ORONGORONGO TUNNEL.
NOTABLE WORK FINISHED.
CO-OPERATIVE CONTRACT.
MR. SEMPLE GRATIFIED.
The piercing of the Orongorongo tunnel on Saturday showed that the engineers’ calculations had been absolutely accurate. The shot was fixed for 2 p.m., and when the fumes had cleared away sufficiently for the men to see the result, there was a ragged hole in the wall of blue rock big enough for a man to crawl through. It was virtually the end of the longest tunnelling job done in the Wellington district for half a century.
“The levels were exact!” declared Mr Robert Semple, the leader of the corporation gang of tunnellers who undertook the big job. He could not say so much to an inch, but the effect of the last double shot showed how accurately the engineers had worked out their calculations, for it had to be remembered that the tunnel was no short drive, but one of over two miles in rough country of unknown formation.
The hard blue sandstone which was met with almost the whole way through, prevailed up to the last shot, and no timbering would be required in the section where the two parties met. Some wet places were found here and there, where heavy timbering was necessary, and this work was done with the utmost care, as on the strength and efficiency of such supports in soft country depended the lives of the men.
Of no feature of the work is Mr Semple prouder than the fact that right from the beginning to the “break through” no serious accident had occurred. He claims it as a unique record and something for co-operative as against contract labour. Lives in plenty had been lost at Otira, Mangapehi, Mount Victoria, and recently on a Government job in the north, but beyond bruised fingers and grazed hands, there had been no serious accident at the Orongorongo job, where it was the men’s duty to care for themselves and leave nothing to chance.
Another Record.
Furthermore, Mr Semple claims that his men have put up a record in tunnel driving on time. It will be remembered that at the time the Wellington City Council wished to commence work on the tunnel there was a very pronounced shortage of men, as the country was still feeling the effect of the war. At that time Mr Semple, an experienced miner and tunneller, put up a proposition to the council to do the work at a certain price, guaranteeing no delay through strikes or anything of the kind.
After considering the matter the council, on the recommendation of the late city engineer, Mr W. H. Morton, resolved to accept the Semple offer, though it was admitted at the time the cost was high. Having secured the job, Mr Semple assembled his men, and a start was made to break ground on the Wainui side of the Orongorongo Range on December 6, 1920.
But this was not the real start, as there was the preparatory camp-building, and, as no power was available for the rock drills, it was all hand steel work for the first 218 ft. of the Wainui Cone. For six months a number of men were employed in making a rough bridle track over the Orongorongo Range, which is 2800 ft. high. All those who have made the journey are aware of the arduous nature of this work, where in places a path had to be cut on the sides of mountain abysses through virgin forest at an elevation sufficient to command a view of the Wairarapa Lake and Palliser Bay and Cook Strait beyond.
Then with the aid of water from the Morton Dam, a power station was provided at Wainui, which gave plenty of power for the air-compressor rock drills, and also for the supply of fresh air at the face, and electric light for camp and tunnel. As soon as the power house was available, three shifts of eight hours were employed on the face. That was from October 15, 1921.
Long Trek to Orongorongo.
But it was not so easy to provide such facilities on the Orongorongo side, to which no road led, and no easy place presented itself. There was the spot, in a chasm-like heavily-timbered valley across a 2500 ft. high range. The bridle track was all right for the packing of flour and meat, but was impossible for heavy weights.
For a year four-horse teams laboured over the Wainui Hill, down the valley round the sea shore into the Orongorongo Valley, and so up the torrent-ripped gulch, to the point opposite Morton Dam. Then came the task of building the intake dam and filter basin, laying the pipes from there through a short tunnel to the site of the power house, near the Orongorongo entrance to the tunnel.
By September 28 of that year, the water was flowing through the 21-inch pipes and the motors were droning steadily. From that date, sure progress was made, and three shifts were soon at work.
Reckoning from the day power was supplied on the Wainui side, the time occupied in making the 7 ft. square drive was two years and four months, but had the power been available on both sides at the same time, even that time would have been markedly lessened. Mr Semple says there are several days’ work yet for his men to clean up at the “break through,” but they should be all out of it before the end of the week.
