The importance of postclosure management

Closed landfills must be properly managed and monitored for up to 30 years to protect the environment and neighbouring communities.

Even closed landfills can pose a series of threats to nearby residents and the environment, including odour generation, the proliferation of diseasecarrying vermin, and surface water and groundwater pollution from poor leachate management.

Capping is an integral part of the management of any landfill. Nico Vermeulen, operations director, EnviroServ Waste Management, highlights that the capping system must be designed uniquely for each site, determined by the individual site’s design and the liner the site has underneath.

“Older sites would have a higher-spec cap. You want to do progressive capping on your site – as you have one or two cells that are filled, you should start the capping process, because this reduces leachate production, as rainwater cannot enter the site,” explains Vermeulen.

Typically, a capping system will have several layers: • a barrier, typically clay or a composite plastic liner • a top soil layer with vegetation on top of the barrier • a drainage layer that captures water

that might leak through the clay layer, as well as any gases that escape from the site – these gases are collected through a pipe system and put through a whirlybird that has an activated carbon filter to absorb potentially odorous compounds in the gas. • a system to collect any rainwater that falls on the surface and remove it from the site. Even with a capping system in place, it takes five to seven years for leachate to stop being produced. Installing and maintaining a good capping system and properly managing closed landfills is therefore vitally important to protect the environment and the growing number of communities living within close proximity to landfills.

Notably, the challenges associated with households living closer to landfills are less problematic when landfills are well designed and managed.

Dr Johan Schoonraad, group technical specialist, EnviroServ Waste Management, stresses that the implementation of the correct buffer zone around a site is essential to prevent people encroaching too closely on the landfill. This also helps to prevent human activity on landfill site itself.

Landfill fires are a serious concern and can be caused by community activity on the site or the incorrect disposal of prohibited waste. In addition, well-designed and -maintained landfills circumvent the risk of the waste collapsing outside the bounds of the site, further protecting communities.

Schoonraad emphasises that where there are problems on closed landfill sites, remediation techniques should be employed to prevent potentially dangerous outcomes such as fire, pollution or collapse.

Ultimately, good management at both active and closed landfills comes down to compliance and enforcement, says Vermeulen. While the legislation is in place, it is up to the relevant authorities to tackle non-compliance and prevent the growing threat of illegal and unregulated dumps.