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What is Dredging?

by Scott Myers

Dredging is one of those things most people don't have to worry about. If you have your own boat dock, however, dredging might become a concern. So, what is dredging, what purpose does it serve, and how often do you need to get it done?

Related Blog: Tips to Maintain Boat Lift


What is Dredging?

Dredging is the act of removing sediment, silt, and other material from the bottom of a body of water. Rivers naturally bring sand and silt outwards into channels and harbors, and this sand and silt settles in the bottom, gradually making the water shallower. Docks on rivers may also collect some of this sediment as it is washed downstream. Ocean currents may also bring sand and silt to the shore, where it stays. This, in fact, is how beaches form and eventually this can turn into new land.

When you have a harbor, of course, you don't want your harbor to turn into a beach.

Another reason for dredging is because this sediment can carry with it pollutants and contaminants, which can then cause problems for fish and wildlife. In this case, the dredged material needs to be disposed of properly.

How is Dredging Done?

There are typically two kinds of dredging in common use. Which kind is used depends on the nature of the sediment, the surrounding area, etc. Mechanical dredging is done by using a track hoe or a dragline to pull sediment up from the bottom, and can be done either from the land or from a dredging barge.

Meanwhile, hydraulic dredging uses pumping equipment to pull the sediment into a pipeline, typically using a barge. The sediment ends up as a kind of slurry. In a few cases you might use hydro-dynamic dredging, which re-suspends the sediment and allows it to be taken downstream; this is only used when the body of water downstream is larger.

Which kind of dredging you use depends on the situation. Mechanical dredging is typically used for large projects and for very heavy sediment, such as rocks. It is also used when the area is more easily accessed from land than water and in very shallow areas where removing water (which a hydraulic dredge does). However, it cannot operate very close to piers or beneath floating docks. Because of this, for most small dock projects, hydraulic dredging is preferred.

Dredged material can be disposed of in a variety of ways. Uncontaminated dredged material might be dumped deeper out in the water using a scow barge, used to stabilize a shoreline or improve a beach, used in wetlands enhancement or habitat development, or even contribute to a land creation project.




How Do You Get Your Dock Dredged?

Typically, you hire a contractor to do dredging. If you live on a waterfront where you and your neighbors have docks, it can be wise to coordinate dredging so you can hire one contractor to do it all at once.

The contractor will inspect the site and determine what method of dredging to use. If the area may be contaminated, they may take samples so that the dredged material can be disposed of properly. The service will include disposing of the dredged material. In many places you will need a dredging permit, so make sure to talk about that with the contractor.  There is also typically a maximum dredge depth to protect wildlife.


How Often Should You Get Your Dock Dredged?

Exactly how often you need to get your dock dredged depends on the amount of sediment being deposited in the area. Dredging too often will disturb and potentially harm local wildlife, too infrequently and you risk damage to your boat.

It's fairly typical to need annual dredging, but you may be able to get away with it less often if there is less sediment. You should talk to your dredging contractor. Always hire a contractor with local knowledge so they know how often similar docks need to be dredged.

Dredging is important maintenance for your boat dock, so don't neglect it. Hire a good dredging contractor and work with them to make sure that your dock remains usable, especially at low tide.


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