Everything you need to know about marine aggregates
The UK has the largest marine aggregates industry in the world and is one of the largest dredged aggregates operator in the market. We supply around 5 million tonnes of material to the UK, France and Belgium each year from reserves spready strategically around the coast. We have licence areas in the Humber, Anglian and Thames regions, South Coast, Eastern English Channel and the Bristol Channel/Severn Estuary.
Marine-dredged sand and gravel is becoming more and more important due to the increasing scarcity of land-won reserves, particularly around London and south east England. Our marine-dredged aggregates are primarily used in ready-mixed concrete, but also in the production of concrete blocks and as bagged aggregates. We supply direct to wharves with our own fleet and also support beach replacement to combat coastal erosion using specialist third party vessels that can pump materials ashore. In markets like London and the Bristol Channel our marine aggregates represent between 70 per cent and 90 per cent of the total sand and gravel supplied and used in the area.
Marine aggregate licensing and laws
Dredging the seabed brings with it a responsibility to protect the marine environment and operators must work within strict controls. Unlike resources on land, which are mainly in private ownership, all offshore minerals (up to the 12-mile territorial limit) are owned by The Crown Estate Commissioners and their exploitation is subject to strict controls.
All of the areas where we extract marine aggregates are held under both commercial and legal production agreements issued by the Crown Estate and environmental-based marine licences issued by either the Marine Management Organisation (English waters) or Natural Resources Wales (Welsh waters).
These licences are only issued by the Regulator after a rigorous environmental impact assessment to ensure that all the potential effects on the environment of offshore dredging (including impacts on the coastline, marine life, fisheries and archaeology) are fully considered and, where required, appropriate mitigation is in place. This is to ensure that best practice is always followed and that our activities do not have any adverse effects on the marine environment.
Heidelberg Materials works closely with Natural England and Natural Resources Wales to minimise the impact of dredging on species and habitats through the development of biodiversity action plans. These help to ensure that the seabed is left in a condition which will encourage the re-establishment of a diverse marine environment.
it is just as important to consider the historic marine environment as well and protocols are in place between industry and Historic England for reporting and investigating archaeological finds on the ships and at the wharves. Finds can include prehistoric remains such as mammoth bones, teeth and tusks from the ice ages, hand-axes and worked flints from early man’s existence in, what is now, the southern North Sea to Tudor cannon balls , shipwrecks and aircraft wreckage from WWII. .
Heidelberg Materials has a marine resources team which is responsible for the extensive permitting and licensing activities necessary to maintain access to these high-quality reserves. This includes ensuring that the navigational and licence information systems are up to date and communicated to the fleet and highlight those areas where dredging may and may not take place. Exclusion zones can be included based on seasonal requirements for fisheries, or on the discovery of a wreck or other features of archaeological importance.
Marine aggregate extraction
Marine sand and gravel resources vary in thickness and quality, as well as their proximity to markets. Unlike land-based quarry sites, production from marine resources does not always take place in the same deposit and is driven by customer demand.
All marine aggregate extraction is undertaken to a high degree of accuracy, with reference to high resolution shallow seismic profile data and seabed core samples. When loading a cargo, the dredger’s position and tracks are displayed on the bridge in real time, together with geological and licence boundaries, to ensure that the best quality resources are extracted – and from the correct location. The vessel’s activity is also constantly recorded by a Crown Estate electronic monitoring system linked to the navigation receiver and the dredge gear sensors. This records when and where the ship is dredging to ensure compliance with licence conditions.
Screening for quality takes place on board the dredgers to limit the amount discarded following dredging and ensure deposit recovery is optimised.
Marine aggregate dredgers (MAD)
Heidelberg Materials Aggregates Marine currently owns a purpose-built fleet of four MADs, including our new vessel, Hanson Thames, which will operate in the North Sea and English Channel.
The new MAD 3500 model, built by Damen Shipyards Group at its Galati yard in Romania, is capable of extracting marine-dredged aggregates in water up to 55 metres deep and has been designed to ensure safe, comfortable operations – even in adverse weather conditions.
Its innovative design provides increased payload and efficiency, which will allow it to carry up to 7,000 tonnes of marine aggregates per trip, as well as significantly reducing fuel consumption and improving operational and maintenance savings.