How old Welsh mines could be used to help heat people's homes

Its earliest records date from 1690 and its remediation work goes on for decades, but the pressing issue on the day Lisa Pinney talks about the renaming of the UK's Coal Authority is coal tip safety in the wake of Storm Bert. Ms Pinney, chief executive of what is now the Mining Remediation Authority, said its teams were out inspecting tips in Wales and England on November 25 after a weekend deluge which sent tonnes of debris from a disused tip down a slope in Cwmtillery, Blaenau Gwent. Some buildings were left deep in sludge and mud.

It was another reminder of the legacy of a mining industry combined with what appear to be more frequent periods of intense rainfall. Inspecting former tips is one of the Mining Remediation Authority's responsibilities and Ms Pinney said water management was the "number one" priority. "It's essential that they have good drainage and that they are inspected and maintained," she said. "Highest risk tips are always inspected after heavy rainfall."

More intense rainfall is predicted as the climate continues to warm because a warmer atmosphere holds more water vapour. "That makes water management even more important," said Ms Pinney, who has headed the organisation for six-and-a-half years after a 20-year career at the Environment Agency.

The Coal Authority, as it was then, was part of a task force which has identified more than 2,500 disused coal tips in Wales, mostly in the south. They are graded according to risk, with 267 in category C needing an annual inspection and 83 in category D requiring twice-yearly inspections. Just over a third of the country's disused tips are in public ownership; most are privately or commercially-owned.

Environment body Natural Resources Wales has weather stations including rain gauges at 10 of the highest-risk tips, and last year it was announced that technology such as drones, tilt meters and sensors were being deployed at around 70 of the 83 category D tips. Just over £44 million has been allocated for coal tip maintenance by the Welsh Government covering a three-year period ending on March 31 next year. Although coal tip safety is, controversially for some people, a devolved matter in Wales, the UK Government pledged £25 million towards the work in its October budget. Calls have been made for more funding for Wales in the wake of Storm Bert.

The Mining Remediation Authority's new name is felt to better reflect its work managing the effects of mining in Britain. It employs around 400 people and works with suppliers and business, including several in Wales. Ms Pinney said it liaised closely with the Welsh Government, councils and the UK's Department for Energy Security and Net Zero, and that its statutory responsibilities haven't changed. "We are not planning any significant changes," she said. The organisation spent £84.8 million last year, with a large proportion of funding coming from the UK Government. A big chunk of expenditure - £37.6 million - was spent on mine water treatment schemes, including operational and capital costs. A further £20.2 million went on public safety work.

Ms Pinney said the authority owns 26 coal tips and has 16 mine water treatment schemes in Wales. The key aim of the 16 schemes is to protect drinking water and treat the iron ore and other chemicals which are found in coal and metal mine water. These pollutants can coat river and stream beds and kill what's in them. "Mine water pollution has a potentially significant impact," said Ms Pinney. Remediation is also very long-term work.

Coal and metal mining goes back hundreds of years. More recently, in 1947, the coal industry was nationalised, with the National Coal Board and then British Coal Corporation running it until the Coal Authority was formed in 1994 to manage a privatised version of what was left of the sector. Ms Pinney said there were "a few" coal mining licences in existence in Wales but no new applications in the system. Looking ahead, she expects artificial intelligence will help with the organisation's large data sets and archives, and potentially cut energy and chemical costs for mine water treatment works.

Naturally-occurring heat in rocks in mines also has benefits which the Mining Remediation Authority is exploring. A district heating system powered by gas in Gateshead, in the north-east of England, expanded recently and replaced its power source by tapping into the warm mine water below. A nearby solar farm helps power the mine water pumps. The network of pipes provides low-carbon heating water for 350 homes, plus public buildings and businesses.

Ms Pinney said heating bills derived from mine water were lower than gas ones. "The Gateshead scheme went from concept to operation in less then three years," she said. "It's really effective. They're looking at putting in a second scheme."

A map showing where mine water has the potential to heat buildings in Wales was published this year. It found that nearly 20% of Welsh homes lay within one of three highest-opportunity areas for mine water heat. It doesn't necessarily mean we'll see lots of district heating systems start springing up but Ms Pinney described it as a real opportunity. "We are working with businesses in Wales and we hope a scheme will go live next year," she said.