Project overview
iEnvi was engaged by a large construction company to undertake Targeted Soil Investigations and In‑situ Waste Classifications (TSI/WC) ahead of trenching works for NBN infrastructure across recreational properties in Brisbane known to contain historical landfill and contamination.
Why the work was needed
Excavation through historic fill and landfill can present risks to human health, construction workers, and the environment (contaminated soils, landfill gas, odour and unexpected waste). The TSI/WC approach focuses testing on soils likely to be excavated during trenching so the contractor can manage handling, segregation, transport and disposal in a compliant and cost‑efficient way.
What we did
- Site inspections across the localised work areas to identify visible waste, fill and potential contamination sources.
- Screening and sampling of soils using a photoionisation detector (PID) for volatile organic vapours and a landfill gas meter to assess landfill gas (LFG) presence and intrusion risk.
- In‑situ waste classification of excavated material to inform on‑site management and off‑site disposal requirements.
- Interpretation of results against applicable health and environmental criteria and historical site information.
Key findings
- Contamination was identified at a subset of locations sampled; detections were localised rather than site‑wide.
- Based on the available data and the nature and concentrations of contaminants detected, iEnvi concluded the contamination at the tested locations was unlikely to cause serious or material environmental harm and therefore did not meet triggers requiring regulator notification.
- Landfill gas screening was used to assess immediate worker safety and potential for gas intrusion; controls were recommended where screening indicated a potential LFG risk.
Recommendations and practical controls
To manage the residual risks and meet the General Environmental Duty (GED) under the Environmental Protection Act, iEnvi provided pragmatic recommendations including:
- Preparation and implementation of a Construction Environmental Management Plan (CEMP) addressing contamination management, dust and odour control, spill response, and traffic/disposal logistics.
- Segregation and stockpiling protocols for suspect fill, with representative sampling and laboratory confirmation where required for classification and disposal.
- Worker safety controls (PPE, induction and on‑site monitoring) when excavating near identified contamination or landfill gas anomalies.
- Waste classification documentation to support lawful disposal routes and avoid project delays or unexpected costs.
- Where landfill gas screening indicates a risk, implement LFG monitoring and engineering controls or work practice limits consistent with risk level.
Commercial and project benefits
- Targeted testing reduces the likelihood of scope creep and unexpected disposal costs compared with blanket investigations.
- Clear waste classification and CEMP recommendations support efficient contractor tendering, approvals and on‑site decision making.
- Documented risk assessment and controls help demonstrate duty of care to regulators and stakeholders, reducing transaction and approval risk during construction.
Practical takeaways
- Use targeted investigations where works are limited in extent to focus budget on areas of highest risk.
- Establish on‑site protocols for segregation and temporary stockpiling before excavation begins to reduce handling and disposal costs.
- Confirm laboratory testing scope and disposal classification requirements early to avoid contractor hold‑ups.
Need help with a site assessment or CEMP for trenching through historic fill? Call iEnvi on 13000 43684 or contact us for a confidential discussion.
Need advice on this issue? iEnvironmental Australia provides practical, senior-led environmental consulting across contaminated land, remediation, ecology and environmental risk.