VESSEL REVIEW | Maas & Mersey – Van Oord’s new water injection vessels for harbour and deep-sea dredging

Dutch marine contractor Van Oord has begun operations with its two newest hybrid water injection dredgers.

Maas and Mersey are both equipped with systems for water injection dredging, mass flowing, and power jetting, in addition to offering increased manoeuvrability and shallow draught. The vessels will be used primarily for maintenance dredging in shallow harbours and can dredge up to water depths of 24 metres. They are also certified as unrestricted seagoing vessels, making them capable of working on offshore projects as well.

Van Oord opted to have the vessels be capable of water injection dredging as a means of making operations more sustainable. The company believes removing sediment "the natural way" is an efficient and environmentally friendly means of maintaining the depth of a range of waterways including navigation channels, ports, and rivers. Also, because of its enhanced manoeuvrability, a water injection dredger can work much closer to embankments and quay walls compared to other types of dredgers, making the innovative vessels better equipped to take on projects in close quarters.

Maas and Mersey were built locally by the Kooiman Marine Group in compliance to IMO Tier III and EU Stage V emissions standards and in close cooperation with Van Oord.

The vessels each measure 43.07 by 12.4 metres with a depth of 3.4 metres. Each vessel is also fitted with a hybrid propulsion system with diesel-electric engines that have a total installed power of 2,044 kW and batteries that can store residual heat that is otherwise lost. This energy can subsequently be used for other purposes including propulsion.

Maarten Kooiman, project manager at Kooiman Marine, said the design of each dredger is hydrodynamically optimised and the hull resistance is subsequently minimised. This allows less power to be installed, which directly results in a reduction in fuel consumption during sailings as well as even fewer CO2 emissions. In addition, the noise level is extremely low, resulting in maximum comfort for the crew.

Two electrically driven pumps deliver water under high pressure, or with a significant volume, through the U-shaped water injection pipe located at the rear of each vessel. With this pipe, water is injected into the soil, releasing sediment that is then flushed away naturally by the current. Multiple injection methods are possible, providing the vessels with optimal usability.

Maas and Mersey also come equipped with dynamic positioning systems, with positioning being aided by electrically driven rudder propellers and bow thrusters. This capability enables the dredgers to operate effectively even under the more challenging conditions in deeper offshore waters.

See all the other news, reviews and features of this month's Marine Projects Week right here.