Lean Quarry landfill site near Liskeard is an important facility for residential and commercial waste disposal in Cornwall. It is located in an environmentally sensitive area and therefore subject to close Environment Agency supervision. The site also accepts waste from Devon, and this extra volume of waste meant that additional capacity was required. Viridor Waste Management Ltd approached SLR Consulting to design a new cell for the site.
A new 45m deep landfill cell was required at Lean Quarry landfill using cost effective geosynthetic materials suitable for a deep application.
The requirement was to design a geosynthetic lining solution that would comprise of a double lining system (GCL and HDPE membranes), geocomposite drainage/protection layer on steep 1 in 2.5 basal side slopes with drainage stone on the cell base (10/20mm layer below the 20/40mm granite).
The geocomposite drainage/protection layer would be exposed to sunlight for several months until the waste was placed, so must be highly UV stable. In addition, to demonstrate adequate protection of the geomembrane, the geocomposite would need to pass a cylinder test to Environment Agency standards. Furthermore, the geocomposite must resist long-term compressive creep under the pressure of 45m of waste.
The designer SLR Consulting worked with ABG to develop a geosynthetic drainage and protection solution that would provide the required puncture resistance and flow capacity and ensure effective geomembrane protection and leachate drainage.
ABG’s Pozidrain Protector 745 geocomposite drainage layer with enhanced protection and UV resistance was specified and installed on top of the 2mm HDPE textured geomembrane on steep side slopes. SIM tests confirmed that the compressive creep was less than 20% in 120 years. Environment Agency cylinder test results for the Pozidrain Protector and stone material from this site indicated sufficient puncture resistance and protection performance, achieving the required factor of safety for the 45m deep installation and 1,200kPa pressure (2.5 times service loading).
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ABG provided technical advice and design assistance, including cylinder testing and flow capacity calculations.
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