Orange-Fish Tunnel

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Construction of the tunnel started in 1966 and opened in 1975 and made possible the irrigation of thousands of hectares of additional land in the Eastern Cape of South Africa, diverting water from the Orange River to the Great Fish River.

With a length of 83 km, the 5,35m diameter tunnel was the longest continuous enclosed aqueduct in the southern hemisphere and the second-longest water supply tunnel in the world.

The intake tower is situated  at Oviston, approximately 25 km upstream of the dam wall. Seen from above, the intake tower is shaped like a four-leaf clover with each leaf containing an inlet gate - all at different levels. In this manner, water can be drawn from different levels to help control the water quality. Each of the four inlets can be sealed off to allow complete de-watering of the tunnel for routine maintenance.

It was engineered in association with Messrs Keeve Steyn and Partners of Johannesburg for the Water Affairs Department of the South African Government.

Former Halcrow senior partner, Sir Alan Muir Wood, the "father of modern tunnelling" worked on many of the world's leading tunnel projects, including the Orange-Fish Tunnel.