The aluminium smelter established an EPA-licensed landfill in 1985, which was capped in 1999. A recent Major Industry Assessment by EPA Victoria, combined with the PSI for the landfill area completed in 2019, identified the need for a Landfill Gas Risk Assessment (LGRA).
The objective of this project was to conduct the LGRA, including an assessment of the landfill cap for fugitive gas emissions, to evaluate the potential for landfill gas migration and associated risks. To achieve this, the following actions were completed:
- Developed a Conceptual Site Model (CSM).
- Investigated landfill gas migration beyond the landfill perimeter.
- Evaluated surface emissions of landfill gas through the landfill cap and nearby areas.
- Conducted hazard identification and risk screening.
- Assessed landfill gas risks to current and potential future receptors, including the creation of a landfill gas generation model.
The LGRA was carried out in alignment with the Landfill Licensing guidelines (EPA Publication 1323.3), with methods outlined in the UK Environment Agency document, Guidance on the Management of Landfill Gas (2004). The fugitive gas emission survey, a critical component of the LGRA, followed EPA Publication 1684 (2018), primarily to ensure compliance with landfill gas action levels.
To support this assessment, a site walkover was performed, inspecting for evidence of landfill gas migration and potential paths for its movement. This included identifying physical signs such as stressed vegetation, bare ground patches, gas bubbling through ponded water, and landfill gas odours. The visit also focused on detecting preferential pathways for landfill gas migration, such as indications of subsurface services.
The fugitive gas emission survey helped determine whether gas emissions exceeded the gas action levels outlined in the Landfill BPEM guidelines. This data enabled the LGRA by providing an accurate assessment of landfill gas concentrations in the environment.
Following the field investigations, an evaluation of landfill gas generation was conducted, referencing the Commonwealth of Australia Department of Climate Change NGER Technical Guidelines (specifically Method 1 for solid waste disposal on land). This evaluation utilised the Australian Government Clean Energy Regulator’s Solid Waste Calculator (2018-2019 Excel model).
A Hydrogeological Assessment (HA) was conducted to understand the nature and distribution of contaminants of potential concern (COPC) in groundwater. This assessment was used to evaluate potential impacts on groundwater quality and environmental values at the closed landfill site, in accordance with PAN (90010815) and Improvement Notice (IMPN-00002078).
Through these efforts, a comprehensive understanding of landfill gas behaviour and potential groundwater risks was developed, aligned with the regulatory guidelines to ensure environmental compliance.