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Wednesday 22 February 2017

Rock salt shortage to leave top roads untreated

Published 08/01/2010 | 05:00

THE country will not have enough rock salt next week to make all major roads passable, the National Roads Authority admitted last night.

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Local authorities are currently spreading 20,000 tonnes of the rocksalt every week, but just 6,000 to 9,000 tonnes will be delivered over the next seven days.

And a similar amount is due for delivery in the week beginning January 18.

But if the sub-zero temperatures continue as forecast, local authorities will not have enough to meet demand, which could result in gardai being forced to close busy roads on health and safety grounds.

An average of 54,000 tonnes of salt is spread on the roads between November and April.

The NRA last night said that an entire winter's supply had already been spread.

Only limited amounts of salt can be held in warehouses, because it deteriorates and must be treated with anti-caking agents.

In November, local authorities had between 5,000 and 10,000 tonnes of rock salt in stock. In December, another 25,000 tonnes was delivered.

Since then, another 20,000 tonnes has been sourced from three different companies -- the Irish International Trading Company (IITC) which imports supplies into Cork, the Irish Salt Mining and Exploration company which operates from Ireland's only salt mine in Carrickfergus, Co Antrim and Lagans in Limerick.

At most, 9,000 tonnes will be shipped into the country next week and another 9,000 the following week. This means there will not be enough to meet demand, unless the NRA can source additional material from road authorities on the continent which are not as badly affected by the weather.

The material costs €130 per tonne. Grit sourced from quarries at €12 per tonne is also used, but it is far less effective.

"Grit is of limited benefit because it doesn't melt ice, it gets impacted and gets caught on tyres," NRA spokesman Sean O'Neill said.

Friction

"It also has what's called a ball-bearing effect on motorways. When the snow melts you have little rocks on motorways which can become airborne. Grit also creates a minimal friction corridor which lasts for half an hour or an hour.

"Sand can also be used but it has the same difficulty as grit, except it gets compacted even quicker and washes into drains.''

There are two techniques to treat roads -- anti-icing and de-icing.

Anti-icing is a precautionary measure where salt is spread before the freeze. It forms a bond-breaker between pavement and snow, and turns into a solution which helps melt ice.

De-icing takes up to three times the resources to remove compacted snow and ice and requires special equipment such as snow ploughs.

Irish Independent

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