McPhillips were commissioned by Avove, a leading infrastructure services and engineering company, to undertake the replacement of an existing 225mm diameter pipe bridge which was damaged and in need of repair.

The works comprised of:

  • Construction of 194m of post and 3 rail fencing
  • Construction and installation of 8 reinforced concrete piers, 2 of which act as expansion joints, along with associated foundations
  • Installation of circa 170m of 300mm diameter ductile iron pipework across the newly constructed RC pipe bridge piers
  • Installation of a concrete protection slab to a section of newly installed ductile iron pipe that didn’t meet STW depth of cover
  • Installation of pipe supports
  • Demolition and offsite disposal of the existing pipe bridge
  • Removal of all existing pipe bridge piers to 1m below ground level
  • Construction of 3 new 1200mm diameter PCC Foul Water manholes
  • Making connections into existing Foul Water Manholes
  • Installation of 2 ‘Witches Hats’ along new pipe bridge
  • Reinstatement of the field

Specific materials were used for this project:

  • Reinforced concrete piers and bases on mass concrete foundations design based upon ground bearing pressures, depths of foundations varying between 900mm and 3.5m.
  • 300mm ductile iron pipe work painted with Hempel Hempadur Black polyamide curing, high solids epoxy paint.
  • Vandgard access deterrent ‘Witches Hats’ (designed to reduce pressure on the pipe in flood conditions and eliminate condensation which might otherwise cause corrosion).
  • Specialist fabricated brackets to fit concrete piers – the saddles lined with 6mm thick UV & weather resistant high-density rubber.
  • Teekay Axiflex (non-axially restrained) Type IV coupling, with EPDM gasket expansion joints protected with fabricated stainless steel shroud.

The challenges

We faced numerous challenges during the works, probably most significantly the challenge of working within a flood plain adjacent to a fast flowing watercourse during the flood season.

Other challenges we faced included:

  • Fabricating the specialist galvanized pipe brackets within the required time frame.
  • Sourcing the Vandgard access deterrent ‘Witches Hats’.
  • Using a spreader beam to install the ductile iron pipework in sections previously bolted together in 14m lengths.

The solutions

We chose ductile iron due to its robustness and adaptability to various geographical configurations and types of environments.

The result

The overall solution of diverting the pipe bridge was completed on budget and within the specified timescales. We worked in close liaison with the client in order to address issues as they arose and presented solutions promptly.

Using a 300mm diameter ductile iron pipe for above ground foul water gravity drainage with expansion joints seemed daunting initially, however the McPhillips team met the challenge head on to produce a successful end result. The works were completed to the full satisfaction of the client.

McPhillips Contracts Manager Simon Westmacott commented…

“This was a fascinating project, something out of the ordinary to challenge the McPhillips team. There were plenty of challenges along the way, including having to work within a flood plain and to tight timescales. It’s not every day we’re asked to divert an above ground ductile iron gravity sewer.“

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