Contaminated Marine Sediments Assessment and Remediation (1989) / Chapter Skim
Currently Skimming:
Developments in Equipment Designed for Handling of Contaminated Sediments
Developments in Equipment Designed for Handling of Contaminated Sediments
Pages 239-261
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From page 239... ...
, which are more suitable for handling contaminated sediments. Several special purpose dredges are described and their capabilities discussed.
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An evaluation of the watertight bucket was made by the U.S. Army Engineer Waterways Experiment Station in 1982 (Figure 11.
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SOURCE: Hayes, 1986. MECHANICAL HYDRAULIC DREDGES Mud Cat The Mud Cat has a horizontal Butterhead equipped with knives and spiral augers that cut the material and move it laterally toward the center of the augers where it is picked up by the suction (Figure 3~.
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From page 242... ...
The Clean-up head consists of a shielded auger that collects sediment as the dredge swings back and forth and guides it toward the suction of a submerged centrifugal pump (Figure 4~. To minimize sediment resuspension, the auger is shielded and a moveable wing covers the sediment as it is being collected by the auger.
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HYDRAULIC SUCTION DREDGES Refresher The Refresher dredge was developed purposely for removal of contaminated materials by a Penta-Ocean Construction Company, Ltd. (Shinsha, 1988~.
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PIPELINE ANT l-BACK F LOW ~ OUTLET VALVE / , ~ r 7? / DIRECTIONAL \ /_ ~ =\ \ ON eBoAARDG'NEG ~ ~` _ \ ON BOARD \ \ NON-POLLUTING SYSTEM MONITORING SOUND MONITOR FOR DREDGING THICKNESS `~ 11 I MONITOR MUD PUMP \ \ I RECORDER DIRECTIONAL ~ \ \ VALVE WINCH I IVI~^L \ TV E ~4 LADDER PUMP \ '< SUCTION PIPE / \ MUD-MEASURING FIGURE 7 Description of a Refresher dredge.
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From page 246... ...
A special suction head was developed by a dredging contractor in the Netherlands to replace the traditional Butterhead (d 'Angremond et al., 1984~. The main design points are as follows (Figure 8~: MINI REFRESHER TnKyo MARU .
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S . Army Engineer District, Chicago .
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Army Corps of Engineers' dredge Dubuque . The Calumet Harbor demonstration indicated that the clamshell dredge generated the largest suspended sediment plume affecting the entire water column.
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6 Name of Hull Ship Type Dimensions Main Pump Ladder Pump Including "Wide Diesel Length: 58.2m 3,200 PS, 950 PS, Single- Sludge Sweeper Electric Breadth: 14m Single-stage, stage. Single- observation No.
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Army Engineer Waterways Experiment Station (Richardson et al., 19829. The operation principle of the pump body is illustrated in Figure 12.
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The conditions around the dredging system, such as thickness, bottom elevation after dredging, and amount of resuspension, are monitored by high-frequency acoustic sensors and an underwater television camera. A large Dozer pump has a dredging capacity ranging from 300 to 500 m /fur.
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RESUSPENSION LEVELS OF SEDIMENT FOR SPECIAL PURPOSE DREDGES The special purpose dredges that appear to have the most potential in limiting resuspension are shown in Table 8. SUGARY Conventional dredging equipment may be operated in a modified procedure to handle contaminated material.
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Driving generator: 190 KW x AC 440 V x 60 Hz x 4P Vacuum pump a~ em 1 Type: Roots system 3 Capacity: -400 mmHg x 44.8 m /min Driving generator: 110 KW x AC 440 V x 60 Hz x 6P Main generator Type: Horizontal drip -proof rest self - excite Capacity: 450 KVA x 3 0 x 60 Hz x 445 V x 8P Continuous output: 5 30 ps x 900 r .
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From page 254... ...
August December 1975 Sandy silt 150 - 200 PCB 224,816 Direct discharge length 300-1,20G m Solidity Removal of deleterious material Direct discharge length 460 m Natural sedimentation Removal of deleterious _ material Direct discharge length 300-800 m Natural sedimentation Removal of deleterious mater) at Sakaide Port July- Silt 90 - 100 He Kagawa Prep.
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From page 255... ...
TABLE 9 Summary Table of Mechanical Dredges Depth Resuspens ion Type Production limitation of sediment Comments Open clam shell bucket Low Watertight Low clamshell bucket 30-40 ft High 30-40 ft Low Experiments conducted in the St. John' s Rearer
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From page 256... ...
256 TABLE 10 Summary Table of Mechanical-Hydraulic Dredges Depth Resuspension Type Production limitation of sediment Comments Mud Cat Moderate 15 ft Low to Extensively moderate used Remotely Low 15 ft Low to New develop controlled moderate ment Mud Cat Clean-up Moderate 70 ft Low to Extensively system moderate used in Japan TABLE 11 Summary Table of Hydraulic Suction Dredges Depth Resuspension Type Production limitation of sediment Comments Refresher Moderate 60-115 ft Low Extensively to high used in Japan Waterless Moderate Low Limited experience Moderate 85 ft Low Experiments to high conducted at Calumet Harbor Wide Moderate 100 ft Low Used in Japan Sweeper TABLE 12 Summary Table of Pneumatic Pumps (Dredges) Depth Resuspension Type Production limitation of sediment Comments Pneumatic Low to +100 ft Low moderate Evaluated by COE Waterways Experi ment Station Dozer Moderate 59 ft Low Used extensively to high in Japan
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Vicksburg, Miss.: U.S. Army Engineer Waterways Experiment Station.
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From page 258... ...
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