How Harwich Haven Authority saves ￡3 million per year by utilising an integrated dredging toolkit

Dredging is a critical operation for maintaining navigable waters, yet it poses numerous challenges, particularly in high-siltation areas like Harwich Harbour. As the busiest container port in the UK – with over 2,000 container ships passing through the port per year – the Port of Felixstowe experiences sedimentation rates that require management of up to three million cubic metres annually, however, traditional dredging methods have become increasingly costly and environmentally taxing.

Harwich Haven Authority (HHA) recognised the pressing need for innovative solutions to help enhance operational efficiency, as well as driving change to mitigate the environmental impact of its operations.

Defining the dredging challenges

The primary dredging challenge is the significant sediment buildup in the Port of Felixstowe’s channels and berths. This consists of 85-90% silt and clay, which poses a risk to vessels trying to safely navigate the waters. This in turn impacts the dredging costs, which equates to 20-25% of HHA's annual revenue. Additionally, the carbon footprint associated with frequent trips to offshore disposal sites by Trailing Suction Hopper Dredgers (TSHDs) necessitated a re-evaluation of dredging practices, especially in light of HHA’s commitment of achieving “net-zero” by 2035.

A new approach

Following years of development, HHA launched Tiamat in April 2023, having already trialled and successfully integrated Tiamat into its dredging campaign calendar. The new approach is an integrated dredging toolkit, which sees Tiamat deployed throughout the year to relieve some of the workload previously managed by TSHD campaigns. Three times a year, the new programme includes increased surveying of navigable mud with Stema Systems’ Rheotune, supported by the use of a plough to finalise the campaign.

To deploy such an innovative strategy, HHA measured the success of the new integrated toolkit against factors including the impact on cost, operational efficiency and the local environment. Which on later inspection, shows that the Authority saves up to ￡3 million per year!

Trials took place throughout 2022 and were successfully completed in 2023, before officially launching the commercial entity of Haven Dredging with Tiamat in April 2023.

For HHA, the toolkit includes:

1.?????? Utilisation of TSHD: The dredging campaign begins with several days of dredging using a TSHD to manage large sediment volumes effectively. The TSHD handles the initial dredging of particularly heavy sand sediments.

2.?????? Transition to Tiamat: Following the conclusion of the TSHD operations, Tiamat is deployed. The innovative hydrodynamic technology in Tiamat is designed to remove the sediment from the seabed and naturally redispose it into the water column at the appropriate depth, minimising the need for offshore disposal – significantly reducing GHG emissions.

3.?????? Survey with Rheotune: RheoTune is deployed to provide an assessment of both density and yield stress profiles of the fluid mud. This enables swift and accurate data acquisition, to assess the performance of the dredging and understand the navigable properties of the mud in the port.

4.?????? Finishing with a plough: Assuming the combined dredging processes have performed to the expected standard, the process concludes with a few days of using a plough to redistribute any remaining sediment, allowing for easy access for further TSHD operations. Tiamat's activity can be carried out from the same workboat which hosts the plough, optimising logistics and reducing mobilisation costs.

The results

HHA has successfully integrated this new approach, which sees Tiamat deployed in conjunction with TSHD campaigns throughout the year, supported by Rheotune and plough operations. Pre-Tiamat, HHA was conducting six THSD campaigns per year, and today, the organisation has reduced this to three to four campaigns, supplemented by three to four Tiamat campaigns.

During trials, Tiamat achieved such great success, showing an average production rate of 9,800 tonnes of dry solids per day, while significantly reducing operational costs to around ￡1 per cubic meter, compared to ￡3-4 per cubic metre for a TSHD campaign.

Tiamat also reduces GHG emissions, with estimates suggesting a reduction to just one tonne per day when using eco-friendly fuels like Hydrotreated Vegetable Oil (HVO), offering an impressive potential for reducing emissions by up to 90% compared to traditional diesel fuels.

Harwich Haven Authority's commitment to trialling and implementing a new approach using an integrated dredging toolkit has offered significant steps forward in enhancing its operational efficiency, while prioritising sustainable practices. Tiamat’s new and established dredging methods has allowed HHA to not only address the immediate sediment management challenges, but also has the added benefit of reducing costs and emissions.?

A multifaceted approach like we have at HHA creates a strong case for other port authorities facing similar challenges. And, with ongoing commitment to monitoring and adjusting practices, we have improved dredging efficiency, reduced capital expenditure and made a positive impact on the local environment for years to come.

For more information on the success of the dredging toolkit at HHA visit the Haven Dredging website here: www.havendredging.com. ?