ELECTRICAL POWER

Northern Advocate, 20 July 1935, Page 10

ELECTRICAL POWER

MORE WANTED. WAIKAREMOANA SCHEME. A KNOTTY PROBLEM. I Special to “Northern Advocate.” 1 WELLINGTON, This Day. The hydro-electric engineering branch of the Public Works Department is taking practical steps to control leakages of water from Lake Waikaremoana with the ultimate object of making available nearly four times the power at present being developed from that immense natural storage reservoir. The lake is 2000 feet above sea level and has an area of 21 square miles, with one outlet presenting a highly interesting problem for engineers. Ages ago two immense cliffs appeared to have been tilted' into a gorge, blocking up the outlet and raising the lake level to a considerable height. However, the immence rocks piled up in such a fashion that they left large gaps through which water could escape at various levels down to possibly 70 feet below the water surface. It is intended' to stop these subterranean leaks, which all occur in the bay of the lake, and if this can be done 400 feet will be added to the height at which water can be controlled for purposes of power generation. The geological upheaval which created the problem occurred so long ago that the strata is thoroughly stable. The work in hand is that of putting down trial bores through this immense ancient slip covered by the lake waters, and the sinking of an exploratory shaft in the lake bed on what will eventually become the site of a control tunnel through which water for power generation will be regulated. With the knowledge gained through sinking of bores and running the shafts through the rocks, the department will be able to stop existing leaks through the conglomerate mass of rocks.

Divers Utilised,

Divers have been utilised to locate the inlet points of these leaks, and chemical methods have also given important information through the tracing of the chemical from the lake water to the point at which it emerged on the hillside above the power house. Experiments are being made with various cement grouting mixtures for sealing-the cracks through which water is escaping. - <■

If the plans succeed, Waikaremoana will be capable of steadily supplying water for generating up to 120,000 kilowatts, though the present station which serves so large an area, extending from Gisborne to Wellington and frequently up the west coast, has a capacity of 32.000 kilowatts. The leaks in the hillside prevent the tapping of the lake water at lake level, and streams from the leaks do not come together until they reach a point 400 feet lower. Then the stream is impounded and power house requirements piped to the turbines in the valley below. Success with the plans now being carried out will enable another powerhouse to be placed above the present one, as an additional head of 400 feet will be available if the whole lake outlet can be regulated through the tunnel at the bottom of the shaft now being sunk. After being used in the proposed upper power-house, the water will still be available for the present plant, and when further extensions are needed the outlet of the latter will be impounded in a shallow lake on what is now a grassy flat, and taken by tunnel and pipe dine to the third station site, giving a fall of 300 feet and bringthe total power output to 120,000 kilowatts. v