Most dredgers have sophisticated discharging systems for efficient unloading at wharves.
Once landed at the wharf the raw material known as 'ballast as dredged', is processed in much the same way as land won sand and gravels by washing and screening, but with a higher emphasis on the salt content of the wash water which is carefully managed. Some producers however sell the product without processing as it is suitable for a variety of end uses in this form.
Greatest demand is for 0/4mm (sand) and for 4/10mm, 10/20mm and 20/40mm gravel. Any oversize gravel is usually crushed before being re-screened into the smaller grades.
Certificates for aggregate properties and compliance to current standards are available from the supplier. This includes chloride ion and shell content.
One of the great benefits of the industry is its ability to deliver large volumes of aggregates to wharves that are close to the point of use in the heart of urban areas, thereby greatly reducing the impact of further transport by heavy lorries. The large-scale use of trains further reduces the need for road transport, and barges are used to deliver to some riverside project such as was the case on a number of projects in Canary Wharf
Further information
British Marine Aggregate Producers Association:
