04.09.15
Farnworth Tunnel work delayed until December
Work to re-bore Farnworth Tunnel – an important enabler of electrification between Manchester and Preston – has been delayed possibly until December, Network Rail has confirmed.
The rail infrastructure owner said that engineers enlarging the 1834-built Tunnel have come across “exceptionally poor ground conditions” and have run into “large swathes of sand”.
Network Rail said “rather than a firm material to bore through, sand pours down into the excavated area halting progress”.
RTM only recently visited the Farnworth Tunnel site alongside the transport secretary after Fillie – the largest tunnel boring machine in the UK – started its journey to build the new 270m railway tunnel. Boring work was even ahead of schedule, and everyone was confident the 5 October completion date would be achieved.
Martin Frobisher, route managing director for Network Rail, said: “This delay is intensely frustrating for our engineers and, more importantly, for passengers who are set to benefit from more frequent, faster, quieter services once this wider programme of work is complete.
“We first hit an area of running sand on August 14 when our engineers saw it suddenly pouring from the working face. This has slowed progress and created big voids, the largest of which needed filling with around 35 tonnes of grout. Again on August 27, sand poured into the excavated area and our engineers had to remove 100 tonnes of material by hand.
“The nature of civil engineering, especially deep below ground, is that you never fully know the exact ground conditions until you start tunnelling or excavating. Taking soil samples acts as a guide but is never 100% accurate because conditions vary greatly with the amount of water present.”
Network Rail added that more than 1,500 soil samples have been taken, each one eight metres in depth, to try and get as accurate an idea as possible of the ground conditions to be encountered, but such testing “can only ever act as a guide”.
Engineers are now pumping resin into the ground to firm it up before 9m-wide Fillie bores through it.
Farnworth tunnel is 276m long and, as at 2 September, 45m had been excavated since tunnelling started on 1 August, leaving a further 231m to go.
Alex Hynes, managing director for Northern Rail, said: “We are deeply disappointed that work to deliver the Farnworth Tunnel project will now not be completed by October 5, as originally planned. This will have a significant impact on the lives of our daily commuters.”
Northern Rail and First TransPennine Express services will continue as planned until October 5. The train plan after this date is currently being determined.