'Mini-Tongariro' tour an eye opener

IPENZ Tauranga branch members visit the Kaimai Hydro Scheme. Photo / Supplied

A field trip to one of New Zealand's most complex hydro schemes was a highlight of Centennial Year celebrations for the Tauranga branch of the Institution of Professional Engineers New Zealand (IPENZ) this month, says Peter de Graaf, asset manager for Trustpower.

The Tauranga-based national electricity generator hosted 28 IPENZ engineers on a tour of the Kaimai Hydro Electric Power Scheme, one of the utility's 22 hydro generation schemes. The IPENZ event aimed to highlight the role the profession has played in the infrastructural development of Tauranga, said IPENZ Tauranga chairman Peter Clark.

"They hadn't realised that we had such a beautiful and valuable scheme right here on their doorstep," said Mr Clark, who described it as a "mini-Tongariro".

Kaimai, located on the Wairoa River, has four power stations - the Lloyd Mandeno (16MW); Ruahihi (20MW); Lower Mangapapa (5.6MW) and Kaimai 5 (0.3MW). The scheme has an annual output of 167.8GWh per annum and supplies power to at least 20,000 Tauranga households.

The Lloyd Mandeno station was named after the pioneering Tauranga engineer who designed and supervised the construction of the first hydro-electric scheme in the area, McLaren Falls, commissioned in 1925.

The Kaimai Scheme, made up of a vast network of roads, power stations, tunnels, rivers, streams, canals, weirs and dams, was described by Mr de Graaf as one of the most interesting power stations in New Zealand because of its intricacy.

IPENZ committee member Warwick Robins said the Kaimai Scheme was a massive engineering feat. It was built during the 1970s and 80s, much of it using traditional machinery and blasting, he said. "The other aspect of this scheme is its beauty - we have man-made lakes, tunnels and canals all snuggled into a pristine environment."