Silent Valley, which runs up from the Welsh town of Ebbw Vale, is being restored and turned into a nature reserve managed by the Blaenau Gwent County Council and Gwent Wildlife Trust. The once post-industrial mining valley, contaminated with metal recovery waste has been cleaned up and the upper valley turned into a modern domestic landfill facility which is capped off and landscaped to become part of the nature reserve. Silent Valley is now one of the most beautiful natural environments in Gwent.
With the finished landfill profiles incorporating 80m long 1 in 2.5 slopes the challenge was to achieve a stable cap without any reprofiling or use of geogrid reinforcement. The aim was to install a multi-layered synthetic cap comprising a 1mm LLDPE textured geomembrane with a drainage capability above the membrane and a gas venting capability below.
The challenge was to provide sufficient drainage capacity on both interfaces and adequate interface shear strength to withstand the dead load of the 0.5m cover soil and live load of the construction traffic whilst placing the backfill material on this critical slope.
The required slope stability was not possible to achieve with standard geocomposites typically used for the landfill cap drainage. A geocomposite with enhanced performance was required for this 1 in 2.5 slope application.
The unique Pozidrain G geocomposite was used to provide drainage, gas venting and membrane protection. Pozidrain G drainage lattice provides additional interlocking and enhanced interface friction with cover soil material on steep slope installations. It has sufficient flow capacity in both long and cross direction to drain cover material and ensure slope stability. Shear box tests against site specific cover soil material and LLDPE geomembrane confirmed adequate Pozidrain G interface friction performance. The project was finished on time and at optimum cost resulting in an area fit for a nature reserve.
ABG Pozidrain G Geocomposite with enhanced frictional properties specifically designed for steep slope installations above and below a capping liner.
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ABG proposed the system and provided design and site specific laboratory test results. Site support during the construction and timed deliveries ensured a successful construction.
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