06/10/2026
Barhale – restoring at Staines North Reservoir.
Right under the Heathrow flightpath sit two large, pumped storage reservoirs, separated by a 1km embankment dam.
Water for treatment and use were once extracted from the north and south reservoirs by five steam driven engines, each with a capacity of 16 million gallons per day and housed in the decorative brick outlet towers and pumped through the Staines Reservoirs Aqueduct to multiple water treatment works on the Thames Water network.
However, one of the more contemporary technologies – Valve No.3, in the North Tower – had failed and needed fixing or replacing to mitigate any potential compromise. Thames Water were swift to prioritise the issue and instruct engineers to resolve the issue.
Barhale – supporting asset resilience.
We were called in to investigate the issue with Valve No.3, and to get it operating properly again by replacing the thrust nut and stem and refurbishing the valve with new spindles. This was a logistical challenge in many parts. Isolating and draining the tower itself was comparatively straightforward.
The first step in resolving the issue was potentially the most dangerous. Engineers needed to descend the shaft, 30 metres deep, inspect, and release the faulty 48" valve, before replacing the spindle on this and three other valves. However, this was a particularly narrow shaft, and the stairs were deemed unsafe - all surrounded by a complex array of archaic pipes and valves.
Engineer safety is always the first consideration, so divers undertook the high-risk activity of installing damboards to enable the complex operation to commence. But the same access issues made erecting the scaffold tower in the conventional way – from the bottom up – impossible. So, our Engineers switched to a more innovative ‘top down’ methodology, creating a floating scaffold system.
The Barhale team installed the bespoke scaffolding towers and undertook non-destructive testing of the shaft ladders to ensure their ongoing viability, and the work was successfully wrapped up when full valve functionality was restored.
