National Grid needs to expand its network of high-pressure natural gas pipelines through South Wales and onwards into Herefordshire and Gloucestershire. This work is important to ensure reliable and economic gas supplies to homes and businesses across the UK.

In stages, we need to install new pipeline sections, starting in Milford Haven in the west, continuing in South Wales, through Herefordshire and onto Gloucestershire. Pre-construction activities including design, evaluation of pipeline routes and consultations started in 2005. Construction began on the first pipeline section, Milford Haven to Aberdulais, early in 2006, and on the second section, from Felindre to Tirley, early in 2007.

The programme comprises the construction of a number of separate pipeline sections, compressor stations and associated works over a period of approximately three years.

These are large engineering projects and each pipeline section went through a rigorous process of consultation and environmental appraisal before consent to construct was granted by the Secretary of State for Trade and Industry. The pipelines are designed to the same parameters as the other 6,800km (4,160 miles) of high-pressure pipelines we have operated safely and securely across the UK for more than 35 years, although they will be operated at a slightly higher pressure - 94barg (1364psi) instead of 85barg (1231psi).

The new pipelines will contain exactly the same type of natural gas as is currently transported throughout the UK.

Why do we need more pipelines?

Until now the UK has been self-sufficient in gas, thanks largely to abundant supplies from gas fields, predominantly in the North Sea. Unfortunately this situation will not continue. At the moment, the UK has more than 21 million gas customers and this number is rising daily. The reality is that the offshore fields are decreasing in output and demand for gas from homes and businesses is growing at such a rate, that analysis shows that the UK will become increasingly dependent upon imported gas over the coming years.

Two new terminals to import Liquefied Natural Gas (LNG) are being built at Herbrandston and Waterston, both of which are near to Milford Haven. The terminals are being developed by South Hook LNG and Dragon LNG. The LNG will arrive by ocean-going tanker, be transferred ashore into LNG storage tanks and then converted back into gaseous form, for onward transportation through the National Gas Transmission System. Although the terminal developers are independent from National Grid, under the terms of our operating licence we have a duty to connect them to our National Gas Transmission System, to ensure that the gas they export is safely and economically delivered to where it is most needed by users throughout the UK.

We therefore need to expand our National Gas Transmission System to connect the terminals at Milford Haven. In addition, the capacity of the existing National Gas Transmission System eastward from Aberdulais is limited by the relatively small diameter pipes which were installed in the early 1970s.
Sections of new pipeline of the same diameter as that planned for Milford Haven to Aberdulais need to be put in place through South Wales and onwards into Herefordshire and Gloucestershire.

Crucially, with the exception of a few Above Ground Installations, once the individual pipelines are in place they will be buried underground, returning the countryside to its natural beauty.

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