Controlled Waters Risk Assessments for Sludge Assets
Client:
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United Utilities plc
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North-west England
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| Services: |
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Controlled Waters Risk Assessment
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| Issues: |
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United Utilities Water plc. (UUW) has Wastewater Treatment Works that are permitted under the Environmental Permitting Regulations (England and Wales) Regulations 2010. These sites were given an Improvement Condition by the Environment Agency to ensure the safety of their sludge related assets. Secondary containment was recommended for all these sites but this is a very expensive and large scale undertaking. It seemed likely that some of these sites might not pose a significant risk to receptors even in the case of a catastrophic failure, and it was therefore decided to undertake a more detailed and quantitative assessment of the risk to controlled waters before any large scale engineering containment methods were considered |
Summary:
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The outcome of the risk assessments demonstrated that the majority of the assets do not pose a risk to controlled waters, either due to the presence of low permeability deposits which provide protection to deeper aquifers or due to the sites not being situated over aquifers at all. Therefore, United Utilities are able to focus resources on the minority of sites where there might be a small risk of pollution following an asset leak. |
ESI collated information on the assets and geological and hydrogeological conditions at the sites. These were used to develop a conceptual understanding of potential source, pathway, receptor linkages. Quantitative risk assessment, using the RAM risk assessment tool, was then undertaken to demonstrate the level of risk these tanks pose. Scenarios included both catastrophic (tank failure) and chronic (small long term leak) tank leaks. Due to the complexity of the geology at many of the sites, the models represented multiple source, pathway, receptor linkages with site specific water balances to apportion the fluxes to the relevant pathways. The model made predictions at both surface water and groundwater receptors.
Please contact ESI for more information on 'Controlled Waters Risk Assessments for Sludge Assets'.
