The Hex River Tunnels, also known as Hexton, in the Western Cape Province of South Africa is a tunnel system consisting of four single track railway tunnels connecting De Doorns in the Hex River valley with Touws River in the Little Karoo.
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The Hex River Pass across the Matroosberg range was a major obstacle to overcome during the construction of the railway between Cape Town and the Kimberley diamond fields in the 1870s. In 1874 surveyor Wells Hood, under the instruction of the railway engineer Thomas Brounger, found a potential route up the 2,353 feet (717 metres) climb from De Doorns in the Hex River valley to the top of the Little Karoo plateau east of the Valley, with gradients of no more than 1 in 40, very steep by railway standards. In addition, he proposed that a short tunnel would be required at the summit. Thomas Brounger's route through the Hex River Pass was selected by 1876, with the line to follow the route from Worcester through De Doorns, up the pass via Osplaas, Tunnel and Matroosberg to Touws River, Matjiesfontein, Laingsburg and on to Beaufort West.
The standard gauge track of 4 feet 8½ inches could not be accommodated economically on the tight curves required by the Hex River Pass. This led to the decision by the Cape Government Railways (CGR) to abandon the use of Standard gauge, which had been used for the line between Cape Town and Wellington, and to install the track across the pass at 3 feet 6 inches (1,070 millimetres) gauge. A subsequent decision resulted in all existing tracks of the CGR being converted to what was to become known worldwide as Cape gauge.
Credit for the fact that most of the present day railway lines in Africa are Cape gauge can therefore be directly attributed to the Hex River Pass. Despite its quick and relatively cheap construction, the pass served the South African Railways for more than a century. It was the starting point of the country's first railway line to the Witwatersrand and opened the way for Rhodes' colonisation thrust into central Southern Africa.[1]
The original tunnel, Southern Africa’s first railway tunnel, is situated at Km 34 between De Doorns and Matroosberg. Just to the east of the tunnel was a siding, approriately named "Tunnel". The tunnel portals were of dressed stone masonry, but the inside was unlined. This tunnel served the railways for 53 years, until the track was relaid in 1929 to diminish a curve in order to accommodate larger locomotives. In the process a new concrete lined tunnel was sunk alongside the original. This latter tunnel remained in use for sixty years, until the line across the pass was closed in 1989.[1][2]
The restrictions on train length and the additional locomotive power required for the ascent eventually led to the decision to construct a tunnel system to eliminate the Hex River Pass altogether. The Hex River Tunnel scheme was initially started in 1945, but was abandoned three years later due to a lack of funds after the project encountered serious technical difficulties at the eastern portal of the longest of the four tunnels. The portal was dug immediately adjacent to the N1 national road some 15 kilometres (9 miles) west of Touws River and took the form of a gradient into a trench cutting, down to sufficient depth to commence tunneling.
The bore was hardly more than about 66 feet (20 metres) deep, however, when ground water flooding brought tunneling to a halt, and the project was eventually abandoned. Instead, the pass was electrified by 1954 and operated with Class 4E electric locomotives, which were amongst the most powerful electric locomotives in the world at that time.[3]
For the second attempt some thirty years later the eastern portal of the longest tunnel was relocated a short distance to the southeast of the original site, while the location of the western portal remained as originally planned during the first attempt. The tunnel system was opened on 27 November 1989. The completed four tunnel system now boasts the longest railway tunnel in South Africa at 13.4 kilometres (8.3 miles) long, with an interior passing siding. Of the other three tunnels, the longest is about 1.3 kilometres (0.8 miles) and the other two about 1 kilometre (0.6 miles) and 500 metres (1,640 feet) in length respectively. It eliminated 8 kilometres (5 miles) of distance and 112 metres (367 feet) of false rise to crest the summit off the old route, with a substantial reduction in curvature and required locomotive power.[4]
With the opening of the new route, the old Hex River Pass line was closed and the electrification infrastructure removed. Most of the track between Matroosberg and Hexpas stations was left in place and is now being utilised as a popular tourist destination.[5]