Strange vapor emerges from Eryri hills due to tunnel shafts. It resembles steam, linked to Victorian railway project.
People made them; no dragons live there. They are part of a cool Victorian project.
The Ffestiniog Tunnel runs under a mountain near Dolwyddelan. The tunnel stretches for 2.5 miles and cuts through slate bedrock. It used to be Europe’s longest unlined tunnel. Trains travel between Blaenau and Llandudno and the tunnel’s highest point is 790 feet.
Three huge shafts connect to the tunnel. Workers built these for steam train ventilation. Steam trains no longer run there now, but walkers feel ghost trains sometimes. They think the trains rumble below.
Air flows through the tunnel like a wind tunnel. Air is warmer in winter and cooler in summer. Diesel trains also warm the air. Rainwater causes problems there, as rockfalls and landslides happen often. The tunnel closed for periods in 2017 and 2019.
The shafts act like chimneys and pull up moist air. That humid air meets cooler air outside, forming vapor. Farmers used rocks from the tunnel project long ago. They built sheepfolds near the shafts with this rock; these structures are falling apart now over time.
Wales still has 53 railway tunnels in use, most of which were built during the 1800s. Many have shafts, about 26 total. Some shafts are easy to see, like at Ffestiniog. Some are sealed and known as “blind” shafts while “hidden” shafts are capped and forgotten. These hidden shafts pose a risk.
A hidden shaft collapsed in 1953 at Clifton Hall Tunnel near Manchester. The collapse created a big crater and pulled down two houses. Five people died in that incident.
A survey found 86 tunnel shafts in Wales: twenty-eight were open, seven were blind shafts, and eighteen were hidden shafts. The nature of 29 others remained unknown. Network Rail started investigations of the sites.
They might need extra safety checks and fixes. At Ffestiniog, they lowered shaft towers and safety rails exist on these tops. They now inspect the shafts remotely. Technicians use special HD cameras. These cameras check the shaft structure for any issues as the shafts have brick tops and rock bottoms.
The Conwy Valley Line opened from 1863 to 1881, and they bored the tunnel from 1874 to 1879. The railroad helped move slate. The line now carries many passengers, about 120,000 people each year, and many are tourists.