Thames Tideway Tunnel

(asked on 1st February 2016) - View Source

Question to the Department for Environment, Food and Rural Affairs:

To ask Her Majesty’s Government what economic benefits are attributed in the Department for Environment and Rural Affairs document of October 2015 <i>Creating a River Thames fit for our future: An updated strategic and economic case for the Thames Tideway Tunnel</i> to (1) the Lee Tunnel, and (2) the Thames Tideway Tunnel.


This question was answered on 15th February 2016

The Lee Tunnel and the Thames Tideway Tunnel (TTT) are key aspects of a wider improvement scheme for the Thames Tideway designed to meet the environmental standards set for the Tideway and achieve the environmental requirements of the Urban Waste Water Treatment Directive.

The updated assessment of October 2015 provided a cost-benefit analysis focused on the TTT in isolation, to inform Government’s decision on whether to proceed with that project as the last major phase of the wider Tideway environmental improvement works. Research set out in this assessment showed that the Lee Tunnel, while having significant local benefit, would not in itself deliver the wider environmental outcomes sought from the overall Tideway improvement scheme. The 2015 assessment therefore assumed no benefits are secured by the Lee Tunnel on its own. It demonstrated the benefits of the TTT, based on an assessment of people’s willingness to pay, to be in the region of £7.4 billion to £12.7 billion (at 2014 prices).

Defra carried out two sensitivity tests on this assumption (published alongside the main results in the cost-benefit annex to the Strategic and Economic case), to ensure the robustness of that decision. One test factored in the cost of the Lee Tunnel to the cost-benefit analysis for the TTT, and the second assumed that the Lee Tunnel reduced the benefit attributed to the TTT by 40%. In neither test did the economic case for the TTT become unfavourable.

Reticulating Splines