Management of Legacy Landfills

Throughout the twentieth century local government has had the primary responsibility for disposal of municipal waste. EHS Support is providing specialty services to multiple local councils who have inherited contaminated sites and are now required to protect potentially impacted communities and comply with regulatory requirements.

Prior to implementation of rigorous engineering and environmental standards, municipal waste was often disposed in open voids – former quarries or sand pits or in trenches excavated into soft sediments. These landfills were dumps – unlined, exposed to the elements and plagued by sea gulls, flies, rats and other vermin. At the completion of filling, the sites were usually covered with soil and allowed to blend into the landscape, sometimes being converted to sports grounds, golf courses or parkland.

The implementation of environmental legislation throughout the late 20th and early 21st century combined with the rapid expansion of urban areas around major cities has brought a focus on threats posed by legacy landfills. Councils, being the owner and responsible party for these former waste disposal sites, are now faced with the task of identifying and mitigating the risks of these sites to human health and the environment. Former landfills now classify as contaminated sites – the soils in the biodegraded waste mass invariably contain elevated heavy metal concentrations and organic compounds and often other contaminants of concern such as PFAS and asbestos. Leachate migration from the waste poses a threat to surface water and groundwater quality and landfill gas migration poses risks to residents in proximity to these sites.


Local government has the primary responsibility to manage legacy landfills and EHS Support provides the necessary experience and expertise to deliver appropriate services to achieve this outcome. Regulatory requirements for management of legacy sites fall into three broad categories – monitoring, assessment and reporting and mitigation.

Monitoring – EHS Support can develop an environmental monitoring program specific to each site. The program may involve:

  • Identification of sampling requirements and frequency sufficient to characterise the site;
  • Soil sampling through hand auger or test pits, including assessing the capping thickness and soil types
  • Drilling of groundwater, leachate and landfill gas observation bores;
  • Sampling and analysis of leachate, groundwater and surface water;
  • Landfill gas monitoring of landfill cap, buildings and services and landfill gas bores.

Assessment and reporting – EHS Support has a team of professionals who supply the necessary services to characterise the site and assess the risk. These services include:

  • Reporting of environmental monitoring results;
  • Annual reporting of results to comply with license requirements;
  • Assessment of hydrogeological risk and reporting;
  • Assessment of landfill gas risk and reporting;
  • Preparation of aftercare management plans inclusive of site specific environmental monitoring plans;
  • Provision of environmental audits.

Mitigation – EHS Support provides specialist services to assist councils in protecting encroaching urban development from risks posed by legacy landfills. These services include:

  • Identification of appropriate buffers to protect residential properties;
  • Drafting of planning provisions to ensure protection of adjacent users;
  • Design of landfill gas interception systems to mitigate landfill gas risk;
  • Development of Remedial Action Plans for contaminated sites;
  • Presentation at community consultation meetings.


EHS Support can assist local government councils by identifying legacy risks associated with their former landfills and developing monitoring and aftercare management plans that are commensurate with the level of risk and their obligations under the General Environmental Duty.

See more of our project experience.