THE MOON ON THE JOB

Bay of Plenty Times, Volume LIV, Issue 9029, 7 November 1925, Page 5

THE MOON ON THE JOB

BUILDING THE WAIKOA BRIDGE. Without the aid of nature it. is dillicult to imagine liuw the engineer of to-day would get> through with many of his undertakings, although one is compelled to admire his ingenuity in pressing nature into his service. Although in many things slow, nature in all her ways is very sure, and nothing is more sure than the rise and fall oi the tide at accurately ascertained intervals. With, this knowledge ever in mind the engineers entrusted with the work of constructing the railway across and along the edge of iauranga harbour have had a jealous eye on the tides ever- since the work commenced, and when the construction of the harbour biidge was in hand the idea was conceived of punting the girders into position and letting the falling tide drop them on to the piers. But the length and weight compelled the more prudent—-although longer and more costly—course of erecting them piece by piece on the spot. The bridge across the Wairoa river, however, offered the desired opportunity. The railway crosses this river practically at its meuth, and a bridge some 840 feet long is necessary. The bridge consists of thirteen spans of 60ft and two spans of 30ft. In the sixteen piers there are altogether 185 piles, each of which consists of 40ft of concrete spliced on to 25ft of softwood. It will therefore be seen that they have had to be driven to a considerable depth to get the requisite foundation. In the sixteen piers there are 500 yards of concrete. The girders are of the ordinary standard 60ft steel plated type, each weighing 23 tons. The method of putting the girders into position is simple yet interesting. The contract for floatng them up the harbour and placing them on the piers was let to> Mr Brooke®, the contractor for the new wharf at Tauranga. Mr Brookes made a start on Monday. He has two punts on which a staging has been erected. The girders are deposited on top of this staging at the Mount, and the punts arc then towed to the bridge site. On Wednesday last Mr F. S. Dyson. the District Engineer of the Public Works Department, afforded a representative of the Times an apportunity of watching the work of placing the girder in position. The launch wth the , girder in tow left the Mount at 7.30 a.m. and the punts were in position at the bridge shortly after 9. The arrival of the punts is timed for slack water at the top of the tide, thus enabling them to be manoeuvred into position quite easily and in a surprisingly short space of time. As soon as the girder is in tlae required position two hydraulic Jacks, ‘each lifting 15 tons, quickly lift one end of the girder, the packing is withdrawn, the jacks are lowered and the girder comes down into position on the bolts without a hitch of any kind. The jacks are then placed at the other end, the process repeated, and half-an-hour after the punts reached the river the girder is bolted down. But time and tide wait for no man, nor will the tide hasten for him. Relieved of their weighty burden the punts naturally lift and the staging jambs on the bottom of the girder, and there it stays until the tide chooses to set it free, A wait of hali-an-hour or more, however, fs -'sufficient, : and once free the punts are brought back to the Mount in readiness for their valuable load—each girder is worth about £6oo—for the next day's tide. ( As already stated Mr Bruoke.s made a start on Monday. Tbe .tides that day were kind. One girder was gut up and placed in position on tbe early morning tide, and another was got in on the evening tide. One girder has gon© into position each day since, and as twelve out of the thirteen long girders can be placed in position with the moon doing tbe heavy li Ting. the whole of the girders .should !h’ in position by the end of the month, and all being well, the rails wi’l also ho laid into the To Puna station yard, a few r 'hain« beyond the river, by that date. The plate’aviiyr R n -., v , v ,.p ,] v towards the river ■ n the Tanranga side and is being rapidlv ■ ir bed -du-d. Just beyond t’ - WRiver ST W. G. Armstr 'ng-Wfo’t'"’''rtb and C-’n?-pany’s contract c tn”'-ie-es. | The nT' + f-r o c s-ooi 1 -- mem < t ? - ■> | settlers or'-.- -wdl L-* ju t how soon ■ an tr'ons f r both rmssongers and goods V r .jn f-m To Puna- to Tauranga. • • • tv , , | >< - »'r> rvtt v ■ i