Robert Sarsby, author of a new ICE Publishing book title Environmental Geotechnics in Practice, discusses ways of improving land-based waste disposal.
For centuries mankind has been dumping all manner of waste materials (both toxic and non-toxic) on land, usually in an uncontrolled, haphazard manner. During the last 150 years, across the globe, there has been unprecedented rapid industrialisation and urbanisation. These developments, coupled with population explosion, have led to disposal and dumping of huge volumes of wastes on land. Inevitably this means that an increasing number of people are living in the 'influence zone' of sites potentially containing landfilled refuse, ground contamination, tips and lagoons.
Past, well-known disasters resulting from on-land dumps of wastes include;
- the fly ash avalanche at Jupille (Belgium) - collapse of a spoil heap resulted in a village 700m away being engulfed by fluid ash that caused the deaths of 11 people
- migration of toxic chemicals from the Love Canal site (USA) - more than 200 people living adjacent site were relocated and it was over 30 years before the state health department declared it safe for them to return
- construction of houses over contaminated fill at Lekkerkerk (the Netherlands) - the entire population of a new residential estate of 268 dwellings had to be relocated for 13 months whilst polluted ground was removed
- inundation of a school by coal mining waste at Aberfan (UK) - a sliding failure within a heap of colliery spoil developed into a flowslide which travelled at a speed of about 25km/hr and killed 144 people (116 of whom were children at school).
Examination of case histories (especially where serious loss and damage has occurred) indicates that there are several factors that play a major role in the failure of waste dumps:
- Most waste dumps have not been designed to a standard that would be expected for a conventional, major work of construction. Their construction often exhibits an unjustified degree of optimism, a casual approach to safety and the sites do not have a real design life. Even after being in position for decades the waste material within a dump is likely to be as harmful to the environment and mankind as on the day that it was deposited, because of its internal state and the nature of the waste.
- The stability of any existing landform or dump is often taken for granted. Many waste masses are in a metastable condition due to, as yet, unquantifiable effects. Closed landfills and contaminated land treated by in situ or containment methods are not immutable and are prone to degradation with time. Problems with the forgoing types of waste masses are often not recognised because there are no outward signs of impending failure and nobody is monitoring the site anyway.
- There is often inadequate provision for the control of water within waste masses. Rain and snow can overload the capacity of lagoons and drainage systems and cause overtopping of containment embankments leading to their disintegration. Precipitation can saturate landfills and contaminated land so that polluted water overflows the containment system and into the surrounding area. Surface flow of water can cause erosion of soil covers and expose wastes, leading to mobilisation and transport of contaminants. Seepage of water through the ground can reduce its strength and also lead to internal erosion and undermining.
Global climate change is now causing increased frequency and severity of extreme weather events, elevated ambient temperatures and rising sea levels. Not only do these changes act to destabilise dormant non-engineered waste deposits, but they also mean that current design standards for engineered waste disposal sites will become inadequate. In future, we are going to see 'failure' of more and more waste dumps, with associated movement of large amounts of materials and contaminants and concomitant harm to humans and the environment.
Recent examples of serious events involving on-land waste deposits include:
Brasilian tailings dams (National Geographic, 2019)
Moscow's landfill problems (BBC News, 2019)
Radioactive waste flowing into an aquifer in Florida via a sinkhole (BBC News, 2016)
Erosion of the cover over toxic landfill (The secret life of landfill, BBC 4, 2019)
Large-scale on-land disposal of wastes is not, and never has been, a sustainable practice because it blights large tracts of land for an indefinite period of time and poses a permanent threat to the surrounding area. Failures of tips and lagoons are causing environmental disasters way beyond their boundaries - the red mud that escaped at Kolontar (in 2010) flooded 8km2 of land and caused Hungary's greatest environmental crisis ever. Mankind has been able to get away with dumping wastes on land for centuries because the waste facilities were comparatively small and isolated. But, due to exponential population growth, land, water and natural resources have become ever more precious commodities. Construction is a major consumer of natural resources and can make itself more sustainable and make disposal of wastes less damaging by re-using such materials wherever possible. This will require a big commitment from the sector as it will need to adapt and develop waste processing methods, material specifications and working practices, as well as convincing clients to pay significantly more for their projects.
To forestall even greater, and more prevalent, problems with waste dumps and repositories in the future, we need to install measures such as;
- require such works to be designed to the same standards as those for conventional civil engineering construction,
- insist that the building of waste dumps and depositories is overseen by properly qualified staff who ensure that construction is undertaken in accordance with specifications derived from their design,
- introduce regular, statutory monitoring, assessment and certification of them after construction,
- make their owners deposit a 'clean-up bond' with the government which will be retained until such time as a site is declared permanently stable.
- Find out more about realities of land-based waste disposal in Environmental Geotechnics in Practice : Introduction and case studies, available in both print and digital format.