Environmental risk assessment of a closed industrial landfill

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Courtesy of ESI Ltd - Environment Specialists

Client: Waste Management Industry

Location: Closed landfill, Warwickshire, UK

Services: Hydrogeological risk assessment and Closed landfill support

Issues: Potential risk to groundwater and surface water, environment and human health. Gaps in available data for closed landfill site.

Summary: ESI undertook a desk study, qualitative environmental hazard assessment, subsequent site investigation and detailed quantitative risk assessment works for this closed landfill site. ESI was able to demonstrate that environmental risks to identified receptors were not significant, and that residual liabilities for our client were not likely to be associated with the closed landfill site. The assessment of risk was accepted by the Environment Agency and Local Authority.

ESI’s client had acquired a company that had previously operated an industrial landfill, taking domestic refuse, residues from the artificial fibre industry, automotive industry wastes and general factory wastes. There were concerns that residual liabilities may be associated with the landfill, and ESI was requested to undertake a desk study and qualitative environmental hazard assessment of the site, located in Warwickshire. The work led to site investigation and detailed quantitative risk assessment.

ESI was able to demonstrate that environmental risks to identified receptors were not significant and that residual liabilities for our client were not likely to be associated with the site.

The tip in question was landfilled through much of the 20th Century by various landfill operators. Historical research indicated that a leachate treatment plant had been installed but was disused and leachate had the potential to discharge to a nearby Brook which in turn discharged to a local nature reserve. 

The environmental hazard assessment identified a number of potential source-pathway-receptor linkages. Sources included landfill leachate (comprising dissolved heavy metals and ammonium, petroleum hydrocarbons, organic solvents and acids and alkalis), asbestos-containing materials in waste and landfill gas. The site was bounded on two sides by canals and underlain by the coal measures minor aquifer. Site use was informal leisure use such as dog-walking.

A detailed site investigation was undertaken which included the drilling of shell and auger boreholes, rotary boreholes, geoprobe holes and trial pitting.  Health and Safety protocols were designed to mitigate risks due to chemical waste and asbestos fibres present in drilling arisings and high concentrations of methane and carbon dioxide deriving from fill materials. Soil, leachate and water samples were taken and submitted for laboratory analysis.

A human health risk assessment was undertaken and site specific assessment criteria (SSAC) were derived for a female child receptor playing on the open space that constitutes the current landuse.  On the basis of the model outputs, it was concluded that the risk to the identified receptor was insignificant.  With respect to methane and carbon dioxide, the identified risk was suffocation at high concentrations in confined areas.  As the site constituted open space, the risk was considered to be insignificant.

Conceptual model development and water balance assessment indicated that discharge of leachate was unlikely to present a risk to controlled waters receptors. Groundwater transport modelling using ESI’s Risk Assessment Model (RAM) indicated that risks to groundwater receptors were very low. The assessment of risk was accepted by the Environment Agency and Local Authority.

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