A design, build, finance and operate notice, which requires response by 7 May, has gone out for a second 1.52km tunnel under the River Tyne in Newcastle, UK.
The project scope is for a 360m long vehicular immersed tube and 1.16km of cut and cover tunnel as well as upgrade of ventilation, signing and emergency escape facilities in the existing tunnel.
The winner could operate and maintain the link for 30-40 years, as well as the existing road toll tunnel and pedestrian/cycle tunnel. Success could be tempered by a requirement in the notice to re-finance any debt on the existing tunnel.
During the early planning stages of the scheme, various bridge, bored tunnel and immersed tube options were considered. The bridge options were discarded due to the visual impact and concerns that they could interfere with the navigatability of the river. The client Tyne & Wear Passenger Transport Authority (TWPTA) has published a comparison of immersed tube versus bored tunnel alternatives as part of its evaluation process.
The capital cost of an immersed tube tunnel was felt to be in the region of US$37M, lower than a bored alternative. This gives significant predicted toll reductions of 19 to 23%, which is a powerful motivator when coupled with a three month shorter construction programme that allows for a 50% reduced schedule contingency. Also against the bored option was the requirement for an increased landfill site for spoil disposal compared to the immersed tube option, which can take advantage of sea disposal for dredged uncontaminated spoil.
TWPTA requires the new immersed tube to incorporate an escape cell for emergency evacuation, but a new bored tunnel would require cross passages at 250m centres for this purpose.
Advisers to the TWPTA are Arup as lead adviser, with Posford Haskoning, Pricewaterhouse Coopers, Herbert Smith and Lamb & Edge. A public inquiry into the scheme was conducted last year and TWPTA are now awaiting the Secretary of State’s decision.
T&TI was told that the procurement process would go no further than identifying a shortlist of possible concessionaires. However, as soon as approval is given, the bid process can move forward very quickly while an application is made for an order under the Transport and Works Act.
If the decision is favourable then construction could start as early as 2006.
