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Cut into the cliffs high above the sea North of Pukerua Bay, is a section of the North Island Main Trunk Railway known as North South Junction. Constructed in the 1880s, North South Junction is a 3.1km section of single track with five tunnels that total 920 metres. It runs along some of the most weather exposed line on the network, with the Tasman Sea and SH1 on one side and steep cliffs on the other. The size and condition of four of the tunnels meant that Kiwi Rail was running trains slower than it would have liked, and was using smaller rolling stock than its commercial clients wanted. Literally making tunnels ‘wider’ isn’t really an option when you are looking at brick lined tubes cut into rock. The best you can do is to lower the floor to create more headroom. The tunnels were first lowered in the 1960s, when diesel trains replaced steam locomotives. They were lowered again in 2000, but fell short of being able to accommodate the next generation of rolling stock without speed restrictions. Kiwi Rail project manager Daniel Headifen explains: “We had two options - simply replace the track and retain the 40km per hour speed restrictions, or spend a decent amount of money to achieve a step-change in performance. A step-change was clearly preferable but came with some major challenges.” Lowering the tunnel floor and relaying the track to gain headroom would be dirty, noisy, dangerous work, requiring people to work 12 hour shifts for over three months in tunnel conditions akin to an underground mine. “Also, by the time we did the tender and got Downer on board, we had a pretty pressurised time frame. Our requirement was that the job had to be completed by Christmas 2010, and Downer was prepared to commit to that.” Led by project director Russell Moylan and General Manager Technical – Commercial Phil Harrison, the Downer team arrived on site in August 2010. The first few months, working on an active railway, were particularly tough. “The tunnels are so small, nothing could be left in there when a train was going through,” says Headifen, “and every man had to be accounted for at any given time. Every day and night for three months – other than Friday nights – the guys were on site drilling, and the freight trains kept running.” “When you got a warning that the trains were coming through,” explains Harrison, “you had to move all the gear – the compressors and drilling rigs – in a regimented and disciplined way. When the train had passed, you had to get the gear back in again.” Disruptions to workflow meant that even though Downer was running a 24/7 operation, the actual time spent working in the tunnels amounted to a 25 hour week. The first stage of the work involved drilling three metre long steel rods into the walls of the tunnel to help strengthen it. Unexpectedly tough rock slowed drilling progress, putting at risk Kiwi Rail’s Christmas and New Year holiday deadline. Downer met this challenge by designing and 54 / DOWNER / IN BLACK & WHITE


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