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J.Murphy & Sons Limited have the Featured Project this week as they have been commissioned by Severn Trent Water to begin works on a 100-year old Victorian aqueduct in Wales. The multimillion pound project aims to upgrade and modernise the Elan Valley aqueduct in mid-Wales.
The aqueduct is 73 mile long and has fed water to the West Midlands from the Welsh valleys to Frankley Resevoir in Birmingham for more than a century.
Severn Trent is upgrading the aqueduct as part of its Birmingham Resilience Project (BRP) and this part of the scheme will see the creation of three new tunnels at Bleddfa, Knighton and Nantmel. The new tunnels will bypass some existing sections of the aqueduct which will no longer be used, but continue to guarantee a continued water supply to Birmingham.
Murphy International Ltd. was contracted to construct the drive shaft and reception shaft at Bleddfa, Powys in Mid Wales. The scope consisted of constructing 1200mm diameter secant piles to form a retaining wall for a shaft at both locations. There were 112 no. piles at the reception shaft up to 9m deep and 125 no. piles at the drive shaft up to 15m deep with 6m long rock sockets. There were also 13 no. steel sheet piles to be driven above the existing aqueduct.
Murphy International Ltd used their Bauer BG28 piling rig and their brand new Bauer BG26 piling rig to complete the bored piles and a Movax mounted on an excavator to install the sheet piles. The shafts were completed over 2 visits by Murphy’s very experienced crews on time and under budget.
Appointed by the main contractor, the Barhale/NMCNomenca JV, Murphy will be constructing the retaining walls for two deep shafts at either end of the new bypass tunnels at Bleddfa, allowing the connection into the existing aqueduct, and start the new tunnel using a Tunnel Boring Machine (TBM).
Christopher Fox, project manager for Murphy, said: “With the existing aqueduct approximately 8m below ground level and directly beneath the work zone, great care has to be taken to ensure that the piles do not penetrate into the aqueduct or that the vibrations caused by the works cause any damage.”
The JV has set up a number of vibration monitors within the aqueduct that trigger an alarm if the maximum reading of 15m/sec is exceeded.
The work on the first shaft was finished at the end of last month and work on the other five will happen throughout 2016 and early 2017.