TEKAPO POWER

Ashburton Guardian, Volume 61, Issue 18, 1 November 1940, Page 8

TEKAPO POWER

PRELIMINARY WORK BEGUN DEVELOPMENT OF NEW SICTIEMF. (Special to the “Guardian.”) CHRISTCHURCH, This Day. Planning to maintain the supply o power to meet the growing demand in the South Island, the Public Morks Department is placing considerable importance on the development of the Lake Teltapo scheme, on winch preliminary Work has begun, stated Mr T G .Beck (District ilDngineer lor the Department). The, Tekapo scheme will not only produce electricity at the lake itself, but it will enable water to be stored for the Waitaki power station. In fact, long before power is produced at Lake Tekapo the new scheme will by its control of river flow, lie pro\ iding the water to drive a new generator at Waitaki. The department, therefore, places the works at Tekapo in the following order of importance: first, construction of a tunnel from the lake to the river; second, construction of a dam at the lake outlet; third, I 'construction of the power-house. The tunnel alone will enable the low winter flow of the Waitaki river to he “boosted” by loweiing the level of the lake as required and the dam will enable a much greater quantity of water to be stoied for the same purpose. Actual construction of the 600 ft tunnel, which will be driven and built with methods entirely new to New Zealand, will not begin until early in the New Year. The present preparatory work consists oi the sinking of a vertical shaft to the lino of the tunnel near the side of the lake and the driving of an adit tunnel at the river end. • Tunnelling will begin from the ends of both these shafts, through which spoil will bo removed by mechanical means.

Mr Beck said that in order to avoid any unnecessary outlay on plant, machines and equipment were being moved to Lake Tekapo as they became available from other jobs. The driving of the tunnel will take a year or more and about 150 men will he employed on tlio job. With the completion of the tunnel it will bo possible to lower the level of the. lake to the point at which the outlet to the Tekapo river becomes dry, which will enable the foundations of the dam to be built with a minimum of difficulty. Tenders have been called by the department for the manufacture of the reinforced concrete blocks with, which the tunnel will be lined. These, as explained previously in these columns, will be bolted together “like a Meccano structure.” No fewer than 26,000 will be required to line the tunnel, which will bo 20ft 4in in diameter. Just as interesting is the method of driving tlio tunnel. Automatic picks and drills will be operated from inside huge cylindrical shields, which will be driven forward into the glacial moraine by powerful hydraulic jacks. With every three feet o‘f progress by the shields another ring of the concrete blocks will be bolted on to the preceding section of the tunnel lining.

The shields are now under construction in the Tomuka workshops of the department, and the hydraulic jacks are being made by A. and G. Price, Ltd., Thames. The castings l'or these are being made by the Alloy Steel Company, Canterbury.