RTL Today has teamed up with PISA, the Luxembourgish science magazine, to reproduce their original videos in English for our site. A few weeks ago, presenter Olivier Catani visited a large salt mine in France. Here, they mine the underground for road salt, used on Luxembourg’s streets. How is it mined, brought up to the surface, and, most importantly, how did they get those massive vehicles down there?
This video is part of the PISA series for RTL Today. Watch all English videos on RTL Play, or discover the wide range of subjects previously covered in Luxembourgish here (there are 13 seasons, mind you! We’ll try and catch up...). Our previous episodes covered the history of the tram, Luxembourg airport, explained how the coronavirus vaccine works, asked why traffic lights always seem to be red, investigated where our tap water comes from, looked at Luxembourg’s railways since 1859, took a dive into the Moselle Valley and its underground Dolomite mines and more...
The mine is located 160m below the surface, and only accessible through a rather small shaft. A group of the country’s last salt miners squeeze themselves into a rather unsettling lift every morning - it descends at 4m per second, something you’d definitely be able to feel in your ears as the pressure changes.
Nicolas Theuer is the production manager of Les Salins du Midi. He explains that the team has a fleet of vehicles down in the mine, but which all had to be dismantled and pieced back together at the bottom. The mine itself is quite large, and allows for cars to be driven around, but the lift is the only way to access the area.
Literally everything is dismantled before it can be squeezed into the lift, including folding (and pressing together) the tires of big construction trucks.
There’s 300km of road in the mine, an impressive network of galleries. So how do the miners make sure they don’t get lost? “There is no GPS, there aren’t many signs, so it really is up to the skill of the miner”, Theuer explains.
Salt was first extracted at this mine in 1856, and the area is roughly 15m2 big. The galleries are 4.5m tall, 13m wide and support themselves.
“We took a little bit of salt. But we didn’t take all of it, and that is essential to guarantee stability”, Theuer says. The pillars keep the mine stable, and of course the team monitors the mine at all times. Anchors in the ceiling prevent big blocks from falling out.
The temperature is roughly 15 degrees throughout the year, and the air is dry, as the salt absorbs the humidity.
Carl Gotthelf Kind was the first to look for salt in Luxembourg. Nearly 200 years ago the mining engineer discovered salt in Germany, and he was convinced this white gold could be found elsewhere. Salt was precious, and used in the days when refrigerators didn’t exist to extend the freshness of food products.
Kind eventually found a water source near Mondorf, which tasted salty. He started drilling in the same spot where today’s thermal bath is located. But Kind was left disappointed - there was no salt, only salty water. His investors, meanwhile, were angry. They had paid for solid salt, which was nowhere to be found.
Solid ground was finally found deep underground, some 100km away near Nancy. 230 million years ago, this part of Europe was covered in sea water, flooded by the ocean, evaporating the sea water and leaving just salt behind. This process continued for millions of years, leaving layers of salt. Nancy was right in the middle of that sea.
Before the salt is blown up, dozens of holes are drilled in specifically designated areas. Three galleries are blasted at the same time. All the miners go up to the surface, while two stay behind to light the fuse. They then take the lift back up. Once everyone is out, the explosion takes place soon after, and the night is used to ventilate the area.
Ventilation is also required during the day. There are two ventilation systems, one that is for all the galleries, and one local system for where the miners are working.
Every year, the team digs 1.5km deeper into the ground. 40 miners work here in total, divided between early and late shifts. However, in its current form, the salt cannot yet be used for the road. It has to be broken up in much smaller pieces, which happens in an automated process. Up to 2,000 tonnes are being produced per day, which can be even higher if winters end up being colder than expected.
