ALFRED MCALPINE is investing more than £16M in new transport infrastructure to shift slate waste from its quarries in North Wales, for use as road sub-base.
The cost of transporting slate waste has until now made it uncompetitive with primary quarried materials. But the aggregates tax, brought in on 1 April, raises the cost of quarried aggregates by £1.60/t, making slate waste a commercially viable product, said Alfred McAlpine Slate managing director Chris Law.
As a by-product of historical quarrying, slate waste is exempt from the tax, said Law.
The contractor plans to ship up to 10Mt of slate waste a year out of its Blaenau Ffestiniog and Penrhyn quarries in North Wales by rail for use as sub-base in road projects across the North and the Midlands.
Over the next 30 years, McAlpine will gradually use up the 340Mt of slate waste that has built up at its Blaenau Ffestiniog and Penrhyn quarries.
If it meets its 10Mt/year target, McAlpine will also satisfy the government's aim of increasing use of recycled and secondary materials from 50Mt to 60Mt/year 'at a stroke', said Quarry Products Association chief economist Jerry McLaughlin.
But McAlpine will have to overcome market opposition, Law predicted. Slate waste has rarely been used outside North Wales, where it has been incorporated into sub-base on the A55 coastal road and dualling of the A5 in Anglesey.
Many engineers and contractors will be unhappy about using a relatively untried material, the company's research suggests.
However, slate 'meets all the performance standards for sub-base and crushed rock. It makes competent aggregate, ' said Law.
Local authority highways departments contacted by NCE said they would be willing to specify crushed slate waste if it meets Department of Transport Local Government and the Regions specifications and can be bought for the right price.
The Highways Agency has already approved use of crushed slate after trialling it in conjunction with a bituminous binder two years ago.