Farrans Construction will deploy TBM Penelope to build a 220m tunnel beneath the river, near Barnard Castle, to enable a new £155m water pipeline to be constructed while protecting the watercourse and the wildlife it supports.

Northumbrian Water’s Project Pipeline: County Durham and Tees Valley involves the construction of approximately 57km of new pipes connecting Lartington Water Treatment Works with around 200,000 customers across the south of north-east England.

Phase 1 of the project will connect Lartington, in Upper Teesdale, with Whorley Hill and Shildon, County Durham. It will be followed by a second phase extending the pipeline from Whorley Hill to Long Newton, connecting to the existing network that serves large parts of Teesside.

In recent months, main contractors Farrans and subcontractor Joseph Gallagher have built the two shafts, one on either side of the river.

Farrans contract director Dave Mellor said the western shaft was 8m in diameter and 32m deep, while the eastern shaft was 7.5m in diameter and 46m deep – the difference because of the rising topography on the east bank.

“A 221-tonne concrete base has been constructed in each shaft – a volume equivalent to 15 wagons of concrete. The 220m journey beneath the Tees will take up to six weeks to complete, going from east to west, before a large crane will lift the machine back out of the eastern shaft,” said Mellor.

Northumbrian Water’s project manager, James Dawes, said the project had been years in the planning and ensuring that key strategic crossings, such as the River Tees, were done in the best way possible for the local environment and communities, had been vital.

“While it would have been possible to cross the Tees using a pipe-bridge, we had to consider such factors as how this would impact the stunning Teesdale landscape that will be here long after our team have completed the project and moved on,” he said.

“The use of no-dig techniques, tunnelling or directional drilling, is becoming increasingly common in our projects, to reduce the impact on our region’s road and rail networks by reducing the need to dig long trenches. However, this is the first time we have employed it to cross a large river and the teams at Farrans and Joseph Gallagher Ltd have done a great job in creating these massive shafts to make this possible.”

The TBM was named by 10-year-old Penny Green, who won a competition run by Farrans.