The New River was opened in 1613 as an aqueduct to carry water from Hertfordshire to central London. It originally drew water from springs alongside its route – sources later supplemented by the River Lea and other water courses.
Barhale will refurbish a section of the New River at two locations, in Hornsey and Waltham Cross, to prevent leakage and extend the asset life.
In Hornsey, the New River is leaking, losing water and gradually eroding the embankment. Small-scale repairs have been carried out to date and previous drainage works have diverted leaked water into the sewer network to prevent flooding but they have not addressed the root cause of the leakage.
Barhale will strengthen the northern side of the waterway with sheet piling, using a silent Giken press-in piling rig to minimise noise and disturbance for neighbours.
Thames Water senior project manager Rachel Whiteman said: “Over the years, we’ve been carrying out several smaller leak repairs and have put in place different solutions to manage leakage in ways that minimises disruption locally. However, our annual inspections have identified further areas of leakage and we have decided that a large-scale upgrade is now necessary. Barhale are water industry specialists and we’re delighted to be working alongside them to deliver this essential refurbishment work, to prevent leakage and extend the asset life.”
Thames Water originally proposed to build a concrete channel but the Barhale team recommended sheet piling instead as a more cost-effective solution. The weathering process of the sheet piling should ensure that the riverside blends into the natural environment.
The path of the New River is tightly constrained as it passes through north London, making access difficult for contractors. Barhale will deploy pontoon barges, initially to carry suction equipment to excavate silt from the river and then subsequently to provide a platform for the lifting crane.
Barhale regional manager John Prendergast explained that the age of the infrastructure and the narrowness of the route presented additional design considerations.
“It’s a bit of a problem getting equipment to the site – hence the decision to use pontoon barges, which we believe is a first for the business. Additionally, the nearness of residents has been a big consideration. Using the Giken system will minimise noise during construction and the decision to use steel sheet piling will ensure that, over time, the works have almost no visual impact.”
Barhale will also be installing sheet piling along a 1.1km stretch of the New River at Waltham Cross, west of the site of the proposed Sunset Studios development. The sheet pile will be of varying length to reach the impermeable London Clay formation to prevent water leakage around the base of the existing sheet piles.
When completed, the gap between the new and old piles will be filled with pea gravel to provide additional stability.
According to Barhale’s contracts manager, Jacques Deneys, the existing tow path would not support the weight of the piling rig so the team has worked with piling specialist Ivor King and OTB Engineering to overcome this issue.
“Once we have installed the first 10 sheets it will no longer be a problem,” he said. “Using the Giken Reaction Base (GRB) system means the entire operation to install the 1.1km of piles will be running on the new sheet pile wall.”
Jacques Deneys also explained measures that Barhale is taking to protect the local ecology: “We are working closely with Frog Environmental to specify an innovative bubble curtain to prevent silt debris dispersing through the river and to discourage fauna from approaching the works.”
Work is scheduled to start imminently with a target completion date of September 2025.
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