Leading construction and engineering firm J. Murphy & Sons Limited (JMS) has begun piling work on a hundred-year-old aqueduct as part of a multi-million pound project to upgrade and modernise the Elan Valley aqueduct in mid-Wales for Severn Trent.
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.
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.”
For the first shaft of a possible six, Murphy is constructing a combination secant pile and sheet pile wall that will act as a cofferdam for the TBM launch shaft. The shaft will be made up of 102 1,200mm diameter piles, which are bored up to 15 metres deep with rock sockets up to 7m deep, and 24 steel sheet piles that will be installed over the existing sections of the aqueduct.
Along with its own Bauer BG28 piling rig, Murphy has bought a new Bauer BG26 to meet the client’s requirements.
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 is due to be completed by the end of January 2016, followed by the other five shafts throughout 2016 and early 2017.