Fishy goings-on prompt tunnellers to plumb new depths

20 August 2009

The Environment Agency is set to start dredging in the bed of the River Tyne for the second Tyne tunnel.

Previously, the Government had made it a condition that the dredging should take place during winter months to avoid the salmon migration season. But new methods of both dredging and disposal mean the operation can now be brought forward to the end of September.

The Tyne is one of the best salmon rivers in England, and studies have shown that each rod-caught salmon can generate as much as £4,600 for the local economy.

The improved system uses a suction-cutting dredger, which will suck sediment and water up and reduce the amount of silt that would be disturbed by the more usual bucket or ‘back-hoe’ dredger.

The silt will then be transferred 1.5km downstream via an enclosed pipe system, and used to fill the now-redundant Tyne Dock. Once the dock has been filled, it will be commercially developed by Port of Tyne Authority. This disposal will avoid an estimated 4,600 lorry journeys through built-up areas, and also means there will be no dumping at sea.

Once the tunnel sections have been placed in the dredged trench ‘clean’ material will be used to fill the trench. This will be inert sand taken from the navigation channel in the mouth of the Tyne, an area regularly dredged by the Port of Tyne Authority.

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