Thames Water has directly contracted Barhale to carry out a third phase of essential emergency sewer works to repair a collapsed sewer adjacent to the London – Woking railway line at Hersham, Surrey.

The collapse could have had major implications for rail services in and out of London and would have created a threat of flooding for local communities.

It is the first element of the Hersham emergency works programme that Barhale has been appointed main contractor on, having been brought into the project originally by Skanska, MWH and Balfour Beatty (SMB), delivery partner for Thames Water’s eight₂O alliance.

The new contract award comes after successful completion of phase one and two of the repair works when the Barhale team replaced 45m of sewer through an innovative trenchless technique and installed a new large outfall manhole.

Phase three is focused on providing future resilience to the local sewer network. It will require construction of a rising main discharge chamber to redirect flows from the existing outfall manhole to the new manhole constructed as part of phase two.

All elements of the works have been designed and constructed to repel any future chemical corrosion

Nick Curtis, project manager at Barhale explained that the works are complicated by the need to maintain the live flows of the rising mains.

“The Barhale team will be able to achieve this through close co-ordination with the Thames Water Pumping Stations Operations Team” he said. “By temporarily isolating the connecting pumping stations for the works directly on the rising mains, we will be able to construct a new chamber without causing any supply interruptions to Thames Water’s customers.

“The sewer collapse could have had an impact on the Southern Western main line from Woking to Waterloo and presented severe flooding implications for the local community. We are delighted to have been able to address the problem with little or no disruption to either residents or rail passengers.”

“Immediately after the sewer collapse it was important to “stabilise” the area both to ensure the safety of passing trains and also to control any impact on the Thames Water network. The successful completion of phase three will ensure that the sewer is more resilient to future problems.”

Mark Taylor, Head of London Infrastructure cited the good work the Barhale team carried out in phase one and two as the reason the civil engineering specialist has now been engaged directly by Thames Water.

Mark said, “The collapse of the sewer was a huge risk mitigated by Barhale in the first and second phase of the works under eight₂O. They showed deep understanding of the challenge and were able to bring some innovative thinking to tackle the problem – for example, in the demountable tunnelling shield they developed for the initial phases.

“For phase three we have taken the opportunity to engage them directly and are confident they will continue to help us to provide more resilience and improvement to the network.”