Abstract: Containment of Particulate Waste in Marine Environment
H. J. Bokuniewicz, R. B. Gordon
Experiments in estuarine, lacustrine, and coastal localities show that dredged material released at the surface is deposited within a radius of less than 200 m from its impact point, a result insensitive to water depth or the volume of material discharged. The deposit self-compacts and expels interstitial water. During the self-compaction of a waste deposit 5 m thick, the advection velocity of waste-water interface is as large as 5 × 10-5 cm/sec during the first few weeks after deposition.
Waste on the bottom of an estuary can be dispersed by the tidal stream, estuarine circulation, waves, and disturbance of the hydraulic-flow field by storms. Allowance for perturbation of the flow field by the deposit of waste material must be made if the waste occupies a significant fraction of the water column. These factors are evaluated from long-term current-meter records at a site in central Long Island Sound used for the disposal of 106 cu m of dredged material. The site is in an area of natural accumulation of silt. The top of the pile of waste penetrates the wave-affected zone. Below this zone tidal resuspension of the surrounding natural-mud bottom and of the waste occurs every tidal cycle and is increased by a factor of three during severe storms. A layer of the w ste less than 1 cm thick is intermixed with sediment from the neighboring seafloor within a few weeks after deposition is completed; subsequent entrance of waste into the water column is due to bioturbation, which can reach to depths of 10 cm. Waste deeper than this remains immobile, out of direct communication with the seawater. These observations are used to design a disposal procedure which will result in maximum containment of the waste.
AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC