Comprehensive Contaminated Land Risk Assessment and Site Investigations
Addressing land contamination requires a structured approach to contaminated land risk assessment that ensures environmental safety and regulatory compliance. Our experts conduct preliminary risk assessments and detailed quantitative risk assessments to evaluate potential hazards associated with contaminated soil, groundwater contamination, and vapour intrusion.
Utilising the latest tools, we assess environmental media such as soil,groundwater, soil vapour, air, and sediments to identify potential risks. Our investigations follow industry best practices, incorporating historical mapping, trial pits, and intrusive investigations to gather sufficient information about potentially contaminated land.
Conceptual Site Model Development for Accurate Risk Evaluation
A crucial part of contaminated land assessment is developing a conceptual site model that evolves throughout the project lifecycle. This model integrates site conditions and contamination sources to provide a clear risk assessment process, ensuring compliance with environment agency and local authorities.
Advanced data visualisation tools like Leapfrog Geo help refine risk evaluations, while contaminant fate and transport modelling using industry-standard software (e.g., MODFLOW, Groundwater Vistas, and Hydrus) enables precise assessments of risks posed by hazardous substances.
Human Health and Ecological Risk Assessments
We prioritise human health risk assessment to ensure that contamination does not pose unacceptable risks to communities, neighbouring properties, or controlled waters. Our approach integrates generic quantitative risk assessments and site-specific assessment criteria to develop a tailored response based on previous site activities and planning conditions.
Actual Contaminated Land Risk Assessment
Investigation of the cattle dip commences.
Mount Margaret estate is set within the lifestyle precinct of Townsville’s Alice River and has been developed in stages since 2012.
In the year following commencement of stage one, the Queensland Government introduced the amended National Environment Protection (Assessment of Site Contamination) Measure.
This posed a significant challenge, as the subdivision was formerly an operating cattle station and listed on the Environmental Management Register (EMR) due to likely use of organochlorine pesticides (OCPs), such as DDT.
Our environmental specialists were engaged to assess the potential impact of the station’s cattle dip and its contaminants on stages one and two of the development. After thorough investigation, we found no evidence of OCPs in the soil and initial land parcels were excluded from the EMR.
With this positive result in hand, we were then appointed to undertake further investigation to ensure all remaining land was also removed from the register.
“Negotiations with site auditor and regulatory bodies successfully minimised the risk to the development.”
Subsequent analysis showed low levels of DDT in surface soil around the cattle dip. Based on Department of Environment and Heritage Protection (EHP) requirements only two options were available, either offsite disposal or onsite containment. However, chemical concentration levels exceeded local landfill guidelines and Townsville City Council wouldn’t allow a containment cell within the subdivision.
The estate’s viability was genuinely compromised. That was until September 2015, when DP identified that the newly introduced EHP requirement for compulsory use of Contaminated Land Auditors may allow a more practical solution.
This legislative change, combined with our skilled negotiation, saw a relaxation of the remediation goals. Supporting evidence also showed the levels of OCP didn’t pose a signifi cant risk to the environment or community, and the resulting Contaminated Land Investigation Document was the first to be approved by EHP on initial submission after the introduction of compulsory CLA’s.
Remediation Strategies for Managing Contaminated Land
Our remediation approach involves assessing remediation feasibility, selecting optimal strategies, and executing plans in collaboration with industry partners. Depending on the contamination type and site conditions, we provide tailored remediation solutions, including:
- Soil remediation: If the soil is contaminated with pollutants or hazardous substances, soil remediation methods can be advised. These can include techniques such as excavation and removal of contaminated soil, soil washing (using water or chemicals to remove contaminants), bioremediation (using microorganisms to break down contaminants), or chemical treatment (such as soil flushing or stabilisation).
- Groundwater remediation: If groundwater contamination is identified, various techniques can be used to treat or contain the contaminated water. These methods include pump-and-treat systems, where groundwater is extracted and treated before being discharged back into the environment, or in situ remediation techniques such as bioremediation (using microorganisms to degrade contaminants), chemical oxidation, or permeable reactive barriers.
- Containment and Barrier Systems: Sometimes, it is not feasible or practical to remove or remediate contaminated materials. In such cases, containment measures can be implemented to prevent the spread of contaminants. This can involve the construction of impermeable barriers, such as slurry walls or geomembranes, to isolate contaminated areas from the surrounding environment. Additionally, engineered caps or covers may be used to prevent exposure to contaminated soil or waste.
Conclusion
Land contamination poses significant challenges to residential development, requiring thorough contaminated land risk assessment and strategic remediation to ensure safety and compliance. As seen in the Mount Margaret estate case, expert site investigations, risk assessments, and regulatory engagement can turn a potentially hazardous site into a viable project. By utilising detailed assessment methodologies, remediation feasibility studies, and containment strategies, developers can mitigate potential risks to human health, groundwater, and neighbouring properties. With the right expertise and proactive
