Civil Engineering January-February 2022 | Vol 30 No 1

Civil Engineering January/February 2022 43 corroborates the confidence with which the National Dam Safety Surveillance Office deferred the rehabilitation project. One can only hope that through effective siltation management, the loss in storage capacity will be minimised in order to ensure that this dam (which served generations before) will still serve many more generations to come. REVIEW BY ALASTAIR MORGAN (PR ENG, FSAICE), SAICE HISTORY AND HERITAGE PANEL Graaff-Reinet’s chief historical source of water supply, Van Ryneveld’s Pass Dam, situated on the upper reaches of the Sundays River, was constructed between the years 1920 and 1925 by the Irrigation Board of the same name, and was engineered by the (then youthful) South African Irrigation Department, forerunners of the Department of Water Affairs. A coffee table book has been published by the Graaff-Reinet Museum whose re- search of the project has been generously supported by numerous local donors (in- cluding owners of valuable photographic material) and volunteers. Selection and interpretation of the photographs was undertaken by retired civil engineer and SAICE member Johannes Haarhoff, to whom we are indebted for the opportu- nity to review this work of most valuable historic civil engineering interest. Eminent names such as AD Lewis and, co-incidentally for South Africa’s subsequent water engineering heritage, the names KR Shand, HR Roberts, J Claassens, WJ Pike, and W Pullen, appear in the professional credits for the design and construction of the dam. A mass gravity structure with an ungated crest spillway, it is of roughly triangular cross-section which tapers from a 30 m base to a roughly 3 m crest, with a total height of 48 m and length of 380 m, commanding a catchment of approximately 3 800 km 2 . An intriguing aspect of the crest spillway design is the entire downstream facing of the dam which is shaped with approximately sixteen levels of distinc- tive alternating and projecting steps, in rather “castellated” fashion, as the primary energy dissipation mechanism – the equivalent to the Roberts Splitter concept of more recent years, which was a design introduced by Col. D F Roberts roughly 15 years later on Loskop Dam and since replicated widely in South Africa and abroad. The book and photographic record trace the history of Graaff-Reinet’s water problems since its founding in 1786, albeit that the town is situated right on the banks of the Sundays River. In addition to the copious dam construction records, the book is replete with photographs from the earliest years of “flimsy structures which were partially washed away with every flood event”, weirs and pipelines from a well dug in the bed of the Sundays River, to old furrows which served the town, and the 100 km network of downstream canals and open channels, flumes and distribution works constructed with the dam, and designed then to also supply the downstream village of Adendorp and Kendrew Irrigation Settlement. Of equal fascination in viewing this construction record today were the ar- rangements for supply and transport of aggregates and rock (by both mule-power and a light Bagnall steam locomotive- powered railway), quarrying and crushing of the hard rock dolerite, concrete batching and lifting onto an overhead cableway (Blondin-style), and concrete supply chute for precise placement, including placement of massive hard rock dolerite boulders within the heart of the concrete structure, control valves and river (flooding) bypass arrangements during construction. The book concludes with numerous photographs showing formal sittings of dignitaries of the day – Irrigation Board members and senior construction staff, and all manner of less formal construc- tion worker photos. Altogether, a most remarkable col- lection of photographs and record of a bygone project designed to satisfy a significant need at the time, and tame the forces of nature, although not without its present-day challenges, but nevertheless a civil engineering construction to be celebrated and archived with pride! For more information Johannes Haarhoff SAICE History and Heritage Panel johannes@haarhoff.org.za Concrete for spillway piers being placed using an aerial cableway in late 1924 Shuttering for steps on the downstream face, with the realigned Van Rynevelds Pass in the background