Manchester places

Monster: salt mining in Cheshire

With the recent wintry weather, Highways Agency and council ‘gritters’ have been out in force to de-ice the country’s main roads and motorways.

It’s owned by Britain’s biggest salt supplier, the Salt Union, whose staff have been working round the clock to meet demands amid reports of dwindling supplies.

Deep beneath the Cheshire plain, the mine has created a vast, subterranean world of unimaginable scale; big enough to fit 700 football pitches inside.

Radio Manchester’s Allan Beswick went down into the mine recently and travelled some of its 140 miles of tunnels to meet Cheshire’s salt miners and visit DeepStore - the UK’s biggest storage facility.

Mining

Cheshire's rock salt was formed 220 million years ago at a time when England was covered by inland seas and dinosaurs roamed the Earth.

Allan Beswick: down in the mine

Hot temperatures slowly evaporated the waters leaving vast salty deposits in the ground beneath Winsford and the surrounding area.

It's been mined since 1844 when the salt was first discovered by local prospectors who, ironically, were looking for coal to make salt from brine. What they found was rock salt comprising 90% sodium chloride and the rest a gritty material called marl.

Used mainly for de-icing roads, rock salt production at Winsford is done these days on an industrial scale.

Traditional methods of digging, drilling and blasting have been replaced with a Continuous Mining Machine or JCM - a 130 tonne mechanical monster that uses tungsten steel picks to scrape the salt from the tunnel walls and ceiling.

True grit: de-icing the roads

Allan Beswick described it as… "a huge steel cylinder the size of a garage with teeth as big as rhino horns, tracks the width of the tunnel gouging the whole of the wall and dropping it into a conveyor belt to be carted off into the gloom where it’s eventually crushed into manageable pieces."

There, he met Ron one of Winsford’s longest serving miners. Ron says he actually prefers working underground:

"I wouldn’t swap. You get underground and time goes quite quick. Work on’t surface and it doesn’t seem that way. I’ve had 40 years underground and I’m used to it now."

Storage

Over the years, millions of tonnes of rock salt have been extracted in Cheshire leaving a vast number of empty ‘rooms’ - which have found an unexpected use.

Vast: space is used for storage

Down in the mine, it’s too dry for mould, too deep for mice, and with a constant temperature (14C) and humidity, the space has proved perfect for safe storage.

The ‘rooms’ are owned by a company called DeepStore which sells the space to hundreds of clients including the Bodleian Library and National Archives.

And there’s plenty of it. Kevin Matthams is the company’s Regional Sales Manager: 

“A single room is probably about a third of a football pitch," he said. "If you compare that to the whole of the mine, where we have 600-700 football pitches of available space, DeepStore has about 3-4% of the mine. And the mine is still producing on a daily basis."

Adding: "We’ve actually calculated that every piece of archived document ever produced in the UK can be actually be stored underground. So we’ve got a long way to actually fill the mine."

And with enough rock salt to supply the UK for 70 years, it's really a matter of how quickly the mine can dig it out.