IMAGE EVALUATION TEST TARGET (MT-3) y /- 4r ^< ^ 1.0 1.1 11.25 ■yuu u 1^ Photographic Sciences Corporation NT a>^ ^ ,v iipt>iiiilble fur tbo fnots Mid opliUoiu Htatud In any of ItH piibllcnUuno* THE COxNSTHUUTlON OF C'OTEAU BKli)UE Geo. a, Mountain, iM. Can. Sor. O.K. To be lend Thuisclay,'3Jrtli Mi.reh. •I' 111 tlie uutuuiii -ul' 188U thu Ciiiiudu Atlantic Kuilway Cuiupany decided to replace the Terry used lor the truuMportutioii oi' i ir» acroHM the river St. Lawrence, between (Joteau Landing -and Valioy- Seld, by a bridii;e, the i'erry being found inadequate lor fche com- .- pany's cunHtantly increa.>iiii)>' biisiuesH. Al'ter nuinoroiiH earel'ul .surveys exteiidiii<^ ovur a period ol' three . neasons, the site linally selected lor llu^ bridge was at the head u'.' the Coteau Rapids, :{7 niiles west of tliis city of Montreal. This site, while it posse.s.sed many advantaii'es of iinportitnce to the com- • pany on the score of economy, on account of the islands situated on the line of the proposed bridge, also ])o.ss('ssed iniiny difficulties from an engineering ])oint of view, principally the depth and velocity of ■ the water. . ■ The width of the river, which at the bridge site is narrower than at any other point in the vicinity, is divided by two i.slands into three distinct chumiels. 'I'lie north or steamboat channel from th« . north shore to (lironx Islaml beinu SSfi fc.'i in width. The centre channel from (jiroux Island to Kouiol Island being 22)tt feet in width, and the south cliannel from tiound Island to the south nhnre being 930 feet in width. The length across Giivux Island beins 9t)5 feet, and across Uotinil L-iand V1'H\ feet, making a total Icuuth of 1(150 feet from north to snulh slioie. with 4025 feet of bridging.- The banks of tli.' river on either side of the bridge site and the intervening i.shmds ai>' low, anil sloping lowaid the water, and it was ■ on this accounl that 11 low level bridge, with a swing over a ])ortion of the north or steamboat eljannel, was ileeideil upon. The ilevalion of the rail level of the bridge, which is a l;|irough truss from end to end, is 25 leet above tin; ordinary summer water level, anil the alignment of (he bridge is a tangent from shore to ; shore, and is divideil into spans, as fnllows : The 1 vth or steamboat • channel beinu eomposed of two lixed .-pans of 175 leet each centre to centre, one of Kill feel eintre to centre, and one swinu .span of ;{55-. feet centre to centre of toe .seats, giving an opening on either side of the pivot pier of Ititl feet in the clear. The centre channel is composed of ten lixid -pans of 217 feet each centre to centre, and ' the south channi'l of four tixed spans of 22;» feel each centre tij. centre. The islands are ul |iiesent crossed by trestle work, which it is the intention of the company to fill and form a solid -cmbu^ik- ment. In the north or steamboat channel adjoining the (Joteau ahorc, the velocity of the current is seven miles per hour, and on account of navigation thi^ course of steamboats and rafts passing down had to be kept clear, and the dredges, barges, and plant usi'd in the coii- Btruetion were in constant danger of biding run into and sunk. The velocity of the current in the c'ntre cluinin'l was between five and six miles per hour, and the shoal water 1000 feet above the bridge line rendered the navii;alion of tlu! tugs and barges very difficult.! In the south channel the velocity of the current being sis miles per hour, and the bed of the river above the bridge line bare rock, great difficulty was experienced in the anchorage. The maximum depth of the water in the north ohanael, in whio|t Wert pUoed four piera, inoludinK tlie pivot ni)*' ..nd two Bbutmeuts, U 30 feet, thu luiaiiuuin being 24 tuet, and thu boringti Hhowod a eoveriDg of from 4 to I) fetit of cemuntud gravel tiiid bouldertt abovt- the bed rook. The maximum depth nf the wiitur in tliu centre ehunnel, iu which were placed aine piem and two iibutnieuts, wiim 2(i foot, the miniiuuin depth being 20 feet, and tiie borings here .showing ii covering of from 3 to 8 foet of crmentod gravel and boulders above the bed rock. The maximum depth of thu water in the south ohuuncl, in which weru placed three pierii and two abutments, was 24 feet, the mini- muQi depth being 20 feet, with » covering of from 'i to G feet over bed rook of ft similar material to that found iu the other ehannelH. No trouble whatever was experienced from the variation of water level, the rise and fall not exceeding " ' 6 ". It might be in place here to uientiou the manner in which the triaagulations were performed to obtaiu the widths of the ditferent obtDOols, and in which the positions for the piers were arrived at. The instruments used were an (tight inch transit, a 300 foot steel tape, and pickets. Owing to the marshy ground on the north shore on either side of the bridge site it was no easy matter (o obtain a base line, and idvau- tage was taken of the winU.tr when these marshes were a solid level field of ice; on them a base line was measured at ri>r1it angles to the line of bridge, and from this base the wi>lth of the north or steamboat channel was calculated. 'I'he hypothenuse of this right angle triangle was then used as a caleula*^ed base line to establish u point on Maple Island, situated mid-way iu the centre channel, and about 1200 below the lin'- of bridge, by connecting this point with a point on line of bridge tn the south shore of tiiroux Island, fave a calculated base from which the width <>i the centre channel was obtained ; these operaiions were carried on in a similar manner from the south shore, and the point on Maple Island was again esiablislieil from this side, giving the adjoining side of the centre triangle, taking this side as a calculated ba>e, the distance across the centre channel was again obtained, checking with the distance calculated from the north side to within .06 of a foot. The point thus established on Maple Island was L'-wd in laying otf the angles for the position of each of the nine piers in the centre channel. A point was similarly established on Swan Island situated in the .south channel about lOOO feet below the line of bridge, and from which the anules were laid otf for the posi- tion of the three piers in the south channel. A point was also established ou Mclntyre's Island, situattnl in the mirth ehaunel about 1200 feet above the bridge line, and from which angles were laid otf for the position of the four piers in the north ehaimd. The angles were taken by two engineers, and by the method known as repeating the angles and the mean of this repetition lakeo. any little variation found iu the three angles of a triangle from ISII" wa.s divided pro portionately among the three ancles. 'I'wii months were spent In this manner during the winter, until the enirineers were fully satis- fied that tH-- widths of the channels and the position of the piers were accurately obtained. A plan was then made on a scale of 50 feet to the inch, and with all distances and angles marked on it. little trouble was necessary to fix the position of a pier at a few moments' notice. The specifications for the substructure required a bottomless caisson 20' in width and 67 ' in length over all. and pointed at both ends, the bow being a richt angle and the stern somewhat more acute : this wa3 done for the purpose of steadying the caisson iu the rapid current, and also to prevent the formation nf an eddy. The walls of these caissons were built of 12" x 12" pine timber, and were stitt'ened by means of 30 uprights fastened 'o the wall on the inner side, and tied across by 46 cross ties placed about 4 foot cen- tres, all of the same material and dimensions, they being heavily spiked and bolted together. The caisson used for the pivot pier was designed in the shape of an octagon 36 ' in width with sides of 17 ' in length, and was built of similar material and dimensions as used in the caissons for the othar piers. 2 The ■peoifioatioDi for the mkioary in the bridge ttbutmenta and piers reqaired to bo first olufM id every reipoot, aad of the beat and largest HtoDe that the quarries afforded. They required ( be Rouod aud durable, free from all drys, shakes, or flaws of any kiod what- ever, and must be of suoh a eharaoter as to withstand the action of *^o weather. Nn course loss than t5" in thickness was allowed. The beds of all stone fur face work, and the backing, where required to receive headers, were dressed parallel throughout, so as to form quarter inch joints, and the vertical joints of the face stone were dressed back square for 9 ", so as to form quarter inch joints. Headers were built iit every course not more than 6' apart, and so arranged with the adjoining courses as to Ittave them equally distri- buted over the faces of the structure ; they have a length in the face of work of not less than 24" and a depth of at least two and one half timea their height. Stretchers required to be not less than 30", aud their breadth must be at least one and one half times their height. The vertical joints must le so urraugel as to overlap those in the course below at least 1 foot. T'lie copings ami bridge seats of all piers and abutments required to be 24" in thickness, and dressed square throughout to quarter inoh joints. The vertical joints of the cutwater stonus were dressed back square to the full depth of the stone. Iron clamps of 10" in length were used in clamping the cutwaters. Dowells of an inch and one half round iron were let through one course and one half of masonry. Over the cutwaters no«c pieces of | inch steel were placed 12' in length and run- ning back 2' on cither side, bolted by means of fox wedges to the masonry. All masonry was laid in fresh ground Porrland cement, thoroughly mixed with (iood, clean, sharp, coarse river sand, in the proportion of one part of cement to two parts of sand. The cutwaters and bridge scats were laid with mortar in the proporiion of one part of oemeut to one part of sand. The (;emfut was tested from time to time by a Fair- banks ceiutiut tustiug machine, and after setting from 10 to 20 days stood a breaking strain of from 275 to 410 pounds to the square inch. The dimen.sions of the piers which are shown in the accompanying sketch are 48' x 11' 6" nt the base and 24' s 8' at the bridge seat, the oivot pier differing from the others in being a cylindrical column of 27' in diameter, with a footing; course of 29' ti". Towards the end of the autumn of 1888 the contract for the sub- structure was awarded to Messrs. Ncelon, McMahon & Shea, of St. Catharine.'!, and during the following winter quarries were opened, stone was cut, barges built, dredges overhauled, and all necessary pibnt put in readiness for the undertaking. On tlje 1st of April, 1889, ground was broken in excavating the foun- dation for the abiitmcmt on the north shore, and this was carried on while waiting the breakinu up of the ice on the lake above. The icH having passed down on the 21st nnd22n'i of April, a dipper dredge was brought down to the bridge site on the morning of the 24th, and ranged up into position to prepare the foundation for pier adjoining the north shore, dredging down stream. This operation occupied 15 days, aud the dredge was then moved over to the position of the next or pivot pier. It was while working at the foundation of this pier that an accident befell the dredge, a raft, composed of nine drams, passing down in the early morning, struck the dredge, stnashing a hole in the stern of about 15" in diameter, and notwithstanding that every effort w«a made to save her she sank a half an hour later, in 28' of water, the bow being pinned up on her spuds held her partly above water at that point, which greatly facilitated the operation of raising her, which was succesb- fully done in a very short period. A similar dredge was placed in position on the pier adjoining the south shore, and worked towards the centre. It was not permitted to make the excavation for the caissons more than a week ahead, when they should be placed in order to avoid any danger of the excavation filling up. To do this dredging successfully in from 20' to 30' of water, and a current of from 6 to 7 miles per hour, required very car«ful mnage- ment and extrnordinary precaution. Frequently during the progms of thii Work oak spuds of 18" x 20" were snapped off. 3 Till! iv«t operntinn wiii the plucinp of llu- ciiisRonH, Thoso when com- pleted were pliiecd between tWM liai;;:es, on each of which was erected a frame to a hei^rht of 'JO' ahove tlie tioek ; across thc,s(> frames two 24" iM|ii«re pi('ccs of oak w.rc placed, aiKJ^from these 1 tacklis of iarp' (|iltt driiplc blocks rccvcl with f." maiiilla rope, triiidi'd hy lend Idoeks, to wiiieiies on lioard the iiarj;cs, wi re iiscil to lift the caissons. 'I'lie tirst caisson was lowered with liydvanlii' jacks from ciddioiise crihsonthe deck of the har.^es; ImiI this method was ftmiid lobe extremely Mow, ami was aliaiidoncd fur ihc lilock and tackle system above described. Thii caissons were provided with .'! anchors, varyinj; in weight from 1^ titH tons, nnd llu harucs with 1 each all hove with H inch steel wire cftblcs. '\V1ien the excavation' was ready the caisson and barges were towed lint into the enrri'nl from where they were built, about 1 mile above the bridj;e site, by from two to live 1 nits, and were allowed to drift down to their position, the l.ius steamhcj' slowly np stream; H()(l feet ubiive thelini' of iirid'^c thViniiiu anchor was let un. I he o'.bers ibllow- im; in ipiick succession. »>n ihc anchor-- lakini; hold the tugs were let .'O and HV I'lavinj Unt fhc calilcs the caisson was allowed to drift down to withfii 25 feel of itsiiositi.in ; it Was here heavily weiL'hted with rail- wav iron, and low.'red to within a few feet of llic bottom. The caislion was then eas.'d back until it was broUiihl to the exact po.sition pivviouslv fixed by triannulation , all that was (hen necessaryto sink it wiis to i'ase away on the tackles sininlta nsly until it reached il.s bearinjis cui the bed rock. Should it not set in true position the tirsl time some of the weijiht was ri'moVcd, loid tin' strain taken upon the tackle,^ when it could be raised without ditlicully ; but it only occurred once or twice that a cais sun had "to bo lifted after once haviuL; licen placed upon the bottom. Wiien it was finally setli'd in position it wa.^ additionally weighted with railway iron. :>nd the t'ooiini; eioir.M' of ma.-oiny was also placed upon the wall of tin eai-son. In lakin;i lln' eai.-.sons down it wassiune tiiiies I'eund li. ces.-ary. owiii:' lo shoal wall r, to raise lliem to a 11 foot dVaft, uftd tor this purpose ihe blmk and laekle system was found exceidingty successful. ■liipliicilig the .■'ai.s.son ailjoininu, the pivol pier on the ^oulh ..ide, cou sfdeVable ditheulty was cNperienci'd. owini; to the ■jr.'at depth of water 30' ■ atld' the vetoiitv of Ihe euni'iil. which al llii> point is the swiftest in till' viiinils oC ih,' lirid.e. :iiid lieinu in close proximity to the steamboa't channel, llie >we|l made li\ llie sle.iinli.ials p.issing doiS'n was'seVefely fell. .Mier Iv.o nuMUce-sful allempls lo place lb.' caisson it filially iapsi/.eil. ilaniajiu'.; one of iIk' li.irv-'i'S used in Ira'n'spnrtiuu it, ami llirowim.: il.- Io;ol of i':iilway iron into ihei'XCiiNa- lion. The lop of the eai--on w.is so liadly dania'..;ed a- to mecssilati' cutting it ilown. ami uslie.; il I'oi- a piir oil. ■<> depdi of water, and build iu'* a new one lo replace il. .\ di-.dgewas auain brou'jiil down to redre'dvie the excavation, uliieli wa- paillv tilled up hy llie loaii eapsi/.ed from the caisson, 'riienexl allempi |o pho-, il wa> -neee»lnl, .ind no fdrthir tnoiblc wasi xperieneed at this point. 'I'lii.- caisson was con sidcVed. next to the octai^ooal laissmi for the pivot pier, the nni-'t diffi- cult oiie of the bridge »n et. The pivot cai.«.-oii on ai'eonnl of ils construclion preseuled a treuien dous resisfanei' to the .iirrenl. ' ;"• Inj-amI a l.iiiie sidewhi'el ^hanier beiu" unable lo Imld it in llie >will wal.r. .S anchor- .'aeh liove with a 1"A inch steel wire cable were lei .jollMIO feel above the bridiii' lili'-, and the cables slacked away ami the caisson dropped back into position Two of the Ih inch steel wiri' cables loanchors were led to blocksmad. fast near the bottom ni the eai-son. ami taken to lindn-r heads on deck, in order to ludd the eais.son in an iipriLdil position, .mil preMiit ils be- ing carried (Uit of pUnub by the .-tiff lurrenl It was at this pier that the only fatal aciideni dnriiie the construc- tion of the work was sustained, re>ulting in the loss of llie lives of two men, both by drowniiej. — one during the eonstrnelion of the subslruu- turc and the other durnm tin' ereeliou of the superstructure. Owing to the current striking the bridge line nearly at right angles, the caissons for the piers in the vntrcs of the chaiiinls were subject to "little or no side current ; but those adjacent to the shores and islands •■ ■ ■ . -4 roouivL'd the full I'orco nf the curri-n) on niii' hkIc nf the how, and !;reat pruoaution hud to ho tukitn to prevent tlieiu from l)ein^ swept out of poHition ; thiH waHdone hy nieiinH of iinehorH pluetMl on the inshore Hide, and from which the eableM were brnu){ht lo theuupDtium fixed iit both bow and ttU'rn of the hnrjieH, iinil in thix iniinner held in |Niiiition till 8UDk. It wus not, fonnd nceexsiiry lo serilie the liotloinsof the eainHonn, an they invnrittbly filU-d elohM- lollie lieil roek, wliieli was renmrkiihly level and dredged thoroughly eliiin. At the early Htuu;eM of the undrrtiikin;; il took three dayx to plaee and Niuk u uuisHon. hu. '-s the work prouresseil (hey were plaeed and Huuk in il day. On the euin^on linalls In in^ si-(lled und \vi'i<:liti'd in i(s position, th« l)urge.s u|K>n which il wus triiiis|)»rl 'd wen' then riMiioved. Uiversi were then Hunt down, and u canvas enrlain, *! feet wide, whivh had been previously nailed on the inside of the eaisson 2 feet from the bottom, wus unrolK-d, and U|iiin this wen: ])iled hui^s of concrete to prevent uny wasii to the eonerete afterwards to he deposited. Unee eomuiunued the eoneri'linu; was eurried on eontinuously day und ni);ht, until uouipli'ted. A lloatinu eletHrie liirlit jilanl furnished the light for the nijiht work. A di'rriek seow wus plaeed alongside the cais- son, und us the eonerete wus mixed it was deposited in iron boxen with false bottoms holding from one lo two cubic yards, und lowered slowly into the eaisson, aiidihe bottom tripped, thus preventing the sepuration of the materials whirli would ensue i'roiii allowing the eon- erete to full tin|iroti'eted through llie waliT. The romposiliou oi; the eorieri'le wus: one purl of Kuglisli i'lU'tland cement, three ditt'en ;it lirands lining usi'd, —White's, Johnsiui s and Union, — one part of sand, and lietrti'i'u tlirei^ and four parts of broken stone (d' 'I" euhe. A bed of eiuiereli' was thus olitaiuiMl. varying in depth from 8' to lli' and all l>rciui;lil lo tin' unilorm Iniglil of 12' below water level, at which point the masonry in all casir- was started from. After allowing the concri'le IH hours for setting, the caisson wa.s pumped out with an H" liorizonlai ei'nlr'fugul pump driven by a 30 horse power engine, both on a seow alongside and connected with the caisson by a niblier suction hose. The pumping of a caisson usually took from 20 to Kt niinuli's. and little or no trouble was experienced in keeping iheiii drv, they beiii.: thoinuglily caulked from top to bot- tom. Whi'ii this was a im|ilis|ied llie masonry was commenced and carried on to completion. Tht^ e(Uicrete was liiund in all cases to have sm llioroughly set us to nuike it as dlihcnit to dress II lo receive llie nnisonry as an ordinary footing course. The caissons w<'rc riprapped on the outside lo the level of the top id' the ccMH-rcle. The stone n-iil for the pieis and abuinienis is lime stone, and wus taken frcun the ipiairii's al Apple Mill and Caughnawaga. the last >tone being laid nii Kecenilier the sixth, Ihns occupying the space of eight uionlbs anil six days in the cnnshncl ion nf the substructure. The (piantities were SIIIMI cubic yards of masonrv. and 7000 cubic yards of concrete, in which were used 25,000 barrels of Portland cement. (n the winter of l^ss, the contract for the construction and «»reetion of the supcrstrueinn' was awarded to the Douiioion Bridge (.'ompany of Lachinc. und preparations were at once commenced for the undertaking. Specifications prepared by the railway company for the super- structure rC4uired that it be of the rivetted lattice type, and the general design finally adopted had a double system of triangular or inclined web member?, inclined batter or end posts extending over one panel and girders of the swin;; span, and the longer fixed spans of varying depth, only llie central upper chord panel of the fixed spans bciag horizontal, the chords sloping each way from the central panel to ajunctioii with the butter posts, the depth of the girders at ends being made just sufficient to give the required clearance between trac^f and portal bracing. The use of iudiocd chords results in small economy of material, reduces wind surface, and gives good depth at centre of span with oorrwponding mnall deflvctimm when Inadcd, nnd hence xmalt w^oond- «ry strains nt siid iifur tlic vunnt'ctinns iirwi'*^ iiioinbi'rM on oliordN. The duptli ni' wutur, t'oroo of uurront, mid niitun* of the bottom «f«re Huah, that tliii Hitting oC t'lilMc work and llic iixsrndiliiiK '>!' tli>< luvtal work in pluui- in tlic iimuhI wny would liiivr Ih'i-ii difficult, u-id sttendud with gri'ul riHk of dis|iliif>-nii>nt dy 'In- ln'iivy wiivox ot'ttin ruDninx down troin Ihu liiki* jusi nbovc tlu' hrid^i'. Th« coDtritctorH tor tlu^ siipiTHlnii'tiii-i- dt'cidi'd to erect tlic spanw in s shelterud bav. iiboiil llirci' niilc^* dlMlaiil I'roin liic hrid}>i-, itnd when fully completed to tiiku them on hurireH. (loiil into |iiiiee, iind lower on to the uiasonry. ThiH waH done in the followinu ininiher : Two scows Itiiilt for thii purpoHe, 90' loiijt by 40' in width, were provided with 4 inrnc tren(le bents on each ; these scows were lashud together with u >puuu ; a iiundier of >]mns in the buy, when erected, by buildin)^ the false work or sta^in^'. on which to erect them along the shore of the bay, and ut ri^'lit angles in this sta);in;; buildinu: out into the Water two pile piers, or trestles, spaced the len);th of the spans apart. On the^e trestles u number of lines of railway iron were laid, and as the erection id' each .span was completed it whs moved sideways out on to the trestles sliding on the railway iron. Before the work of fluatin;; the spans into place bcuaii, seven spanM had been assembled and rivetted complete, and moved sideways ou the trestles into position, to bo taken otf in turn by tlic barges, thus eiia* bliug the work of assembling and rivvttini; to pro<;ress without inter- ruption. Spans have before been tiouted on hariMS into position, but it i:i thooghtthis is the first iiiitanee in which a lai>;e inimher of spans hftve been made ready and storeij until it vm-^ desireil to place them ou the masonry, and also the first time false work has been .so built that the apana when afsembled could be moved olf it ami loaded on barbies, without tearing down any port ion of tlie false work or iiiterniptiii^ the work of erection, the usual eour.se huvin^r been to erect the span un staging built over the water, and t^i take down enough of the trestles to admit of the barges beinu placed beneath the span. The erection of the superstructure was eomiueneed on the Ist Sep- tember, 1889, and the last span wa» floated into po.sition on the 19tL February, 1890. Trains going over the entire structure on the follow- ing morning. Tho entire bridfjc thus occupyinj; ten months and twvnty days in construction. G