All about WATER INJECTION DREDGING

water injection dredger eco 150

Water Injection Dredging: what, when, how?

Water bodies including harbours, ports, canals and rivers carry sediments, which eventually settle on the waterbed and in time, result in siltation. Siltation reduces waterway access for ships, and can lead to flooding. Therefore, regular maintenance dredging is necessary to maintain appropriate water depths and safe navigation. While traditional dredging techniques are an effective solution for removal of accumulated sediments, it can be a costly process, especially for smaller ports and harbours. Water Injection Dredging (WID) is a dredging method, which is considered more environmentally friendly and cost efficient, but requires specific soil and environmental conditions.

Water Injection Dredging Diagram

Water Injection Dredging Principle

WID method involves water injection into the sediments. Therefore, a water injection dredger contains a series of nozzles located on a jetbar, which spray water. In contrast to traditional dredging methods, WID does not involve any suction, pumping or transport of the dredged materials.  More specifically, water injection dredging process can be divided into the following four steps:

  1. Injection: large amount of water is injected at low pressure into the sediments in the bottom of the waterway.
  2. Transition: the injected water loosens the sediments and creates a water and sediment mixture (fluidised soil layer). This layer results in lower density than the sediments, but higher density than that of the surrounding water.
  3. Transport: due to the difference in material densities, the fluidised soil layer is transported through the natural phenomenon of water currents, minimizing the disturbance to the natural ecosystem.
  4. Settlement: once the sediments reach deeper waters they settle down again. This process does not involve removal of materials from their natural ecosystem.

Benefits of Water Injection Dredging

Water Injection Dredger 150 3D model

3D model of our Water Injection Dredger 150

When applicable, water injection dredging features a range of economic and environmental advantages in comparison to more traditional dredging methods. Some of these are listed below:

  1. Water injection dredgers are small and compact sized. Some, including our Water Injection Dredger ECO 150, can even be transported in a single container. This makes the dredger easier to mobilise than larger dredging vessels.
  2. Due to its compact size, water injection dredger is especially manoeuvrable. Thus, it can operate in locations that are difficult to access, such as close to river or canal embankments or in smaller harbours.
  3. Water injection dredging does not require additional equipment such as pipelines or boosters. As a result, a water injection dredging project is less complicated, requires less organisation and can be started as soon as the dredger is delivered on site.
  4. Since additional support equipment is not needed, water injection dredging process becomes less costly and does not disturb shipping traffic when in operation.
  5. WID requires very little energy for water injection, in comparison to energy required for heavy material suction and transport. Therefore, fuel consumption of a water injection dredger is low, resulting in low operational costs.
  6. In the right conditions (e.g. water depths, currents, materials), water injection dredgers have high production rates. This leads to shorter project execution time frames and lower costs.

Environmental Impacts of Water Injection Dredging

Environmental Dredging Landscape

Aside from the above mentioned time and economy related advantages, water injection dredging is unique for its environmentally friendly characteristics. For example:

  1. This dredging method does not include sediment suction and removal. It uses natural phenomena including water current and gravity as a means of sediment transport. Accordingly, fluidized materials (1-3m thick) travel horizontally alongside the waterbed, while the surrounding water remains unaffected. In comparison, traditional dredging techniques involve vertical transfer of dredged materials throughout the whole water depth.
  2. Dredged sediments remain within the natural environment, avoiding the possible shortage of necessary materials in the ecosystem.
  3. Water injection dredging requires significantly less energy than traditional dredging methods, which involve suction and pumping of heavy materials. As a result, water injection dredgers have a much lower fuel consumption, and therefore, significantly lower CO2 emissions per m3 of dredged materials.

Is Water Injection Dredging an applicable dredging method for your project?

All application images

Water injection dredging is considered a cost-efficient, effective and environmentally friendly dredging solution. It is especially suitable for maintenance dredging and in locations that may be difficult to reach for larger vessels. Nevertheless, this method requires very specific conditions for safe and efficient dredging operations. Therefore, it is necessary to assess the environmental impact and conditions in and around the dredging location. Some of the points to consider include:

  • There must be a lower area at the end of the dredging site, where the dredged sediments can be transported to and settle.
  • For water injection dredging to be an efficient dredging method, river currents or tidal flow should be present. This will ease the natural transportation of the materials.
  • Sediments should not contain contaminated materials, as this can spread pollutants and cause harm to the environment.
  • There should not be any sensitive marine life such as shellfish beds, corals or the like in and around the dredging area.

Water Injection Dredgers

Water injection Dredger ECO 150 Arrangement

Water Injection Dredger ECO 150 Arrangement

There is a large variety of dredging equipment engineered for water injection dredging applications, ranging from small to larger vessels. However, water injection dredging method is usually most applicable for smaller maintenance dredging projects. An example of such applications can be reoccurring harbour or canal deepening. Dredge Yard specializes in manufacturing small to medium sized dredgers, which are ideal for maintenance projects. Last week we introduced our new addition to our dredger family – Water Injection Dredger ECO 150 – a compact, manoeuvrable, easy to operate dredger. See Water Injection Dredger specifications here.

Are you curious if water injection dredging can be the right method for your project? Do you need more information on the suitable equipment or price? Contact Dredge Yard here, we will be happy to advice & get back to you within 48 hours.

More Information on Water Injection Dredging

Water injection dredging is getting more attention again due to its environmental and economical benefits. Therefore, “Impacts & Benefits of Water Injection Dredging” is going to be one of the key topics at the 4th European Dredging Summit held in Rotterdam, Netherlands on 6-8th March 2019. European Dredging Summit focuses on sustainability, challenges and opportunities with the European dredging industry. See More information here.

Find more information on the history and principle of Water Injection Dredging on TU Delft article here.

For more details on Water Injection Dredging click here.