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Building the Upper Dam
ZEALANDIA Ecosanctuary
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Building the Upper Dam

ZEALANDIA’s upper dam is a peaceful spot with the tranquil waters of the upper lake on one side, and a view over the treetops and down the lower valley on the other. But things would have been very different back in 1907 when the dam was being constructed.

Although by then the lower dam had been in use for 30 years, more water was needed, especially for the residents of the fast-growing city’s higher suburbs and for fighting the fires that frequently broke out among Wellington’s wooden buildings. Building the upper dam was a large-scale undertaking and the valley would have been a hive of noise and activity. The photographs below show some of the infrastructure that was put in place during construction, and if you look carefully, there are still signs of this in the valley.

Huge amounts of building material had to be brought in to create the concrete for the dam, which was 15 metres wide at the bottom, narrowing to 1.5 meters at the top. Three thousand cubic metres of sand were brought in from Island Bay, along with over 2000 tonnes of cement, while a further 9000 cubic metres of stones came from quarries within the valley (one of which is probably where Tūī Terrace is now). All this was transported on a specially constructed 2 foot (60cm) gauge tramline to the dam. Teams of horses were used for the flat part (up to near the wooden bridge by the Te Mahanga track) and then a steam-hauled tramline took the material up the steep slope to the top of the dam. This steep route still exists – a stony track running uphill towards the west side of the dam.

It was estimated at the time that the horses could do four times more work because they were using a tramway rather than plodding along a muddy track.

At the top of the slope was a tin hut that housed the machinery for operating the tramline, as well as a huge structure where the concrete was mixed by a steam-powered mixer.

One of the most impressive sights of the whole operation would have been a 200 metre-long flying fox that was strung on steel wires across the valley from one side to the other. This was used for transporting a box filled with concrete across the dam to the required position, where a worker would empty it out. The flying fox is described as operating continually from morning to night ‘with regularity and precision’. The tower in the Discovery Area above the dam is a replica of one of the anchor points for the flying fox; the original tower would have been on rails so it could move from side to side.

The Discovery Area also used to be a temporary home for the workers building the dam, with a hut for 28 men and tents for several more.

From the Discovery Area, the rock dam path takes you down past the ‘rock dam’, another piece of dam building infrastructure – this provided a water supply for the concrete-mixing operation.

So next time you are in ZEALANDIA, take a stroll up to the discovery area tower and imagine the flying fox with its loads of concrete, the noise and the smoke from the tram and the cement-mixing machinery, and the teams of workmen toiling away and picture that huge sweep of concrete gradually taking shape across the valley.

 

Article by Roy Sharp and Louise Slocombe

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