High-voltage cables were installed in the disused Victorian railway tunnels in the 1960s, bringing new electricity supplies to the Manchester area from power stations east of the Pennines.
The decision to put cables in the tunnels rather than building new overhead power lines across the moors was made after representations to a public inquiry by the Peak Park Planning Board. The tunnels were bought by National Grid's predecessor organisation, the Central Electricity Generating Board (CEGB), and are now owned by National Grid.
The Woodhead Tunnel cables form part of the 400,000-volt transmission system, which runs between National Grid's substations at Thorpe Marsh, near Doncaster and Stalybridge, east of Manchester.
These cables are now nearing the end of their operational life and need to be replaced to ensure continued safe and secure electricity supplies to Greater Manchester.
It is not possible to install new electricity cables alongside the existing cables in the Victorian tunnels for two reasons.
Firstly, to ensure continued safe and secure electricity supplies for Greater Manchester, the existing cables need to remain in service while new cables are installed. Because of the confined space, there is not enough room to carry out major engineering works to install new cables in the tunnels alongside the existing "live" 400,000-volt cables.
Secondly, despite a great deal of maintenance work over the years, the condition of the Victorian tunnels has continued to deteriorate and they would require considerable civil engineering works at substantial additional cost to be made safe for long-term use for any purpose.
Therefore the replacement cable circuits have been installed in the third, more modern, Woodhead Tunnel, which dates from 1953. This tunnel was closed in 1982 and was bought by National Grid in the early 1990s with this purpose in mind.
This project forms part of National Grid's ongoing national investment programme and represents a significant investment in the region's power network.
National Grid will soon begin to dismantle out of use gasholders at Prince of Wales Drive in Battersea, London.
The gasholders originally stored town gas produced at a local gasworks. When the gasworks closed, the gasholders were used to store natural gas. Thanks to improvements and investment in the national gas network, gas can now be stored in the pipe system, making the gasholders redundant.
The gasholders site will be cleared to deliver new homes, making an important contribution to Nine Elms on the South Bank, an area earmarked by the Mayor of London to create 16,000 new homes and 25,000 new jobs by 2020.
We are presently planning the project in detail, including surveying the site in order to fully understand ground conditions. This will allow us to carry out the project promptly and safely.
Work to dismantle the gasholders is planned to begin this summer and will take up to a year to complete.
The works are currently ongoing, via the entrance at Dunford Bridge. As the vast majority of the work takes place within the tunnel itself, the impact on the environment, the local community and visitors to the area is much less than that usually associated with major engineering works.
However, some work is also required at the Woodhead tunnel entrance, the terminal pylons and the sealing end compounds at both ends of the tunnel.
National Grid will take care to manage the transport of materials to and from the site at Dunford Bridge. Access for heavy loads will be required at certain times, and we will contact local people with information about this nearer the time. We apologise for any inconvenience this may cause.
A comprehensive traffic management plan, developed in conjunction with the highways departments of the relevant local authorities, will help to keep vehicle movements to a minimum and ensure the safety of local residents and other road users throughout the duration of the project.