TerrAffix

Frongoch Mine

The Frongoch Mine site required phytoremediation of the contaminated soil in an area of reclaimed mine tailings.

We used TerrAffix-Mine to reduce the mobilisation and bioaccumulation of heavy metals within both the polluted soil and the vegetation to prevent further land and water pollution.

TerrAffix-Mine consists of biochar which locks in heavy metal pollutants such as copper, zinc and nickel, preventing water pollution. This makes it a highly effective and sustainable phytoremediation solution for the contaminated land around Frongoch Mine.

22 days after seeding a previously barren landscape is greening up.

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Frongoch Trials TerrAffix 2018 grassed up 22 days after seedingb Frongoch Lead and Zinc Mine post capping Balancing pond prior to treatment Banks prior to treatment Gullying and erosion in the spoil Spoil material Scattered tufts of isolated grasses Frongoch-terrraffix-mine-hydraseeding-with-biochar-(5-of-21) TerrAffix-Mine-being-hydraulically-applied Frongoch-terrraffix-mine-hydraseeding-with-biochar-(21-of-21) Frongoch Trials TerrAffix 2018 grassed up 22 days after seeding
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Frongoch Trials grassed up 22 days after seeding

Site Problems

  • Poor physical soil structure requiring soil amendment
  • Soil polluted by heavy metals including lead, copper and zinc
  • Vegetation contaminated by heavy metals leading to hardy and metal-tolerant invasive species flourishing in the area (NRW, 2013)
  • Large areas of saturated soil contributing to water pollution of local water courses, which has in turn decreased the abundance of aquatic life
  • High levels of heavy metal leaching continuing to be a problem, even after previous soil remediation works, due to Ceredigion’s high rainfall and the finely grained mine tailings

The whole area is approximately 0.1km² and made up of mine waste heaps, bare ground, an area of reclaimed, flattened mine spoil (reprofiled in the 1920s), a balancing pond and an adit.

Our brief was to treat the area of re-profiled spoil for soil contamination on this historic heavy metal mine site.

The area included slopes of between 20% and 35%.

Solution

  • Previous soil remediation had lessened the slopes of the polluted mine tailings. The core areas requiring soil remediation were capped with clay to prevent water percolating through the spoil and causing the leaching of heavy metals into local water courses.
  • Where clay capping was not possible and in areas where there was low organic matter, a two-stage process was used:
    • The first soil amendment treatment involved laying down an organic layer to stabilise the later phytoremediation material.
    • The second stage of the process involved applying a combination of a proprietary hydroseeding base, TerrAffix-Hydrasoil, plus TerrAffix-Mine with an appropriate resilient seed mix, specifically designed for the contaminated and saturated soil of the mine spoil.
  • In combination with the proprietary mix, TerrAffix-Mine provided nutrients and minerals for the seeds, which enabled rapid establishment of vegetation more appropriate to the area than the previous metal-tolerant invasive species.
  • Soil structure, soil aeration and water retention within the root zone of the growing plants was enabled, ensuring the long-term maturation of the plants.
  • Soil remediation was quickly established by TerrAffix-Mine’s active ingredient of biochar reducing the mobility and bioaccumulation of heavy metals from the contaminated soils into and within the vegetation.
  • The successful plant growth increased the roughness of the reclaimed site and the Leaf Area Index of the vegetation. This meant a reduction in the impact of rainfall caused less soil erosion and stronger, more stable roots, which has in turn led to better land drainage and less likelihood of future problems caused by leaching.
  • TerrAffix-Mine’s biochar content ensures that the area’s carbon sequestration abilities have established a functioning ecosystem in this previously heavily polluted area. The longer term benefits of CO² sequestered by photosynthesis as the vegetation matures ensure that this phytoremediation project will only continue to have positive impacts on the wider environment.
  • 22 days after seeding the landscape in the trial plots were transformed, TerrAffix-Mine out performed all the other products trialled.

Frongoch Mine is an abandoned lead and zinc mine situated in a rural Ceredigion valley 17km southeast of Aberystwyth, mid-Wales.

One of seven mines in the Frongoch Fault surrounded by hilly pasture.

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