LOAD & HAUL
TRUE GRIT on display in Ireland
At Irish Salt Mining and Exploration’s Carrickfergus mine, surefooted articulated dump trucks are hauling extracted salt to keep roads safe in winter – whatever the weather
S
alt has been among the earth’s most abundant and essential minerals since the dawn of time. Composed primarily of sodium chloride
(NaCl), it is known as rock salt, or halite in its natural, crystalline form. In 2015, total world production
of salt reached 273 million tonnes, according to market research company Statista, with the top fi ve producers being Canada, China, Germany, India and the USA. Situated to the north of Belfast,
Northern Ireland, Irish Salt Mining and Exploration’s (ISME) Carrickfergus mine was developed specifi cally to mine de-icing rock salt for winter road maintenance. Founded in 1965, ISME is positioned in a prime location, thanks to its proximity to the coast, as well as the construction of a ship-loading terminal, which enables the company to develop a successful export market. T e company’s 55-strong workforce currently produces between 300,000
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to 500,000 tonnes of road salt per year, and provides local authorities across the UK with rock salt to help keep the road network open during the icy winter months. Scottish local authorities are its biggest customer, followed by Ireland and then the rest of the UK. “Our job is simple,” says Derek Moore, mine manager at ISME. “We make the roads safer!”
Rock solid progress Mining at Carrickfergus uses the ‘room and pillar’ dry mining method. T ere are fi ve seams of salt, but ISME only mines one extensively, due to the thickness of the seams. T is is because 3.5m (12ft) of salt must be left above the excavated rooms as a support. At its deepest point, the mine
reaches 305m (1,000ft) below ground. “T e deeper you get, the larger the pillars,” explains Moore. “But on average the room sizes are 15.3m (50ft) wide and 9m (30ft) high. In the older part of the mine, they are just 6.7m (22ft) high, while the
pillars are 39.6m2 (90ft2 (130ft2 ) in
the newest part of the mine, and 27.4m2
) in the older parts.”
T e geology of the area is fairly simple too. T ere are no gases or moisture to contend with, which makes mining a simpler process too. Moore explains: “We drill; we cut; we blast; we muck out.” During mining, the salt bed is
undercut then drilled and blasted. Blasting happens at the end of each 10-hour shift, usually around 17.30, and sees three faces advance 3m (10ft) each time. T e next morning’s fi rst job is roof scaling, using a rotary cutting head designed specifi cally for the purpose. T e broken salt is then loaded into one of ISME’s seven Terex Trucks haulers, including two new TA400s, and hauled to the crushing plant. Crushing and screening are completed underground before the fi nished product is transported, via a 2km long network of conveyors, to the surface.
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