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ST CONSTRUCTION OF THE 1 ENHANCED BARRIER SYSTEM IN THE WORLD www aquatan com 27 11 974 5271 aqua aquatan com
INTRODUCTION Geosynthetic materials have been successfully installed as effective barriers in various types of earth and concrete structures over the past 50 years However as technology and research in the geosynthetics field evolved it was found that composite liners have certain limitations and that heat can significantly decrease the service life of geosynthetic components According to the highly respected US Environmental Protection Agency current standards do not adequately address toxic pollutant discharge frequently resulting in toxic chemical seepage from unlined ponds and dry waste landfills into ground and surface waters Although the Agency s concerns refer mainly to pollution caused by coalrelated products the reality is that clean water is the source of life and hence it is critical to a sustainable future The worldwide survey of regulatory standards for waste management and pollution control GRI Report No 34 of 2007 GRI s Second Worldwide Survey of Solid Waste Landfill Liner and Cover Systems indicated that authorities Page 2 of 8 prefer geosynthetic composite liners for pollution control over clay and modified soil liner systems COMPOSITE LINER A composite liner can be defined as a flexible membrane liner in intimate contact with a mineral liner The mineral liner can either be a compacted clay liner CCL or a geosynthetic clay liner GCL THE EBS PROVIDES DESIGNERS WITH A PRACTICAL LOWMAINTENANCE AND COST EFFECTIVE SOLUTION TO ADDRESS THE REQUIREMENTS ENFORCED BY REGULATORS The performance of such composite liners should be evaluated based on total solute transport which considers both advective losses and diffusion of volatile organic compounds VOCs from the waste stream Foose et al 2002 Construction phase influences The climatic conditions that are prevalent during construction can significantly reduce liner performance Sunshine may induce desiccation cracking of the clay component in particular of pre hydrated and uncovered GCLs as well as induce wrinkles in the geomembrane which would lead to increased advective losses Excessive rain on the clay component can lead to displacement of the fine fraction at the interface and resultant pervious zones while wind too can displace the fine fraction which is critical to controlling impermeability Hydration of the GCL component of a composite liner prior to its exposure to leachate is required However this hydration should take place after application of a normal load Vangapaisel et al 2002 This is extremely difficult when the GCL is part of a composite liner and isolated from soil moisture by either the leakage detection system or underlying secondary liner geomembrane Pre hydration by means of spraying water on the GCL immediately prior to covering with a geomembrane induces damages such as squeeze of the bentonite and preferential flow paths through desiccation cracks The failure to pre hydrate a GCL prior to its exposure to
ST CONSTRUCTION OF THE 1 ENHANCED BARRIER SYSTEM IN THE WORLD www aquatan com 27 11 974 5271 aqua aquatan com
