Pyrite Investigations Expert Witness: Ballymun Youth Centre, Dublin
Introduction:
We were engaged to represent Irish Asphalt (Lagan Group) as part of a multi-disciplinary team investigating damages and alleged causes at Ballymun Youth Centre in Dublin. Giles Sommerwill and John Campbell presented expert evidence on ground conditions, foundation design/condition, site investigation techniques, data interpretation and the conceptual ground model. Our evidence supplied the court with context regarding a number of ground related factors that may have contributed to the damages observed within the building, to counter allegations that the damage was solely attributable to the supplied aggregate condition.
Details:
We were engaged to represent Irish Asphalt (Lagan Group) as part of a multi-disciplinary expert witness team investigating damages and alleged causes at Ballymun Youth Centre, Dublin. Pyrite itself is not a problem, but when it is exposed to moisture and oxygen a series of chemical reactions can occur. In such conditions, pyrite will oxidise to form sulfuric acid (H2SO4) and other products. The acid may in turn react with other minerals found in the rock. If calcium carbonate is present in the rock, it will react with the sulfuric acid to form calcium sulfate (CaSO4.2H2O) in the form of gypsum. Gypsum, formed in the manner described, has a significantly greater volume, approximately twice that of the source pyrite. The growth of its crystals, in between the laminations of weak rock, has the effect of prising open cracks and causing further expansion.
James Elliot Construction (JEC) alleged that aggregate supplied by Irish Asphalt (Lagan Group) had not been fit for purpose, and damages had resulted to their building following the alleged conversion of Pyrite by the mechanisms described above.
As part of a multi-disciplinary expert witness team, we undertook site investigations and sampling to assess material properties and in-situ ground conditions to develop a conceptual ground model for the site and the founding strata encountered. Techniques included hand sampling, sand replacement testing, dynamic probing, cable percussion drilling, extensive laboratory testing, and inspection of foundations.
The information obtained was collated into an expert report and the findings were presented to the court in 2010 and 2011. In addition to presenting findings of the engineering-team, we directly engaged in discussions with JEC’s experts to discuss and agree the interpretation of their data. We also provided direct support to the legal team throughout the trial.
Giles Sommerwill is a Specialist in Land Condition (SiLC), a UK Registered Ground Engineering Specialist and Chartered Engineering & Environmental Geologist with significant experience of Land Condition Assessment, Risk Communication, Remediation, Design and Implementation across the Geoenvironmental and Geotechnical sectors in the UK and abroad.
His specialties include:
- Land Condition Assessment
- Contaminated Land and Brownfield Assessment
- Hydrogeological Risk Assessment
- Engineering Geology and Geotechnics
- Flood Risk Assessment
- Risk Assessment and Risk Communication
Giles has over fifteen years in the field and often works in multi-disciplinary teams advising other engineering and design professionals on the implications of ground hazards; this involves undertaking design, planning, management and reporting of ground investigations, including investigations for new developments, and many bespoke studies including the assessment of hydrogeological settings, materials for earthworks, the impact of abandoned mine workings, remediation and stability assessment of soil and rock slopes/landslides.