|The Proud Builders on Their Bridge Over Canal du Nord|
The Canal du Nord in the Somme Sector was a big obstacle for the Allies to cross when they resumed the offensive in 1918. Begun in 1913, this canal was still under construction at the outbreak of the war. The canal formed a kind of huge trench without water. In September 1918 it defined a front between the British and the German Armies. A British offensive was under preparation by the end of September 1918. If the attack was to succeed, a bridge would have to be built to carry supply vehicles and also to allow for the passage of reinforcements. Earlier in the war the New Zealand Tunnelling Company had shown remarkable engineering ingenuity and developed a sideline specialty in bridge building. They were selected to build the bridge. Its completion done well within the range of German artillery, is considered one of the greatest engineering feats of the war.
The construction site was not easy. The site was at the point where the Hermies-Havrincourt road crossed the Canal du Nord. The canal passed through a cutting 100 ft deep with a distance of 180 ft between the tops of the smooth brick walled sides. The New Zealand Tunnellers would join two bridges together to form only one large construction. From an engineering point of view the task verged on the impossible.
On the morning on 27 September 1918, the First and Third British Armies attacked the German front line located near the Canal du Nord. The offensive was the starting signal for the New Zealand Tunnellers bridge-building to begin. In order to optimize the performance, the whole force was divided into two shifts. The first worked from dawn to midday and the second took over from then till dark. At 6 a.m. the New Zealand Tunnellers began work on the skeleton of the bridge. The plan envisaged the erection of the bridge on the west side while on the east side two wooden towers were constructed to pull and to carry the bridge over the canal.
The bridge structure was placed on slides which would guide the bridge over the canal. In four days, the structure was ready for the great manoeuvre. A counterweight of 20 tons built with rail tailings was placed at the end of the bridge. Winches were installed on the two towers, which could lift a total weight of 70 tons.
By 5 p.m. on 1 October the launching operation began. Two days later, the structure was slowly slipping away from the other side of the canal. But the weight of the bridge tilted the frame slightly so that it was now 12 foot below the level of the bank. The two wooden towers had only served to pull the bridge over the canal, not to lift it.
The supreme part of the manoeuvre started. Any failure at this time would have spelt disaster. Both winches operated and slowly lifted the iron structure. Inch by inch, the frame was closer to the level of the bank. Around 6pm, the bridge was lifted several inches above the ground level of the bank. The bridge was slowly pulled for the last time and linked both sides of the Canal. It was an amazing engineering feat for men who had never erected a bridge under such conditions.
On the site today are a pair of one way bridges one of which bears close resemblance to the Tunneller's bridge of 1918.
Source: The New Zealand Tunnellers Website at:http://www.nztunnellers.com/