HOPE FOR ARAPUNI.

Stratford Evening Post, Issue 67, 16 October 1930, Page 5

HOPE FOR ARAPUNI.

Professor Hornell expresses the view that the. general surroundings an'd power development possibilities at Arapuni are such that the locality is very suitable for the economic development of hydro-electric power. Concerning the class of country if may be said that it by no means excludes the possibility of creating a successful water power station on the site. He has no apprehension as to damage likely to occur 'from water leaking from the lake by way of Acacia Gully. He finds that the main dam is

correct iri its position in regard to the ultimate proposed power output, but that as there is evidence that the dam i s leaking at some places in the foundation, even at the present lowered water level .With the river

at its original state, it is essential that the origin of any appreciable leakage be located and that the leaks be carefully grouted' under pressure so as to stop effectively water passing under the dam or through the rock foundation. Professor Hornell is also of the opinion that opportunity should bo taken further to strengthen the country adjacent to the main dam, particularly on the western abutment, by reinforcing, grouting and waterproofing the sides of the fl head race between the head race bridge and the junction of the head race with the lake.

DESIGNED ON SOUND LINES. 1 Iri reply to questions relative to the development of the scheme, the professor states that the works are 1 sited in such a way as to ensure the maximum power available consistent with reasonable expenditure. “In 'general,” he remarks,” it may be said that the works as executed have been designed in accordance with sound principles of engineering. From the civil engineering point of view I have no adverse criticism to pas s upon the general location 1 of the different parts of the plant in relation to each other. On the electrical side of the problem I can make no comment. As far as can be seen from a detailed visual inspection' on the site the constructional work has been well carried Discussing the question as to whe_ .or the crack, .which took place on June 7 might have been foreseen, the professor expresses the opinion' that although the original plans and specincauous indicate that the

Public Works Department was not unmiucltui of tlje possible necessity tor lining portions of the race, it took a justifiable risk in' not carrying out tnis lining when the work wa s constructed. He is of tne opinion that features such as the driving and operation ot tne pensjtock tunnels and the weight of the outdoor transformers’ station had very little efiect in causing the rupture, .o also holds the jiewi that the tarn, that the' crack ha 3 occurred will have no effect in preventing the continued operation of the existing power station, and that there is no need for apprehension in extending the power station in its present site to the full capacity anticipated, ABA MX) MRU Vi' NOT FAVOURED. He can see no reason for abandoning the present headrace or power s iation it the remedial measures suggested by him are carried out. With regard to definite consolidation' of the falls ; the report is not conclusive in that Professor liornell states that in view of the magnitude of the works involved he would require further time to make a more detailed examination’ before giving a finally considered opinion. So far as his investigations have enabled him To go he is of the opinion that the effect of water entering the columnar rhyolite rock between the spillway and The head of the falls may have had a considerable effect in causing the rupture at the falls, and for this reason lie has suggested the waterproofing of the channel. In making this suggestion he stresses the point that as the power station is

PROFESSOR HORNELL’S REPORT BEFORE THE HOUSE.

CRACK NOT A BAR TO OPERATIONS. I*v Telegraph—. Press Association. WELLINGTON, Last Night. The report of the Swedish hydro-electrical engineering expert, Professor P. G. Hornell, on the) Arapuni power scheme, was presented in the House of Representatives this afternoon by the Minister of Public Works, the Hon. W. B. Taverner.

further developed the amount of water which will be passing over the falls for considerable portions of the year will be very considerably reduced. THE DIVERSION Tim EL. In regard to the diversion tunnel the expert is of the opinion that this should not be completely closed up with concrete, but rather than.' a second gate should be provided immediately above or below the present one so that repairs can be executed to the gates if necessity arises in after years. The professor considers that a considerable amount ol; grouting should be done in and around the diversion tunnel and immediately up-stream of the main dam, and he further suggests that the diversion tunnel should be plastered with a gunite surface. Finally Professor Hornell draws attention to the fact that throughout he has done very little by way of estimating the cost of the various sections of the work. “I feel that without considerably more knowledge of local conditions and prices I could not do this with any degree of accuracy,” he states, “In view of the fact that I have described the works proposed in some detail I have now no doubt but that the engineers of the Public Works Department could provide estimates with a fair degree of accuracyE

MINISTER’S STATEMENT. In a further statement upon Arapuni Mr Taverner said that after consideration of the expert's report he had considered it advisable to obtain further information in relation’ to the consolidation of the erosion .below the spillway, icorn-* monly called the falls. The locality had considerable bearing upon the subject. In a letter to Professor Hornell, read by him, the Minister asked that a more definite recommendation should be made in regard to what should bo done ac. the falls, and he asked particularly whether it was considered that there wag any risk of further extensive erosion should the plant be operated before the complete protective work at the falls had been carried out.

In liis reply Professor Horueli said lie was of tne opinion tiiat if remeuiai measures for hampering, tne speed ot uesiruetiou were executed us outlined m nis report tnere would be no risk in bringing tne power station into commercial operation ueiore uie anal ai'restation 01 tne erosive processes in tne spillway cnanuci w uerever tins siioum lie dune. 'file remedial measures proposed in nis report mignt even be sufficient to make any consolidation of the falls unnecessary, especially if tne power station were soon tuny developed to its ultimate proposed capacity. “Tneretore i consider it inadvisable from a technical and an economical viewpoint to apply any scneme of consolidation of the fails without very careful investigation of tlie different possibilities," Professor Horueli said. “In the event however that in' the course of time the Huai ai'restation of the erosion' should he deemed necessary, a definite scheme should be worked out beforehand and as soon as possible, ready to be applied when the heed arises. Preliminary considerations of different possible solutions have made me arrive at the conclusion that the arrangements required could he executed at a much lower outlay than that authorised. i.. -Ja. A BREST PNG EPOS lON. “Finally I would call attention to the important point that the work for the final arrestation of erosion' in Hie spillway channel can he executed without affecting the operation of the power station.