Hervey Range and Stuart Landfill Capping with Bentofix® X10F Coated GCL
Townsville City Council in the north of Queensland Australia is one of the largest regional cities in the northern part of Australia home to some 200,000 residents. The Townsville Waste Services Department issued documentation for contract in late 2014 for capping and stormwater management of its 2 largest waste facilities at Stuart landfill and Hervey Range.
Waste Facility 1: The Stuart Landfill
The Stuart Landfill Site required a previous cap to be extended and surface water to be managed through the use of berms and channels directing stormwater runoff to sediment ponds and leachate ponds to be constructed to collect continuing leachate creation from the cell.
Council engaged Golder Associates to design these facilities and the sealing element selected for the cap extension was the latest improvement in Geosynthetic Barrier Clay (GBC) Liner technology in Bentofix® X10F PE Coated GCL/GBC. The previous capping of the site used a more traditional Bentofix® GCL without coating. The advantages of the new Bentofix® X10F GBC were the PE coating offered a frictional surface for good interface shear on steep slopes and this coating faced upwards to provide greater safety against bentonite desiccation meaning the cover soil thickness could be reduced and further provided additional safety against possible issues of ion exchange and root penetration. The coating also provides an instant barrier layer against landfill gas, even prior to hydration. The installation occurred in late 2015 by the successful contractor and is performing exceptionally well.
The capping included a gabion structure to support a steepened toe area, a geogrid to relieve tension in the cover soil at steep angles reinforcing the veneer of soil and a Turf Reinforcement Matting (TRM) to protect the cover soil and reinforce vegetation.
Waste Facility 2: The Hervey Range Landfill Site
Council engaged Golder Associ The Hervey Range Landfill Site required a cap to be installed and surface water to be managed through the use of berms and channels directing stormwater runoff to sediment ponds. The site to be capped was quite difficult due to the long slope lengths, relative steepness and adjacent waterway. The long slope lengths were divided into continuous runs that suited roll lengths to be supplied and rolls were lapped within intermediate trench berms that doubled as a means to remove runoff water from the slope surface.
As with Stuart Landfill, the design was completed by Golders and the same Bentofix® X10F friction coated GCL was selected for the same reasons/benefits as above. The GCL was installed with the coating upwards as discussed above.
A geonet composite drain was placed on top of the coated GCL for surface water drainage. With the Bentofix® X10F PE coating facing up against the drainage composite, the GCL was protected against any potential bentonite erosion as suggested in GRI-GCL 5 and ensured the GCL did not intrude into the geonet.
Where required on steep slopes, a geogrid reinforcement was used on top of the drainage composite for veneer stabilisation.
Interface shear testing was conducted with material from site during the design and construction phase to check the stability of the capping design.
To prevent gas migration from the closed landfill being capped, the Bentofix® X10F material was installed with butyl tape sealing the joints between adjacent Bentofix® rolls. This was applied to the coated side.
Bentofix® is the original needle-punched, thermally locked GCL introduced globally by the Naue company of Germany in 1987. This robust, versatile product provides the highest safety standards and cost efficiency available. Once hydrated, Bentofix® is an effective barrier against liquids, vapors and gases.
As Bentofix® contains the highest quality natural sodium bentonite, an immediate swelling occurs following installation to ensure a water tight seal and continued protection against possible unexpected mechanical damage during installation or in the future. The sodium bentonite powder is sandwiched between two layers of encapsulating geotextiles to absorb tensile loads imparted on the GCL and provide excellent multi-axial strain behaviour. Bentofix® needle-punched GCLs retain their sealing capability under high elongation ensuring continued performance under potential differential settlement in landfill capping systems.
Bentofix® addresses the often critical issue of interface friction angle with the surrounding soil / other components and the mechanically bonded nonwoven geotextiles provide the shear resistance necessary for even the most demanding applications. This fibre reinforcement prevents lateral migration of the bentonite.
Some 100,000 m2 of Bentofix® X10F BFG5300 coated GCL was procured and successfully installed over the 2 sites through the installation partnership of the main contractor and liner subcontractor. Works were completed in 2016.
Installation of Bentofix® coated GCL is quick and easy. It is unrolled on site and overlapped at the longitudinal joints without the need for additional bentonite or additional work. Technical support and site visits were provided by Global Synthetics as the distributor of Bentofix® GCL and this led to the project being completed successfully.
If you would like to know more about our Geosynthetic Clay Liners, Geonets or any other products on offer please go to our contact us tab at www.globalsynthetics.com.au and you can speak with our experienced Global Synthetics representatives relevant to your location.