animals. Compatibility of the borrow material to the proposed beach is an 

 important engineering and biological consideration, especially if inshore 

 borrowing in areas of fine sediment is proposed. Rehandling of fill material 

 between borrow areas and the beach should be avoided, particularly in the 

 vicinity of live coral reefs or other sensitive resources. This practice tends 

 to increase sediment suspension which may be detrimental to marine resources. 



Consideration should be given to shallow dredging over large areas in low 

 wave energy environments rather than deep dredging in a few locations (Thompson, 

 1973; Pisapia, 1974; Taylor Biological Company, 1978). Although the biological 

 damage will be initially greater, recovery would be expected to be much quicker 

 in the shallow dredge area. 



Local directions in tidal flow and currents should be anticipated before 

 initiating dredging, and the operation adjusted to prevent sediments from 

 crossing live coral reefs or other sensitive resources. Dredging should be 

 done during current conditions which will carry the suspended sediment toward 

 deeper waters and away from coral reefs and other sensitive resources. There- 

 fore, monitoring the direction of currents during open water dredging or 

 disposal is recommended. 



XII. SPECIAL RECOMMENDATIONS 

 1. Coral Reefs . 



Damage to corals can be caused directly or indirectly. The direct effects 

 of dredging involves physical damage by the cutterhead of the dredge, the 

 anchor and cables dragging across a reef, or undermining of a reef by erosion 

 following dredging. Indirect damage is done by suspended materials and turbid- 

 ity which should be minimized as much as possible. The following special 

 recommendations apply to coral reefs: 



(a) Abundance and habits of fauna associated with corals should be 

 studied before project features are developed and sited. A number of 

 animals found closely associated with corals will be affected, 

 inadvertently. This type of information will help in minimizing 

 these impacts. 



(b) Dredging in the immediate vicinity of live coral reefs should 

 be avoided if possible. Courtenay, et al. (1980) observed damage to 

 corals within a 220-meter radius of a borrow area at Hallandale Beach, 

 Florida. Maragos (1979) studied the impacts of sand mining in Hawaii 

 and concluded a buffer zone of 100 meters was sufficient to prevent 

 damage to corals related to dredging. It appears, based on these 

 studies, that a buffer zone should be established around live reefs to 

 minimize the impacts of dredging. A zone of potential impact should 

 be established based on field measurements of sediment and turbidity 

 distribution around an operating dredge and the dredge positioned to 

 minimize the impact on coral reefs. 



(c) Where appropriate, dredging contracts should provide for peri- 

 odic shutdowns of the dredge if suspended sediment flows toward live 

 coral reefs or other sensitive resources and a new buffer zone 

 established. 



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