Waste & Containment

The preferred lining system for landfill to the early 1980s was a Compacted Clay Liner (CCL) which was fundamentally designed to minimise the passage of leachate. With increasing waste volumes and more hazardous leachate chemistry, CCLs have potential to react adversely with a resultant loss of performance and potential for leachate contaminating groundwater. The design aim now is to contain and collect leachate which is achieved through engineered geosynthetic lining systems. The preferred composite lining system for landfills has become a polymeric primary liner (generally HDPE), with a secondary liner below comprising of either a CCL or Geosynthetic Clay Liner (GCL).

Geofabrics offers comprehensive lining systems comprising our Elcoseal GCL (made in Australia) and Coolguard, a speciality geomembrane designed for applications in extreme chemistry.

Our solutions for the landfill sector also include cushion geotextiles for liner protection including Texcel and bidim at a fraction of the cost of a sand protection layer.

Trinet triaxial geonets provide a cost effective alternative to traditional gravel drainage layers on steep side slopes. The heavy duty geonet provides high flow rates under large confining pressures as the three dimensional structure is able to maintain a stable shape which resists crushing. The replacement of a gravel layer with Trinet will remove the need for liner protection geotextiles.

Megaflo flat panel drains provide a simple alternative to trenched round pipe drainage systems which are difficult to construct and are often weak points in any lining system. Megaflo is able to resist large vertical loading encountered in many landfill applications, properly designed systems have proven effective under fill depths of up to 70m.

The leachate collection system is designed based on the potential leachate volumes generated but the primary function is to prevent heads acting directly on the lining system. The traditional configuration is a 300 mm drainage aggregate covered by a bidim separation geotextile.

bidim C Range nonwoven geotextile is the World’s first commercial conductive geotextile made possible with imgne® X3 geotextile graphene technology. bidim C Range offers an effective, lower cost means for designers and installers of lining systems to undertake liner integrity surveys in newly constructed containment cells. 

The technology built into bidim C Range only requires overlap of the geotextile to deliver the conductivity required for pin hole detection in a membrane layer above using standard liner integrity survey equipment. There is no welding required and the geotextile does not contain any wires - meaning installation does not require special skills or equipment. Just roll it out with approximately 100 mm overlap on all edges. Spark or arc testing can be conducted to ASTM D7953 at as low as 1kV. 

All landfills require some sort of capping system to prevent continued leachate generation and prevent the dispersion of gas which has a harmful effect on the environment.  The choice of liner for a landfill cap is heavily dependant on the likely settlement of the waste in the landfill cell. Factors such as depth, compaction level, and make up of the waste will impact on the potential settlement. In cases where large differential settlements are expected, the use of traditional lining membranes such as HDPE (max. strain 0.25%) and compacted clay liners (max. strain ~ 7%) are not recommended. GCLs provide a distinct advantage in this area with allowable elongations ranging from 15% for the standard grades, to 30% for the heavy composite grades.

Geofabrics has experience in construction methodology and is able to advise on techniques and products that suit the site specific application as well as site specific shear testing.

Geosynthetics can be used extensively to cap tailings dams or waste rock detentions. Capping can be achieved using low permeability Elcoseal GCL and geomembrane barriers to meet regulatory guidelines, incorporating Megaflo and drainage geocomposite layers to remove head pressures acting on the liner. Geosynthetics can be used in permeable barriers to rehabilitate waste rock and problem soils, providing flexible solutions to treat dispersive/reactive soils, restrict Acid Metalliferous Drainage and Acid Sulphate Potential. Reagent barriers containing media designed to enter solution and treat subsoils can be encapsulated in bidim geotextiles,with careful analysis of the filter properties enabling the choice of suitable geotextile such as Texcel or bidim.

Significant quantities of gas are generated from the decomposition of waste in a landfill.  The most common gases produced are methane, carbon dioxide and other odorous compounds.  It is essential that these gases are vented and captured by an efficient gas collection layer to minimise air pollution.  If gas collection is not provided, breaches in the capping / closure system can occur.

In capping layers, the use of Flownet biaxial geonets is often used to remove gas from below the liner and prevent ‘boils’, or localised areas of high gas pressure, occurring in the liner. The gas is able to flow quickly through the two dimensional structure to discharge points where the gasses are treated.

Removing fine sediments from site runoff can be a costly exercise, sediment management should include surface erosion products and silt fences to minimise volumes entering suspension. A cost-effective alternative is to make use of geosynthetic dewatering systems. Geotube® dewatering technology uses high strength geotextiles with unique filtration and retention properties to provide solutions to mining and mineral processing. Dewatering of waste water and sludge is commonly achieved by pumping the slurry into permeable geotextile tubes, treating with site specific flocculants and allowing the moisture to either evaporate through the geotextile or drain through the geotextile pores under significant pressure. The run-off from the dewatering process can be reused or treated and returned to native waterways while the sediment or waste can be reprocessed or detained.