The diversion tunnel extended through the dam. The base of the dam was cleared of loose rock and rubble before filling with concrete. The man standing on the tunnel is directing workmen on the ground to clear loose rock. A bucket brought in by a crane removes the loose material.
On top of the far end of the tunnel a pump is mounted (the rectangular box) which was used to prevent a build up of water in the working area.
The drainage gate was built around the Mangapapa river diversion tunnel. Illustrated is the upstream side.
Work on Lower Mangapapa Station commenced in 1976, the station being commissioned in April, 1979. This scheme consists of a 27 metre high concrete arch dam in a narrow ignimbrite gorge about 500 metres upstream of Lake McLaren. Lake Mangapapa extends as far as the tailrace of Lloyd Mandeno Station and has an area of approximately 17 hectares.
The upstream base of the Mangapapa Dam diversion tunnel was made of sheet steel, and cut to the shape of the river bed with a gas torch.
Reference: "Tauranga 1882-1982: The Centennial of Gazetting Tauranga as a Borough" edited by A.C. Bellamy. Tauranga City Council, 1982.