Construction World December 2015

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Civil Engineering Contractors

Kusile Combustion Waste Terrace

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WBHO was awarded the Kusile Ash Dam contract in 2011, but due to permitting issues, construction only commenced in the third quarter of 2012. A major component of this contract is to line the proposed ash dam area. This opera- tion consists of a complex layer of different liner materials all aimed at preventing harmful substances from coming into contact with the environment. The sequen- tial set of operations involved in achieving this target is summarised in the following major operations:

1. Topsoil removal: vegetation is cleared and grubbed from the work area, topsoil is then removed and stockpiled for later reclamation works 2. Surface preparation: Exposed soil is ripped to 200 mm depth, moisturised, blended spread and compacted to achieve a smooth organic matter and stone free surface to receive the first bottom HDPE liner layer. 3. Bottom liner: The approved soil surface is then covered with a 2 mm double textured liner, welded, quality checked and handed over. 4. Bottom geotextile: The bottom HDPE liner is then covered and protected with an A8 Bidim layer. 5. Geo-cell: A 50 mm geo-cell matt is stapled together and stretched out over sloped areas, this is to prevent erosion in the leak detection area. 6. Washed river sand: a 100 mm washed river sand laver is spread over the Geo-cell and A8 bidim layer, which acts as a leak detection layer. 7. GCL: A Geosynthetic Clay Liner layer is then placed to cover the washed river sand layer. 8. Top liner: the GCL is covered with a 2 mm double textured liner, welded, tested, quality checked and handed over. 9. Top Geotextile: The top 2 mm HDPE liner is protected by an A8 Bidim layer.

10. Drainage layer: The liner and associated sandwich is them covered with a 300 mm drainage layer of G5 gravel. 11. Drainage pipes: A network of 50 mm perforated drainage pipes is then installed 200 mm deep in the drainage layer, cradled by washed sand and rapped in A4 Bidim. 12. Tie in: the perimeter of the HDPE liner ties into a leak detection channel connected to a concrete drain. This tie in consists of two rubber gaskets between the concrete and a stainless steel baton with holding down bolts every 250 mm. The first two contractual milestone dates on this contract was achieved and final comple- tion is expected within the allotted contract period in 2016.

Project information • Company entering: WBHO Construction

• Project start date: April 2012 • Project end date: April 2016 • Client: Eskom

• Project team: Kusile Executive Team • Main contractor: WBHO Construction • Principal agent: Eskom • Project manager: WBHO Construction • Consulting engineer: Worley Parsons • Design engineer: Knight Piésold Consulting Engineers • Project value: R1,1-billion

2 15 BEST PR O JECTS

CONSTRUCTION WORLD DECEMBER 2015