What Type of Crossing

THE NEW TYNE CROSSING

What Type of Crossing?

What Type of Crossing?
During the early stages of the scheme, different types of bridges, a bored tunnel, and an immersed tube tunnel were considered. The final decision concerning the type of crossing took account of many factors including technical feasibility, environmental impacts, cost and disruption to the communities of East Howdon and Jarrow.

The TWPTA considered a wide range of benefits and potential drawbacks when selecting the preferred method of tunnel construction and decided that an immersed tube was preferable to a bored tunnel.

The construction cost of an immersed tube tunnel would be significantly lower than a bored tunnel, resulting in a lower toll charge.

A Comparison of the Immersed Tube and Bored Tunnel Alternatives
Design Consideration	Immersed Tube Tunnel	Bored Tunnel
Approximate Capital Cost (at 1999 prices)	139 million	163 million
Estimated Tolls (1999 Prices)	£1.10 to £1.55	£1.35 to £2.00
Construction Programme	36 months ± 3 months	39 months ± 6 months
Property Demolition and Community Effects	• 21 dwellings • St Peter’s School • The Gaslight pub (Grade II listed) • AMEC offices & workshop •Grange Nursing Home •Newsagent •YMCA Drop-in Centre •Temporary loss of Riverside Park • Significant landscape and severance impacts,but opportunities for regeneration schemes	• 15 dwellings •Newsagent •YMCA Drop-in Centre • Less severance and lower landscape impacts, but permanent loss of open space
Other Property Effects	Acquisition of land for construction including AMEC yard at Howdon and RMC MercantileDock site. Permanent acquisition of part of Rohm and Haas site	Ground settlement could affect up to 25 properties resulting in damage that could require either minor redecoration or minor structural repairs
Traffic	There would be little difference in the traffic volumes able to use either tunnel. By 2021, it isestimated that an average of 50 000 to 55 000 vehicles could be using the Tyne Tunnelseach day. However, the higher tolls associated with the bored tunnel would slightly reducethe number of motorists wishing to use it
Noise	The potential for significant noise and vibration impacts during construction is greater in Jarrow, and more people are likely to be affected under this option	The potential for significant noise and vibration impacts during constructiom is greater in East Howdon and Howdon
Noise	Following the implementation of noise mitigation measures, no significant noise or vibration effects would be associated with either option during operation
Air Quality	The potential for significant dust during construction is greater in Jarrow, and more people are likely to be affected under this option	The potential for significant dust impacts during constructiom is greater in East Howdon and Howdon
Air Quality	No significant air quality effects would be associated with either option during operation
Spoil Disposal	• Sea disposal of dredged uncontaminated spoil from river (140 000 m 3 ) is a preferred waste management strategy • Remaining surplus spoil (210 000 m 3 ) would be directed to licenced landfills	• All surplus spoil would be disposed to licenced landfills • No sea disposal required because no river dredging would be undertaken
Marine Ecology	Minor, reversible impacts at the site of river bed dredging across the Tyne	No impacts on marine ecology
Fish and Fisheries	Potential for impacts on fisheries, including salmon and trout, but could be mitigated by construction controls	No fisheries impacts
Safety	Both options would be built to current safety standards, and would include provision for emergency escape routes separate from the road tunnel. The bored tunnel would permit some emergency links to the existing tunnel, which the immersed tube would not

Safety in tunnels is of paramount importance. The existing tunnel was originally designed in accordance with the relevant standards at the time. It has been updated since and has a exemplary safety record. However, a new tunnel would significantly improve the inherent safety of the existing tunnel as a result of its conversion to one-way (northbound) traffic flow. An immersed tube tunnel would have a separate escape cell for emergency evacuation incorporated into the design. This is not possible with a new bored tunnel, but it could be connected by linkages at 250 m centres to the existing tunnel, thereby providing routes of escape from both tunnels. Improved ventilation equipment, monitoring and controls would limit the build-up of smoke in the event of a fire. A study has been undertaken to assess the risks posed to a new immersed tube tunnel by marine hazards in the River Tyne. Marine hazards include anchors dropping onto the tunnel structure, or ships sinking directly onto it. The marine hazard study concluded that risks which might arise on the River Tyne are negligible.

The overall environmental impacts of the immersed tube tunnel during construction would be worse, particularly through Jarrow and for the river works, but they can be minimised by careful design and management of construction activities.

Having balanced the relative environmental, economic, social and engineering benefits and disadvantages of both options, the TWPTA resolved in May 2001 to apply for a Transport and Works Act Order to authorise an immersed tube tunnel scheme. This resolution was reaffirmed in February 2002.