In 1850, when the first four ships arrived at Lyttelton, there were only two ways of reaching the township of Christchurch; by scrambling up the foot trail over the hill or by taking a boat over the Sumner bar and up the Avon river.
In 1853, the Canterbury Provincial Council considered possible rail routes and how to finance them. Finance was the barrier and the scheme was shelved until 1858 when the Superintendent of the Province, Wiliam Sefton Moorhouse exhorted his council to “consider and determine the best method of securing safe and expeditious transit of our marketable productions to the place of export”.
A Provincial Commission consulted Robert Stephenson, eminent son of the famous George Stephenson. With his health declining, he passed the matter to his cousin George Robert Stephenson, who favoured the direct line, 6.25 miles (10 km) long, with a tunnel 1.6 miles (2.6 km) long. He recommended the firm of Smith and Knight of London as contractors to complete the work within five years from late 1859.
It is claimed that the tunnel was the first to pass through the wall of a volcano. The London contractor thought this was too difficult and so abandoned the contract. True or not, the boring attracted much geological interest and Julius von Haast, the noted geologist, was greatly involved in exploration, interpretation and advice to the engineers. Moorhouse, anxious to press on, had Edward Dobson, the Provincial Engineer (who was responsible for the whole undertaking from 1854 onwards), open up the access cuttings at each end of the tunnel and commence tunnelling on a day work basis in anticipation of a further contract being let.
The new contractor was Holmes and Company of Melbourne, who undertook in 1861 to carry out the contract for £240,000, of which the tunnel itself, complete with stone portals, was to cost £195,000. The contract price did not include locomotives, rolling stock and station buildings. The works were to be completed in five years.
Boring went on from both portals and in 1867 a breach was made from the Lyttelton heading into the Heathcote one. Rails were laid through the tunnel and by mid-November the first locomotive went through. Passenger services began in December but the tunnel was not complete. For another three years, after the last train passed through each evening, work gangs occupied the tunnel until morning, completing the drainage and widening works.
The railway had been operating between Christchurch and a temporary terminus at the Ferrymead wharf since December 1863, the locomotives and rolling stock having been brought in parts over the Sumner bar and assembled in the open. The broad gauge of 5 feet 3 inches was decided on by expediency. The Melbourne to Essendon Railway, built to that Victorian gauge, had an unused locomotive that was not required because traffic had failed to develop as the company expected. Holmes and Company required an engine for ballasting duties and the purchase of this engine, built by Slaughter Gruning and Company of Bristol, apparently determined the gauge matter. The province had originally stipulated a 5 feet 6 inches gauge as used in India.
The Canterbury Railways’ broad gauge lines extended to Rakaia in the south and Amberley in the north before the gauge was changed to the standard 3 feet 6 inches by December 1877. Narrow gauge trains had been using the Moorhouse tunnel from April 1876.
Since the gauge conversion, the tunnel itself has been altered very little, although heavier rails, improved signalling, electrification and, more recently, dieselisation have come progressively.
Electrification was investigated by the British firm of Merz and McLellan in 1925 and, in the following year, the tender of English Electric for the overhead contact system and six 1,200 horsepower electric locomotives was accepted. The electrified service was opened in 1928, with 24 passenger trains and 12 freight trains each way each weekday.
When the Tunnel Road was opened, there was no longer a need for an intensive rail passenger service and much of the port freight also went by road. The electric locomotives and substations were phased out in 1970 and replaced with diesels.
This place has been recognised by Heritage New Zealand as a Category 1 historic place (List no.7172):
IPENZ “Engineering to 1990” project
This item of New Zealand’s engineering heritage was recognised as part of the IPENZ “Engineering to 1990” project, which the Institution organised to help celebrate the country’s sesquicentenary in 1990. A plaque was unveiled to mark the significance of this railway tunnel as part of the development of the nation.
Matthew Wright. "Engineering – 19th-century engineering", Te Ara – the Encyclopedia of New Zealand, last modified 15 November 2012.
The tunnel runs beneath the Port Hills, with portals in Heathcote and Lyttelton, Canterbury.