Tiamat’s a cost effective solution for navigable mud, says Haven Dredging
Back in 2023, Harwich Haven Authority announced what it billed as a cleaner, greener, cheaper and more efficient method of dredging. Now that system has been commercialised by Haven Dredging. In essence, Tiamat (as it’s called, pictured in image above) is designed to be mounted onto a small workboat and carries pumps to enable diluted silt to be washed away with the tide.
“It’s a handy, cost effective solution for providing consistent navigation into ports and harbours,” says Jake Storey, executive director of Haven Dredging and CFO of Harwich Haven Authority.
Here, Storey details Tiamat’s benefits for controlling navigable mud.
“Safe and accessible passage across waterways is key to keeping vital trade and pleasure routes open and thriving. Whether from a commercial shipping perspective or that of a leisure craft owner, travel in and out of harbours, movement through ports and onto the high seas is important. There are a number of characteristics that can both support and hinder this, one of which is the lesser discussed, navigable mud.
“Navigable mud is a sediment layer found in waterways, primarily composed of fine particles such as silt and clay, organic matter and water. Its formation is the result of natural processes on and near waterways, and unlike other sediment types, navigable mud has the distinctive characteristic of being semi-fluid, which allows yachts and tankers alike to navigate through it, under specific conditions. For safe and consistent navigation into ports and harbours, it’s important to keep space available under a ship’s keel. Without this, there is an increased risk of grounding and costly damage to vessels, compromising safety and operational efficiency.
Strategies to manage navigable mud
“Innovative strategies are needed to ensure the management of navigable mud is controllable. The key lies in reducing the volume of mud that needs to be dredged, which can be achieved through more precise surveying and better alignment of mud management practices, aligned to environmental and operational goals.
“Advanced sonar systems, real-time monitoring tools and predictive modelling can all provide a more accurate understanding of mud dynamics. By improving the precision of surveys, maritime operators can identify areas where mud accumulation poses a significant risk to navigation, while also recognising zones where dredging may be unnecessary. Precise measurements of density and yield stress profiles of fluid mud can be surveyed simultaneously, providing nautical depth determination in real-time and high-resolution fluid mud data of the harbour.
“However, whilst dredging is a favourable option to ensure keel clearance and moving waterways, it is important to note that it is a habitat for various marine organisms that thrive in these nutrient-rich environments. Navigable mud therefore supports many marine ecosystems, which become particularly vulnerable to the disturbances caused by dredging.
Costs associated with traditional dredging
“From an operational perspective, the costs associated with dredging can be substantial. The financial burden includes not only the dredging operations themselves, but also the transportation and disposal of dredged material. Additionally, the frequency of dredging operations, driven by the accumulation of navigable mud amplifies these costs.
“As we see these developments in technology, greater demands for efficiency and more consistent operations, we’re also seeing vessels on the water getting bigger.
“The instinctive response might be to dredge more – after all, larger yachts and ships have deeper drafts, demanding more space to move without the worry of running aground. However, fluid mud does not necessarily create a barrier to navigation, so it’s important that ports find advanced management strategies that allow these vessels to pass safely, without the need for continuous dredging.
“Advancements in environmentally conscious tools such as Tiamat are therefore beneficial. By “Dredging with Nature”, the innovative hydrodynamic dredging machine redistributes sediment within the water column, allowing the natural tides to take the sediment away.
“As we continue to innovate, regulations are becoming more and more stringent, with the aim of protecting and future-proofing our sector.
“Defining and effective management of navigable mud is a critical step forward for our sector, and highlights the importance of industry collaboration and innovation in addressing complex maritime challenges. This in turn ensures harbours and ports can accommodate larger yachts and ships, protect ecosystems and reduce the carbon footprint, and offers an opportunity for innovation and sustainability in the industry.”
Understanding Tiamat and how it works
Designed to be mounted onto a small workboat or multi-cat of between 25-27m with an A frame, Tiamat is lowered into the water to the depth required. It consists of a frame carrying three pumps – two to inject water into the sediment overlying the bed of the harbour, and a third pump to extract the diluted silt, pump it up and release it into the water column at an appropriate depth to be washed away, naturally, with the tide.
‘Generally speaking the larger the port project, the more cost-efficient dredging becomes using traditional dredging techniques – trailing suction hopper dredgers and cutters for instance. But for the regular maintenance of smaller harbours, the technology of Water Injection Dredging can be an effective, economical and environmentally sound solution,’ says a paper from the International Association of Dredging Companies published in 2013. It says the first Water Injection Dredger (WID) became operational in 1987 in the Netherlands.
Similar to WIDs, Tiamat still injects water into the seabed, however where WIDs fluidise the sediment and create a density current, this sediment then moves due to gravity. Tiamat has a suction pump which extracts the diluted sediment up a pipe, which is then released into the mid water column and transported away by tidal currents.
Tiamat has been integrated into the Harwich Haven Authority’s own dredging programme, in parallel with ongoing research and development. Trials of the machine to date include independent environmental impact assessments conducted by leading experts in dredging practices, Royal Haskoning and HR Wallingford, and further independent reviews by the Environmental Agency and Natural England. Following each trial and subsequent discussion of the results and impressions of the vessel’s crew, improvements have been made to the machine and to working practice. This vast expanse of knowledge building has allowed for a complete redesign of the authority’s dredging strategy,
Plus, in the first study conducted into agitation dredging noise in harbours, Tiamat was confirmed to be below the safe levels for marine mammals and fish.
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