The guidelines focus on bulk ground gases (ground gases that occur at percentage concentrations), particularly methane. This is because these are not dealt with in other guidelines in NSW (including the National Environment Protection (Assessment of Site Contamination) Measure 1999), and because they are commonly encountered at potentially hazardous concentrations in a wide range of land uses and geological settings. However, the guidelines also address trace ground gases, providing cross-references to other guidelines where appropriate.
These guidelines are not intended to address on-site issues associated with active landfills that are currently managed through the landfill licensing process; i.e. under an Environment Protection Licence (EPL) issued in line with the Protection of the Environment Operations Act 1997 (POEO Act). However, they will be useful when considering off-site issues associated with such landfills and during landfill closure and post-closure stabilisation.
The guidelines are not intended to be a comprehensive manual of field investigation procedures or mitigation design. References to appropriate sources for such information are provided.
Section 2 of these guidelines describes the issues relating to ground gases as they have been encountered in Australia and overseas.
Section 3 sets out recommended approaches and procedures for assessing and characterising sites that may be impacted by ground gases.
Section 4 focuses on assessing the risks associated with ground gases, while Section 5 – which is closely linked to Section 4 – outlines options for managing and mitigating those risks.
Section 6 describes the planning and regulatory process relating to ground gases in NSW.