Landfill Leachate
Summary
Landfill leachate is liquid that forms when water percolates through waste material in a landfill or waste-filled area, dissolving and mobilising contaminants. Leachate can contain a complex mixture of organic and inorganic substances and may pose risks to soil, groundwater, surface water and the surrounding environment.
Landfill leachate is a key consideration for sites located on or near former landfills, waste disposal areas or uncontrolled fill, particularly where redevelopment or groundwater interaction is proposed.
Definition
Landfill leachate is contaminated liquid generated as rainfall, groundwater or surface water passes through waste material, extracting soluble and suspended contaminants. Leachate composition varies depending on waste type, landfill age and site conditions, but may include nutrients, metals, hydrocarbons, salts and other dissolved compounds.
If not contained or managed, leachate can migrate into surrounding soil, groundwater or surface waters.
Why Landfill Leachate Matters
From an environmental perspective, landfill leachate can degrade groundwater and surface water quality and may impact ecosystems beyond the source area. Once released, leachate contamination can be difficult and costly to remediate.
From a planning and development perspective, the presence or potential for landfill leachate can constrain land use and influence design, construction and remediation requirements. Councils and regulators commonly require assessment of leachate risk to demonstrate that development will not result in unacceptable environmental impacts.
Landfill leachate is often linked with other landfill-related issues, including contaminated soil, groundwater impacts and landfill gas generation, requiring an integrated assessment approach.
Common Sources of Landfill Leachate
Landfill leachate may be present where land has been used for:
Licensed or unlicensed landfill operations
Waste disposal or dumping
Historical tip sites or refuse pits
Areas of uncontrolled fill containing mixed waste
Industrial or municipal waste facilities
Leachate generation may continue long after waste disposal activities have ceased.
When Landfill Leachate Is Typically Assessed
Assessment of landfill leachate is commonly required where:
Development is proposed on or near former landfill land
Groundwater contamination is suspected or identified
Excavation or dewatering may intercept contaminated groundwater
Environmental due diligence identifies landfill-related risks
Regulatory authorities request confirmation of site suitability
Assessment is typically undertaken as part of an Environmental Site Assessment, Detailed Site Investigation or groundwater investigation.
Legislative and Regulatory Context
Landfill leachate is managed under contaminated land and environmental protection frameworks.
In New South Wales, regulators and councils assess landfill leachate risk under EPA guidance and planning legislation, particularly where groundwater or off-site impacts may occur. Similar regulatory expectations apply in other Australian jurisdictions.
Regulatory focus is on identifying leachate pathways, assessing risk and implementing appropriate management or remediation measures.
How We Can Help
Confluence Environmental assesses landfill leachate as part of contaminated land, groundwater and development support services.
Our services typically include:
Desktop review of landfill history and site conditions
Groundwater and leachate risk assessment
Sampling and analysis of groundwater or leachate where required
Integration of leachate considerations into site investigations
Reporting to support planning approvals and regulatory compliance
We focus on providing clear, defensible advice aligned with site-specific risk and regulatory expectations.
Related Terms and Concepts
Contaminated Land
Groundwater Investigation
Groundwater Sampling
Environmental Site Assessment
Landfill Gas
Environmental Due Diligence
Development Application