SELWYN COUNTY COUNCIL.

Globe, Volume XXI, Issue 1712, 15 August 1879, Page 3

SELWYN COUNTY COUNCIL.

A special meeting of the Selwyn County Council was held yestorday, the Hon. John Hall in the chair, to consider reports in reference to the Malvern water race and other matters. The chairman delivered a statement as follows :—The business requiring your attention today is very limited. As directed at your last sitting, a report has been furnished by Mr Wobßtor upon the recommendations contained in the joint report of Messrs Dobson and Bell with reference to the damage done by the flood to the Malvern water race. As I was given to understand that it was the intention of the resident engineer's department to make further provision for the water whioh traverses the railway extension to Springfield, _ I have dolayod communicating with the Minister of Public Works until the character of these alterations was ascertained. The information on the subject is not yet quite complete. The further report from Messrs Dobson and Bell, which they were requested to furnish on the subject of the continuation of the Malvern water race, has been received and will require

careful consideration. As I gather that it is your wish that some experience should be obtained of tho working of the prejent race before any continuation of it is undertaken the latter question must stand over for the present. Gravel and Pound Reserves recently vested in tho Council.—l have not yet received the opinion of our solicitor on the subject of the leasing these reserves. A return is being prepared showing which of them are already leased, and the terms and the rental for which they are let. You will probably therefore be able at your next sitting to arrive at some definite conclusion with regard to the best mode of dealing with these reserves. Subsidies from Colonial Treasury.—l regret that the subsidies for the six months ending the 30th June last, which should byjlaw have been paid during tho past financial year, have not yet been received. Under existing circumstances it would probably be useless to apply for them. Templeton Eoad Diversion.—The committee on road diversions has presented a report on a proposed exchange of roads in the Templeton road district, and recommends that the decision of the ratepayers be confirmed.

An application for a slaughtering license having been considered and dealt with, The Council proceeded to tho special business of tho meeting, namely, the question of the Malvern water race, upon which Messrs Dobson and Bell had been retained to report. At last ordinary meeting a report from those gentlemen was road, and referred to the Council's engineer, Mr Webster, for a further report.

Mr Dobson sent in a report relative to the repairs of Ellesmero Bridge, and a report was read as to certain matters of detail in connection with tho Malvern water race.

The engthy report from Meters Dobson and Bell was then road to the meeting Following npon the above, the secretary read a report from Mr Webster as follows : Lombard Buildings, Heretord street, thristehurch, August, 1879.

To tfce Chairman Solwyn County Council. Sir, —I have to acknowledge the receipt of your letter, dated 25th ult., forwarding a copy of Messrs Bell and Dobson's report on the Malvern water race, with the view of affording me an opportunity of making such remarks as may seem to mo to bo necessary. 1. I have already in my report, dated 2nd July, stated that I attribute the displacement of the falls to the nnderscour, against which at the time of the flood there was not any protection, except in the case of tho eight which remain undisturbed. Had the whole of the falls been secured to piles driven into the solid shingle or to sills extending into the banks of the race, without packing at the back with gorse, I do not think tho case would have been improved, as the water would still have parsed under the falls and scoured the channel, so that the longer they remained in position the greater would have been the injury caused by erosion to the banks of the race ; but had all been packed with gorse, tho wings filled in with the same material, a hurdle as described in the report beforo alluded to placed in front of the cushion, I am of opinion they would have stood the test so far as the water did not reach higher than the ground level, which would allow 2ft. on the crest of each fall, or Gin. more than it was considered possible they would have ever been required to carry. At the lower end, where the water cut through the banks and across the race, I do not think any material would have prevented serious damage to the works ._ 2. With reference to the railway lino there can be but little doubt that it collected the water at tho creek crossing, and that the new concrete culvert caused the breach in the bank of the race, admitting the flood water at the upper end. It is true the that the flood overflowed the weir placed there as a protective, but the quantity would have been small compared to that which entered through the opening in the bank. I therefore fully concur in the necessity for remodelling the line, and think that with proper protective works the recurrence of a similar flood would be impossibie. 3. The straightening of tho creek at sm. 47c. is very requisite, 'and the recommendation to replace the culvert by an open timber viaduct essential. A new bridge at the road crossing will also have to be provided, as the present one is a very rickety structure. 4. The bnilding of the supply and overflow weirs with concrete, having sluice gates to govern the water, has been proved a necessity by the late flood, and I think that the creek crossing particularly required something more substantial than timber, as it appears to be the most dangerous point on tho whole line of works : also that the overflow channel through Eeserve 1241 is requisite, as the present outlet is only a roadside drain.

5. These works will certainly not cost less than the amount stated. 6. The opinion that the race will not for some time carry water except in flood time, owing to percolation through the shingle, and that the bottom will require to be puddled, or otherwise made watertight, I cannot agree with, and would remark that the first flood discharged water into the race to a depth of 9in.; that it passed the whole length in a few hours, and continued to flow till stopped by the foreman of works. Now this was not by any means an excessive quantity, as the race was designed, when finished, to carry 18in. and I consider 9in. the minimum supply when all the works are in order. Therefore, if at the first, when the race was dry, and capable of absorbing the greatest amount of water, the smallest quantity it is likely to receive at any future time flows the whole length, and continues to do so, it is only reasonable to suppose that as the percolation will decrease daily, in a short time the race will serve its purpose equally well with those portions previously finished, which are unlined, and from the first have carried water. Further, in support of my opinion, I quote the following from a letter on the Oamaru water supply, published in the "Lyttelton Time 3." ** For the first two and a half miles after leaving the settling pond the races traverse a shingly flat, situate between the low lying hills on the south of the river and the river itself. Some would imagine that the water must be lost whilst traversing such a long length of apparently porous ground, but such is not the case, although no attempt has been made to line the race, and the shingle, which is of a loose character, ha 3 been cut into a depth varying from 18in. to 4ft. 6in. 7. With reference to the surface drainage, I have always been of opinion that it should not be allowed to enter the race, that it should bo carried across by culverts or fluming, and certainly agree that it is best to take it under, where possible. The arranging and providing a better system for the district is much required, and necessitates the co-operation of the Government, County Council, and Eoad Boards ; should this bo done, Btorm water would not continue to bo a continual source of annoyance. 8. The observations on the works at tho tunnel agree in many respects with opinions expressed by mo from time to time in my monthly report to tho Council, especially as regards the open race, the dam, the insert of tho tunnel, and the sluice gates, but with reference to the brickwork of tho tunnel being solidly packed, I have been informed, and I think the statement is correct, that the timber lining used in its construction was allowed to remain, whereas it should have been removed and tho cavity between the brickwork and earth filled with concrete, therefore I do not consider the tunnel safe to carry a full head of water, and am of opinion that it will require constant and careful supervision under any duty it may be required to stand.

9. That the invert will suffer with excessive scour of shingle is certain, and precautions were being taken to prevent its entering the tunnel. The alterations in the sluice gates, I think, should keep out the shingle, and the addition of the pit in the floor may not be required, especially as it will always be necessary to have a resident caretaker, whose duty it will be to keep down the shingle by using the flushing sluices. The openings of these and the retaining walls are worn, the repairs proposed are therefore requisite. 10. I do not think there need be any apprehension of tho stream leaving the right bank, as during the time I have had charge of the_ works no difficulty has been experienced in keeping a full flow direct to tho sluices. Should these bo lowered, the probability would bo still less. Tho estimated amount of water that tho tunnel can discharge with safety is forty-fivo millions of gallons in tho twenty-four hours, and the amount that I constructed the race to carry wa.3 fifty millions. The question of using tho old creek bed in place of continuing Tthe race along the reserve presents a different aspect to what it did when I first had it under consideration. At that time the railway was not surveyed, and therefore it was not considered. I thereforo now fairly admit all tho difficulties of constructing it by tho side of the line, and the greit obstacle presented by tho Springfield station, and think that under those circumstances it will be advisable to adopt the old channel, and by straightening and otherwise improving its course fit it to carry tho necessary amount of water. 11. Having now touched upon all the points of importance, tho main point at issue appears to be timber versus concrete, and with reference to this I would refer to the report of tho committee at tho time of my appointment as your Engineer—" Thoy recommend that tho engineer be instructed to go at once into the question of using timber, heart of totara or hoart_ of black birch, for tho necessary direct falls instead of concrete, which has been used at present, as they feel convinced that a very large saving conld be effected by using timber, and that falls of old seasoned timber would last a very long time." 12. After fully considering this, laccepted tho responsibility of using timber being then, as now, convinced that it would answer, although it must bo admitted that it cannot be compared

with concrete for strength and durability. This, &owever, was counterbalanced by the cost, which I always understood was a very serious obstacle io She continuance of the work. 1 would, therefore, submit that further trial should be made with wood, and that two falls be constructed on the creek at the end of the upper race, that that be subjected for two weeks to tho heaviest flow of water that can be brought to bear upon them; this will prove their stability, and enable the Council to decide finally as to the material for future use, as the late accident to the works is not conclusive, and to condemn the use of wooden falls on the present experience cannot be considered satisfactory. I have the honor to be, sir, Your obedient servant, John Webster. Engineer. The Council, after some discussion in committee, decided to postpone further action till next ordinary meeting. Mr Enys moved, and it was carried — " That as the Bafety of the Malvern water race may be seriously affected by the provisions made for carrying flood water across tho extension of the Malvern railway, the district engineer bo requested to furnish a statement and plan of the works proposed, and to confer with Messrs Dobson and Bell upon the question, as it affects the water race."

Mr McMillan moved—" That a letter be addressed to the district engineer, drawing attention to the fact that the railway station at Sheffield as at present erected has been placed on a portion of the Three-chain reserve, which has been vested in the County Council for the purpose of a water race, and that on the water race being continued the removal of the station would therefore become necessary." The following resolution, moved by Mr Enys, and seconded by Mr Perryman, .'was also carried:—" That the decision of the ratepayers re the stoppage of the road running between the sections 4009 and 2107, in exchange for a strip of land one chain wide down the west side of sections 2106 and 2197, in the Templeton road district, be confirmed." The Council then adjourned.