SRS CrisafulliDredge Line Presentation

Flump – Remote Controlled, Unmanned Electric Dredges

• Electric poweredo Direct drive from motor to pump increases efficiencyo Electricity from the grid eliminates refueling and is usually the

cheapest source of power o Remote sites require a generator or installing electrical serviceo All power is transmitted to the dredge through a single cord

• Wireless remote controlo Handheld transmitter controls pump, speed, direction, and deptho Operator does not need to be floating out in a lagoono Limit switches and automatic sequences are available, limiting the

amount of supervision that is necessary

FLUMP Features and Capabilities

FLUMP Features and Capabilities

• Cable traverse onlyo Simple, straight, repeatable dredging passeso Lowest power requirements

• Traverse distances over 500ft (150m) are not recommendedo Requires more tension and stronger anchors to keep cable tighto If the cable droops below the water surface, the floating discharge line

may float over it and get tangled as the dredge approacheso Slack in the cable allows the dredge to drift side-to-side or twist

Rotomite SD-110 and 6000 Manned Diesel Dredges

• 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

ANCHOR POINT

Cable Traverse System – Drawing of a four-post layout

Cable Traverse SystemSetup Considerations

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 SystemOperation

• 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 SystemOperation

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

Traverse Anchoring Methods: Stakes

Traverse Anchoring Methods: Concrete Blocks or Equipment

Traverse Anchoring Methods: Bollard Posts

Cable Traverse SystemConsiderations

• Most effective and efficient system for rectangular lagoonso Effortlessly keeps the dredge going in a straight lineo Less power required to keep the cutterhead pushing forwardo Allows the dredge to travel back and forth in the same path, digging

deeper with every passo Less pronounced effects of wind/current pushing on the dredge

• Traverse distances over 500ft (150m) are not recommendedo Requires more tension and stronger anchors to keep cable tighto Sagging cable may get tangled with the discharge lineo 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.

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.

Floating Discharge LineRigid floating pipe with hose flex sections in between.

Solid foam floats are pressed onto the pipe and extremely durable.

Liner Protection SystemRemovable wheels and cage keep the cutterhead from digging down

through a solid lagoon bottom or snagging part of the liner.

Liner Protection System

Dredge Performance:What Gets the Job Done

All discharge photos pictured here are from Crisafulli dredges.

Dredge Performance:Pumping Water

Dredge Performance:Getting into the Sludge

Dredge Performance:About as thick as it can get.

4% -5% 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)

20% - 30% by weight ~15% by weight

Dredge Performance

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SRS Crisafulli Dredge Performance in Water

50HP Flump75HP FlumpRotomite SD110Rotomite 6000

Flow Rate (cubic meters per hour)

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Dredge Performance:Budgetary Estimates

• 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. o There are other effects such as viscosity that are hard to account for.o 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 volumeo 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

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SRS Crisafulli Dredge Performance in 1.3 SG Sludge (SI)

Rotomite 6000Rotomite SD11075HP Flump50HP Flump8in Discharge6in Discharge

Flow Rate (cubic meters per hour)

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s)Dredge performance curves are adjusted down for spe-cific gravity ONLY and do not apply to viscous or non-Newtonian fluids.

Rotomite 6000 has 8in discharge; others use 6in.

Discharge curves are for an aluminum pipeline 200m long with 5m of vertical rise.

Denotes Dredge Operating Point

Dewatering Methods

• Non-Mechanical: Geotextile Tubes, Drying Bedso More simple in nature, no moving partso Requires less energy, but more space

• Mechanical: Filter Press, Belt Press, Centrifugeo Smaller footprint, maybe less affected by raino Subject to breakdowns and maintenance

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.

Geotextile fabrics are designed to filter water out of mud and other sludges.

Pump the slurry into them and let water drain out.

Dewatering: Ecotube Geotextile Bags

Flocculants and coagulants are usually added to the mixture to make the solid particles settle faster.

Dewatering: Ecotube Geotextile Bags

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: Ecotube Geotextile Bags

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.

Dewatering Method:Requires Further Research

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!

What is the next step?

• How much funding is available for this project if it takes one year?o What if it takes two years? Five years?

• How much of the project must be done right away?o 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?o 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?

Determine the acceptable balance of cost and speed for this project.

• Geotextile tubes 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

For large projects like this, dewatering is always more costly than dredging.