By 2012, the capacity of the landfill site at Mpofana, near Mooi River in KwaZulu-Natal, was reaching saturation point.

Having started as a local refuse site for domestic waste, mainly from the Bruntville settlement, this informal landfill could no longer cope with the volume of waste being dumped there. It was decided to construct a new landfill site using Kaytech’s EnviroFix geosynthetic clay liners, as much for their easy and rapid installation as for their durability and cost effectiveness.

Due to the complete lack of a waste selection process, Mpofana Landfill had also become a dumpsite for any form of waste. Of major environmental concern to the uMgungundlovu District Municipality, was contaminated water seeping from this landfill site into the pristine Mooi River, which flows just a few hundred metres down-valley. This would pose serious health risks to nearby communities as well as those living further downstream.

A matter of urgency

After consultation with Umgeni Water, the largest supplier of potable water in KwaZulu-Natal, and civil engineer Stemele Bosch, it was decided as a matter of urgency to formalise the Mpofana Landfill site. To prevent any further pollution of the environment, a new, formal landfill cell was carefully designed to accommodate ever-increasing waste and more importantly, to contain any contaminated water. For this purpose, a composite liner comprising Kaytech’s EnviroFix X800 geosynthetic clay liner (GCL), together with a 2 mm HDPE liner as covering was specified as a vital part of the design.

The alternative to using EnviroFix for the new landfill was to use compacted clay layers, which are extremely timeconsuming and demanding to install. Further problems would be locating the correct natural clay in the relevant quantities, which would then require transportation to site, before careful compaction at the correct moisture content in order to achieve the desired permeability.

Since EnviroFix can, in many cases, completely replace or significantly reduce the required thickness of the compacted clay layer, less excavation and compaction are required while containment volume is increased; in a landfill site, increased airspace equates directly to increased revenues. With Kaytech guaranteeing the permeability of its EnviroFix liner and due to the ease and speed of installation provided by this top-class product, it was a simple decision for consultants from Umgeni Water to make.

The liner investigated

A proudly South African manufactured geosynthetic clay liner, EnviroFix is produced by needling a uniform layer of sodium bentonite between two durable, outer layers of geotextile. Sodium bentonite is a naturally occurring clay mineral with a structure comprising charged platelets. When it comes into contact with moisture, it swells considerably. When this occurs under confinement, it forms a lining with a low permeability, equivalent to that of approximately one metre of compacted clay.

The Thermal Lock process, a proprietary heat-treating process, is used to modify and more permanently, lock the needle-punched fibres into place. Unique properties, including increased internal shear resistance and long-term creep resistance, result from this procedure.

During installation, the needle-punched fibres hold the bentonite in place and prevent the liner from separating. EnviroFix is more durable over a wider range of installation conditions and, because it is needlepunched, any adverse effects of premature hydration during installation are greatly reduced. A further advantage in using this product is that the clay component is no longer the limiting factor on side slopes; low permeability on steep slopes is assured without sacrificing slope stability. EnviroFix is superior to compacted clay layers in terms of desired consistent permeability values by orders of magnitude.

Besides being the ideal product for lining landfills and caps, EnviroFix is also suitable for use in liquid containment structures, canals and as a secondary containment barrier in aboveground tank impoundments.

Contract intricacies

Houston Earthmoving Trust was awarded the contract to install EnviroFix as per Kaytech’s installation guidelines. Using a spreader bar and a TLB, the contractor was able to install 9 000 m² of EnviroFix X800 in only eight days, thereby expediting the construction process and completing the new cell in a far shorter period than the alternative option would have taken.

In conclusion, by installing this outstanding Kaytech product, manufactured according to a stringent quality control programme, the contractor was able to save time and money, thereby reducing the project costs. Ultimately, uMgungundlovu District Municipality will save as maintenance costs at its new Mpofana Landfill will be minimal, and more importantly, there will be less risk of pollution to the surrounding environment and local communities.