Five ballast tanks will now be constructed inside each of the four tunnel sections before the bulkheads seal the sections ready for floatation and submersion in early 2010.
There were a number of challenges in this part of the project; as well as working to a tight deadline, at only 34m wide the dry dock provided very little working space around the sections. Engineering challenges included the amount of reinforcement bar required and the accuracy with which it had to be placed to ensure that the tunnel was built in the correct profile to match the riverbed and riverbanks. The consistent quality, availability and delivery of such large amounts of concrete was also a major factor in the success of the project.
The £18m contract was awarded to VolkerStevin marine by Bouygues Travaux Publics and is only the third vehicle tunnel in the UK to be built using the immersed tube engineering technique. When complete the tunnel sections will lie parallel to the existing Tyne Tunnel creating a dual carriageway in both directions.
VolkerStevin Marine is a Joint Venture which utilises the specialist skills of sister companies VolkerStevin and Volker Stevin Construction Europe. Both part of Netherlands based VolkerWessels.