KELBURN VIADUCT

Dominion, Volume 22, Issue 34, 3 November 1928, Page 8

KELBURN VIADUCT

SAFETY ENDANGERED BY SLIP ALL TRAFFIC SUSPENDED For a long time the viaduct, or wooden bridge, which connects western Kelburn with eastern Northland, has been under suspicion of being insecure for modern heavy traffic. This opinion has been crystallised by the rather heavy slip which occurred at the eastern take-off on Thursday evening, when some 500 tons of loose earth- and rotten rock slid down the face of the hill, and sprawled across the tramtracks on the Karori Road, extending five feet beyond the outer rail. An early start to clear the spoil was made by a big gang yesterday morning, and by 10 a.m., with the assistance.of the big mechanical shovel (which lifts two yards at a time), the trams were able to get through, and the normal running was resumed. As all the space available was needed for the shovel all ordinary traffic was diverted to the old road up the hill —the ‘“Devil’s Elbow” —which takes off a couple of hundred yards below the viaduct. At the rate the stuff was being handled yesterday (the spoil is being dumped into a convenient little gully right opposite the slip) the major part of the slip should be cleared away by this evening. The fall away of the loose earth from the top reveals that the none too massive concrete foundations at the Kelburn entrance to the bridge rest upon a foundation of rotten rock, now about perpendicular in a line with the concrete foundation on the northern side, and the danger lies in the risk of that rock disintegrating now that it is fully exposed to the weather, should this vertical rock face deteriorate, as expected, the, one section of the foundations must suffer, and under the vibratory action, caused by the increasingly heavy traffic, the bridge, it is judged, must become unstable. The viaduct is constructed of ironbark uprights, and struts, bolted together, but though it has been erected for over a quarter of a century, its supporting timbers have never been given so much as a coat of paint. The only evidence of paint on the understructure are dabs of red oxide on the bolts. As the position stands at present the whole of the viaduct is under close examination. Engineers with steel tape measures were engaged throughout yesterday in taking all the measurements of the supporting timbers, and are examining each one as to conditions. They are also delving into the ground round about the concrete foundations on each side to ascertain there strength (or weakness). When this data is collected the city engineer (Mr. G. A. Hart), who spent some time on the job yesterday, will furnish a report on the bridge, and what he considers should be done to make it safe for traffic.