Book Description

In response to the concern over the potential impact of dredged Material dispersion, Task 6C of the Dredged material Research Program was established to develop the capability for predicting the nature, degree, and extent of dredged material dispersion in the vicinity of dredging and open-water pipeline disposal operations. In addition, methods for controlling this dispersion were evaluated. This report synthesizes the results of eight contract research studies and summarizes the available literature concerned with turbidity generation by different types of dredging operations. Water-column turbidity generated by dredging operations is usually restricted to the vicinity of the operation and decreases rapidly with increasing distance from the operation due to settling and horizontal dispersion of the suspended material. Turbidity levels around dredging operations can be reduced by improving existing cutterhead dredging equipment and operational techniques, using watertight buckets, and eliminating hopper dredge overflow or using a submerged overflow system. During open-water pipeline disposal of fine-grained dredged material slurry, 97 to 99 percent of the material descends rapidly to the bottom of the disposal area where it forms a low gradient fluid mud mound. The relative degree of dredged material dispersion at open-water pipeline disposal operations can be best controlled by using different discharge configurations. Water-column turbidity can be all but eliminated by using a submerged diffuser system at the end of the pipeline.