7/5/2023 0 Comments Clamshell dredgeSpecific Objectives of StudiesĪnnual monitoring: (1) to determine the placement location, thickness, and spatial extent of the deposited dredged sediment and evaluate changes in these characteristics through time (2) to sample the deposited dredged sediments and determine their physical and bulk properties (3) to conduct a volumetric evaluation of the deposits through time and (4) to evaluate the consolidation and erosion of the deposited sediments after placement (5) to recommend the most appropriate placement method and volume to management agencies to minimize the potential for adverse environmental impacts. The clamshell bucket dredge method was used in the northern Chesapeake Bay prior to 1997 and up until 2010. This method usually produced positive relief features in the placement area. The clamshell dredge scooped sediments relatively intact into waiting scows which were then towed to the designated area and released the sediment onto the bottom. This method of dredging and placement was last used in the northern Chesapeake Bay in 1997. The majority of the sediment settled to the bottom where it spread outward under the force of gravity and tended to fill the basin. Hydraulic dredging created a slurry of sediment and water which was pumped through a pipeline to a basin-like depression in proximity to the channel. Each produced a distinctly different deposit. Two different methods were generally used to dredge and transport sediments from channels to open-water sites: (1) hydraulic cutterhead suction dredge with transfer of the sediments via a connecting pipeline and (2) clamshell bucket dredge with transfer of the sediments via towed bottom-release scows. Prior to that time the Maryland Geological Survey conducted studies on the sediments placed in the open water sites. State law banned this method in 2010, and open water placement is no longer utilized. Prior to 2010 one option for disposing of the dredged sediments from channels outside of the Port was to place the material in open-water sites in the Chesapeake Bay. This process is termed maintenance dredging because it maintains the channels at the depth authorized. Coastal and Environmental Geology Programĭredge Material Placement and Behavior ConsolidationĬontact: Stephen Van Ryswick ( and routine dredging of the shipping channels is required to enable vessels to access the Port of Baltimore.
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