Project outline

In June 2013, Murphy was appointed as Bristol Water’s design and construction partner for the AMP5 Large Diameter Trunk Mains framework. The works saw the replacement of over 45km of trunk mains as Bristol Water looked to safeguard water supply for their customers.  

The framework was split into five packages:

  • Shipton Moyne to Tolldown: 6.4km of 450mm diameter PE pipe installed using a close fit structural insertion method inside an 18 inch Cl main and 4.2km of 450mm diameter PE pipe using an open cut method
  • Knowle to Victoria:  5.5km of PE pipe ranging from 315mm - 630mm diameters installed mostly by slipline insertion with the occasional use of open cut insertion
  • Bedminster to Bristol Bridge:  6km of 6730mm diameter PE pipe installed within an existing 27 inch main, using a slipline method
  • Barrow to Chelvey: 6.5km of PE pipe ranging from 355mm - 500mm diameters insalled using the slipline insertion method with some small sections installed using the open cut method.  Works also included installation of 1.7km of 400mm diameter PE pipe within existing 18 inch steel using a closefit structural method
  • Filton to Chase Reservoir:  4.2km of 450mm - 560mm diameter PE pipe installed within the existing 18 and 24 inch mains using the slipline insertion method.
Key challenges

The Shipton Moyne to Tolldown scheme was situated in a very congested area with a constant stream of heavy traffic. In order to avoid the most congested areas and significantly minimize disruption a design solution was adopted to slipline the existing main. The enabling works were designed so as that in commissioning and de-commissioning the main would be able to handle thrust forces placed on the closed and isolated valves. ‘Flushing’ and ‘sampling’ points were also used to assist in commissioning and de-commissioning.

The locations of all the enabling works were carefully selected by the delivery team, designers and client. This made sure that the works were designed to cater for all network requirements and also fitted the construction sequences and programme. In an area where a structural solution was required within the host main, the construction team worked with the designers to offer a close fit structural solution which would make sure that the maximum flow characteristics were maintained.

Most of the schemes were undertaken on either major or minor highways. Works were along strategic trunk routes, with the priorities being to keep bus routes clear and keep temporary traffic light systems to a minimum. The project team worked closely with stakeholders such as Network Rail, local bus companies, shopping centres, hospitals, emergency services and local authorities in order to achieve this and to further explore how to reduce disruption.

Accommodation works and road closures were scheduled to take place overnight, on weekends and during public and school holidays in a further bid to minimize disruption. Excavations within the highway were fully supported with temporary works designs created for each. All reinstatement works were completed first time and in some high trafficked areas, foam concrete backfill was used to minimize future settlement.

Project delivery and innovations

By staggering the start dates of each of the work packages the team were able to transfer relevant lessons learned and innovations from package to package.  This, together with a collaborative approach and extensive experience on similar projects completed for United Utilities, Thames Water and Severn Trent Water meant the team were able to complete all packages within the tight timeframes set by the client.

Murphy signed up to the Bristol City ‘Code of Conduct’, incorporating this into the induction process and consequently allowing the growth of shared values across the team. Murphy also worked closely with Bristol Water ecological consultants on detailed environmental and ecological management plans.

Value was added to the project by the team who continually strived to use their expertise to provide the client with recommendations that would save both time and money. This was made possible by the strong relationship between Murphy and Bristol Water that allowed for successful collaboration. By working with Bristol water’s repair and maintenance contractor the team were able to buy stone and recycled materials together, making significant savings. This collaborative approach was the key to minimising disruption to the public and saving costs by sharing equipment over the entire framework.

Key facts
  • Delivered on time and on budget.
  • Over 98% of waste produced was recycled.
  • Murphy were awarded Bristol Water’s ‘AMP6 Capital Works Framework’ on the basis of the project team’s performance on this framework.

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