River Dredging

What is Waterway Dredging?

Dredging is the removal of sediments and debris from the bottom of lakes, rivers, harbors, and other water bodies. It is a routine necessity in waterways around the world because sedimentation—the natural process of sand and silt washing downstream—gradually fills channels and harbors.

Water depth isn’t a constant thing — nor is it something we should take for granted. Because commercial vessels carry and transport the greatest portion of the world’s goods, waterways are all-important maritime highways that boats and ships count on to be safe and navigable. Unfortunately, nature doesn’t care about commerce, so the process of sedimentation — or the accumulation of silt, sand and other debris — continuously occurs as streams, rivers and currents deposit sediment downstream.

Left unchecked, sedimentation can pose a direct threat to maritime traffic in waterways, ports and harbors. That’s why the most prudent preventative action you can take to avoid issues is the employment of a waterway dredge. In fact, the removal of silt and other unwanted materials from waterways through dredging is such a popular and proven solution that the National Oceanic and Atmospheric Administration — or NOAA — actually calls it a “routine necessity.”

 

Benefits of Waterway Dredging:

  • Maintaining existing waterways:Dredging is an important step in waterway maintenance. By removing the accumulated debris, dredging can restore the waterway to its original depth and condition. Dredging also removes dead vegetation, pollutants and trash that have gathered in these areas.
  • Creating new waterways:Many ports are building new waterways with dredging to reach new trade centers and improve the efficiency of transporting goods. Dredging ensures cargo vessels of all sizes can dock and do not run aground.
  • Increasing waterway depth:As sediment builds up on the bottom of the waterway, it reduces the depth of the water. Dredging strips away the accumulated debris, which can restore the water body to its original depth and reduce the risk of flooding.
  • Cleaning ponds and lagoons:Ponds and lagoons contain stagnant water, they often can become mucky and have a foul odor. By using dredging, one can remove the accumulated sediment that has caused this making for a healthier body of water.

 

INDUSTRIAL FUNCTIONS

Many companies use water dredging equipment to help with industrial and construction projects. Because dredging can assist with many different business sectors, it has many different industrial functions, including:

  • Excavating:Sediment removal plays an important role in the preparation for construction projects such as bridges, docks and piers by performing the necessary underwater excavation work.
  • Reconfiguring for larger ships:By deepening and widening a waterway, dredging can make it passable for larger cargo vessels, which can have a positive economic impact. Dredging waterways can also help ensure boats can still pass through during low tide, creating longer windows for docking. 
  • Gathering construction materials:The sediment removal process is sometimes used to gather sand, gravel and other debris used to make concrete for construction projects.
  • Cleaning canals:Canals experience heavy traffic that can cause a build-up of sediment and other debris. Dredging canals can clear unwanted sediment to create better waterways for all kinds of boats. 
  • Mining for precious metals: In certain bodies of water, the sediment can contain traces of precious metals such as gold and diamonds. Dredging can aid in excavating this mineral-filled sediment.

 

ENVIRONMENTAL FUNCTIONS 

Dredging is a great way to improve and maintain aquatic ecosystems. You can apply dredging to many environments and can help aid ecosystems in several ways, including: 

  • Improving water quality:Dredging can remove contaminants that occur due to chemical spills, sewage accumulation, buildup of decayed plant life and storm water runoff.
  • Preserving wildlife and ecosystems:Dredging helps ecosystems by removing trash, sludge, dead vegetation and other debris. It keeps the water clean, preserves the local wildlife’s ecosystems and remediates eutrophication — the excess of nutrients in the water due to runoff. By solving eutrophication, you stop the excess growth of plant life, which can cause oxygen deprivation.
  • Replenishing shores:Storms, offshore mining, natural disasters, like hurricanes, and human-made disasters can cause a beachfront to erode over time, which can change its landscape and impact the local ecosystem. Dredging can help to restore the beachfront to its original condition and reverse the effects of soil erosion, keeping the local ecosystem, its native plant and aquatic wildlife intact.
  • Removing trash:Dredging can assist in keeping waterways clean by removing trash and debris from beneath the surface.

Water way DREDGEr TYPES

  • HYDRAULIC DREDGE: A hydraulic dredge works by sucking a mixture of dredged material and water from the channel bottom. The amount of water sucked up with the material is controlled to make the best mixture. Too little water and the dredge will bog down; too much and the dredge won’t be efficient in its work. There are two main types of hydraulic dredges – hopper dredges and cutter suction dredges.
  • HOPPER DREDGE: A hopper dredge is well-suited for dredging materials ranging from soft mud and silt to dense sands and clay. It can maintain operations in relatively rough seas and because of its mobility be used in high-traffic areas. It is often used at ocean entrance channels and is very productive in deep water and wide open spaces. A hopper dredge is nimble and can transit quickly to dredged material placement sites under its own power without the need for tug assist or towing.
  • CUTTER SUCTION DREDGE: A cutter suction dredge (CSD) sucks dredged material through the intake pipe at one end and then pushes it out the discharge pipeline directly into the placement site. Since a CSD pumps directly to the placement site, it operates continuously and can be very cost-efficient. Most CSDs have a cutterhead on the suction end. A cutterhead is a mechanical device that has rotating blades or teeth to break up or loosen the bottom material so that it can be sucked through the dredge. Some cutterheads are rugged enough to break up rock for removal. A CSD is mounted (fastened) to a barge, not usually self-powered, towed to the dredging site, and then secured in place by special anchor piling, called spuds (see sidebar).

A CSD is able to work in a range of water depths and has the ability to dig its own flotation if the existing ground is very shallow or above water. It’s very efficient in areas with thick shoals, where the cutterhead is buried in the bottom. Water pumped with the dredged material is generally contained in the placement site until the solids settle out.  Once settled, the water is generally returned to the waterway.

A CSD comprises the cutterhead, the spuds, the pipeline and the pontoons to float the pipeline.  The connection of the spuds and cutterhead to the waterway floor, along with the floating pipeline, may sometimes limit a CSD’s ability to maneuver during inclement weather conditions.

CSD operators can adjust their approach to projects depending on the season by using anchors to help “walk” the vessel forward and efficiently utilize the floating pipeline.

  • MECHANICAL DREDGE: A mechanical dredge removes material by scooping it from the sea floor and placing it into a barge or an approved placement area. Dipper, backhoe and clamshell dredges are types of dredges that are suitably named in accordance with their scooping buckets.

Mechanical dredges are rugged and can work in tightly confined areas. They are mounted on a large barge, towed to the dredging site, and secured in place by anchors or anchor pilings (otherwise known as spuds). Mechanical dredges are often used in harbors, near docks and piers, and in relatively protected channels.  Usually two or more disposal barges, called scows, are used in conjunction with a mechanical dredge. The operation generally consists of a series of barges. While one barge is filled with material, another barge transits to the placement site and then returns to repeat the cycle, allowing for near continuous and uninterrupted operations.  Mechanical dredges are particularly efficient on dredging projects where the placement site is several miles away.

Clamshell dredges are designed to handle loose to medium dense soils and dredge materials, while backhoe and dipper dredges are used to remove consolidated or hard-packed materials and can also be used to clear rock and debris. Hooded or enclosed buckets are utilized to control the flow of water and to prevent contaminated sediments from seeping back into the water column.

 

TAQA Services in Waterway Dredging:

  • TAQA enjoys a network of relations with globally renowned manufacturer of waterway dredging equipment & machinery manufacturers, in Europe, Turkey & the Far East.
  • TAQA can perform case studies to evaluate the dredging needs in a certain location, and produce proposals & regular dredging programs to follow, to guarantee long term functionality of rivers & canals.
  • TAQA is able to source the required machinery, that is suitable for the case in hand.
  • TAQA also offers training, in both operation & maintenance for the end-user’s staff.