CITY WATER SUPPLY.

Colonist, Volume LIII, Issue 13225, 30 September 1911, Page 2

CITY WATER SUPPLY.

REPAIR OF THE LARGE DAM

EXPENDITURE OF £300 AUTHORISED.

At a meeting of the City Council last night tho following report by Mr J. G. Littlejohn was read: —

"I inspected tho big dam on Saturday last and found that, on the inside, the foundations from the scour pipe to the western abutment have been exposed by the digging of a trench along the foot of the wall. A large hole has been tunnelled into the face ontlie eastof the pipe line, and the eastern abutment has been undercut and tunnelled round the end. On the outside, two large holes have been tunnelled into the face of the wall, and the reinforcements have been cut. The plaster has been stripped from a large portion of the wall at the western end, and it has been greatly damaged in other places. To the loft of the scour pipe a crack shows traversing the wall from the foundation to the top, and on the right another crack shows starting at the top and extending two to three feet down the wall. Corresponding cracks show on the inner face, and the inference is that they extend right through. These cracks are unsigKtly and givo an appearance of insecurity, but the wall has stood sufficient tests to show that there is a margin of safety even in its present dilapidated condition. Tho wall is constructed with a core of poor quality broken rock without sufficient fine material to fill the voids. It is clear such material must allow the water to escape wherever the plaster on tho upstream side has been broken, and that leakage will appear at the back wherever the plaster on that side has been removed. It does not follow that the water escapes from the back of the wall directly opposite a leak on the upstream side, and tho points of exit are no guide to the position of leaks on the front of tho wall. Foreman Konning was clerk of works during a portion of the construction, and lie states that an impervious facing was put on the wall and extended into the rock below the base of the wall from the eastern abutment to tho scour pipe. This I believe has been verified in the various inspections which have been made. It is apparent however, that from the scour pipe to the western abutment the wall is based on inferior rock which is not watertight, and that the facing was not let into the rock as in the other half of the wall. I inspected the wall again on Monday last when the stream was in flood, and as was to be expected, it showed copious leakage all along tho back, but the main leakage appeared to be in the abutments at both ends and some distance above the foundation. In order to test the wall for other weaknesses than are apparent, it will be necessary to repair the upstream face and to plaster the rock below the foundations which have been exposed. The work might have the effect of stopping the leakage and tho Council could then consider the further work necessary for putting the dam into permanent use and tho ad--1 visability of removing any doubts as to the stability of tho structure by adding two or three light buttresses to the back of the wall. The cost of tho work at present proposed should not exceed £300. If it is successful then the cleaning out of the storage basin will have to he faced. The vegetable growth and mud should be removed before it is filled for uso otherwise the complaint that tho water is inferior will surely be repeated." Mr Littlejohn also wrote that ho could not undertake the responsibility of supervising a contract for the repair of the weir in the absence of working plans upon which a contractor could ascertain quantities or base a tender and the engineer certify to progress payments. Mr Jickcll's was a sketch plan only, and tho specifications did not provide for certain contingencies which should be covered before a, contract was let. He enclosed specifications drafted by himself. The Finance Committee reported as follows:—

Mr Littlejohn reported as to an examination he had made of the big dam during tho recent flood and of tho course he suggested should be adopted for the purpose of endeavouring to stop the leaks and render tho clam serviceable until more permanent work can be carried out. The Committee recommend that Mr Littlejohn bo authorised to carry out the work he proposed at an estimated cost of £300, and that the work be put in hand forthwith. Cr Hampson moved that the Finance Committee's recommendation be ulopted. Cr Fell seconded the motion. Cr Adams opposed the expenditure if £300 on the largo dam. That sum would go a long way towards putting the addition on the weir, and that was tlie soundest proposition before them. A rope way could be erected at small cost to convey material to and silt from tho weir. A road or tramway was not required. Cr Fell said the proposed expenditure on tho large dam did not involve the abandonment of tho weir. Ho supported tho motion. Cr Snodgrass said ho was impressed by the fact that the leakage from the largo dam Was not so largo as he had supposed. But they had to consider the fact that tho high levels could not be properly supplied from tho large dam. They should try to devise some scliemo by which those people could get an adoquato supply. He could not go past his own experience, although he did not live on what were generally known as the higfi levels. He still thought the only thing for them to do was to repair tho upper weir. Cr Harley said this subject was getting on 'his nerves. Some people couldn't understand., and others wouldn't. He was sorry to liavo to ineludo Cr Snodgrass in that number. They were all of the one mind that as long as water could bo got from the upper weir they would get it from there. Nine-tenths of tho people could he supplied from the large dam in time of drought, and why should they not be supplied. When they could not get water from tho weir the high levels could not get it any way. Ho could not see what objection there was to spending £300. If that sum would mend the dam it ought to be done. When the lower dam was boing used tho high levels could not got water in any caso. Tho Mayor agreed that the expenditure proposed would be warranted. As to exceeding that sum the Council would no doubt exercise great care.

Cr Kershaw said that after seeing the dam himself his opinion had changed. He thought it could be repaired for £300 or even less. But lie did not think it would bo any good when it was repaired. (Laughter.) However, lied would favour the expenditure, £300 was not much to throw away. He was very pleased with the upper weir, and found much less silt there than ho had expected. It could be left for this year, The Mayor said the weir was about tv third silted up. A very small expenditure would stop any more silt coming, in. Cr Hampson moved that tenders bo invited, in pursuance of the resolution adopted at last meeting, for the extension of the upper weir, in accordance with Mr Littlojohn's specifications. Cr Fell seconded the resolution. After 6ome discussion the Mayor moved as an amendment that Mr Jickell be asked to supply complete working specifications and plans, and that the work be carried out in accordance therewith. It was hardly fair to Mr Jickell, in view of the discrepancy in the estimates, to carry tho work out on other specifications than his. Cr Taskei- seconded the amendment. After a long discussion the amendment was negatived. The resolution was carried. Ayes: (5) Crs Farley, Hampson, Fell. Mer-, cer. and Adams ; Nors : (4) The Mayor j and Crs Kershaw, Tasker and Snodgrass.