ONE of the world's oldest navigable canal tunnels completed near Northwich 250 years ago is undergoing a major health.
The Canal & River Trust (CRT) is carrying out a detailed survey of Preston Brook Tunnel, near Dutton, using a combination of traditional hands-on techniques and cutting-edge technology.
The 1,138-metre-long tunnel, which carries the Trent & Mersey Canal, was built between 1766 and 1775 and is regarded as one of the oldest operational canal tunnels in the world.
Engineers are carrying out the work overnight to minimise disruption to boaters, allowing navigation through the tunnel to continue during the day.
The inspection will see specialists travel through the tunnel by boat checking for any structural changes, including cracks and damage to the brickwork.
As part of the programme, structural engineers will also carry out rope-access inspections of four air shafts and a construction shaft reaching depths of up to 17 metres.
Alongside traditional tools including poles, hammers, and spikes, the team will use drone fly-through surveys and 3D mapping technology to create a detailed picture of the tunnel's condition.
The findings will help determine whether any major repair work is needed.
Construction of Preston Brook Tunnel began under the direction of canal pioneer, James Brindley, one of the leading engineers of the Industrial Revolution.
Following his death, the project was completed by his student Hugh Henshall in 1775.
Today, the tunnel has heritage status, with its portals and two air shafts protected as Grade II-listed structures.
Peter Simpson, CRT's principal engineer for tunnels and culverts, said: "A trip through the tunnel is like stepping back in time.
"It's amazing to think it was built by hand using pickaxes and shovels more than 250 years ago.
"It's extremely atmospheric, but not many people get to see inside the tunnel because there is no towpath, so it can only be experienced by travelling through it by boat."
Peter said inspections such as this are vital to protecting the country's historic waterways.
He added: "The Trent & Mersey Canal is arguably more popular than ever before, and this crucial inspection is an example of the vital work our charity carries out to protect, maintain, and repair the nation's historic waterways.
"Looking after extraordinary structures such as Preston Brook Tunnel requires significant expertise and investment, and we're grateful for the support of our volunteers, donors and supporters who help us preserve this remarkable heritage and keep it alive for people and nature to enjoy for generations to come."
CRT cares for 2,000 miles of canals and rivers across England and Wales.
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