The Heronbridge mains duplication scheme is a £7m investment undertaken by United Utilities to ensure it can continue to meet the demands of its customers in the Chester, Wirral and Ellesmere Port areas.
The new pipeline follows a similar route to the existing pipe and secures the transfer of raw water supplies from the River Dee to Sutton Hall Water Treatment Works, where the water is cleaned and distributed as fresh drinking water. The scheme consists of three parts, a 1200mm diameter steel pipe jack through a tunnel, an 1200mm dia. open cut ductile iron pipe lay and difficult horizontal directional drill (HDD), with thanks to Donegan Civil Engineering, seen to be at the out limits of the UK water industries capability.
The foremost section of the 1.7km route was crossing under Chester Approach, a major gateway into Chester City centre, and so approximately 450 metres of horizontal directional drilling was required to install the pipeline underneath the busy road whilst pedestrians and road users experienced zero disruption. This required a new pipe size and specification, never previously manufactured and used in the UK water industry, new manufacturing capabilities were needed and so United Utilities engaged GPS PE Pipe Systems. Working with LiMA a Lang O’Rourke and Atkins joint venture they engaged a specialist company known as VSH (Visser & Smitt Hanab) from Holland.
To ensure the pipeline could meet the hydraulic requirements and cater for the future growth of the area, an 800mm pipe was required, but, due to the directional drilling stresses, a minimum 80mm wall thickness was needed, resulting in a required specification of PE100 800mm SDR 11 pipe, a size never previously produced in the UK.
Manufactured in 12m lengths for ease of storage and handling on a site within a busy public area, the pipe was then jointed using the butt fusion technique above ground and pulled into the reamed annulus to ensure a robust pipeline was in place.
The installation was not without challenges; with working on the River Dee embankment there were several environmental considerations that were carefully mitigated by drilling underneath the historic carriageway and surface. The varying ground conditions that the drill needed to navigate, including sandstone, soft clay and hard clay, also caused an array of technical challenges. It was testament to the careful planning, collaboration with all parties in the supply chain, and precise installation capabilities that ensured the drilling successfully traversed the ground and came up in the exact location along Chester approach without any settlement concerns.
Successfully completed within 12 weeks, the new pipe was effectively installed and pressure tested to meet the project requirements.
Commenting on the project, Daniel Smith, project manager at United Utilities said: “This new pipeline is vital to ensure we can continue to meet the demand of a growing population. This was a challenging and complex project managing the risk of such a large directional drilling element making it not only unique but a difficult task to find partners that could deliver the required solutions. Finding specialists from other industries that could demonstrate expertise and offer assurance and certainty was key to the success and credit to LiMA. The team from Holland brought an incredible energy and comradery best illustrated by the photographs provided with this article.”
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