Brownfield land carries a long tail of risks invisible at site inspection. Foundation design, gas protection, and contamination remediation interact in ways that surprise unprepared clients.
What is made ground?
Any soil that has been placed by human activity: building rubble, industrial fill, refuse, dredging spoil. Variable in depth, density, and composition — often the worst material for foundations.
The three risk categories
1. Geotechnical (settlement)
Made ground has unpredictable bearing capacity. Foundations laid on it can settle differentially as the fill compacts. Standard mitigation: pile through made ground to stable strata below.
2. Contamination
Industrial brownfield often contains hydrocarbons, heavy metals, asbestos. Risks:
- Harm to construction workers and future occupants
- Aggressive ground conditions damaging concrete and steel
- Statutory obligations to remediate
Phase 1 (desk study) and Phase 2 (intrusive investigation) reports identify contamination. Cleanup costs range from R400k for capping to millions for excavation and disposal.
3. Ground gas
Decomposing organic fill (former landfill, gasworks, peat) generates methane and CO2. Gas migrates through soil into buildings.
- Methane is explosive in air at 5–15%
- CO2 is asphyxiating at sufficient concentration
- Protection: gas membranes, ventilated voids, monitoring
SANS 10400-J (ground gas) classifies gas regimes and prescribes protection levels.
Site investigation requirements
- Phase 1: desk study (R16,000–R50,000)
- Phase 2: intrusive investigation, boreholes, sampling (R60,000–R300,000+)
- Phase 3: remediation strategy if needed
Foundation strategy
- Pile through made ground to competent strata (most common)
- Raft over reinforced ground if fill is shallow and uniform
- Ground improvement (vibro replacement, dynamic compaction) for large schemes
Construction phase risks
- Unexpected obstructions (slabs, buried tanks, foundations)
- Contaminated arisings requiring licensed disposal
- Asbestos in fill — survey before any breaking work
- Worker exposure controls
Cost impact
Brownfield development typically adds 8–20% to construction cost vs greenfield equivalent, driven mostly by foundation and remediation.
MCFAR works regularly on brownfield schemes across South Africa.
Need expert engineering on your project?
MCFAR GROUP has been delivering structural engineering, building, and plumbing services since 1998. Talk to our team about your build, retrofit, or renovation.
Request a QuoteFrequently Asked Questions
Should I avoid brownfield sites?
No — they often have planning advantages and central locations. Just budget realistically for investigation, remediation, and foundation.
Who is liable for contamination?
Current owner may inherit liability for historic contamination. Always investigate before purchase.