Omanawa Falls station turns 100 (+ video)

An engineering wonder of old New Zealand sited next to one of the Bay's beauty spots, the Omanawa Falls, has celebrated its 100th birthday.

The Southern Hemisphere's first underground hydro-electric power station, rescued from becoming a derelict ruin by Michael Davis, is ready to hum into its second century.

It faced a bleak future until the Te Kuiti-based hydro developer stepped in to save the neglected and vandalised station eight years ago.

Blasted and hand-hewn into the side of a ravine, this testament to the fortitude and vision of the Bay's early engineers fired his imagination when he first stepped into the gloomy, dripping cavern holding the powerhouse in 1988.

Although not spiritual by nature, he felt the hairs on the back of his neck stiffen, so when the opportunity came along 20 years later to save the station from the ravages of vandals, he grabbed it with both hands.

Although the little station was now pushing 1.8 million units of electricity a year into the national grid, his main motivation was to save a significant engineering monument, both for New Zealand and the world.

"It is a brilliant set-up," Mr Davis said.

The eerie interior of the cavern with its spine of concrete pillars marked with the letters TBC showed the scheme was the brainchild of the Tauranga Borough Council back in the days when bulbs were starting to replace lamps and candles.

Mr Davis said it was a museum piece, with the bonus that it was a functioning power station generating enough electricity to power 300 homes.

Looking at the effort needed to build an underground power station in such challenging terrain, he was full of admiration for this feat of engineering. "Even to get the gear in these days would be a huge ask."

Amazingly, the oldest mechanical part of the station, the 115-year-old Escher Wyss turbine that drives the generator, continued to operate without a hitch. The turbine and generator originally powered a gold quartz crushing plant in the Karangahake Gorge.

Technical issues along with years of neglect and vandalism meant it was not realistic to restore the original generator. It was now an impressive presence at the side of the powerhouse, adding to the amazing atmosphere that included redundant machinery and control panels.

Mr Davis praised the perseverance of Jim Berryman, the electrical engineer who restored the turbine and now keeps everything ticking over in the fully automated power station. He also paid a tribute to the Tauranga City Council's parks and recreation team leader Warren Aitken for helping to make it happen. "If not for Warren, the power station would not be going today."

He has a 35-year lease over the council-owned power station which will soon be getting its single biggest mechanical investment with the installation of a new direct-drive generator.

It will be coupled to the slow revving 275 rpm cast iron Swiss turbine that he was confident would last another 115 years.