The origin of the word “dredging” comes from the old English word “dragan“, which means to pull, to extract. Dredges typically involve a layer of soft material that forms when plants, debris, soil, or leaves settle to the bottom of navigable waters. Over time, these deposits can affect maritime traffic or the proper functioning of that waterway.
The reasons for carrying out the dredging process are multiple. However, most of the time, dredging is carried out for waterway maintenance purposes and to ensure the necessary flow of water by reducing/eliminating silting (silting means the filling or raising of the bed of a watercourse, the bottom of a lake or reservoir, by depositing the material transported by the flowing waters – plant remains, sediments, alluvium).
How Much Does Dredging Cost?
The cost of dredging is anywhere between $7 and $25 per cubic yard, depending on several factors such as the nature of the material that is dredged, the amount of the material that has to be dredged, and the place where the material can be placed once it is taken out.
However, as the degree of this job varies greatly, the term of dredging is very broad. So, the prices are not fixed, and it may be quite difficult to find a contractor that can give you a quote over the phone. For instance, you can just use a large bucket and do the job from the bank of the canal, if you only need to deepen a drainage canal. Expect to spend a few hundred dollars per hour on this type of work.
On the other hand, you should be prepared to spend much more if the work is more complex than just restoring the canal depth, like deepening a harbor or a shipping channel. Major works like these, for which you need heavy machinery will be priced with thousands of dollars per hour. It depends on the type of job and what tools are necessary to do it.
According to the Dredging101.com website, the dredging job is priced, in general, by the cubic yard of the material that will be dredged. In order to determine the cubic yards, take the acres that are going to be dredged and multiply 1,600 cubic yards per foot of material depth.
For instance, if the depth of the material that is going to be dredged is six feet and you have a ten-acre lake, then the formula will be 10 x 6 x 1,600 = 96,000 cubic yards. If we consider the estimates mentioned above, you should budget around $960,000 (at a price of $10 per cubic yard).
It is highly recommended to ask for quotes from local contractors in your area because every job is very different and unique. You can give them information about your job and they should offer you an estimate for free.
Factors that affect the cost of dredging
The permits you need will have to work on both federal and local levels. These can be obtained by the contractor or by you personally.
The square footage and depth
The cubic feet will be determined by the depth of the water and square footage, as we mentioned above. Most of the contractors will start calculating their quotes this way.
The lay of the land
This refers to the access at your job site. Is it located in the middle of an open area, or are there many houses built along the shore? Obviously, it will be harder to work with the equipment if access to the lake is more difficult.
Sediment that has to be disposed of and the place where it can be dewatered
When removing the sediment, this must be placed somewhere to allow it to be de-watered and then disposed of again later. In general, the contractors choose an open and flat area where they can create a pad for placing the de-watering bag.
Dredging procedure overview
Over the years, different dredging techniques have been developed. The preparation of the dredging activities involves the choice of the appropriate technique, depending on the matters at hand and other factors.
This constantly used piece of equipment, the hydraulic crane, is a type of batch excavator that uses the bucket in constant cycles during operation. The fully loaded cup is brought to the surface and the contents are emptied into the means of transport used (truck or barge) or on the water’s edge.
Cutter suction dredger
Dredging equipment used during continuous excavation processes and stabilized by supports or winch cables. The cutter is equipped with a suction opening, connected to a dredging pump. The cutter excavates the materials and mixes them with water. The obtained mixture is pumped to the processing plant through the discharge pipe. A large amount of water must be present in the mixture in order for it to be pumpable.
The boat for unclogging
A de-clogging boat or sludge collection boat is a floating bulldozer-like machine specially developed for cleaning ponds or small waterways. The machine is used especially in situations when work at the water’s edge is difficult.
This type of pump is used for the suction of dredged materials from the bottom of the water. The mouth of the dredging pump, which can be extended using a suction pipe, is guided towards the center of the dredging area to maximize contact with the dredged materials. The dredge pump can be mounted on a tractor, crane, or boat.
What are the additional expenses?
Before they even begin the work, most contractors will ask for a pond evaluation. This will be another cost to consider in case you haven’t had one yet. Expect to pay hundreds to thousands of dollars for a pond assessment, depending on the factors presented above.
Most states require local or even federal permits for dredging because this is a very complex process.
Important things to consider
Dredged materials are often transported immediately, either to a processing facility (for dewatering and further treatment) or to a landfill. In some cases, dredged materials are spread along the banks of waterways. In this case, the ecological impact must be taken into account.