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THE EAST RAND Water Care Company (ERWAT) recently completed the upgrading of its 45 Mt per day Hartebeesfontein wastewater care works near Tembisa and Kempton Park.
Owing to the dolomitic subsurface conditions and the possibility of sinkhole formation, the design of various structures required the extensive use of Geomembrane products as underlays to prevent any possible seepage through the structures into the underlying strata.
BALANCING TANK
A 1500µ Hyperliner Geomembrane was installed under the entire area of the balancing tank, which was then overlayed with a 200 mm thick reinforced concrete slab. This membrane was also installed over the 45° sloping wall areas and under the wall/floor support beam.
Hyperliner, an ethylene vinyl acetate material, was chosen because of its excellent multiaxial deformation characteristics. This allows it to be easily installed into difficult three-dimensional corners.
The construction of this structure required close cooperation between Aquatan Lining Systems and the Grinaker-LTA concrete teams to ensure that the membrane was not damaged or ruptured during the difficult concreting operations. Close liaison was also maintained with the designers, ARQ Consulting Engineers, to ensure the watertight sealing of the membrane to the penetrating inlet and outlet structures. These structures had to be modelled due to their intricate nature. Construction traffic was carefully controlled to...