HARNESSING THE WAIMAKARIRI.

Press, Volume LVIII, Issue 11012, 9 July 1901, Page 3

HARNESSING THE WAIMAKARIRI.

MR E. HAY'S EEPORT. Ths-Special Committee having in charge the question of the harnessing of the Waimakariri came to tie conclusion that it would be >well to seek some outside opinion on the subject. Accordingly they arranged wi£h Mr Hay, a gentleman who had had considerable experience alike in hydraulic and electrical engineering, to' furnish them with a report. Mr Hay, with Mr Dohson, the City paid a visit to the proposed line, and went over it, furnishing a report which appears below. At the City Council meeting prior to the one held last night the report came up, but it was decided not to read it as it had not been considered by the Special Committee. Last night, in the City Council, his Worship the .Mayor said that with reference to tne report of -Mr Hay as to the Wainiakariri scheme, he thought, seeing that there was a, good deal of interest felf in the- matter, that though the Special Committee had not reported, the report should be read. He understood that the Special Committee had delayed the consideration of Mr Hay's report pending the receipt of some information from tie City Surveyor. It was decided to take the report as read, with a view to its publication. . * The report was as follows: To the Mayor of Christchurch. Sir — In accordance with the instructions of your Engineer, under date of 17th April last I nave tliie honour to report an the proposed schema of introducing electric power end lightly into Christchurch, the current for the same being-generated by water-power fi-onj tie river Waimakariri, as set forth in Mr DobsoD s report, and in accordance with instructions My report wiil deal with water-power only. The projects that have been brought under my notice are two in number, and known es follows:—(1) Rock Poid, (2) Gorge Bridge. One of the most important points to be first considered is the minimum quantity of water likely to be Jbcainable fronnthe Waimakariri when that river is at the lowest, and that level will be rttained, I should say, during continued' winter frosts. In order to be practically assured on this point, it would be necessary ■hat the levet of the river should have been loted over a period of years, and gaugings aken when tJise standard indicated a low iver, such measurements being taken at soma iite where the course of the flow was 'traight and equable. By this means a amy approximate estimate of the minimum quantity of water available from the iv-er for power purposes could , have been obtained. Unfortunately, nothing of the md ias been done, and the mere opinion f the casual observer is the only estimate vailable. At the time of my visit tie iver was running off probabfy twenty times he quantity required for the scheme, but bat fact will not be much assistance, but should think, judging by the immense raterebed drained by this river and its ributaries, that tihie water-power required nder this scheme could always be obimable. Before'going into the question of tie actual water required for power purposes to generate the required electrical ower, I will consider the collateral advanages or otherwise of the two schemes aleady mentioned. THE ROCK FORD PROJECT. The point of intake for this supply is ituated on the north bank of the Waimakain, nearly opposite to frtoe mouth of the Lowoi river. The rock crops ou# on the orthside only, the other bank of the river dirg formgd by the delta of the Kow<ri tver. The Waimekariri river is wide at ■us point, and divided into a number of bannels by shingle banks, and I think that speaisive iluead works would be necessary to' nsure a sufficiency of water being secured >r th* proi>osed race, and as the river is npinging on the .gravel terrace immediately :>ave the rocky bank, there is every possi*ility of the river being still further diverted * cm its piesent course, and the great width : tba river ait this point will render the isk of controlling the channel a very dif- i :ult one. The race will be in 'heavy block' • sideling cutting, and owing to its posi»n on the north, side of the river, under the gh terraces, the frost and south-westerly eather will be considerable factors in the instant disintegration of the land slopes, id cause slips and falls of gravel into ie channel, thereby involving in■eased cost in. ths works of instruction and maintenance The ogth of the race is four and a half miles, eluding nearly half a mile of tunnelling! tide the distance. from ths power-house to ms. church js six miles longer than prosed under the Gorge Bridge scheme,, so at if similar or better conditions exist wsr down the river, there is nothing to pa.n«d by adopting this site. GORGE BRIDGE PROJECT. Tha point of intake proposed for this heme is a iew chains above the Gorge idg9 and it has bsen suggested that the esent intake tunnel should b 3 enlarged d the race now in existence utilised in c formation of the new carrter required for a increased body of water. • It may here noted that, owing to-the configuration of c country, any race constructed in open fc must follow generally the line of the preit race, and! before any works are com■liced arrangements must bs made with i Board, or owners, to include (heir race the new scheme, and supply them with a tarn quantity of water, omd also arrange • stopping the water entirely durinc the instruction of the new race. The race bo constmcte-.i will bs about six miles in igth, of which one half is in easy country, iue the rema-ndcr is on tire steep terrace c mg at the foot of which the flood-waters the Waimakariri infringe, and the gravel a in parts is considerably eroded by the ion of the wind and rain, and the present re has been under cut in places, necessitat- : the construction of timber to ry ever the water. The line of country the last three miles is certainly not an al one for constructing a race upon, and will be necessary to bench out a laree ■tion of tlia hillside in order to set solid >und upon which to carry the new race. b machine site on which it is proposed to ct the generating station is at the foot the main terrace, on the banks of- the umakariri, and the land there is, to some ent, subject to the silting action of tba ?r, and the frontage will have to 'be proted. There ia, however, a better site >ut twenty chains further down the river, ere, possibly, a little more fall may be ilable, and a permanent foundation for power-house and machinery obtained hout the risk of encroachment by the \r. There is no doubt that the Gorge Ige project, in many ways, presents suior facilities for the required purpose over t of the Rock Ford, and if any scheme of kind is entertained, I am of opinion that Gorge bridge project should be adopted. POWER. he power required to be delivered in isteburcli is 3000 horse-power at the disuting station, and, in order to allow sufnt margin for loss in turbines, belts, isformers, and electrical transmissions, dnk that sufficient water should be dered at the turbines in order to develop ) horse-power. The fall at the point ielivery liaving been fixed at ninety , the required flow of water will be 489 c feet of water per second, and allowing per cent, for sundry losses by bends, , the capacity of the race must be equal discharge of 525 Government heads of ;r. From the levels furnished there purports to be a fall about seven feet per mile, and ■dimensions of a race sufficient to carry estimated quantity of water required Id be eleven in width at tie bottom, i half to one side -slopes, and 4ft. 6in i, the race to be lined with concrete of iverage thickness of not less than 9in i i, the inside faces to be worked up as jth a? possib'c. The calculation is d on Garaguillet and Kotter's formtfise experiments. HEAD WORKS AND RACE. _je hea<J tunnel, as suggested, should, be altered as shown on plan, and the ingress of the water provided for by several opjnings, instead of confining it to one; by this means the risk of all the river being diverted away

from one opening only is <iecreased, as also the choking of the same by shingle. The rut*,, in. my_ opinion, should be in concrete, «rom end to end, to a height of 12in above the calculated water level, m order to utilise all the fall available, aud to guard against Jeakage, μ-iiich, it must be remembered, would be much heavier in a wide channel cerrving four oi- five feet of water, than in one "a lew inches Seep. The race, also, would be smaller in a point to be considered when it bus to be benched out. of a steep terrace iace. On the sides of race a level bench, '6ft in width, must be left, in order "to provide a platlorjn for the weatherings of the gravel slopes andl small slips, which can be cleared away by face men before the fallen debiis can fand its wav into the river. , .

GENERAL REMARKS ON THE PROJECT. The present race at the time- of my' visit was carrying some tea or twelve headsjtf

water and is quite a small aliair compared to one carrying upwards 01 heads, and it. must be remembered that while it, is a matter of no moment whether mc present supply is stepped iw a lew hours or even days it is or supreme importunee that no stoppage should Occur on the larger race, whereov the supply oi electrical current for lighting, traiuwaya, pumP in f > *? d private power installations wuuid suddenly cease, in a work of this nature there are undoubtedly manypossible, and even probable risks of: the S now of water from the river being interrupted such as (1) the blocking of the inlets at the flood time with sinngle; (2) the diversion of the river channel by the formation oi new shingle -banks; (3) tiie accumulation of gravel, silt, and shingle in the tunnel inlet and race; (4) tlw necessity of cleaning the race from time to time; (b) break away in the ground carrying the race; (6) wash-Mite; (7; slips from the slopes of cuttings above the race, 'ihese accidents are incidental to wery water-race, but, of course, are more or less frequent in accordance with the seasons and nature of the country. 1 think considerable difficulty will be experienced in keeping the gates at the inlets clear of shingle, the gate at the inlet of the present race is occasionally completely blocked, while the formation of a shingle bar in front has necessitated a new channel baing cut in order to lead the water back to the inlet. This trouble in the present instance is of no great consequence as ten or twelve heads oi water can easily be turned into the tunnel, but the turning of 500 or 600 heads of water from a new course back into an old one is not such an easy matter. Ib might be found necessary after the proposed works were finished to construct expensive head works to overcome the shingle difficulty. The accumulation of gravel and silt in the tunnels and races will certainly take place, and must be removed or the area of race will ba curtailed and ita discharge diminished, and the removal of this gravel must be effected either by the use of -scouring outlets or manual labour, either of which operations will necessitate lowering the water level in the race, and Consequent loss of power at the turbines. Your committee must, therefore, in embarking on a work of tSls kind face the possibility ofj such contingencies and the consequent inconvenience and loss to their ratepayers and customers.

FEASIBILITY OF THE SCHEME. I have no doubt that the actual works for conveying 500 or 600 heads of water from the Waimakariri to the site of the proposed! power house can be successfully carried out, and, subject to the risks I have pointed out,' utilised for the purpose of providing power for the generation of electricity- for transmission to Christchurch, and I estimate the cost of tihe work from the intake at the Waimakariri to the pipe ihead,,.sa* the termination of race, ine;uding inlets, tunnels, race excavation, concrete lining, benching, new race, .and piping at £54,700. To this amount would have to be added the cost of iron pipes to turbines, with foundations for same, but these items could not be closely estimated Until it was decided what claSs and numbff of turbines were to be used. Tutbines, with connections, generators, switch-boards) transformers, ..exciters, meters, buildings,' etc., would also have to be estimated for, but I have not considered anything with regard to this part of* the scheme, as it did not lie witihin;ihe scope of my instruc..tw>ns. *.■,. ..■..-.. ■ , . ■ .....

LEGAL POSITION. Council should certainly fortify themwlvea with a legal opiaion as to tkir pasitum with regard to existing rights, as it might be foimd ttot the construction of taeu , - works would .haw a, prejudicial effect on the Lctokfis of tihe other mas, and thereby land the Corporation in expensive litigation damages, or a Supreme Court id j unction. -,■-.-

' RECOMMENDATION. Personally, I would advise that the Corporation obtain the necessary powers with a view of leasing or selling their concession to a syndicate who might be willing to nnd tba necessary capital, and construct <ui4 run the works under municipal conditions and control; the Corporation retaintng the power to buy cart the whole con"f *: »* stated periods shoflld they, think it politic to do and I make this- suggestion after giving the whole subject careful consideration, ac I feeL that I cacnot reoomniemi the Council themselves to embark m this undertaking I append am estimate of the works as ..recommended .by'me,'which is fairiv ap"-pi-o-ximate, but no accurate estimate can be formed until antral nirroy is made of the wxio.e line, of race. The plan herewith shows the proposed intake at the Gorse •Bri-ctge, and t.'ie new line of tunnel If there are any points I have not touched" upon, ■or on which I have not made mvsell clear, I. shall be clad to fumjfeh any fai-aer information in mr po.-«ession —I have, eta., R, HAY, M.1.0.E , F.G.S.

ESTIMATE OF COST. The estimate cf-the cost, of the Christ-chnrch-VVamiakariii electric power and scheme is as follow.;

Intake tunnels and gates 4 C OO Jixcavations for channel I7\nn Concrete lining " '" tk'f™ Flumii * •■••..- ;::; .::: IS? Totai - - ... 54/700 ACTION OP THE COUNCIL It was resolved, that the senior member U TT? '^ Ch Mr W ' W - Collins. -\ .M.R:. ] be asked to take charge of the Bill g 'T? Coundl the necessarj power o undertake the scheme. '