No Drilling For Six Weeks

Press, Volume CIII, Issue 30424, 24 April 1964, Page 3

No Drilling For Six Weeks

(H Z. Press Association) INVERCARGILL, April 23. Drilling at the face of the Manapouri tailrace tunnel at Deep Cove was suspended in the early hours of today and will not resume for about six weeks. However, there will be continued blasting in the tunnel before the main drilling jumbo, sliding floor and mucking out machines are installed and in use. The final blast at the tunnel face went off just before midnight last night when it took the tunnel to a total of 908 ft in length. While the floor of the tailrace is being blasted out to make the tunnel floor drop from the portal at a steady 3 per cent grade, drilling of the 12ft by 12ft adit tunnel will continue. The tailrace was driven j 119 ft high and its full 31ft wide on a 3 per cent grade for about 550 ft Then the grade levelled out to

horizontal and the drilling continued at 28ft by 31ft Now the floor will be plasted out to continue the 3 per cent grade, making the height of the face 31ft for full face drilling from then on. The adit tunnel is about 500 ft long. It meets the tailrace 300 ft in from its portal The portal of the adit is 100 to 150 yards up the Lyvia valley from the portal of the tailrace proper. This tunnel will carry power, water and air lines into the tailrace. Bechtel Pacific’s tunnel supervisor at Deep Cove, Mr E. Smith, said this evening that the adit tunnel was

about five feet in from the face of the cliff. It was not yet “underground” since the contractors had found they must take great care at the portal entrance because of the nature of the ground and the cliff face. They were blasting out the portal in sections, about five drills at a time.

No jumbo will be used in this timnel since it is relatively small. Individual drills will probably be mounted on tripods as the adit is driven full face once it is underground. Mr Smith said it would probably be early next week

before blasting on the floor of the tailrace was begun. First air and water lines must be taken back about 350 ft to where floor blasting would begin. The main three-deck drilling jumbo mounting 18 drills, a sliding floor to receive blasted rock, mucking machines to load the rock into rock cars, the cars themselves, the locomotives to pull them, and the rails for them to run on must all be installed before driving in the tailrace will resume in about six weeks.