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APPENDICES TO MINISTER'S STATEMENT. APPENDIX A.—ARAPUNI HYDRO-ELECTRIC-POWER WORKS. STATEMENT BY THE HON. W. B. TAVERNER, MINISTER OF PUBLIC WORKS. 28th June, 1930. In accordance with the undertaking I have recently given to the press, I desire to make the following statement to the House regarding Arapuni:— At about 4 a.m. on the morning of Saturday, the 7th instant, water was noticed on the floor of the battery-room at the back of the power-house, having found its way in through the power-house drainage system. On the officer at the pumphouse end of the penstock structure near the spillway weir being communicated with, he found a crack approximately 2 in. wide between the end of the spillway proper and the structure adjoining same. Other water was found issuing from a number of points on the cliff behind the power-house. Wellington was immediately advised, and some of the principal officers of the Department left immediately for the scene, arriving the same night. In the meantime a crack had been traced on the surface of the ground, running from the one first observed through the hill between the old gorge of the Waikato River and the present headrace. This crack was not continuous, but was observed in a number of places all trending much in the same way and ending a short distance below the Falls where the water from the headrace drops back on to the Waiteti Flat. Wherever these cracks existed in alluvial ground they disappeared during the first rain which fell afterwards. After observing the flows through the hill and the movements, it was decided that it was advisable to lower the water so that it would not. overflow the spillway, and thus give an opportunity for better examination. Accordingly the gates in the diversion tunnel were opened, and by the following morning the spillway ceased to overflow, and further examination was made. In the meantime I had departed for Arapuni, and with the engineers made a thorough inspection ; and, after carefully going over all the evidences of earth movement, a decision was arrived at that the water should be drawn down until the headrace was dry. This was done, the lowering of the water to this extent being accomplished by Sunday, the 15th instant. On the water leaving the headrace and forebay it was found that the cracks already observed ran approximately on the lines of the headrace for several hundred feet farther than had been observed on the dry land, and. the drainage water was disappearing down these cracks. As the water in the headrace lowered during this week the leaks through the hillside at the back of the powerhouse and elsewhere had decreased in sympathy, and shortly after the complete emptying of the headrace they fell away very greatly, and by Tuesday, the 17th instant, had entirely ceased. Certain cracks were observed in the back of the power-house on the first morning of the trouble, and a small quantity of water was seeping through these. This, of course, stopped when the other leaks stopped. As the water in the forebay and headrace was lowered, the cracks tended to close, and when the water pressure was entirely removed it may be said that in a general way the cracks closed up to half the width at which they were at the maximum. The maximum width of the cracks was 2 in. at one point, gradually fading away to a hair crack at each end. This is now 1 in., and fades away to nothing in a shorter distance than previously. Very careful measurements both by direct measuring from known fixed points and by triangulation from parts of the country remote from the scene of movement all indicated that the movement, small as it was, was definite and in the direction from the penstocks to the tailrace —in other words, towards the gorge in which the Waikato was running prior to the diversion in 1928. At the time of my visit on 9th June investigations indicated that some movement had taken place in connection with the power-house, the turbines being slightly out of true level. It was also ascertained that the high-level suspension-bridge spanning the gorge had sagged to some extent, presumably on account of movement of one of the supporting towers. Also, the heavy-traffic lowlevel bridge just below the power-house gave indications that movement had taken place there. All these displacements support the theory that whatever movement took place was inwards towards the old gorge. It was apparent almost from the first that extensive work would be necessary to make good the position, and that the plant would of necessity have to be shut down for a considerable period. The entire emptying of the lake was therefore decided upon, and the lake was finally drained on the morning of the 24th June. As the water in the lake was lowered certain overhanging material from the cliff wall above the intake to the diversion-tunnel slipped away at intervals during the night of 13-14 th June with the result that the gates of the diversion tunnel became blocked on three occasions. The blockage was overcome by raising the gates and thereby increasing the opening, the pressure of water sweeping the slipped material through the diversion-tunnel. Apparently the gates were not affected by these blockages, as they were successfully operated again immediately afterwards.