HYRDO-EIEGTRIC WORKS.

Matamata Record, Volume III, Issue 148, 4 September 1919, Page 3

HYRDO-EIEGTRIC WORKS.

Investigations at Arapuni. ■•" '■' ''.3lj£ investigations being made by tlft Government at the Arapuni rapids in the Waikato river to ascertain the suitability of the site .for the erection of hydro-electric power works are proceeding apace, and the preparations have readied ail advanced stage. An interesting description of the work in hand was"given to a "Record " reporter when lie visited the site a few days ago, by Mr. C. B. Scaly, engineer in charge of the work. " The work we are engaged in," • Mr; Sealy, "is merely to make ', investigations to prove absolutely the suitability of the site for a dam before anything definite can be de-cided-.ui>on. In order to do this, we are examining the dam site by means of a scries of shafts and drives to exactly determine the' nature of the material on which and in which we will have to build the dam. The material has got to stand compression and porosity tests, and in connection with these tests the drives and shafts before mentioned are necessary. In the same way the foundations for a > dam are tested. Eight drives are in course of const ruction, four on each side of the river. The foundation scheme provides for the sinking of a shaft on each side of the river and the connection of these drives with horizontal drives. Tt is intended to carry these shafts below the level of the river-bed, " and to join them by a tunnel under the river. All these drives and shafts are located on the site of the proposed dam, or within the limits of the site. The strength and the porosity of the soil or stone met with in tho drives will be thoroughly tested, and provided they withstand the tests, the site, will no doubt be regarded as a suitable one for power development works. From the investigations that have been made 1 have uo reason to believe that the tests will not prove satisfactory. An important feature of the scheme is that if the site is approved of by the Government, not a pennyworth* of the work that has been done will be wasted, but that all will be included in the work required in connection with the erection of a dam. Briefly, the work in hand is required to prove' whether or not the sides of the river will stand the dead-weight of the pressure of water that would be held by a dam, and to absolute- ' r ly ensure that the dam would not on completion." Mr. Sealy described proposed in the event of fts« site being approved and the Government deciding to go on with the hydro-electric power scheme for Arapuni. At Arapuni the Waikato River rushes through a gorge of about two miles long and 140 ft wide. From the top of the cliffs on either side of the river to the present water level is about 166 ft. The river is about 40ft deep at present, and rushes through the gorge at a tremendous velocity. Just above the proposed dam site is a point at which an old river bed of the Waikato joins the present river bed, and it is proposed to construct two diverting tunnels in the vicinity of the dam site for the purpose of diverting the water of the river into the old river bed, thus leaving a dry river bed for the construction of the dam. The dam will be mode of concrete, semi-circular in shape, and will be 48ft wide at its widest part and 10ft wide on the top. The dam will be 140 ft long and 166 ft from top to bottom. In making the dam semi-circular in shape, the arch will face upstream, and will thus give the maximum resistance' to . the flow of the river. When the dam is completed, the water will flow along'the old river bed, which is roughly 130 ft above the exist--1 ing water level. The old rivercourse will form a natural head- , race. The water will then be turned back into the existing river bed at the bottom of the gorge at a point three-quarters of a mile below the dam site n and- at which' site it is proposed to erect a powerstation. By this means and by the construction of further tunnels, a head or fall of 135 ft will be provided, which together with,a head T of 35ft already provided by the fall { of the river, will give a head of - J " 170 ft when' the work is completed. The 35ft head just mentioned is greater than the total given at the Hora Hora power works, said Mr. Sealy. With the fine gorge, the amount of water available, and the old river bed near at hand, Nature has provided an ideal water-power generating site, and, as Mr. Sealy said, it only remains for man's ingenuity to convert the means provided for his own uses. Referring to the potentialities of the scheme, Mr. Sealy said the damming of the Waikato at Arapuni would result in the formation of a deep-water lake 20 miles in length. The depth would range from 135 ft to 150 ft. This lake would be a great inland waterway, jffiith a wharf and railway station at Arapuni on the completion of the power works and the Te Awamutu-Putaruru railway, which it is intended should, pass

over the dam at Arapuni, an enormous impetus would be given to settlement and.trade and in opening up of large tracts of liinjterland of Wharepuhauga on the southern side of the river and Waotu and the T.T.T. Company's land on the eastern side. Regarded from the point of view of the settlement of the country, it is difficult to guage the immense benefits that would accrue to the country by the completion of the Arapuni power development scheme, quite apart from the primary object of the proposal to provide electric power and light that could be supplied to towns and districts hundreds of miles away.