Assessing the Risk of Pollution from Historic Coastal Landfills

In England, 1264 historic landfills are in coastal and estuarine locations that are low-lying and at risk of flooding and/or erosion if flood defences are not adequately maintained. With increases in sea level, extreme weather events and coastal erosion predicted due to climate change, it is increasingly likely that these landfills will be inundated or breached, which could result in the release of contaminants through leaching or direct release of waste into the intertidal zone. Prior research has focused on the risk of pollution from landfill leachates under normal operating conditions, i.e. waste is fully contained and the landfill is not flooded. This is the first research to assess the risk of estuarine and coastal pollution in the event of historic coastal landfills in England being inundated or waste eroding from them. An investigation of two landfills in Essex has found that contaminant concentrations in a variety of solid waste materials exceeded sediment quality guidelines, indicating there is potential for adverse effects on flora and fauna if historic landfills erode and waste is incorporated into coastal sediments. Leaching experiments have demonstrated that seawater flooding of landfills could increase the proportions of metal contaminants released by up to 5,450% compared to freshwater flooding, but adverse effects on surface water quality from leached metals are unlikely for the research sites due to high levels of dilution in the estuary. The large number of historic coastal landfills, and limited management resources, mean it is necessary to prioritise allocation of remediation funds to sites which pose the greatest pollution risk. Previous methods required extensive data collection to assess the risk of pollution from eroding waste. A new risk screening assessment method is proposed that utilises existing datasets to assess the risk of pollution from historic coastal landfill sites and prioritise them for further investigation/remediation