$3.5m rescue for Martha Mine icon

The Cornish miners who built it would be astonished to see the effort being made to preserve Waihi's 102-year-old pumphouse, by shifting the structure 301m.

"It's certainly an unusual project, if not unique," said Malcolm Lane, a spokesman for mining company Newmont Waihi.

The company, which runs Waihi's Martha Mine, is footing the $3.5 million bill for the shift, made necessary after the building developed a distinct lean when the disused No 5 mineshaft collapsed in 1961.

The pumphouse has a tilt of about 30cm, or 1.5 degrees, and Newmont Waihi, charged with preserving it as part of its resource consent for the mine, was told last year it would have to be moved to stop it from toppling.

With the Hauraki District Council, a community group and the Historic Places Trust, it was decided to move it out of the subsidence hazard zone and closer to the town.

But shifting the 21m-high, 2000-tonne structure posed a few headaches.

The first step was to compact the land around the pumphouse to make sure it could take the building's weight - the equivalent of five fully laden Boeing 747s or 50 heavy trucks.

Next, a network of steel beams and reinforcing was built inside and outside the pumphouse to brace it for the move.

Now engineers are drilling five tunnels through the pumphouse's foundations which will be reinforced with timber and steel.

Through these tunnels, a monster concrete grid of "slider beams" is being built for the structure to rest upon.

That's after it has been cut from its existing foundations, centimetre by centimetre, by a monster diamond-tipped circular saw.

It will then be lifted by hydraulic "flat jacks" - picture a dinner plate with another turned upside down on top - to get it on to the slider beams.

Once fully supported on the beams, hydraulic rams attached to the beams, will begin to slowly push it.

Each time it is moved, more beams will be joined to the existing ones to extend the platform and the building pushed along until it makes its way to its new home. It will move 26m to the south first, then 275 to the west.

The first big push is expected next month.

The public hasn't had access to the pumphouse since the 1980s but Mr Lane said it was hoped that both residents and visitors would be able to visit it after the move.

"It's a pretty exciting project and we are going to get something which is very good for the town out of the exercise," he said.