THE DESIGN OF DREDGED SPOIL CONTAINMENT BASINS USING MASS SEDIMENT PROPERTIES

Laboratory studies of the settling and consolidation characteristics of a representative sample of Chesapeake Bay sediments were performed in order to refine existing methods for the design of spoil disposal basins. Settling and primary consolidation characteristics of these sediments were determined and correlated with the in situ sediment properties. This allows prediction of the rate and ultimate amount of settling and consolidation which is required in order to estimate the area and volume of the spoil basin.; Sediment cores more than one meter in length were taken for 20 different fine grained sediment types. Physical sediment properties represented by the particle size distribution, in situ water content, organic matter concentration and Atterberg limits were measured at three depths in each core. Correlation analysis shows that the Atterberg limits are closely related to the percent silt and clay, organic content and the in situ water content. Multiple regression techniques give equations relating the sediment properties to the Atterberg limits. These equations, which explain up to 85 percent of the variance in the limits, can be used to estimate the limits from the basic sediment properties. The limits are useful in prediction of sediment shear strength, compression index and dredged spoil behavior.; Experiments were conducted in the laboratory to determine the effect of sediment properties, initial slurry concentration, initial depth of slurry, temperature and carrying water salinity on the behavior of dredged spoil slurries. Sediment type and initial slurry concentration were found to be dominant in controlling the spoil behavior. Other factors had a limited influence on sedimentation and consolidation of the spoil. Relationships were developed using multiple regression techniques to predict the settling and consolidation behavior of dredged slurries based on the sediment properties. These predictive equations can be used to determine the area and volume of the containment basin required for spoil disposal.; Existing spoil basin design procedures were applied to the design of three basins present in the Chesapeake Bay area. The results were compared with those obtained by a new procedure using the predictive equations developed in this research. The new procedure provides estimates closer to the actual basin dimensions than the earlier methods in two cases and in the third case the estimates are approximately equal. This method represents a considerable improvement over bulking factor design methods currently in use in the Chesapeake Bay and does not require extensive laboratory testing of slurries as required for the methods developed by the U.S. Army Corps of Engineers Dredged Material Research Program.