THE CHALLENGE:
The site had been used historically by the Ministry of Defence for disposal of ordnance and
for target practice by long range guns. Heavy metals present in the ordnance had leached
into surrounding soils and were also entering a nearby stream via surface water runoff. The
elevated soil metal concentrations were toxic to plant life, which had caused the area to
become barren of vegetation leading to significant surface erosion. The site was located
within Snowdonia National Park and was both remote and very sensitive with respect to
ground disturbance and access. Ground conditions were extremely poor with a thick layer
of near-surface peat underlying the area.
OUR SOLUTION:
Soilfix implemented a remediation scheme which comprised:
• Land drainage to divert away surface water that was running into the treatment area;
• Import, spreading and mechanical in-situ mixing of Bio-char (charcoal made from
biomass) into the soils using bespoke mixing attachments fitted to an excavator. The
biochar acts to reduce the leachability and bioavailability of heavy metals present in the
soil;
• Seeding and re-vegetation of the area, with the grass cover helping to prevent further
surface water runoff and erosion;
• Wide-tracked excavators, tracked dumpers and timber bogmats were used to reduce
ground pressure of plant working on the peat;
• Continuous watching brief maintained for unexploded ordnance by a specialist
contractor. Two controlled explosions were carried out by Army engineers during the
works
• Careful reinstatement of access routes and working areas post-treatment to the
satisfaction of all landowners and stakeholders.
All works were completed in summer months to required leachability criteria with
significant re-vegetation occurring within 6 months.
