The final form and scale of the penstock intake structure (forebay) is illustrated on the right, in the picture above. There is a temporary cover over the entrance.
In the illustration on the left a hose from a concrete pump is filling the prepared reinforcing space with concrete.
Two hoses supplying compressed air to tools for compacting the poured concrete are visible - one compacter being held almost directly in front of the concrete hose output.
The intake structure has a vertical access shaft to the penstock tunnel.
MANGAPAPA POWER STATION FOREBAY
The rectangular slot corresponds to the position of the inlet gate. For flood protection, a mound of earth was left in front of the main inlet, while construction was in progress.
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.
A 3 metre diameter concrete-lined tunnel 400 metres long leads from an intake and access shaft structure to the power station through a bifurcated steel penstock which supplies two horizontally mounted turbines with a centrally mounted induction generator. At the time of completion it was believed to be the largest induction generator in the world. The generating head is approximately 32 metres and the output about 17GWh per year. The total cost of this scheme was approximately $6,804,000.
Reference: "Tauranga 1882-1982: The Centennial of Gazetting Tauranga as a Borough" edited by A.C. Bellamy. Tauranga City Council, 1982.
