New plan kinder to environment

Jun 27 2009 by Tony Henderson, The Journal

TT2 claims the revised proposal for the dredging of the Tyne brings substantial benefits over the original plan.

The £260m tunnel is being built using the immersed tube technique which involves laying four prefabricated concrete units in a dredged trench across the river.

The concrete sections will be covered up by backfill to restore the river bed. The original plan was to use a bucket dredger to scoop up material on to a barge. It is now planned to use a suction dredger.

TT2 says the new plans would:

Cut the dredging period from five months to six weeks and reduce impacts on the river with greatly reduced sediment plumes by using an enclosed underwater pipeline.

Eliminate the need to dump material in landfill or at sea and save around 4,600 lorry movements of dredged material.

Support economic regeneration through reuse of the dredged material to enable Tyne Dock's redevelopment.

TT2 said it was obliged, under original licensing and approvals, to consider if there were alternatives to the disposal of the dredged material by dumping at sea or landfill.

Port of Tyne brought up the dock opportunity in October last year. There was not enough time to incorporate the new proposal into the original dredging window, and seek the necessary approvals for the revised approach, said TT2.

Due to the delay to the dredging, created by the decision to pursue the opportunity at Tyne Dock, there is no longer any flexibility within the programme.

“This means that if unforeseen circumstances arise that create an additional delay to the project, such as adverse weather conditions preventing progress, there is a risk that the December 2011 milestone will not be met,” said TT2.

“It is therefore extremely important that all possibilities of reintroducing some ‘float’ into the programme are pursued. It is in the best interests of all parties that the project is completed on schedule, and thereby also avoids any contractual penalties.”

Trevor Jackson, managing director of TT2, said the Tyne Dock proposal “allows us to make a positive contribution to the regeneration of the North East as well as enabling us to carry out this vital construction activity in such a way that minimises impacts to the environment, the public and river users.”

Approximately 10% of the material to be dredged is contaminated with material believed to have accumulated from coal tar at the former Jarrow gas works. This material is already in the river and at risk of being disturbed and released in an uncontrolled manner, says TT2.

Under the proposal, the contaminated silts will be removed during the first stage of dredging activity and placed at the bottom of Tyne Dock and capped.