Tunnelling | Right: QEII inlet relining
Below: QEII outlet discharge at Boormans Field
j tunnel walls and invert. This was done manually using scrapers and trollies which were then emptied in the tunnel using a vacuum system. Steel fixing was completed and then the tunnels
were both relined. Shutters were installed in situ by the team, with concrete poured and cast in place. The team were working at a rate of 39m of tunnel concreted per day. The concrete was pumped down the shaft and along the tunnel, into the crown of each shutter section. The maximum distance of pour from the pump was 560m, utilising a 4 inch pipeline.
Challenging
Below: QEII Reservoir inlet and outlet tunnels Google Earth map
Communication in tunnels often presents a challenge as it requires maintaining contact over long distances, where there is likely to be minimal signal. Barhale’s team decided on the use of traditional baby monitors as they are simple and effective devices. This was a resounding success, with functionality that enabled clear communication over distances of 500m within the tunnels. There were numerous challenges to overcome
during the course of the project, not least those presented by the global pandemic. In line with Barhale’s company approach, the site took every effort to keep workers safe. This included social distancing, increased hygiene measures and regular temperature and COVID testing checks. Two of the four project sites were close to residential developments. While acoustic barriers were used to reduce noise from 24-hour working, relationships with the community were closely managed to understand any end-customer issues. Barhale’s customer manager regularly visited residents throughout the project. Through ongoing, open dialogue, it was possible to listen to concerns and to work with the operational teams to find best solutions to any problems. The site at Walton Treatment Works (inlet tunnel access) was a live Thames Water site, so access and movement around site was carefully co-ordinated with Thames Water Operational Teams to avoid any impact on site operations. The collaborative approach between Barhale’s and Thames Water’s teams extended to permitting Barhale full access to the necessary part of the treatment works via a secondary entrance gate, with a full compound set up within the boundary of the treatment works.
Award winning As a direct result of its hard work and commitment to
the project, the Barhale team were awarded Thames Water’s Project Pride Award. This accolade recognises and rewards projects working as part of the Capital Delivery AMP7 Framework that achieve Health and Safety Excellence.
Barhale put in every effort to beat the outline construction programme and worked in collaboration with Thames Water to finish four months ahead of schedule. This was a significant efficiency saving for Thames Water, allowing the reservoir refilling operations to commence in November 2021 prior to the Winter flows in the River Thames, and reducing the logistical challenge of sourcing water from elsewhere. ●
16 | January 2022 |
www.waterpowermagazine.com
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