Barhale to clear mussels from London tunnels

13 January 2023

Barhale has secured a £9m package of schemes under Thames Water’s Raw Water Tunnel Inspection & Refurbishment programme.

The civil engineering and infrastructure company will inspect 35km of raw water tunnels across West and North London removing debris, silt and invasive species, such as Zebra mussels, which are found across the network. It is anticipated that in the most affected tunnels as much as 140m3 of mussels will be removed. The tunnels will then be inspected and any structural repairs will be carried out.

Barhale will also inspect and replace/refurbish the large (up to 2.4m diameter) internal valves at sites including: Moor Lane shaft (gate and butterfly valves); Ashford Common shaft (gate and butterfly valves); Queen Mary Outlet – Hampton Leg (gate valves); Wraysbury Shaft (butterfly valve); and Queen Mother (penstock). Two gate valves at the King George VI Reservoir will also be refurbished.

The work, which comprises 12 schemes, is being delivered under the AMP7 Lot 5 Framework. Barhale will work closely with Thames Water to manage the isolation programme.

Barhale director Phil Cull sees the programme as a key element in the maintenance and upgrade of London’s water supply.

“This is a hugely important part of London’s water infrastructure and we are delighted to get the go ahead from Thames Water,” he said. “We have built a huge amount of expertise and experience on the Thames Water network and to be selected on this project is great vote of confidence in our team’s capabilities.

“While maintaining good flows through the raw water tunnels is essential, it is also of paramount importance that works are delivered efficiently and on time to ensure there is no unnecessary pressure on the system.

“We have been working closely with the Thames Water team to optimise isolations and are bringing a great deal of new thinking developed through the maintenance of the Thames Water Ring Main to the Raw Water programme. We will again be collaborating to minimise the length of isolations and to maximise what is achieved during each one.”

Barhale regional manager John Prendergast said the work built on the successful delivery of the first three years of the Thames Water AMP7 Tunnels and Aqueducts programme in which Barhale had already completed monitoring and maintenance on almost half the length of the Thames Water Ring Main tunnels and a further 9km of raw water tunnels.

Work is expected to be completed in 2025.

In December Barhale was awarded a £4.5m contract by Thames Water to reinforce a sewer to minimise the impact from HS2 tunnelling. Barhale will install a 75m length of non-structural liner to north London’s Middle Level Two (ML2) sewer to protect it while HS2’s TBMs pass underneath.