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The Story of the Sendelingsdrif Pontoon
by Dr Peet van der Walt: International Transfrontier Park Project Coordinator
The design and use of pontoons is an interesting world wide and century’s old technique used to transport people and goods across rivers. Only a few pontoons are still in use in the African river transport business. Technical progress has increasingly favoured bridge building. The 16 October 2007 inauguration of the pontoon at Sendelingsdrif in the lAi-lAis/ Richtersveld Transfrontier Park signified transport history whereby the older technique was favoured over the new. This pontoon is only the second of its kind in the country – the other is along the Breë River in the southern Cape.
Sendelingsdrif has been a traditional crossing place for missionaries visiting the nearby historical Nama settlement Kuboes since 1806. The river, with names galore, was for centuries a linear oasis for migrating stock farmers in search of grazing in this transitional riverine zone that helped bridge the grazing gap between winter and summer rainfall.
The lower Orange River is known for a series of fords – Olyvenhoutsdrift (Upington), Schuitdrift (intensively used from 1874 – 1951), Velloors-, Pella-, Aris-, Ramans- and Sendelingsdrif. The use of these fords by man crippled the river by altering seasonal flow rhythms. The river's grandeur has been under more pressure since the 1970s by a series of giant tourniquets that have changed the flow regime and the drama of nature’s glory. These tourquinets are the dams in the middle reaches of the river, including the then Hendrik Verwoerd (1972) and P M K le Roux (1978) dams, followed by the Khatse (1997) in upper Lesotho.
In more recent years, the construction of four high water bridges (Upington, Onseepkans, Vioolsdrift and Oranjemund) and the Upington – Karasburg railway line, gradually nullified the use of fords.
The old Yscor zinc mine in Rosh Pinah (1963) and the Octha / Reuning diamond mine (1965) kick started the pontoon business (1974) at the present site. A low level concrete crossing (1972) was first put to the test some 700 m stream up. This was later aided by the spectacular Jan Haak river road (1980s) on Namibian side on route to Noordoewer – named after the then Minister of Mines.
The 43 year long pontoon use at Sendelingsdrif is characterized by many a tantalizing account of reckless characters. Infinitely resourceful smugglers took Namib oryx over the border, to ensure weekly fresh bread for Rosh Pinah, or to transport school children there and back. Many an elusive visionary with a strong frontier spirit, so typical for this canyon country knew the crossing well.
Pont building was initiated by the Rosh Pinah mine around 1974. The first pont used a boat-like angle iron frame, kept afloat by six steeldrums, and kept online by a ‘preventer’ cable anchored to both sides of the river and fed through eyebolts welded to the pont at either extremity. The operation of the rigging was by winch from the Octha side. A vehicle needed to be parked in reverse on the pont because the craft turned around on route. Many a car found a watery grave and the pont itself was washed away twice in the eighties.
Fred van der Colff, mine manager at Rosh Pinah, then took lead in the construction of the next pont. A skillfully designed box like structure was designed to carry two vehicles or a 34 seater bus. Well constructed of 4.0 and 6.0 mm steel plate on a good system of centerline and transverse bulkheads and stiffeners, the new pont was sturdier than its predecessor. Longitudinal stiffeners are in place to support the main deck / roadway. Access to pontoon was by hinged landing ramps. Powered by a 40 HP 4-stroke outboard motor with a 180 º swirling action is ideal the trips back and forth.
Pont operation was without any major hiccups until the 1998 flood anchored it in the riverine bush near the historical Sendelingsdrif. From 1994 – 1998 Sendelingsdrif served as a non-official border post. When the Transfrontier Park negotiations started in March 2001, a pontoon operation at the present Sendelingsdrif was targeted as the transfrontier icon.
The then head of the now operating Skorpion Zinc mine project team, Norman Green, promised to salvage, refurbish and to put the pontoon into operation at no cost to the Joint Management Board of the Ai-Ais / Richtersveld Transfrontier Park. The then chief engineer Owen Williams and colleagues provided the necessary skill for this project, aided by Kumba Resources, NAMDEB, SANParks, and Allied Cranes. The thickness and damage to the hull was tested with ultrasound, painted with epoxy layers for low maintenance, and longitudinal stiffeners added for further support to the shallow draft vessel.
Symbol of cooperation
This 2 200 km long heritage river of hope signifies freedom, adventure and untrammeled beauty and is part of a world wide Great River family – lifelines in vast countries thirsting for water. The pontoon inauguration signifies the dawn of an eco-development force consisting of strong partnerships which embrace a joint management plan for the Desert Biome, recognising that the regions biological and cultural diversity are assets with potential lasting benefits to impoverished communities.
- Why has this site rendered optimal pont use for 43 years?
- the rock precipice on South African side activates a whirlpool during a flood event, deepening the river somewhat with a scouring affect, and
- some 500 m downstream is a slightly elevated natural rocky barrier, ensuring an operating water level for the pontoon over longer periods.
- Normal breadth of the river 97 m Distance between iron towers 242 m
- Average water depth 2,3 m Maximum depth 6,7 m
- Average water speed 500 mm / sec Flood speed 3 m / sec
- Length of pont 12 m Width 4, 5 m Depth 1,01 m
- Volume of pont 58, 16 m³
- Safe maximum carrying capacity 15,8 ton (15 800 kg)
- Three compartments ensure maximum floating capacity – with water tight 6 inspection holes
- Shallow draft vessel drawing an average of 12 cm and a maximum of 315 mm fully laden