Mapping for high pressure gas pipelines in South Wales

Abstract

ObjectivesIn order to mitigate against environmental impact, to satisfy the design criteria and to ensure the long-term integrity of the construction, the Transmission Department of Wales Gas sought geotechnical advice on the routing and design of a major gas transmission system. This system was being built to reinforce the gas supplies to the industrial valleys of South Wales. The opportunity was taken to apply geomorphological mapping at an early stage in route planning so as to avoid abortive design work on alignments which might subsequently prove unsuitable or too costly to engineer (Fig. 1). Pipeline engineers welcomed the approach, which commenced by obtaining an understanding of the client’s objectives and industry design guidance. Working as part of the project team, engineering geomorphologists provided guidance from initial routing studies through detailed design to construction, which was completed without contractual conflict arising out of unforeseen ground conditions.The ProjectGas supplies to the industrial valleys of South Wales developed in piecemeal fashion outwards from the individual coking plants set up by collieries in the valley floors. The introduction of natural gas from the North Sea in the 1970s provided the opportunity to invest in a new transmission system emanating from the new high-pressure grid on the north edge of the Coal Field basin.The ‘backbone’ of the project is a 30 km north-south, high-pressure, welded steel transmission/storage pipeline (oversized up to 1200 mm diameter to permit storage by pressure-packing) linking the North Sea feeder main at Dowlais, near Methyr Tydfil, with the Cardiff feeder main at Nantgarw, near Caerphilly (Fig. 2).