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Groundwater flow and PFAS risk modelling

Groundwater flow and PFAS risk modelling

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SECTOR

Government

SOLUTIONS

Groundwater and water resources

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Christopher Sandiford

National Contaminated Land Group Lead, Senior Principal

Overview

This project involved groundwater flow and PFAS risk modelling, to assess the potential future risk to an important drinking and irrigation water resource from an existing PFAS source and plume. The modelling provided supporting information for future resource management decision making and risk mitigation strategies protective of the resource.

Questions to be answered by the modelling included:

What is the risk to existing water supply borefields?
How far has PFAS already spread, and along which pathways?
How quickly could PFAS reach future supply bores if risks are realised?
Which future water supply strategies are safest, and which are risky?
How might potential management options (e.g., optimisation of groundwater extraction, distributed rather than centralised water supply, and/or managed aquifer recharge) mitigate these risks?

To answer these questions, the following modelling approach was adopted:

Single-layer design, focused on the aquifer most relevant to PFAS migration, and the two-dimensional (lateral) nature of the PFAS migration risk problem.
History matching, adjusted until the models reproduce groundwater levels and lateral hydraulic gradients, recharge and pumping responses, along with historical PFAS detections. The models are “trained” to represent the key physical drivers of historical PFAS migration from the PFAS source to known PFAS detection locations. These same processes likely affect future PFAS migration risks; learning from the past is critical to development of a reliable predictive tool.
Particle tracking, involving release of thousands of virtual PFAS “particles” from the PFAS source to assess whether PFAS could reach water supply borefield receptors under realistic hydraulic and geological conditions.
Ensemble model runs, involving hundreds of conditions based on different plausible hydrogeology and pumping patterns to reflect uncertainty and provide a basis for probabilistic assessment of PFAS risks.

3D block diagram of model grid and elevations

Challenge

Complex hydrogeological conditions, tropical (wet-dry) climate, significant and widespread groundwater extraction for a variety of commercial and private purposes.
Limited site-specific aquifer property data (conductivity, transmissivity, storage).

Outcome

Probability distributions of PFAS detections in groundwater under different resource utilisation scenarios.
Identification of optimal management strategies to reduce risk.
Technical support for management decision making.

Barry Mann

Senior Principal Hydrogeologist

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Michele is an Environmental Engineer with over two decades of international experience in Australia and Europe, specialising in contaminated sites investigation, risk assessment, and remediation across various sectors including Waste, Oil and Gas (both upstream and downstream), Infrastructure, Manufacturing, Power, and Land Development. He has successfully coordinated the design and implementation stages of numerous multidisciplinary projects and has served as the technical lead for the environmental aspects of several landfill rehabilitation projects. In his capacity as technical lead, Michele was accountable for the technical quality of the projects delivered by his team. His responsibilities included ensuring compliance with guidelines and regulations, reviewing data analysis, quality, and interpretation, and confirming that the project outcomes aligned with the proposed scope. As a Principal, Michele has made significant contributions to business development by maintaining regular contact with clients, identifying opportunities, and preparing tenders/proposals. An integral part of his role also involves the development and mentorship of junior staff. Michele is recognised as a Suitably Qualified Person (SQP) for the assessment of contaminated sites in Queensland and has a proven track record of approvals from various Contaminated Land Auditors and the Department of Environment and Science. Over the past 11 years in Australia, he has acquired an in-depth understanding of the State and Commonwealth Environmental and Waste regulations and their application. Throughout his professional journey, Michele has enjoyed his involvement in transactional due diligence and insurance claim projects, engaging with diverse stakeholders such as lawyers, finance auditors, commercial managers, and insurers. These experiences have honed his skills in managing stakeholder expectations and ensuring project deliverables meet the specific needs of clients and the objectives of the projects.