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Gallagher E.M.,Tetra Tech Inc. | Tonks D.M.,Tetra Tech Inc. | Shevelan J.,Low Level Waste Repository Ltd | Belton A.R.,Tetra Tech Inc. | Blackmore R.E.,Tetra Tech Inc.
Geotextiles and Geomembranes | Year: 2016

Investigations have been undertaken at a 16 ha landfill capping to assess performance of the geomembrane component some 20–25 years after installation. The site has been the subject of quite extensive monitoring together with hydrological and other studies. Although environmental monitoring has shown no major concerns, there have been discrepancies in calculated water balance, leading to the recent investigations reported here. The capping, which is an interim solution, comprises about 1 m of cover soils over 0.375 mm LDPE geomembrane and surrounded by a perimeter drain. A robust final capping system will be constructed at a later date. Various remedial works were undertaken between 2010 and 2014 at the cap perimeter drains, also at a series of gas vent/probe holes through the geomembrane, to address the discrepancies in water balance, and the opportunity was taken to investigate the condition of the geomembrane which revealed a series of unanticipated gaps in the geomembrane. These investigations were subsequently extended over the whole cap to characterise the nature and extent of those defects and assess likely causes. The series of investigations reported here represents a significant case history, one of relatively few, and which describes: 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 and highlights the importance of construction processes including construction quality assurance to ensure the integrity of geomembranes following placement is not adversely affected, also the need for good records management to assess system performance in service and plan future interventions. © 2016 Elsevier Ltd


Gallagher E.M.,Coffey Geotechnics Ltd | Belton A.R.,Coffey Geotechnics Ltd | Shevelan J.,Low Level Waste Repository Ltd
Geotechnical Engineering for Infrastructure and Development - Proceedings of the XVI European Conference on Soil Mechanics and Geotechnical Engineering, ECSMGE 2015 | Year: 2015

Investigations have been undertaken at a 16 hectare landfill capping to assess performance after some 25 years. The site has been the subject of quite extensive monitoring, hydrological and other studies. Although environmental monitoring has shown no indication of large scale failure, there have been discrepancies in calculated water balance and it was thought these may be due to 96 gas vent/probe holes which had been installed through the geomembrane. The capping comprises about 1m of cover soils over 0.375mm LDPE geomembrane. Work was undertaken in 2013 to investigate these penetrations and improve the membrane- To-probe interface by installation of suitable geomembrane 'boots'. These remedial works were successful, but revealed a series of unanticipated gaps in the geomembrane. Further investigations were undertaken to characterise the nature and extent of those defects and assess likely causes. This paper describes the approaches adopted to pursue the additional investigations; the findings of that work; options considered to address the issues; and the intervention strategies which are under consideration in response. © The authors and ICE Publishing: All rights reserved, 2015.


Knight G.,AREVA | Greenwood S.,AREVA | Laker A.,Low Level Waste Repository Ltd
Nuclear Engineering International | Year: 2010

A UK nuclear industry group has developed a website, www.rwbestpractice.co. uk. that mentions best practice in waste minimization database (BPWMD) containing more than 130 data sheets on best practice techniques for waste minimization of solid, liquid and gaseous radioactive waste. The information in the BPWMD is stored within a data sheet that can be viewed in an online template or as a printable report. Each data sheet includes information under the headings that includes process description, key instrumentation and control, secondary waste arisings, and source/reference list. Each data sheet enters an extensive program of internal and independent review and approval prior to publication in the BPWMD to ensure a high level of accuracy in the data provided within the BPWMD. The Environment Agencies' Requirements Working Group (EARWG) BPWMD is a live document to be used by each operator as they move through their authorization or permitting cycle.


Limer L.M.C.,Limer Scientific Consulting Ltd | Thorne M.C.,Mike Thorne and Associates Ltd | Cummings R.,Low Level Waste Repository Ltd
Radioprotection | Year: 2011

The LLW Repository Limited has recognised the potential importance of the processes being considered in the BIOPROTA 14C working group and funded the development a new 14C model that addresses the exchange of gas in a soil-plant-atmosphere system. This model considers two regions in the above-ground atmosphere and utilises concepts from the field of micrometeorology to describe the exchange of air between these regions and losses from the area of interest. The lower layer only experiences molecular diffusion processes in relation to the movement of molecules of CO2, whereas the upper layer experiences some degree of turbulent mixing as a result of winds which flow over the area of interest. The thicknesses of these layers depend upon the canopy density, which will affect the light intensity and thus the rate of photosynthetic uptake of carbon in the canopy profile. Model results demonstrate the impacts of 14C-labelled gas from the soil upon the calculated 14C concentration in plants for a variety of plant species (pasture and garden crops) and subsequent doses to human exposure groups. The technical modelling work described has been funded by the LLW Repository Ltd in support of its 2011 Environmental Safety Case. © 2011 EDP Sciences.


Baker A.,Low Level Waste Repository Ltd | Cummings R.,Low Level Waste Repository Ltd
Mineralogical Magazine | Year: 2012

This paper provides a summary of the research programme undertaken in support of the Low Level Waste Repository's 2011 environmental safety case (ESC). The programme has been developed, based on an understanding of safety issues and the requirements of the ESC. The research requirements to underpin the safety case have been identified by means of an auditable process, and subjected to scrutiny by both the regulators and a peer review group. Key research priorities for the future are identified. © 2012 The Mineralogical Society.

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