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Title: Disposal alternatives for new work dredged material, deepening of Norfolk Harbor
Authors: San Diego State University. Department of Civil Engineering.
United States. Army. Corps of Engineers. Norfolk District.
Stark, Timothy D.
Briest, George R.
Keywords: Craney Island
Norfolk Harbor
Soil consolidation
Dredged material management
Geotechnical engineering
Slope stability
Strip drains
Issue Date: Aug-1993
Publisher: Geotechnical Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; GL-93-15.
Description: Miscellaneous Paper
Abstract: This publication describes the evaluation of various disposal alternatives for the estimated 12 million cu yd of maintenance and new work dredged material resulting from the proposed deepening of Norfolk Harbor from elevation -50 to -55 ft MLW. The U.S. Army Engineer District, Norfolk, Virginia estimated that 3 million cu yd of the dredged material will consist of sandy material which is suitable for dike construction. The remaining 9 million cu yd will probably consist of cohesive material and will require a disposal alternative. The disposal alternatives included (1.) expanding Craney Island using underwater dikes, (2.) stabilizing the existing perimeter dikes using berms constructed of suitable dike material, and (3.) raising the west perimeter dike from el +34 to el + 40 ft MLW and raising the north and east perimeter dikes from el +40 to +45 ft MLW. It was concluded that Craney Island could be expanded using underwater dikes located along the six alignments proposed by Goforth (1986). The underwater dikes could be constructed using the sandy dredged material and the 9 million cu yd of cohesive material would be contained by the underwater dikes. Extensive slope stability analyses of the perimeter dikes showed that a number of different combinations of water berms, road berms, and land berms are suitable for stabilizing the existing perimeter dikes. The berms would be constructed using the 3 million cu yd of sandy material while maintaining a safety factor of 1.3. In this alternative the 9 million cu yd of cohesive dredged material would be ocean dumped. Extensive stability analyses also showed that the west perimeter dike could be raised from el + 34 to el +40 using a road berm to el +26 ft and a water berm to el +6 ft MLW. As a result, the confmed dredged material on the west side of Craney Island could be raised to el + 36 ft MLW. It was also concluded that the north and east perimeter dikes could be raised from el +40 to el +45 ft MLW and the confined dredged material increased to el +41 ft MLW with satisfactory factors of safety. The dikes would be raised using the 3 million cu yd of sandy dredged material and the 9 million cu yd of cohesive dredged material would be deposited in Craney Island.
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