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Portsmouth
Factfile |
 Portsmouth |
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Dredging - Marine Aggregates |
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There are 2 types of dredging technique available and their use is dependent on the type of deposit located. Anchor dredging involves a ship anchoring over a deep deposit with its pipe drawing up the sand and gravel. Trailer dredging requires the ship to drag its pipe along the seabed sucking up material from more evenly distributed deposits. A large dredger can load 5,000 tonnes of sand and gravel in around 3 hours. |
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Once loaded, a large ship may deliver the equivalent of 250 lorry loads of aggregate to a processing plant or aggregate wharf. Some sand is sent directly sent to customers, without being processed, while the remaining materials are thoroughly washed and graded, with any over-sized gravel being crushed into the smaller grades. Quality is very important and the whole process is carefully monitored to ensure that the end product meets rigorous British Standards. |
Photograph courtesy of BMAPA |
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Not only are marine aggregates used in a variety of projects, they are also used to replenish our beaches, which help to protect our coastline from erosion. During the 1990s, over 20 million tonnes of marine aggregates were used on Britain's beaches to fight the effects of coastal erosion. |
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