MILFORD HAVEN TO ABERDULAIS HIGH
PRESSURE PIPELINE

Vital’s External Works expertise covers many rail-related aspects, none more extensively demonstrated than that employed during the now-completed National Grid Milford Haven to Aberdulais gas pipeline.

The high-pressure main - the UK’s largest – cost over seven hundred million pounds, relying Vital’s
long-established expertise for design consultation, the obtaining of Network Rail approvals, plus infrastructure monitoring of eight railway crossings, three of which by open-cut across disused, but still operational branch lines, the remainder utilising state-of-the-art Herrenknecht tunnelling machines to
drive 1.2m dia. steel carrier pipes up to 11m deep below the running lines.

The pipeline, some 120km in length, is classed as of strategic national importance, carrying 20% of the overall gas consumption of the U.K., the overall responsibility for construction a joint venture consortium between Nacap and Land and Marine.

Apart from Network Rail, the route crosses 341 private landowners, plus 4 Regional Authorities, the need to avoid sensitive road hazards and traffic delays during the delivery of thousands of tonnes of plant and materials neatly resolved by Vital’s team of engineers, who installed specially-designed heavy duty rail crossings at strategic locations along the route. Unlike conventional, much lighter units, these are supported on substantial timber bearings, and swung into position between trains, careful monitoring ensuring that essential gauge and rail height clearances are properly maintained at all times.

Although the majority of ground was composed of hard rock, this in itself was not without its problems, in several instances requiring the carefully-controlled use of monitored explosives in order to create deep launch and reception shafts. Conversely, a sudden section of water-bearing sand caused a drop-shaft to rotate out of vertical alignment, necessitating dewatering and ground stabilization before tunnelling work beneath the railway could finally resume.

In both instances, Vital provided the necessary specialised vibration and rotation monitoring, together with regular geotechnical inspection, in order to ensure that the stability of the operational railway and safe passage of trains remained unaffected throughout, regular up-dates being transmitted to both client and Network Rail after each and every set of readings.

Today, traversing the hills and valleys of this mainly rural area, it is difficult to trace any evidence of the
now-buried pipeline as you traverse the hills and valleys of this mainly rural area, the 22 metre wide
top-soil stripping, stringing and welding of pipe-work long forgotten as  original ground levels are restored, fences and hedgerows reinstated, and bird song replaces the steady drone of heavy earthmovers.