Selecting the Right Type of Dredge

What Size Dredge Will I Need?

As a prospective dredge owner, perhaps you are most curious about what size of dredge you will need to complete your project. The answer depends on several factors, such as environmental conditions and details of the project.  Having an idea of the project or type of projects you plan to complete will help determine the type of dredging equipment that best meets your requirements.

When evaluating a dredge and prior to purchase, contractors, homeowner associations, municipalities, and marina owners, should consider:

• The volume of material to be dredged
• The appropriate disposal method
• Dredging depth and pumping distance to the disposal area
• Contamination level of sediment and overall production
• Maintenance, storage costs, wages, benefits, insurance, dredge permits, and other ancillary equipment when not in use.

Regardless of the type of project, dredging is a challenging and complex undertaking.  A way to assist with reducing the number of uncertainties upfront is to work with a reputable dredge manufacturer who is interested in helping you to select the right type of dredge designed for your specific dredging application.

Dredge Types

Hopper dredges

Hopper dredges are self-propelled oceangoing vessels that are designed to gather sediment using drag arms that trail alongside the dredge on the bottom of the waterway.  Once the materials have been collected, they are stored inside the “belly” of the dredge, referred to as the hopper. The captured sediment is then transported as the dredge travels to the placement area or disposal site.    The two most popular methods of discharge for this type of dredge include:  1)  Dumping by opening the hopper doors located underneath the dredge; and 2) Pumping the sand onto shore using a side caster pump Hopper dredges are typically used for island-building, dredging deep seas, open water applications, and building large ports. Hopper dredges often have difficulty operating in shallow locations, excavate with less precision than other types of dredges, and are more costly to purchase and repair.

Auger dredges

Auger dredges utilize a horizontal Archimedes’ screw-shaped excavator and operate by using cables and pully positioning.  They are used for removing specialized solids and remediation. Auger dredges are sometimes ideal for unmanned operations in lagoons and wastewater ponds where human access is undesirable or dangerous. These vessels can also be used for a marina, lake restoration, or agricultural water projects.  All systems are designed for maximum versatility and transportability and can be customized for specific applications. Auger dredges are best utilized in water depths ranging between

4 ft. (1.2 m) and 30 ft (9 m). The wide auger dredge heads are less effective on surfaces that contain a rough or hard compacted waterbed. However, these dredges are very effective for use in lined ponds as they may be supplied with auger wheels to protect the bottom from being punctured.

The Bucketwheel dredge

Bucketwheel dredges operate like a cutter suction dredge on spud and anchor systems, typically with the use of a spud carriage. Bucketwheel dredges are ideal for aggregate mining and excavation of harder material. The bucketwheel dredge is efficient and precise, cuts equally well in either direction and offers simplified depth control. Bucketwheel dredges can have more expensive upfront purchase prices than most dredge types and is over-built for maintenance digging of fine grain elements.

The Cutter Suction dredge

The Cutter Suction dredge uses a basket cutterhead excavator to loosen material to be dredged and is defined by the diameter of the dredge’s discharge pipe. The dredge’s rotating cutterhead surrounds the suction intake line drawing-in free-flowing materials which can move a slurry of liquid and solids from the suction end through the pump along a discharge pipeline to a disposal site. or directly onto a shoreline where they are used for beach or land reclamation purposes. The dredge is held in position by two spuds at the stern of the dredge when the cutterhead is engaged in dredging. Cutters have two basic functions:

1. Loosen and break up materials from the bottom of a waterway into smaller fragments that are compatible with the dredge’s pumping system.
2. Intro the crumbled debris into the high-velocity stream at the suction intake in a prescribed capacity where the materials will be then pumped and transported via a dredge’s hydraulic pipeline system.

Smaller cutterheads can be dismantled into sections and easily transported. These vessels are traditionally used for sand and gravel mining, beach and shoreline reclamation, waterway maintenance, channel development deepening and widening, port maintenance, and environmental remediation projects.  Cutterhead dredges operate uninterrupted, offer precise control, are versatile, and are considered an industry workhorse. Cutterhead dredges do have limitations, including difficulty handling large fragments and working in deep-sea conditions.

Things to Consider Before Purchasing a Dredge

Those who are considering purchasing a dredge should understand:

• If you are dredging more than six months a year, it might make sense to buy a dredge, train personnel, and ensure you have the right operational plans in place before buying the dredge.
• It can be hard to retain qualified dredge operators throughout the year if you are not operating a dredge year-round.
• Review the trade-off between short-term costs versus long-term investment.

Ellicott Dredges, LLC is a world leader in cutter suction dredges. Our dredges are designed to protect the environment, improve and maintain safe waterways, and mine resources for economic development. More than 2,000 Ellicott® brand dredges have been delivered to over 100 countries. For more information about Ellicott’s line of portable cutterhead suction dredges, call +1-410-625-0808, or complete our online project questionnaire, and someone will contact you shortly.