TerrAffix Soil Solutions has worked with the Coal Authority and Environment Agency to successfully develop a new restoration treatment to dramatically address the soil erosion and pollution stemming from the UK’s legacy of metal mining dating back to the Victorian era.
The company has been recently acquired by the RSK group, comprising 175 environmental, engineering and technical services businesses committed to the UN’s Sustainable Development Goals.
TerrAffix has been working at the re-profiled Garrigill Burn spoil tip in Cumbria, within the North Pennines Area of Outstanding Natural Beauty and a UNESCO Global Geopark, at a height of 440 m above sea level
Technical Director Siôn Brackenbury said: “In the UK, there is a legacy of metal mining stemming from the earliest Bronze Age workings to extensive mining during the Victorian and Edwardian periods driven by industrialisation. By the early 1900s, most workings had closed, leaving a legacy of polluted spoil with significant metal deposits. These spoil heaps remain within the landscape as dune-like areas, progressively eroding and polluting the wider environment.”
He added that, working with the Water and Abandoned Metal Mines programme (a partnership between the Coal Authority, the Environment Agency and Defra together with Nottingham and Swansea universities) the TerrAffix team was delivering a programme of research and development to institute techniques for the establishment of vegetation on spoil. This work built upon PhD and MSc projects sponsored by the company and TerrAffix was able to call on the assistance of RSK group company Salix, which provided the biodegradable erosion control blankets for the trials.
Siôn said: “Only a year into the project, the vegetation is well-established on several plots, with roots achieving a depth penetrating into the spoil to bind the upper surfaces that were previously unvegetated, preventing erosion and providing new areas of habitat for invertebrates.”
Dr Hugh Potter, Water and Abandoned Metal Mines Programme Manager at the Environment Agency, said: “Our monitoring showed that each year, about three tonnes of lead, cadmium and zinc was being washed into the River South Tyne at Garrigill, which causes serious pollution. The first stage of solving this problem was to re-profile the spoil heaps but that still left the highly contaminated wastes susceptible to erosion by rain. Working with TerrAffix, we have created biologically active soil to encourage the growth of plants that are native to the local area (pictured above).
“The results so far on some of the trial plots are very encouraging. Hopefully, the techniques used at Garrigill will help us to sustainably decrease pollution from other abandoned mines across England, while also promoting biodiversity and capturing carbon dioxide.”
Different land restoration treatment formulations have been applied either by hydroseeding or manually. TerrAffix designed the solution using widely available plant biomasses, such as bracken plus amended biochars manufactured from forestry waste materials.
Siôn said: “These mine sites are very unfavourable to plant growth, since the soils have toxic levels of metals, are free-draining, often highly acidic and low in organic matter. The TerrAffix treatments are creating soils that encourage the distinctive “Calaminarian” (metal tolerant) plants to grow – these are priority habitats for biodiversity.”
He added: “These landscapes botanically have much in common with coastal grassland, supporting species such as sea thrift and sea campion, as well as some typical acid grassland species. Work being undertaken within Wales is looking at the genetic profile of plants adapted to metal mine conditions to see if they differ from their counterparts growing in non-contaminated areas.”