South Wales Gas Pipeline, United Kingdom

As North Sea reserves around the UK are being depleted, the country must look for alternative sources of gas to supply to both households and industries.

New supply sources are coming from Russia and Norway, as well as pipelines from Europe. But one of the UK's major sources of gas (over 23% by 2012) is the new South Hook and Dragon LNG terminals in Milford Haven, West Wales. These gas projects are now nearing completion and will provide gas from the Middle East via LNG tankers to the gas grid.

One of the problems with the new projects was that the pipelines connecting this area of Wales with the nationwide UK gas grid were not large enough. Consequently a major pipeline construction project was undertaken to provide a new 48in (1,220mm) high-pressure gas pipeline from Milford Haven in Pembrokeshire to Tirley in Gloucestershire (national gas network), a distance of 197 miles (316km). The pipeline had been estimated to cost around €700m but this rose to €1.08bn.

Opened in November 2007, the South Wales gas pipeline is capable of carrying one fifth of the natural gas consumed by the UK. The underground pipelines are 1,220mm in diameter and 316km in length.

A new pressure reduction installation (PRI) will be constructed near to Tirley, Gloucestershire, to ensure the pipelines can operate at their maximum capacity.

The National Grid submitted a planning application to Tewkesbury Borough Council in December 2008 for the permission to build a new PRI on land in Tirley. The construction of the PRI will be completed in 15 months once permission is granted.

Gas pipeline controversy

The construction of the South Wales gas pipeline stirred up a great deal of protest from climate activists and environmental campaigners during its construction. Part of the route (16-mile section) passes through the Brecon Beacons National Park and although the park authority objected it went ahead, the National Grid has taken expert advice and is restoring the affected parts (as the pipeline is 1.2m underground). Land restoration will be completed by the end of 2009.

Campaigners have raised concerns about the safety of the pipeline as it is one of the first such high-pressure installations in the UK. In addition some sections have passed through seismically active areas of South Wales such as Trebanos, which has concerned local residents about the possibility of leakage.

Finally, the safety of the LNG installations at Milford Haven have been called into question from the point of view of collisions between tankers as it is such a busy port and also because it is a potential target for terrorist attack.

There have been many protests against the pipeline and planning decisions have been hurried through their due process at many local councils along the route of the pipeline. However, the pipeline has been ruled to be 'a critical part of the future energy needs' of the UK by the DTI.

South Wales pipeline route

Planning for the pipeline started in 2003 (the route was decided in January 2004 to March 2005) and the land-based pipeline was deemed the best option as a subsea alternative was considered to be too expensive (land acquisition occurred between March 2005 and April 2006). The pipeline has a much higher operating pressure than normally seen in the UK. The pressure is 94bar(g) (1,364psi) as opposed to 85bar(g) (1,231psi).

The pipeline originates at Herbrandston from the South Hook LNG facility, one of the biggest in the world, operated by Qatar Petroleum and ExxonMobil. The pipeline then picks up the smaller Dragon LNG terminal at Waterston and proceeds to Milford Haven and then onto Aberdulais in the Neath Valley (75 miles, 120km).

At Aberdulais the Cilfrew pressure-reduction station reduces the pressure of the gas and turns flow into the South Wales gas grid. This section (phase I) was completed in April 2007, following DTI consent being granted in December 2005.

The contractor for the Milford Haven – Aberdulais section was Nacap Land & Marine joint venture. The pipeline continues onto Felindre where there is a compressor station to repressurise the gas.

From there the pipeline runs to a further pressure-reduction station in Tirley near Gloucestershire, before joining the UK grid for the remainder of the country.

The Felindre to Tirley section marks phase II and began construction in February 2007, following DTI consent being granted in the same month. The contractors for phase II include Nacap Land & Marine joint venture (Felindre to Brecon) and Murphy Pipelines Ltd for the Brecon to Tirley section.