The scheme was approved in 1946 and it was decided that full-face working would be employed in the long tunnel.
With this method and working two faces simultaneously, it was expected that 3.5 kilometres (2.2 miles) complete with lining could be achieved annually, with the whole tunnel completed in four years.

Tunnelling on the subsidiary tunnels and external earthworks commenced immediately, but start of work on the long tunnel was delayed due to special equipment that had to be designed and ordered in 1946.
While awaiting the special equipment, the western (Cape Town side) and eastern (Johannesburg side) portals were established by heading and benching, and short 20 metres (66 feet) sections of tunnel were driven at both ends by 1948.
The original eastern portal (coordinates 33.405814°S 19.9008°E) was dug immediately adjacent to the N1 national road some 15 kilometres (9 miles) west of Touws River and took the form of a cutting into a gradient to sufficient depth to commence tunnelling.
The scheme was approved in 1946 and it was decided that full-face working would be employed in the long tunnel. With this method and working two faces simultaneously, it was expected that 3.5 kilometres (2.2 miles) complete with lining could be achieved annually, with the whole tunnel completed in four years.
Tunnelling on the subsidiary tunnels and external earthworks commenced immediately, but start of work on the long tunnel was delayed due to special equipment that had to be designed and ordered in 1946. While awaiting the special equipment, the western (Cape Town side) and eastern (Johannesburg side) portals were established by heading and benching, and short 20 metres (66 feet) sections of tunnel were driven at both ends by 1948. The original eastern portal (coordinates 33.405814°S 19.9008°E) was dug immediately adjacent to the N1 national road some 15 kilometres (9 miles) west of Touws River and took the form of a cutting into a gradient to sufficient depth to commence tunnelling.
Hex River Tunnels