Background Information and Challenge
The Northern Area Waste Management Authority (NAWMA) manages waste and resource recovery for the Cities of Gawler, Playford and Salisbury, the Barossa Council, and other regional Councils in South Australia. NAWMA’s Uleybury landfill incorporates best practice principles and receives domestic and residual industrial waste that cannot be effectively recycled, re-used, or recovered.
With ongoing demand, the landfill facility is progressively expanding with a 15,000m2 extension of the existing landfill cell to increase capacity.
The Engineering Designer identified a range of issues to consider during the development of the design:
- Resilience of the liner in the landfill service conditions.
- Stress crack resistance of the liner.
- Ability of the liner on the batter slopes to accommodate movement of the overlying waste.
- Friction interface between the liner on the batter slopes with the underlying coated GCL and overlying geotextiles.
- Wrinkle growth due to exposure and thermal expansion and contraction and ambient temperatures ranging from -5°C to +45°C.
- Welding compatibility of new liner geomembrane material with the current geomembrane liner installed in the existing landfill cell.
After discussing the landfill expansion project goals with the Engineering Designer, Layfield proposed a 1.5mm Enviro Liner® 6000 with a textured bottom and white top sides (EL6160).
Enviro Liner® 6000 geomembrane material was selected due to its excellent chemical resistance and superior environmental stress crack resistance with greater elongation properties to accommodate potential movement. The texturing, with an asperity height of 0.4mm on the bottom side of the liner, would help increase the friction interface between the liner and the coated GCL. The white top surface of the Enviro Liner® 6000 would significantly reduce the liner’s thermal expansion and contraction and corresponding wrinkle growth. The existing UV package would provide sufficient UV stability for the liner while it was exposed on the batter slopes.
After manufacturing the geomembrane, additional high-pressure oxidation induction time (HP-OIT), stress crack resistance (SCR), and oven aging testing were undertaken in addition to the standard suite of MQA testing by Layfield to confirm material properties.
The installation contractor completed several on-site welding trials to determine the optimum welding parameters for welding the new Enviro Liner® 6000 to the existing landfill cell liner. The material was then progressively installed over several weeks, coordinating the final preparation of the earthen surface, installation of the GCL, geomembrane, and cushion layers.
The Enviro Liner® 6160 material has provided excellent properties during the construction phase of the landfill expansion, fulfilling all of the Engineering Designer’s requirements.
The stability of the liner on the batter slopes due to the textured surface and minimal wrinkling due to the white top surface has allowed trouble-free construction of the landfill cell.