Cost Of Not Raising Lake

Press, Volume CX, Issue 32382, 22 August 1970, Page 44

Cost Of Not Raising Lake

(N.Z. Press Association) WELLINGTON, August 21. According to a computer the additional cost of not raising the lake might be s7m a year, the general manager of the Electricity Department (Mr E. B. Mackenzie) told the Manapouri Commission of Inquiry yesterday.

If Te Anau were not controlled power continuity would be diminished, he said. Te Anau works to cover any eventuality, including a rise in lake level to the 500-year flood level, would cost §575,000. A permanent dam must be built on the lower Waiau, whatever the event, he said. Construction of the dam was a legal obligation. During the examination of the Comalco representatives, Mr F. D. O’Flynn, on behalf of the Save Manapouri movement and the Royal Forest and Bird Society, had drawn the conclusion that with the company’s entitlement at the higho,-t possible figure the requirements could be met without raising the lake, Mr Mackenzie said. It had been stated that this would leave the Crown with 57 gigawatt hours as its share of the power. A gigawatt is 1000 m watts.

But Mr Mackenzie said that on this basis the cost per kilowatt hour unit for the Crown’s share would be 5.5 c, which was rather’ expensive. The Crown might be liable to provide a continuous power demand of 120 megawatts using a New Plymouth station. Annual operating charges would be at least $5,958,000, but this would be offset by an increase in the payment by Comalco of about §2,250,000.

The Electricity Department agreed with Comalco that Lake Manapouri should be raised as far as necessary to obtain the maximum potential that was economically feasible.

To the question from Mr O’Flymi whether the department agreed that the raising of the dam and the lake should be stopped at the point when the cost of the next unit generated would be the same as a unit from the cheapest alternative source

ot supply. Mr Mackenzie said the decision not to go beyond 820 ft was taken on that basis. Mr Mackenzie is the last witness due to be called to give evidence before the inquiry, which started hearing material in the first week of June. It is expected that final addresses by counsel will be heard in about a week. Continuing his answers, he said it would be advisable to build the dam to the 610 ft level initially rather than build to 583 ft and then extend. The extra cost to build

d to 610 ft was now sl.3m, but d if it were extended at a later it date the extra cost would be about sl.9m at today’s cost, it not allowing for unavoidable o escalation due to inflation. i- On many works the departg ment had found it better to if build to completion for many it reasons, particularly that of si public relations. a Replying to a question from the Commission itself e on what might be the best reo suit gained from the lake at ft 610 ft as compared with at n 583 ft, he said peak output c- would be raised from 630 to d 690 megawatts.