Aliaxis provides a bespoke solution for directional drilling on the River Foyle

The Challenge

Aliaxis are proud to have supplied a £3m project to construct a new gas mains pipeline underneath the River Foyle, Ireland. The project is one of the largest directional drilling projects ever undertaken in Ireland.

The Solution

Firmus Energy embarked on the project to consolidate the gas supply on the cityside of Derry, which was only served by a single gas supply crossing the Craigavon Bridge. Offering security for the existing network, along with catering for growing network capacity for new developments, the completion of this project has ensured the safe provision of gas to more than 10,000 households.

There were very specific requirements for the pipeline for this project, as it needed to be a high quality, robust solution able to withstand the rigours of Horizontal Directional Drilling (HDD) installation. Once commissioned, it then needed to be capable of maintaining its performance when fully operational at 50m deep under the water level of the River Foyle.

The 660 metre pipe was to cross the River Foyle from the Thornhill area of the Cityside to Strathfoyle in the Waterside and specialist drilling contractor, McCormack Drilling, was tasked with the design and construction of the pipeline.

Due to the nature of the application, our technical support team was brought in at the specification stage to provide advice and recommendations on the design of the pipeline. Due to the concerns of the long term structural stability of the pipeline, a thicker pipe than is normally used for the transportation of fuel gas was needed, with 355mm SDR 7.4 Orange PE pipe specified.

McCormack Drilled a 660mm diameter hole through weathered schist and rock 50m under the river bed in preparation for the pipe. The pipe was laid out using Thornhill College school grounds and joined using butt fusion welding to ensure a robust joint that would stand the test of time and the strains of installation under the river bed.

Utilising school grounds to lay the pipe prior to installation meant that there was a very specific timeframe for the installation as access to the school grounds could not be blocked during the week. As a result, the pipeline was moved into position at the weekend and pulled though the hole under the river in one continuous 10-hour operation overnight, to minimise disruption to the local community.

Looking at where efficiencies could be made in terms of logistics and installation, we produced the pipe in 13.5 metre lengths, instead of the standard 12 metre length. Reducing the number of pipe lengths for the project minimised the number of deliveries needed, reducing transport costs and cutting carbon emissions. In addition to the logistic benefits, a lower number of pipe lengths also reduced the number of butt fusion joints required, to increase joint integrity on the pipe and aid the speed of installation.

Commenting on the project, Fintan McCusker from McCormack Drilling said:  “The complexities of this project meant that there was very specific requirements for the pipeline. The Aliaxis UK technical support team provided excellent guidance and recommendations regarding the design and then had the manufacturing capabilities to produce this bespoke size pipe for us. Ourselves and the client visited the Aliaxis production facility  to see the pipe being manufactured and speak to the operations team about the pipe performance, which offered us the reassurance that the pipe would meet, and indeed exceed, the specific criteria for this project.”

Aliaxis UK offers a range of pipework solution for directional drilling “no dig” applications including various SDR pipe options across both gas and water including the market leading barrier pipework system, Protecta-Line.