Potential pollution risks of historic landfills on low‐lying coasts and estuaries

Abstract

Historically, it was common practice to dispose of landfill waste in low‐lying estuarine and coastal areas where land had limited value due to flood risk. Such ‘historic landfills’ are frequently unlined with no leachate management and inadequate records of the waste they contain. Globally, there are 100,000s such landfills, for example, in England there are >1200 historic landfills in low‐lying coastal areas with many in close proximity to designated environmental sites or in/near areas influencing bathing water quality; yet, there is a very limited understanding of the environmental risk posed. Hence, coastal managers are more likely to select conservative management policies, for example, hold‐the‐line, when alternative more sustainable policies, for example, managed realignment, may be preferred. Some historic coastal landfills have already started to erode and release waste, and with the anticipated effects of climate change, erosion events are likely to become more frequent. Strategies to mitigate the risk of contaminant release from historic landfills such as excavation and relocation or incineration of waste would be prohibitively expensive for many countries. Therefore, it will be necessary to identify which sites pose the greatest pollution risk in order that resources can be prioritized, and to develop alternative management strategies based on site specific risk. Before such management strategies can be achieved there remain many unknowns to be addressed including the extent of legacy pollution in coastal sediments, impacts of saline flooding on contaminant release and the nature, behavior and environmental impact of solid waste release in the coastal zone. WIREs Water 2018, 5:e1264. doi: 10.1002/wat2.1264 This article is categorized under: Engineering Water > Sustainable Engineering of Water Science of Water > Water and Environmental Change

Risk screening assessment for ranking historic coastal landfills by pollution risk

“…Liquid sludges contain chemical wastes, sewage sludge, and industrial wastewater mixed with municipal solid waste (Environment Agency 2013), but no information could be found to indicate how hazardous they are in relation to other waste types. However, as historic coastal landfill sites typically pre-date regulations controlling which chemicals are disposed of (Brand et al 2018), liquid sludge landfills may contain chemical wastes that would not be accepted at modern landfills for special waste, therefore, in the absence of better data they have been assigned the highest hazard rating. Landfills where the contents are classified as unknown have also been assigned the highest hazard rating as they may contain liquid sludge.…”

“…There are insufficient data to determine the release of contaminants into the water column by leaching (Brand 2017;Brand et al 2018). However, it is possible to rank the hazard posed by leached contaminants using the amount of waste eroded and waste type as proxies for the maximum mass of contaminants that could leach, and by considering dilution in the receiving waters.…”

“…For example, in England there are over 1200 historic landfills in coastal and estuarine locations that are low-lying and have a high risk of sea flooding (i.e., ≥0.5% annual probability) and (or) erosion if not adequately defended; without intervention, 10% are anticipated to start eroding by 2055 (Brand et al 2018). The likelihood of these historic coastal landfill sites flooding or eroding is increasing due to climate change effects, such as increased sea level and more frequent extreme weather events, and this may have consequences for pollutant release.…”

“…Inundation would increase leachate production, but significant dilution in open waters would minimise risk. Solid waste is usually fully contained and isolated from the marine environment by capping materials, and is often protected by flood defences (Brand et al 2018); however, historic landfills and their defences are increasingly at risk of breaching, because inundation will increase the probability of failure through erosion, piping or excessive seepage (Bujis et al 2007). …”

“…This poses a significant challenge to coastal managers as mitigating the risk from all historic coastal landfills is likely to be prohibitively expensive (Weber et al 2011;Cooper et al 2013). Therefore, it is essential to prioritise regional and national expenditure by mitigating those sites that pose the greatest pollution risk (Brand et al 2018).…”