A specialist amphibious tractor was sent into Standedge Tunnel to clear a blockage caused by this winter’s heavy rainfall.
The tunnel, Britain’s longest and deepest canal tunnel, has had to be cleared after around nine cubic metres of sand, gravel and other debris was deposited by a swollen stream.
The stream flows into the tunnel about 250 metres from its entrance at Diggle.
Given the nature of the work a specialist mining consultant had to be hired to ensure the tunnel can re-open to visitors next month.
The 200-year-old tunnel is 3.25 miles long and passenger boats run regularly during the spring and summer from the visitor centre at Marsden.
Over two days the blockage was cleared by an amphibious dredger, known as a Truxor.
Mark Weatherall, senior project manager at tunnel owner the Canal & River Trust, said the tunnel was an “amazing engineering achievement” popular with boaters and tourists, adding: “It’s important we carry out this specialist work to get the tunnel and navigation open to the public.
“Working deep underground in a tunnel on a floating dredger is quite unusual and poses many new problems which, I am proud to say, the team has successfully overcome in a short period of time.
“Not only have we had to bring in specialist equipment, we’ve had to take specialist advice from a mining consultant who is experienced in confined spaces to make sure that the work is undertaken in a safe and efficient way.”
Standedge Tunnel, opened in 1811 as a route through the Pennines for cargo including wool, coal and even horse manure, is known as one of the Seven Wonders of the Waterways.
Visitors can take two hour trips right through or 30-minute journeys inside and back.
The tunnel is due to open for the summer season on March 19.