Construction of the Hurlingham Retail Development, consisting of a 5600m2 Pick ‘n Pay Supermarket and approximately 750 m2 of line shops, included the challenge of containing the stormwater in two earth dams on the property. Property Development company Abland was responsible for heading up this development at the intersection of William Nicol and Republic Road in Johannesburg.
As part of the stormwater control on the site, contractors Stablid called in Geosynthetic experts, Kaytech to propose a solution for the lining of the earth dams. As a first step Kaytech recommended extensive smoothening of the surface, as a substantial number of large rocks were visible in the dams, which would damage any dam lining installed. Thereafter they proposed installing Kaytech’s X800 Envirofix® Geosynthetic Clay Liner.
These Geosynthetic Clay Liners (GCLs) are needle punched reinforced composites, which combine two durable geotextile outer layers with a uniform core of natural sodium bentonite clay to form a hydraulic barrier. The sodium bentonite clay utilised in EnviroFix Thermal Lock is a naturally occurring clay mineral that swells as water enters between its clay platelets. When hydrated under confinement, the bentonite swells to form a low permeability clay liner with the equivalent hydraulic protection of approximately one metre of compacted clay.
By needle punching fibres through the sodium bentonite clay layer, a completely uniform, reinforced GCL is produced – with shear strength and stability advantages important to any application.
The two earth dams on the Hurlingham location would serve as attenuation ponds for all stormwater on the site. The stormwater would be collected and fed to a 450 mm stormwater pipe and from there into a gabion structure which would serve as a filter to keep rubble out of the ponds. These gabion structures would be maintained and cleaned out weekly.
After the surface was prepared and smoothened, the Envirofix® X800 (2,000 m2) was laid and covered with a 300mm G5 material. The 300mm cover soil was compacted in 150mm layers to 93% Mod AASHTO. EnviroFix provides exceptional liquid containment due to its low permeability, high internal shear strength and protective soil covering. It can be used in reservoirs, water features, irrigation canals, as well as industrial ponds and lagoons.
Envirofix is more versatile than compacted clay. The Thermal Lock GCLs are part of an important trend toward the combined use of geosynthetics and clay materials in containment applications. In a typical composite liner system, GCLs work synergistically with polyethylene and other geomembrane materials to maximise liner efficiency.
To manage the water levels within the ponds a manhole was installed directly on top of the cover layer. This drain consists of a 160mm inlet pipe installed at the base level. In line with the inlet pipe a 300mm stormwater pipe was installed under the concrete spillway at a 2% slope angle. Should the water levels rise above the manhole a concrete spillway was constructed to allow water to flow over.
With Kaytech’s EnviroFix, the Hurlingham Centre can be assured that its two earth dams will contain any amount of storm water that comes its way.
For more information on Kaytech products and systems, visit www.kaytech.co.za