GHD tackled a critical challenge at RAAF Base Pearce - PFAS Management Area Plan Delivery
At a glance
GHD was faced with the critical task of assessing and remediating a potential PFAS contamination threat at the 900 hectares RAAF Base Pearce and the surrounding area. This was particularly crucial as the neighboring community relied on groundwater as their primary source of drinking water.
The challenge
GHD has been supporting the assessment and remediation of the 900 hectares RAAF Base Pearce and a three kilometre radius of the surrounding area. The initial characterization of PFAS in the surrounding area was particularly important as groundwater was the neighbouring community’s key source of potable water. Conducting a preliminary site investigation that identified 19 potential sources area both on and off the Base. Preparing a detailed site investigation (DSI) report that characterized the extent of PFAS contamination in the environment.
The completion of the DSI and risk assessment led to the preparation of the PMAP, outlining (and prioritizing) the areas of concern, whether they were source, pathway or receptor-based and the remedial/management methods that could be employed.
Our response
GHD was subsequently retained by the Department of Defence as the Lead Consultant for the delivery of PMAP at the Base. GHD’s technical responsibilities for this phase of the project have included:
– A Base-wide mass flux study to assist in establishing a baseline for ongoing remediation performance monitoring. The flux study utilises a combination of telemetry-enabled autosamplers and data loggers combined with conventional groundwater, surface water and sediment monitoring methods to quantify PFAS flux from the Base over a range of seasonal conditions.
– Development of Remediation Action Plans (RAPs) for the two former fire training grounds, which are the most heavily impacted PFAS source areas on the Base. As part of the development of the RAPs, GHD has undertaken the following supplementary studies to establish a robust understanding and approach to remediation of each source area that will withstand external scrutiny:
• Additional delineation sampling and developed a 3D model to represent the extent and mass of PFAS impact;
• Wash-down and lysimetric testing to refine understanding of key PFAS migration pathways; and
• Implemented PFAS-stabilisation/immobilisation trials using carbon-based amendments.
– Development of a technical specification to support the remediation of a former fire training ground by construction of an impervious capping structure. Development of the technical specification has included geotechnical and hydrological studies to inform the capping design and surface water drainage.
– Site attendance and validation activities associated with the remediation of a grounds maintenance area that was historically used for storage of AFFF. The remedial approach involves targeted excavation of localised PFAS soil impact followed by placement of an impervious capping layer to reduce PFAS flux from the area. On completion of the remedial work, a Remediation and Validation Report will be prepared.
The impact
The ongoing efforts at RAAF Base Pearce by GHD promise a brighter future for both the community and the environment. With contamination effectively addressed, residents enjoy the security of clean drinking water alongside a protected environment. GHD's commitment sets a precedent for responsible PFAS management, paving the way for a healthier future across the globe.