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BEST
PR
O
JECTS
22
CONSTRUCTION WORLD
DECEMBER
2015
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:
Civil Engineering Contractors
A1
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.
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
Kusile Combustion Waste Terrace
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.