Thames Water – Axford Pipeline

Posted on: Mar 06, 2023

Posted by: OCU Group

This project was for the construction of a 17.6km clean water pipeline including the construction of a new water Booster Station, modifications to Whitefield Reservoir and its valve house and the construction of nineteen HDDs (Horizontal Directional Drilling) crossings of areas of significant engineering difficulty. The works formed part of an overall scheme to provide an alternative water supply to facilitate the cessation of abstraction from Ogbourne WTW (Waste Water Treatment) and reductions of abstraction from Axford WTW.

Works at Dorcan comprised the provision of a new Booster Station facility, a below ground concrete structure which to house up to 4 booster pump sets and associated operating equipment, and a steel framed superstructure to be constructed to house the booster equipment that incorporates specific security requirements. The build was located on land adjacent to the Marsh which was notorious for flooding and water discharge and had to be managed in accordance with all statutory requirements.

Scope of Works

The water pipeline installation consisted of 560mm HDPE, 500mm HDPE and 4.2km of communication duct. The project had many unique challenges, including a HDD under the M4 Motorway, crossing local county wildlife sites, floodplains, tunnelling under the Main Great Western London to Bristol Railway Line and Archaeological sites of interest, which included the roman town of Durocornovium and Whitefield Iron Age / Bronze Age ditch.  The strip preparation was a slow and methodical process, involving up to 30 Archaeologists on site at any one time.  OCU managed and controlled site access for these Archaeologists who were all subject to site inductions and update briefings.

Key Aspects of this project delivery included:

  • Surveying works of underlying soils and Topography
  • Survey works to undertake the installation of the water pipeline, communication ducting and HDDs
  • Provision of site establishment and logistical requirements to facilitate the 19no. HDD Crossings and associated civil works
  • Provision of all Temporary Works designs as necessary for the HDD works and associated civil works
  • All excavation and backfilling works associated with installation of the pipeline and communication duct
  • Butt fusion welding of over 17km of PE mains
  • Tunnelling works under a major Railway including the insertion of 500mm diameter welded steel mains through the newly constructed tunnel and up through 16m deep segmental shafts
  • Mechanical construction of large diameter valve and connection arrangements.
  • 18 major live connections
  • Major building construction and remodelling
  • Crossings of major Railway, Motorway and Trunk Roads
  • All works constructed to current Water Industry specifications
  • Construction of a new Pumping Station at Dorcan and a Pumping Station Extension with new pumps at Whitefields Reservoir