THE WAIWAKAIHO BRIDGE.

Taranaki Daily News, Volume LII, Issue 264, 14 December 1909, Page 4

THE WAIWAKAIHO BRIDGE.

JJA.NCEI! UK COLLAPSE. IMMEDIATE REPAIRS DECIDED UPON. The state of the foundations of til; W'aiwakailio bridge has caused tile County Council some concern for months past, and there was a long discussion upon the matter yesterday, during which it became evident that the position was a very serious one.

Kl-'FEC'T OF TilE RAILWAY BRIDGE.

The chairman reported that be had met Messrs McLean and Jones, two (tie Railway Department's engineers, in connection with the uuniagc done to the \\ aiwakaillo bridge. Messrs Orbelil (Orbell and Mackay) and Palmer (Sl.uiden and l'aliuei j were also present win) them. At first the railway engineers had declined to admit Ltiat the railway bridge had anything to do with the undermining ot the foundations of tile county bridge, but he had stuck to it, and at Jengili impressed on them that the Couneii really had a claim upon the Department lor some assistance in the matter oi remedying the present state ot alia ire. Although they had considerable diffidence in expressing an opinion as Lo the best means of overcoming the ■... Mr, McLean bad favored the construction of some protection similar to that placed iu front of the piles of the railway bridge, with a weir below the bridge but rather further down than the present one. Mr. Brown said lie had drawn the engineers' attention lo the removal of stone from the river in the vicinity of the bridge, anil they had agreed with him that the limit of al) yards' distance was too small. Air. .McLean promised assistance in the ewiiL ol the Couneii attempting to secure an amendment of tile Puulic Works A-;t which would increase tile distance n.i either side of a bridge whence it .\ i unlawful to remove stone front the river-bed. As an outcome of the conference it had been decided that win >i the Council had decided upon a scheme for the protection of the bridge, t-io plans should be submitted to the Department, with a request for some finan.-iil assistance; and they would give the maltcr their full consideration.

REPORTS BY EXPERTS. Messres Orbell and Mackay reported: "Owing to stone being taken from (lie river-bed some little distance below lbbridge, the river at this point has iioiv a greater fall and consequently a greater velocity than evidently was an ticipatcd when the bridge was built, and this is causing a considerable amount of scour at the pier foundations. The railway bridge, with its wat-r----divert crs, being only about threee chams further up the river, 'lias apparently caused the river to divide into three channels, and as each of the railway piers happens lo he above the centre of each span of the county Jiridge. the !■•- still is (bat each of tile three centre pieces is in these channels. It will l-e obvious from this that a bank has formed 'behind each of the railwav piers, and extends as far as the county bridge. In our opinion, if water-divert-crs are placed about 25 feet upstream iu a line with the piers of the county bridge the water would be diverted frn ii the piers and that a similar bank wo.ii.l form lieliind the water-diverters, and so protect the piers. The would be similar to the railway ones, that is, three piles to be driven forming a "V" sliajie opposite each pier. It is very hard to say what, if will cost to drive the piles in tlie 'iied of the river, but we consider it should not cost more ITian Cl5O foV the three sets. In regard to the Fitzroy end pier Mr. Cloller

informs us tfmt the bottom of the I'icr is about six feet below the present water level, the lower portion of the pier bring built without boxing, and if this is 550 it will onl 4 v be neeeosnrv to length* cn the wing wull on the downstrum lide a distance of about eight feet, our ('stimuli? of which is about £20." .Messrs S hid den and Palmer "The weir put in to raise the level of the river-bed at this bridge has given u'jiv on the western side, about half only remaining in place. This has had the effect 01 causing the water to sec towards the \Vcstern bank and of cutting nut a deep channel oil that side to some extent damaging the loundalions of the centre eonuete pier und the western abutment. U is quite w lain thiit the continual removal of stone from the river below the bridge lias had the effect of permanently lowering Iho river-bed at the site of the -bridge, and this will 110 doubt continue unless some means be adopted to chock the >oom\ ;mi<l restore the bed of the rm l r at the bridge to somewh?re near iu former level The only way to accomplish thi> will Ixi bv means of a wirir of some description, and we suggest that ®nc be constructed rather lo.ver down than the site of the ree- iins of the present one. We suggest I hat it bo I'Ohslrueted of boulders in wire netting of about six-inch mesh, and made of No. 10 galvanised wire. This description of work has been found to answer «nl!staetorily in shingle river-beds: in various parts of the Dominion, and we thhiK libit it will probaolv lie the cheapest method of obtaining the desired result. Any oilier description of weir miUit have its foundations carried down to a considerable depth below the river-b&l, with correspondingly increased cost. It will also be desirable to do some little repairing work nt the foundation of the centre concrete pier and at the western abutment, in the way of underpinning, etc.. we feel confident that the construction of a weir such as we sugwill soon cause the riverbed to fill up again to the requisite height, it appears that whatever is done should be done without delay, and in the meantime we would suggest that the remains of the old weir be moved wherever necessary to prevent the water cutting ir. the piers anil t.he bank. We do not think it will be any use trying to repair the old weir, and though the construction of such a one as we have outlined will probably lie £250, wo do not fcr.l justified in recommending any other course, as anything less substantial could only be looked upon as a more or less temporary expedient." CONSENSUS OF OPIXIOX. The chairman said that the whole of the engineers present had been satisfied that one of the causes of the scour was the removal of stone from the river-bed. All the local engineers were of opinion, too ,that the railway bridge was one of the causes. THE DISCUSSION.

Cr. Tate said he had known the rnvr practically all his lifetime, and he was convinced that both these causes wets having their disastrous effect. He moved that, cut-waters be placed To prfotect tlie piers. Cr. Carter couldn't see that these cutwaters would do much to strengthen the briil-re. The cut-water would doubt-le-s divert the scour, but what was gonig (o be done to bring the bed of the river up to a more normal level? Only the erection of a weir could do that, and the work of making the weir should bo proceeded with at once. Cr. Hopson couldn't see that the weir vntiid do very much good. He wo.ul favor the cut-waters, to sec how they would act.

Cr. Andrews was strong in his n,dvecacy of the weir, which in oily a fo>v freshes would bring up the level of 'ip river-bed. Tie mentioned the success of the weir in tile Stony river, a mott rapid stream by far.

The chairman sattf lie didn't claim io W an engineer, but he had seen a hit in Mis time, and worked on bridges, and he thought, the erection of a weir was th" proper course. Hut the weir pri. posed would bo waste of monev, for it would not boh]. If the Council wen prepared to erect a weir costing £00') lie would vote for it; if not. then Mr. Orbell's sclieme of cut-waters must be taken. But so long as the railway bridu-e remained, with those cutwaters, then there would always he the necwsilv of ent-TVatcrs to prevent the scourHi/ out around the piers of the eonmv briilw.

f r. Carter said it seemed to be accepi. Ed 'hat 111" in-eat cause of the scour was '.lie removal of such large quantities Of Slone from the river-bed. The cutwaters >tou!i? never remedy that. Cr. Tate, replying, said the ridin K finance would nut bear the cost of the erection of a weir, which, to raise the bed of the river by three o r four Vet at the bridge would need to be built to n height of ten feet or more. The roinoval of stone would continue, md eventually the foundations would be scoured out. He asked the Council to rememoer that Hie Fitzrov Town 110-u-1 bail to bear lulf the cost of maintenance.

r. (.artel- moved, as an amendment, tli.it (he (Jovi-rnnient bo approached With a view 0 f obtaining a report from Mr. (i. T. Murray, the District Road Elgiiieer. Iu speaking to the ameudmenc, ie stated that there would be more chance of (ioveniment assistance before the expenditure was undertaken than afterwards.

( r. Andrews seconded the amendment. (r. Stevens urged that there was no time to wait for an additional reporr,. lie drew attention to the fact that ri»ht I "rough Taranaki's history the big "freshes'' iu tin- rivers had been in Febt'l'ary. and that in that month the Wai. wakaiho and several other bridges li.id been washed awav. He urged the immediate erection of the cutwaters.

The amendment was lost, only Crs Carter, Andrews and Allanson 'voting for it. The motion was carried, and it was decided to forward plans of the proposed wor!{ to the Raihvav Departmeut and to the Fitzroy Town Board. I lie matter of having tlie work done by contract or by dav labor was left to 1 tie chairman, to arrange with the engineer, Mr. Orbell, whose scheme the Council adopted.