Salt of the earth

AS Oldham slithers and shivers in the worst local cold spell for 30 years, a humble mineral is keeping roads and motorways open and allowing some form of normal life to go on. Rock salt from Winsford in Cheshire has been as sought after as gold as councils across the country run out of the ice melting crystals. Janice Barker found out more about Britain’s oldest working mine.

Winsford Rock Salt Mine is capable of extracting 30,000 tonnes of rock salt a week, and has nearly 140 miles of underground roads.

But the main challenge through the current severe freeze is prioritising customers with low stocks and liaising with the Government to ensure supplies go where they are most needed.

Winsford’s rock salt industry goes back 2,000 years, and it has Britain’s oldest working mine, almost 650ft under the Cheshire countryside.

Staff have pledged to work round the clock to keep roads open and drivers safe.

Pre-winter deliveries in early November have all been used up and the worst continuous spell of severe weather across the country for years has led to massive additional demands.

Councillor Mark Alcock, the cabinet member overseeing Oldham’s gritting campaign, said: “Winsford is a lifeline. If that goes down the whole country will grind to a halt.

“We are extremely grateful for the work they are doing — it is a fantastic job.”

Winsford’s rock salt deposits were discovered in 1844 when local prospectors were searching for coal.

The salt deposits formed 220 million years ago when England was covered by inland seas. Hot temperatures evaporated the waters leaving large salt deposits in and around Cheshire.

Winsford’s rock salt formation consists of four layers sandwiched in clay and limestone. When it was first opened, miners were lowered down in buckets and the rock salt came up this way too.

They used tallow candles to light the way and worked with picks, shovels and explosives, and the salt was moved to the surface in barrels.

The original miners used the room and pillar method of mining, leaving large pillars of salt intact to hold up the roof — a method still used today.

Now there are 23 million cubic metres of empty space in the mine, with over 137 miles of tunnels and the temperature is a constant 14°C all year round.

A worked-out part of the mine is operated by DeepStore Ltd, a records management company offering a secure storage facility. Confidential Government files, hospital patient records, historic archives belonging to The National Archives, and business data are stored in the mine, where the dry and stable atmosphere provides ideal conditions for long-term document storage. By the late 1800s the Cheshire salt market had reached over-capacity and became chaotic.

Winsford closed in 1892 due to competition from the Northwich salt mines, but got a second chance when the last of the Northwich mines flooded in 1928.

It reopened soon after and this time things were different — they had technology on their side.

Before continuous mining machines were invented the only method of extraction used at Winsford was the drilling and blasting technique.

It was used for nearly 70 years and, despite a few changes and advances in machinery, the basic five-point technique remains unchanged.

Undercutters with tungsten cutting picks hack out a slot at the base of the face, holes are drilled, charged with explosives and then detonated.

A typical blast yields 1,250 tonnes of salt.

Winsford has the largest wheeled loading shovel in any underground UK mine — it carries up to 18 tonnes in its bucket — and a crusher system and conveyor belt transports the salt to the shaft to take it to the surface.

Salt has also made its mark on the towns around Winsford like Northwich, Middlewich and Nantwich.

They all take their names from salt production, with “wych” often meaning “brine town”.

And Winsford’s landscape was also shaped by salt —Winsford Flashes along the course of the River Weaver were formed in the 19th century after subsidence caused by brine extraction, where the rock salt deposits were dissolved and washed out by water.

As the ground slumped into the voids, the River Weaver widened at each point, until lakes were made where arable land had once been.

In the late 19th century, Winsford Flashes became popular with working class day-trippers from the near-by industrial centres of Manchester and the Staffordshire Potteries.

The town also boasted an outdoor brine pool, which opened 75 years ago, and closed in the 1970s.

It was a cold water pool, which opened from May to September, but shut after a series of bad summers.