Mclarens Falls Power Station
Construction of Mclaren's Power House

Mclaren Falls Power Station - intake structure- 1981

Stakeholders of Mclaren Falls Power Station Scheme - at Mclaren Falls - circa 1925

The McLaren Falls power station, was decommissioned in 1989. A bypass was later installed to allow the continued release of recreational flows into the Wairoa River on set days each year. This facilitates activities such as rafting and canoeing.


 
 
 
 

MCLAREN FALLS POWER STATION


 
Mclarens Development Map.
Mclaren Power Station Generator Former
 

"Because of the obviously increasing demand for electricity Mr Lloyd Mandeno put forward in June, 1921 a scheme to develop a waterfall on the Wairoa River. (Later named by him McLaren Falls after the couple that operated the cook house, who had lost a son in the First World War). He stated that 3,000 to 3,500 horsepower could be obtained.

A poll was put to the rate payers on 15th December, 1922 for an $180,000 loan. The Borough then having a population of 2,000 had already mortgaged itself for $140,000 on its electrical enterprise. The poll was carried by a majority of 441 to 45 mainly due to determined electioneering by people like Mr Walter Jones, the Chairman of the Electricity Committee.

The overall layout of the McLaren Falls scheme is as in the diagram at the top left. A concrete arch dam was built in a narrow gorge where the water was normally 6.7 metres deep. A 487 meter long 2 metre square diversion tunnel was driven from just above the water below the present bridge to the river above the dam site. A branch to this tunnel was then driven under the deep pool at the dam site to drain it while the dam excavations and filling were carried out.

Lloyd Mandeno at Mclaren Falls circa 1925
 

A bunkhouse for up to fifty men was erected just between the existing sharp bend of McLaren Falls Road and the present lake. The work force peaked to seventy men. A storage shed derrick and crane were constructed on the Wairoa River near the Omanawa Bridge. Cement and other supplies were carried to this point by punts and thence to the Falls by road.

The powerhouse and arch dam were constructed using the local rhyolite rock for fine and coarse aggregate. All structures were designed so as to impose low stresses on the concrete. The quarry for the power house rock was situated downstream on the same side, the rock being transported by manually-pushed trolleys on rails.

The static head was 26 metres, the arch dam being 24.5 metres high. After two and a half years of design and construction the first of two 1,400kW vertical shaft turbine-generator sets was started up on 25th June, 1925, the second starting a few months later. A third tunnel was built to divert the Mangakarengorengo Stream into the twenty hectare Lake McLaren. The total cost of the scheme was $165,764."

Reference: "Tauranga 1882-1982: The Centennial of Gazetting Tauranga as a Borough" edited by A.C. Bellamy. Tauranga City Council, 1982.