28
CONSTRUCTION WORLD
JUNE
2014
PROJECTS AND CONTRACTS
DWSP is designed to cater for the
long term needs of the impor-
tant lowland areas of Lesotho.
In particular, it will provide a new
raw water supply for the country’s capital,
Maseru, and the surrounding area, which has
historically suffered from water shortages.
Ash Resources has supplied approxi-
mately 22 000 tons to date of its classified
siliceous fly ash DuraPozz® to Sinohydro,
the Chinese contractor for the key compo-
nent of the MDWSP, the Metolong Dam,
which impounded on 17 February 2014,
together with its inlet tower and associ-
ated pumping station. A further estimated
11 000 tons is required to complete the dam
contract, which is expected to be achieved
in September 2014. Ash Resources has also
delivered approximately 4 000 tons of fly
ash to other contractors and ready-mixed
concrete producers for the construction of
the MDWSP’s water purification works, a raw
water reservoir and portions of the pipelines.
Metolong Dam is a 83 m high roller
compacted concrete (RCC) dam with a design
crest length of 280 m, constructed on the
Phuthiatsana River, approximately 35 km
from Maseru. Contractor, Sinohydro estab-
lished an on-site batch facility to provide
the estimated requirement of 280 000 m³ of
RCC and 40 000 m³ of conventional vibrated
concrete (CVC). The Beijing based contractor
is a global top-ranking construction and
hydropower group that is involved in a range
of projects on the African continent and has
worked on major international projects such
as China’s Three Gorges Dam, the world’s
largest water scheme.
“Our association with Sinohydro began
over three years ago with the construction
of the Kariba North Bank project in Zambia,”
says David Kanguwe, Ash Resources’
commercial manager. “For Metolong Dam,
they required a consistent quality classified
fly ash and wanted to deal with a company
that had a track record for reliable supply of
large quantities of quality fly ash to major
dam construction sites.”
A high fly ash content in the RCC for
construction of a dam helps to control heat
of hydration during mass concrete pours.
Arising from discussions in Maseru with
consultants, Arcus GIBB and Sinohydro,
Lafarge’s Quality Department Southern Africa
(QDSA) advised on the mix designs for RCC
and CVC and conducted laboratory evalu-
ations. The outcome was that Sinohydro
accepted QDSA’s mix design recommenda-
tions for the RCC mix to contain 66% and the
CVC mix (grade 25/38) 52% of Ash Resources’
DuraPozz® classified siliceous fly ash.
The recent abnormal rainy season has
had a significant impact on the Metolong Dam
construction programme, which has contrib-
uted to pushing back the anticipated comple-
tion time of April by five months. Delivering
to the Metolong project site had its own
challenges: in addition to coping with border
crossing delays, the final 18 km of dirt road
were frequently flooded and damaged by the
rains. Apart from this, the very nature of dam
construction leads to considerable variance
in the fly ash usage – when the conditions
were right, the contractor did major non-stop
pours, and the consumption of cementations
materials increased dramatically. However,
Ash Resources has a great deal of experi-
ence to call on from the days of supplying
the Lesotho Highlands Water Scheme and,
in particular, supplying almost a quarter of a
million tons of fly ash for the construction of
the enormous Katse Dam.
“While being able to guarantee supply
of large quantities of consistent high quality
fly ash from our SANS 50450 certified plants
is a major competitive advantage for us,
our aim is to satisfy a construction contrac-
tor’s needs in all respects,” adds Kanguwe.
LESOTHO’S
METOLONG DAM
close to completion
Ash Resources, South Africa’s leading manufacturer and
supplier of fly ash products, is adding the Metolong Dam
Water Supply Programme (MDWSP) to their impressive track
record of water infrastructure projects in Lesotho.
Approximately 33 000 tons of DuraPozz® classified fly ash for the construction of Metolong Dam, once
completed in September 2014, would have been supplied by Ash Resources.
Sinohydro batch plant on the Metolong Dam site.
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