 

 might involve: (a) larger areas, (b) larger volumes, and (c) long-term use of sites. 

 Commercial removal, if by leases or permits, should be controlled by detailed dredging 

 specifications that should be strictly monitored and enforced. However knowledge on 

 which to predict effects of extensive and continued offshore dredging is lacking. If 

 commercial sand dredging operations are concerned with removal or extraction of minerals 

 from the sands, then tailings and potential pollutants would also have to be considered. 

 This, however, is a separate problem. 



The two factors for which information is lacking and on which reasonable predictions 

 of effects of extensive dredging activities must be based are: (1) fill-in rates or physical 

 recovery rates in borrow pits, and (2) abilities of biotic components to withstand or 

 recover from dredging activities. Solutions of these problems do not require complicated 

 techniques, or complex instrumentation. Both are uncomplicated observation-type studies. 

 However, dredging operations of various intensities in varying areas must be studied. 

 Knowledge would result from monitoring studies made during and after dredging. 



b. Turbidity and Sediment Effects. Sherk and Cronin (1970), have summarized the 

 knowledge of turbidity and sediment effects in their bibliography, "The Effects of 

 Suspended and Deposited Sediments on Estuarine Organisms." This work reveals little 

 concrete, long-range detrimental effect due to either turbidity or sediment. The authors 

 were concerned with estuarine areas, but the effects should be even less important in 

 offshore areas, though perhaps less predictable. 



Offshore dredging areas should lie beyond the oyster beds, of prime concern in silting 

 and smothering studies, and far beyond coves and quiet bays where settling effects would 

 be expected to be most pronounced and dangerous. Offshore sands and gravels, coarser 

 than the average channel dredge material in inshore areas, would not cause such siltation 

 effects as are caused by finer sediments. Scouring effects, however, may be serious where 

 strong currents sweep coarse material across reefs. (Levin, 1970). The general conclusion, 



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