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SRS Crisafulli

SRS Crisafulli. Dredge Line Presentation. Flump – Remote Controlled, Unmanned Electric Dredges . Electric powered Direct drive from motor to pump increases efficiency Electricity from the grid eliminates refueling and is usually the cheapest source of power

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SRS Crisafulli

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  1. SRS Crisafulli • Dredge Line Presentation

  2. Flump – Remote Controlled, Unmanned Electric Dredges

  3. Electric powered • Direct drive from motor to pump increases efficiency • Electricity from the grid eliminates refueling and is usually the cheapest source of power • Remote sites require a generator or installing electrical service • All power is transmitted to the dredge through a single cord • Wireless remote control • Handheld transmitter controls pump, speed, direction, and depth • Operator does not need to be floating out in a lagoon • Limit switches and automatic sequences are available, limiting the amount of supervision that is necessary FLUMP Features and Capabilities

  4. Cable traverse only • Simple, straight, repeatable dredging passes • Lowest power requirements • Traverse distances over 500ft (150m) are not recommended • Requires more tension and stronger anchors to keep cable tight • If the cable droops below the water surface, the floating discharge line may float over it and get tangled as the dredge approaches • Slack in the cable allows the dredge to drift side-to-side or twist FLUMP Features and Capabilities

  5. Rotomite SD-110 and 6000 Manned Diesel Dredges

  6. Diesel powered • Self-contained power system • No power cord to string out with the discharge line • Self-propelled by hydraulic thruster • Discharge length not limited by traverse cable or power cord lengths • Optional cable traverse drive can supplement self-propulsion • Operator on board for better situational awareness • Optional air conditioned cab enhances operator comfort • Foam-filled aluminum (SD-110) or steel (6000) pontoons • Variable-speed pump powered by hydrostatic drive Rotomite SD-110 and 6000 Features and Capabilities

  7. ANCHOR POINT Cable Traverse System – Drawing of a four-post layout

  8. Figure out: • Which direction to dredge • How the discharge line should be routed • How the electrical power gets to the dredge • Where to put the anchors • How everything will adjust as the area is covered Cable Traverse System Setup Considerations

  9. Begin dredging • Adjust speed and depth for optimum solids flow • Ideally, those settings can be maintained and the dredge will not require further operator input until the end of the traverse is reached Cable Traverse System Operation

  10. At the end of a dredging pass: • Flush discharge line with water • Turn off pump and reverse dredge • After the dredge has returned to start: • Lower cutterhead to new depth and resume dredging forward along the traverse cable • After the desired depth has been reached: • Adjust the lateral cables so the dredge follows a new path next to the previous one Cable Traverse System Operation

  11. Traverse Anchoring Methods: Stakes

  12. Traverse Anchoring Methods: Concrete Blocks or Equipment

  13. Traverse Anchoring Methods: Bollard Posts

  14. Most effective and efficient system for rectangular lagoons • Effortlessly keeps the dredge going in a straight line • Less power required to keep the cutterhead pushing forward • Allows the dredge to travel back and forth in the same path, digging deeper with every pass • Less pronounced effects of wind/current pushing on the dredge • Traverse distances over 500ft (150m) are not recommended • Requires more tension and stronger anchors to keep cable tight • Sagging cable may get tangled with the discharge line • Slack in the cable allows the dredge to drift side-to-side or twist • It is MUCH easier to install and operate the dredge if the water is deep enough for it to float over the material. Cable Traverse System Considerations

  15. Notice the traverse cable and dredge being pushed out of line. This happens when the dredge cut is not symmetrical. The effect is more pronounced as the traverse distance increases.

  16. Floating Discharge Line Rigid floating pipe with hose flex sections in between. Solid foam floats are pressed onto the pipe and extremely durable.

  17. Liner Protection System Removable wheels and cage keep the cutterhead from digging down through a solid lagoon bottom or snagging part of the liner.

  18. Liner Protection System

  19. All discharge photos pictured here are from Crisafulli dredges. Dredge Performance: What Gets the Job Done

  20. Dredge Performance: Pumping Water

  21. Dredge Performance: Getting into the Sludge

  22. Dredge Performance: About as thick as it can get.

  23. 4% -5% by weight Dredge Performance

  24. ~15% by weight 20% - 30% by weight Dredge Performance The best way to compare dredges is to see how their pumps perform in a material with universally understood properties: water. (Next Slide)

  25. Centrifugal pumps are limited to fluids with a specific gravity less than 1.5. A dredge can usually be operated to maintain 1.3. • Dredging at 15% solids is usually very good. • Wastewater sludge is not just dirt mixed with water. • There are other effects such as viscosity that are hard to account for. • The same Flump that produced 20% solids has had trouble producing 6% solids in wastewater. • Settled sludge usually can’t be pumped at its original consistency • Thinning the sludge with water increases its volume • 1 cubic meter at a 1.5 specific gravity doubles in volume to 2 cubic meters of sludge after it is mixed with water to a specific gravity of 1.3 • Thinning the sludge with water increases its volume Dredge Performance: Budgetary Estimates

  26. There are many different methods for dewatering. Which is best depends on many factors and cannot be determined until all aspects of a system have been evaluated—which is a job for consulting engineers. • Non-Mechanical: Geotextile Tubes, Drying Beds • More simple in nature, no moving parts • Requires less energy, but more space • Mechanical: Filter Press, Belt Press, Centrifuge • Smaller footprint, maybe less affected by rain • Subject to breakdowns and maintenance Dewatering Methods

  27. Geotextile fabrics are designed to filter water out of mud and other sludges. Pump the slurry into them and let water drain out. Dewatering: EcotubeGeotextile Bags

  28. Flocculants and coagulants are usually added to the mixture to make the solid particles settle faster. Dewatering: EcotubeGeotextile Bags

  29. The water that seeps out of the bags can be collected and pumped back into the lagoon. That extra water will keep the dredge floating and mixing the material to a proper pumping consistency. Dewatering: EcotubeGeotextile Bags

  30. Geotextile bags are usually the best choice for dredging operations, as they are extremely easy to understand and use and are able to handle directly whatever flow the dredge can produce. This is the first (and currently only) method SRS Crisafulli evaluated for this project. Research into other possibilities is still underway. Preliminary Results: As reported to SRS Crisafulli, the total volume of all San Jose and Pampa de Perros primary, secondary, and tertiary lagoons equals well over 400,000 cubic meters of material. The bags alone to contain that volume will easily cost over $3 million. Hiring engineers to determine the best system would be a worthwhile investment! Dewatering Method: Requires Further Research

  31. Determine the acceptable balance of cost and speed for this project. • How much funding is available for this project if it takes one year? • What if it takes two years? Five years? • How much of the project must be done right away? • Will it be sufficient to dredge a portion of the lagoons immediately, then use a slower, smaller-scale method for the rest? • Will these lagoons need to be cleaned again in 15 years? • How will it be done then? • Will a continuous dredging process and permanent dewatering facility be set up to keep this situation from happening again? What is the next step?

  32. For large projects like this, dewatering is always more costly than dredging. • Geotextiletubes will cost the same whether the project takes one year or two because they hold a limited volume and cannot be reused. • Drying beds will increase in size and cost as the rate of dewatering increases. • Mechanical dewatering systems can be purchased in varying sizes and quantities to accommodate the desired dewatering rate. • Mechanical dewatering systems are not one-time use and can be permanent installations or portable facilities. • The optimum size and quantity of dredges can easily be matched to the dewatering system that is chosen. Deciding Factors

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