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Combined Basal Drainage & Membrane Protection
Modern landfill design requires a leachate drainage layer up to 500mm thick at the base of the cell. This fills hard won void space with equally hard won primary drainage aggregate.
Geofabrics LFX composite drainage layer
Geofabrics LFX is a composite drainage layer to be used in conjunction with only half the depth of aggregate whilst maintaining the same leachate extraction performance.
LFX provides numerous benefits to landfill engineering:
- Reduces use of expensive and scarce primary aggregate
- Void saving to allow more efficient and productive use of space
- Reduced haulage of construction materials to site – a single truck of LFX can replace up to 90 trucks of aggregate, delivering benefits to both client and contractor
- Using the composite means much lower material, transport and installation costs
- The CQA inspection can be carried out in a factory environment
- The drainage core has a proven flow rate and has been tested up to 1000kPa allowing for use in the deepest landfills.
Following European legislation, most engineered landfills are lined typically with 1m of compacted mineral liner overlain by a 2mm thick HDPE geomembrane, a thick geotextile protector and a thickness of drainage stone to collect and convey leachate. Because of concern for the longevity of landfill containment systems, the legislation has taken a conservative approach to landfill design, requiring drainage stone layers up to 500mm thick and forcing waste management contractors to fill hard-won void space with equally hard-won drainage gravel. The environmental need to incorporate safety in design militates against the environmental need to maximise void space and minimise the use of a quarried or dredged stone.
The UK Environment Agency has always welcomed innovative development in the engineered landfill lining industry. Engineered liners have evolved from dilute and disperse to a highly sophisticated engineering solution that has European legislation at its heart: the development of LFX represented an important step forward in the use of high-performance geocomposites as a leachate drainage medium in landfill containment systems.
A series of laboratory and field trials, and site installations, has been achieved as a result of collaboration between waste management companies, design consultants , Geofabrics and the Environment Agency.
Pilsworth Landfill Site, in the North of England, was the first site to use the LFX system. The site was considered typical of landfill cells in the UK and had the advantage of having two cells under construction, both with very similar shape and adjacent to each other. This allowed one to be built conventionally using a primary-aggregate, leachate-drainage blanket, and the second with a combined aggregate/geocomposite, leachate-drainage layer.
A direct comparison was made as the rainfall, waste streams and topography would effectively be identical.
Trial Study Conclusions
This project was undertaken cautiously and steadily involving all the relevant stakeholders in the project. The result has been a well-developed trial which could potentially have a large impact on the design of engineered landfills.
It has been shown that all the benefits identified can be realised with consequent cost savings, additional revenue and reduced environmental impact:
- Reduced consumption of primary aggregate
- Reduced number of truck movements lessening environmental impact
- Reduced costs for site operators
- Reduced carbon footprint
- Increased sustainability of landfill as a waste disposal option
- Increased landfill void space
- Increased ease and speed of construction
- The application of BATNEEC (Best Available Technique Not Employing Excessive Cost)
- Factory-produced and quality-assured geocomposite
An independent report concluded that the composite system is effective for leachate drainage and membrane protection. Using LFX will permit the reduction of the granular drainage layer thickness by up to 50% with the consequent reduction in both direct and indirect costs as well as a significant reduction of the environmental impact of delivery trucks.