Carney Construction operatives installing cladding and formwork for specialist reinforced concrete pouring for a large STW project

Deephams STW Shaft

Project overview

Deephams STW required extensive investment of over £40 million for improvement works. The first stage of works was to construct a new pumping station to increase the flow rates going to the new STW. J Murphy Construction acted as Principal contractor for Thames Water.

Key info

  • Start date: May 2010
  • Completion date: December 2012
  • Form of contract NEC: Option B
  • Total value: £7.2million+

Under a NEC contract Carney Construction were appointed as the Formwork Reinforcement and Concrete specialist sub-contractor for this project. This began with the construction of the lining and base plug for a 21.2m diameter 24m deep shaft to house the new specialist pumping equipment following the super deep secant piles by others. Carney started by constructing large concrete capping and ring beams in situ on the excavation down before using a climbing platform and EFCO ring shutters to form the perimeter.


Safety & Environment

To ensure safe access was provided Carney utilised a climbing platform which could be positioned up to the working level where large EFCO type shutters were used to provide a fair finish and large rates of pour when climbing up the shaft wall.

There were no lost time incidents on this site despite working around heavy plant with complex access arrangements.

For connecting works Carney completed difficult blockade-type works with hour-by-hour planning to ensure phases could be completed while flows were being backed up the original Victorian inlet tunnels. This included complex in-situ concrete construction with specialist benching material to deal with extremely high flow rates during short curing durations.

The main shaft excavation required large ring beams to be constructed to tight construction programmes with safe access considered throughout. Ladder use was removed for all non-essential activity and electric scissor lifts were used before this practise became normal within the industry.


For this scheme Carney utilised the longstanding relationship we have with formwork suppliers to gain value and maximising possible pour depths while maintaining the highest levels of quality, opting for a high quality steel shutter where there was a risk of material growth hampering works effectiveness and lower quality better value formwork pans for large covered tanks not to be accessed or part of process operations.

Throughout the works Carney used the approved Carney ISO quality procedures for managing signoff and sectional completions to allow integration of assets into the Thames Water asset base.

This project was entered into and won the Concrete Society Award for 2014.

Productivity & Programme

Carney were able to provide a service which adapted to meet design requirements incorporating various types of coupler and connection joints to promote speed of construction. Additionally technical benching which could slow down in-situ construction was precast onsite in a designed compound yard designed by Carney to allow for lifting straight into position. This sped up construction and reduces access issues for constructibility.

The shaft was able to be constructed in large depth pours due to the steel formwork taking excellent pressures with rock anchors and various other holding connections into the structural male piles, speeding up the shaft lining while reducing the number of pours required.

Conclusion & Summary

Carney have been praised for their flexibility and adaptability on a logistically challenging site with difficult project specification and customer expectations. We have proven a collaborative approach to both design change and changes to method of working. This has helped Murphy to deliver this project to the strict programme and cost requirements despite frequent unplanned scope changes:

  • Carney hold many specialist tradesmen within the working area capable of safely delivering high quality technical FRC works in difficult to access areas with tough time constraints.
  • Carney helped develop many of the methods of construction used to achieve the improved programme and quality required for this project to succeed.
  • Technical knowledge of connecting to existing running lines has been maintained and is being utilised in delivering various projects for our supply chain.
  • The client were very happy and utilised Carney Construction on the subsequent £270million AMK joint venture, which was to deliver extensive covered tanks for waste streams for significant flow increases to treatment works required to meet environmental targets.

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