| Otira |
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| cities, towns and communities in new zealand | |
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Otira is a small township seven kilometres north of Arthur's Pass in the central South Island of New Zealand . It lies on the western approach to the pass, which is in a saddle between the Otira and Bealey River s high in the Southern Alps . The township was originally a stop on the Cobb And Co stagecoach from Canterbury to the West Coast. The railway line was then built from Greymouth to Otira, with the pass itself still navigated by coach, until the railway tunnel was opened. The township is principally old Railways housing, much of which was constructed in Hamilton and shipped south to be reassembled on site. Close to the town are two major feats of Civil Engineering : The Otira Tunnel, and the Otira Viaduct. OTIRA TUNNEL The Otira Rail Tunnel, constructed between 1907 and its opening on August 4 1923 , runs under the mountains of the Southern Alps from Arthur's Pass to Otira - a length of a little over 8500 metres. The gradient is close to 1 in 30, and the Otira end of the tunnel is significantly lower than the Arthur's Pass end (a drop of over 250 metres). At the time of its construction, it was one of the longest rail tunnels in the world. Due to its length and gradient, gases such as Carbon Dioxide and Carbon Monoxide could easily build up, potentially making the tunnel both unhealthy for the train's occupants and unworkable for its engines. Thus, the tunnel was Electrified with a 1500 V DC overhead system. A small Hydroelectric Power Station was built near Otira to provide electricity. Due to the increasing age of the electric locomotives ( EO Class ) and upgraded diesel locomotives (such as the DX Class ) this system was discontinued and the overhead electrification removed. The removal of this section of overhead signalled the end of electrification in the South Island. To overcome the fumes problem, an ingenious combination of doors and fans is used. When a train passes through from the Otira end, a door is shut over the entrance, and a large fan extracts the fumes that build up. Once the fumes have been extracted, the door is reopened. OTIRA VIADUCT Above the town of Otira is the other engineering feat, the Otira Viaduct. Completed in 1999, this spans a 440 metre stretch of unstable land, replacing a narrow, winding road which had been constantly prone to avalanches and slips. REFERENCES |
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