Dredging And Dredged Material Disposal
Dredging and Dredged MaterialDisposal OverviewTimothy WelpU.S. Army Engineer Research andDevelopment CenterVicksburg, MS
The process of dredging consistsof the following stages:- Excavation (loosening or dislodging) ofthe material from the bottom.- Removal of the loosened material to thedredge vessel.- Transportation of the material to theplacement area.- Placement of the material.
Basic Dredge Types Mechanical– Clamshell– Backhoe Hydraulic– Pipeline– Hopper Other / Combinations
Factors in Selection ofDredging Equipment Physical characteristics of sediments,Quantities to be dredged,Dredging depth,Distance to disposal (placement) area,Physical environment of and between areas,Contamination level of sediments,Method of disposal (placement),Production required,Types of dredges available.
Two Types of Dredging Maintenance Dredging: Removal ofsediments accumulated in the channelsince the previous dredging project. New Work Dredging: Removal ofsediments which have not beenpreviously dredged - virgin sediments channel deepening.
Percentage by Class of WorkAveraged from FY96-FY05
Clamshell (Bucket) Dredge
Source: Great LakesDredge and Dock
Backhoe (Bucket)Mechanical DredgeCourtesy: GLDD
Mechanical Dredges can ExcavateSediment at In situ Percent SolidsSource: Cable Arm
Hydraulic Offloaders
Advantages of MechanicalDredges Rugged and capable of removinghard packed materials, Can remove debris, Can work tight areas, Efficient for disposal at long hauldistances.
Limitations of MechanicalDredges Difficult to retain fine loose material inconventional buckets, Production low compared to pipelinedredges, Resuspension can be an issue,especially in presence of debris.
Self-Propelled Hopper(Hydraulic) Dredge
DragheadDragarmAssembly
Outline
Split-Hull Hopper Dredge
Advantages of Hopper Dredges Only dredge type for rough open water, Can move quickly to job under its ownpower, Minimizes traffic interference, Improves navigation depth quickly, Economical for long haul distance.
Limitations of Hopper Dredges Cannot work in shallow depths,Cannot dredge continuously,Excavates with less precision,Difficulty dredging hard banksDifficulty dredging consolidated materials
Hydraulic Pipeline / CutterheadDredge
CutterheadSource: Great Lakes Dredge and Dock Co.
Source: Great Lakes Dredge and Dock
Floating Line
Shore Line
Submerged Line
Booster PumpSource: Great Lakes Dredge and Dock
Spider Barge
Advantages of Cutterhead PipelineDredges Capable of excavating most types ofmaterials, Can pump directly to disposal sites, Can dredge almost continuously, Can dredge some rock types withoutblasting.
Limitations of Cutterhead PipelineDredges Limited capability in rough open water, Most are not self-propelled, Difficulty with coarse sand in highcurrents, Pipeline can be an obstruction tonavigation, Debris in sediment can reduceefficiency.
Percentage of Work by Dredge TypeAveraged from FY96-FY05
Horizontal Auger DredgeSource: Ellicott Dredges LLC.
Water Injection Dredge
Dredged Material DisposalAlternatives Open Water Placement– Ocean Estuarine Lakes Rivers Confined Disposal– Confined Disposal Facilities (CDFs)– Contained Aquatic Disposal (CADs) Beneficial Use Applications
Planning Considerations Project Requirements– Volumes and Frequency of Dredging– Planning Horizon– Stage of Evaluation Material Characterization– Physical and Dredgability– Chemical / Biological Regulatory or Other Constraints
Open Water Placement Site CharacterizationSite Designation / SelectionMaterial SuitabilityDesign EvaluationsOperational ConsiderationsControl Measures / Management ActionsMonitoringSite Management Plan
Confined Disposal Facilities CDFs used because:– More economical for some projects– Most common option for material unsuitable foropen water Regulated under CWA– Discharge to US waters by definition– 404 permit– 401 state water quality certification
Confined Disposal Facilities Site characterization / selection Engineering design Operational considerations Contaminant pathways and controls Long-term management Monitoring
Contained Aquatic Disposal(CAD)
Beneficial Use (BU)Applications BU is alternative of first choiceNeeds and opportunitiesMaterial suitabilityLogistical constraintsRegulatory requirements vary– CWA / MPRSA– Other
Beneficial Uses Categories- Wetland Habitat / Shoreline Protection- Beach Nourishment.- Mine land Restoration.- Recreation.- Agriculture.- Island Habitat- Construction Fill.- Construction Materials.
Basic References EM Dredging and Dredged Material DisposalEM Beneficial Uses of Dredged MaterialEM Confined Disposal of Dredged MaterialTechnical Framework for Environmental EvaluationsOcean Testing ManualInland Testing ManualEvaluation of Dredged Material Proposed forDisposal at Island, Nearshore, or Upland ConfinedDisposal Facilities Identifying, Planning, and Financing Beneficial UseProjects Using Dredged MaterialAvailable from http://el.erdc.usace.army.mil/dots/guidance.html
The EndQuestions?
EM Dredging and Dredged Material Disposal EM Beneficial Uses of Dredged Material EM Confined Disposal of Dredged Material Technical Framework for Environmental Evaluations Ocean Testing Manual Inland Testing Manual Evaluation of Dredged Material Proposed for Disposal at Island, Nearshore, or Upland Confined Disposal Facilities .
DREDGING TECHNICAL MANUAL, “THE MANAGEMENT AND REGULATION OF DREDGING ACTIVITIES AND DREDGED MATERIAL DISPOSAL IN NEW JERSEY’S TIDAL WATERS,” OCTOBER 1997 The Department’s dredging technical manual titled, “The Management and Regulation of Dredging Activities and Dredged Material Disposal in New Jersey’s Tidal Waters” dated
Lake Ogleton Dredge 2 173 Marley Creek Dredging 182 Parker Creek Dredging 2 184 Rock Creek DMP Restoration 178 Rock Creek Dredging 166 Rockhold Crk County Dredging 159 Rockhold Crk Fed Channel Drdg 175 SAV Monitoring 163 Sloop,Eli&Long Coves Retrofits 180 Snug Harbor Dredging 167 Upper Magothy River Dredging 165 Upper West River Dredging 181
management of dredging and disposal of dredge spoil material in the Marine Park. Target audience Agency staff; applicants for permissions to undertake dredging and/or dredge spoil material disposal activities in the Marine Park. Purpose 1. The establishment of a formal dredging and dredge spoil material disposal policy is seen as an essential
area during O&M channel dredging, via a hopper dredge and associated piping/pumping of the dredged material to a potential project area. Depending on the type of material needed and the nature of the proposed project, dredging and piping/pumping from the main channel may serve as a potential source throughout the study area.
channel, berthing area, or marina. Dredged material is the accepted technical term for any and all sedi-ment, water, and debris removed during the process of dredging. Dredging is a necessary component of the sound economic management of our maritime infrastructure and can also be an environmental necessity
Dredged Material Placement Sites scow loaded with 3000 cubic yards of dredged material. . placement Tracking this recovery is a primary objective of the DAMOS Program (see reports #188, 191, 192, 193 for recent examples) water sediment. BUILDING STRONG .
the Columbia River FNC. The Corps anticipates using any of these types of dredging equipment to maintain the Baker Bay FNC and Chinook FNC. Mechanical Dredging . Clamshell Dredge . The Corps frequently uses clamshell dredges to maintain small navigation channels. Clamshell dredging is typically performed using a bucket operated from a crane or a
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