Water injection dredging is a relatively new hydrodynamic dredging technique that is reported to be low-impact, economically viable and environmentally sound.
This dredger, "Mass" is owned by Dutch company Van Oord, and was built in 2021.
It is operating in Harwich Harbour, around the main shipping channels which serve the Port of Felixstowe, the UK's biggest container port.
A water injection dredger carries a series of nozzles located on a jetbar, which is lowered close to the sea or river bed, which spray water. In contrast to traditional dredging methods, WID does not involve any suction, pumping or transport of the dredged materials. The process works like this:
Injection: large amount of water is injected at relatively low pressure into the sediments in the bottom of the waterway.
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.
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.
Settlement: once the sediments reach deeper waters they settle down again. This process does not involve removal of materials from their natural ecosystem.
Water injection dredging is especially suitable for maintenance dredging and in locations that may be difficult to reach for larger vessels, but the are some factors to be noted:
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.
This video was filmed at around 6am on Saturday 3 June 2023 by me, Chris Gosling, using a Panasonic HC-770 HD camcorder.