In this article, Eugene Gallagher, Geotechnical Associate, from the Manchester, UK office, describes a series of investigations into the performance of a 16 hectare geomembrane capping at Low Level Waste Repository, which is the UK’s principal facility for disposal of low level radioactive waste. 

The investigations were undertaken between 2010 and 2014 and some 25 years after installation of the interim cap.  This represents a significant case history, one of relatively few, describing the approaches adopted to pursue the series of investigations, the findings of that work, options considered to address the issues, lessons learnt and the intervention strategies which are under consideration in response. It also has implications for other landfill caps as it highlights the importance of construction processes, including construction quality assurance to ensure the integrity of geomembranes following placement is not adversely affected. The article also stresses the need for good record management to assess system performance in service and plan future interventions.

The article was co-authored by Low Level Waste Repository Ltd’s John Shevelan and Coffey, a Tetra Tech company’s David Tonks, Andy Belton and Ria Blackmore.  The paper followed an invitation by the editor of Geotextiles and Geomembranes to the lead author to contribute to a special issue on Developments in Geosynthetics for Environmental Protection, published in June 2016.  Eugene Gallagher was also invited to present this topic at a joint Institution of Civil Engineers (East Midlands) and International Geosynthetics Society evening talk on 17 April 2016 at Loughborough University, UK. 

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