AT ARAPUNI

Hokitika Guardian, 15 May 1931, Page 5

AT ARAPUNI

MINISTERIAL SURVEY.

EXTENSIVE CONCRETING WORKS.

WELLINGTON, May 13. The Minister of Public Works (the Hon. W. B. Taverner) having inspected the progress of the remedial measures at the Arapuni hydro-electric undertaking. informed a correspondent of the “•'rimes” that operations are classed under twenty-three heads and everything is proceeding well, shifts being worked all round the clock on the most important features. There are 430 men employed' as an extra staff. Five drainage tunnels are being driven for the removal of water which may collect beneath the spillway cimunel causing hydraulic- pressure in the cliff. They range from the upper end of the new impervious channel, which is being constructed in the spillway, down to the new concrete structure to protect the face of the falls.

OPERFLOW CHANNEL. In the overflow channel a start lias been made in the laying of the two lower courses in the Jieadrace which will act as a filter , bed; and tenders have been called for the manufacture of concrete paying slabs to constitute the upper finishing course. The headrace channel, for about 1500 feet above the spillway dam, is being made water, tight, with a poroils drainage channel beneath it. A drainage and inspection channel has been driven beneath the

whole of this work and the extent of this operation be. guaged from the fact that the plant includes petrol motors, tractors, twenty-three scoop teams and a power excavator. MAIN DAM. At the main dam grouting operations are proceeding and, as additional control gates are to be provided in tlie diversion tunnel, a pilot shaft 7ft by sft is being sunk. This, 'said the Min. ister, is a very dejicate. engineering expedient, as the size of the gates and the pressures involved are considerably beyond those of similar hydro-electric undertakings elsewhere. ■ ■ •

CHECKING EROSION; - Erosion, at the waterfall is being checked by’ extensive concreting. Work in progress comprises' excavating and trimming of- rock’and is well advanced. An important’ feature is the drilling of grouting holes’to consolidate this portion of the 'country and 4500 feet have already been driven. A' deep pool at the foot of. the falls has disappeared, having being filled .with excavated rock, though adequate measures have been taken to discharge soakage water, which will go through a tunnel emptying into the main channel of the river near the low level bridge. In the power house the machinery of . the No. —4- uhit -is- on—tlie» speF-and contractors expect shortly to commenceplacing the steel lining in the water supply tunnel to this unit. ( QUESTION OP TIME. The Minister was-asked' if vey eimbk'd him to predict time when g-g the whole scheme would be again operating. He replied that it was not pos- .jh" sible to state any definite date, though all sections of the work were proceed • M ing up to schedule. However, the C-~. task of concreting the falls was very >£•■- extensive and wa s regarded as of vital yimportance to the successful operation of the scheme. This section of the work would have a vital bearing on the date of resumption. The period suggested by Professor Hornell of nine months ago the completion of the remedial measures he had recommended did not include this work on the falls.