Transport issues need to be addressed to take advantages of resources such as slate, says a report on the future of quarrying across north Wales. The study identifies slate waste as a major source of "green" aggregates for the construction industry.

However, without improvements to rail infrastructure, the study warns that the full potential of slate "cannot be realised".

The joint report by councils and industry is now out for consultation. The document from the North Wales Regional Aggregates Working Party (NWRAWP) has been drawn up to meet demands by the Welsh Assembly Government that the industry is sustainable.

Aggregates, which include rock, sand and even building rubble, are vital to construction projects across the UK, providing the base for making cement, and the solid foundations for roads and buildings.

In a 143-page report, NWRAWP notes that the slate industry centred in Gwynedd has stockpiles of between 270 - 370m tonnes of waste slate.

"Indeed, this represents one of the greatest resources of secondary/recycled aggregates in the UK," it states.

The industry in Wales has been set a target of using 25% of recycled or so-called "secondary aggregates" by 2009.

"South Wales has already achieved this level. There is a reasonable prospect of north Wales also reaching this proportion by 2009 if waste slate utilisation continues to increase," the report added.

Once shunned by the construction industry, slate waste has seen a leap in its popularity for building projects after the UK treasury imposed a tax levy on virgin quarried rock.

It makes the waste rock almost £2 a tonne cheaper, which is a huge incentive for an industry that will use an estimated 290m tonnes of aggregates in Wales and England this year.

But the NWRAWP report claims that this market advantage could be wiped out by the cost of using lorries to transport slate out of sites such as Bethesda and Blaenau Ffestiniog.

"It has long been recognised that the main potential markets in terms of tonnage are located in England, but that there are substantial logistical issues," it said.

"The most efficient and sustainable means of meeting this challenge is to use rail and water transport.

"This would require either new railways, the upgrading of existing railways, or the rebuilding of former rail routes to link either the main north Wales coast railway and/or upgrade of ports such as Penrhyn (Bangor), Caernarfon, Conwy or Porthmadog."

The report from NWRAWP has now been put out for public consultation until April. Those consultations will then help form picture for the future of quarrying in north Wales until 2021.