International Association of Hydrogeologists Australia

IAH NSW – June Tech Talk

A Phased Approach to Geophysically Mapping a Contaminant Plume

Presented by William Dean

Produced by IAH NSW

Date: Tuesday 11 June 2024
Time: 17:30 for an 18:00 start
Where: AECOM Office – 420 George Street, Sydney, Level 5
Online: Teams Link

Contact Sebastien McCulloch on 0402 823 691 for access.


The accurate mapping of contaminants in the sub-surface can be a costly and time-consuming task but is very much one of critical importance. Understanding the pathways with which contaminants spread, the depths they reach, and how they interact with local hydrogeological settings enables the accurate planning and introduction of remediation schemes. Through the introduction of a trial geophysical survey at the onset of a project, a geophysical response was able to be assigned to the contaminant which was then traced to significant depths at distance from the contaminant source.

The case study is of a confidential site in the UK, showing how Electrical Resistivity Tomography (ERT) was used to map a contaminant plume of a highly conductive liquid from the near surface to a depth of ~140m BGL, and at a distance of up to 1km away from source. This information was collected in multiple stages, as the extent and depth of the contaminant was revealed from each prior phase, resulting in an evolving understanding of both the reach and apparent flow paths of the containment. The results were verified by targeted, intrusive sampling after each phase to ensure the validity of the geophysical results, and for more accurate hydrogeological characterisation.

This presentation documents how a staged geophysical survey can be used to support and target an intrusive investigation, allowing for rapid collection of data in a non-intrusive manner, resulting in minimal disruption to the surrounding area/community. It highlights the value of engaging with novel techniques that can often be considered an afterthought and shows the value of correct planning and preparation on major projects.


William has 8 years’ experience as a geophysicist operating in a range of sectors from environmental to geotechnical and everything in between. He is a Senior Geophysicist at Macquarie Geotechnical, having worked previously for AECOM in the UK on several major environmental and infrastructure projects. He has extensive experience in leading siteworks in multiple geophysical techniques, the processing and reporting of those results, and most importantly, delivering results which are of value to the client/wider project team.

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