Page 156 - Bulletin 18 2014

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By the end of the war, however, signs of a water crisis were beginning to reappear. Ninham

Shand by now an established consulting engineer, came up with a proposal to raise the
Steenbras Dam wall once again. (Fig. 3.38.) He was familiar with a new technique known as

prestressing, and believed that a 2-metre high extension could be pinned on to the top of the
dam wall. M. Andre Coyne, the French inventor of the system, confirmed that the job cold be

done, and by this means the capacity of the dam was increased by 60% in 1954.

A large new dam at Wemmershoek was designed by Ninham Shand and took care of

increased demand through the 1960s, after which the Department of Water Affairs took
responsibility for the construction of all large dams, and the supply to Greater Cape Town

was augmented by allocations from Voelvlei (1971) and Theewaterskloof (1985). Before

each new facility came on stream there would be water shortages and associated restrictions,
but the Bulk Water Undertaking was managed by a succession of very competent water

engineers – Don MacKellar, Denis Hodson, Tom Madsen and John Saunders who ensured
that difficult situations never devolved into real crises.

An Innovative Scheme

There was another twist to the Steenbras story. Walter Powrie, Neville Pells and Robin
MacKellar, partners in the company that had been founded by Ninham Shand, were toying

with the idea of using the pumped storage technique for supplying electrical power at peak
demand periods for the Western Cape, and when, in the early 1970s, Cape Town began to

experience just such shortages, Denis Palser, the City Electrical Engineer, took an interest.

The pumped storage concept is a very useful way of storing excess electrical energy. During

peak consumption times water flows under gravity from a higher to a lower dam, turning a
turbine which drives the generator producing electricity and thus helping to satisfy the

temporary demand. But in the wee small hours of the morning, when the coal-fired power

stations of Mpumalanga produce electricity for which there is no normal demand, this excess
power is used to drive pumps which return the water to the higher dam.

The Shand engineers realised that Steenbras Dam, perched high on the mountains above

Gordon’s Bay, would be ideal for such a scheme. However the existing dam would need to be
raised by a few metres to provide the best conditions for the generating process – but there