Tunnel triumph for persistence

Press, 30 March 1989, Page 13

Tunnel triumph for persistence

The building of the Lyttelton rail tunnel was perhaps the greatest achievement of the Canterbury Provincial Council. At the time it was virtually the longest rail tunnel in the world, the first to be cut through the crater wall of an ancient volcano, and financed by a population of a mere 10,000 people. In true Canterbury style the project was surrounded by extensive debate and dissention. But it was the persistence of William Moorhouse, the second Superintendent of Canterbury Province, and the accurate use of the scientific method by Julius von Haast, provincial geologist and later first director of the Canterbury Museum, which allowed the tunnel to be completed earlier than would otherwise have been the case for the province to prosper. When the first four ships arrived at Lyttelton in 1850 the colonists had to haul everything they owned over the steep Bridle Path, or sail it around over the Sumner Bar. The Canterbury Association had planned to have a road available to the first colonists, but this plan had gone awry because steep rock was encountered in the Evans Pass area. At about the same time a message had arrived from London saying that Canterbury Association funds were running low and strict economy was to be employed, so the project was shelved. Access between the port and

the burgeoning Christchurch dominated the minds of settlers during the first few years of the Provincial Government. James Edward Fitz Gerald, first superintendent of Canterbury Province, was instrumental in persuading the council to vote funds necessary to complete the road from Lyttelton to Evans Pass and down to the Heathcote Ferry. On August 24, 1857, Fitz Gerald and entourage crossed the Heathcote in the ferry punt, launched at Sumner, ascended Evans Pass and commenced the perilous descent to Lyttelton, during which it was reported that two of Fitz Gerald’s passengers in his dog cart discreetly got out and walked. The route, however, was not adequate for a growing Christchurch and hinterland, and heavy traffic had to go by boat over the treacherous Sumner Bar, where there were often long delays, and then up the Heathcote to the Ferry Wharf.

Exports from the port increased greatly in the first half of 1858, and Fitz Gerald’s successor as Superintendent, W. S. Moorhouse, announced the decision to construct a railway tunnel.

Canterbury was settled at a time of great rail expansion in Britain, and many settlers assumed a rail connection would eventually be made by tunnel between Christchurch and Lyttelton.

The majority of settlers favoured a tunnel, but a bitter controversy developed between Moorhouse and Fitz Gerald, the latter favouring a more roundabout three-stage route with a high-level railway, steep gradients and a comparatively short tunnel.

As an interesting aside, FitzGerald, the leading opponent of a direct tunnel, established “The Press” in part as a platform to attack Moorhouse — the first edition appearing on May 25, 1861. He wrote rather grandi-

osely in 1864, “I intend to make it the best paper in the Southern Hemisphere. Even now there is no paper quoted so often al! over New Zealand ...” In November, 1858, a local committee under the chairmanship of Edward Dobson was set up, and three commissioners, one of whom was Fitz Gerald, were appointed in London “for the construction of railways in Canterbury.” The choice of route was given to George Robert Stephenson, nephew of Robert Stephenson, the renowned British rail engineer. Stephenson came out strongly in favour of the direct route and estimated a cost of £250,000 for which he thought it would be possible to obtain a reputable English contractor. The commissioners were favourably impressed, and Messrs Smith,. Knight, and Company, were appointed to construct a tunnel for £235,000. A loan bill for £300,000 was passed by the Provincial Council in 1860 and work commenced at the Lyttelton end. There were no precedents as to what might be encountered in the wall of a volcano, and perhaps the contractors were feeling nervous about their tender because very quickly a mass of hard basaltic rock was encountered and a raise in the contract price was requested and refused. The contractors withdrew from the contract. It was a setback for Moorhouse, but he was not to be put off. He summoned 36-year-old Julius von Haast, who at the time was on geological surveying work in Nelson. Haast already had a high reputation and was commissioned to report on the probable extent of the hard rock. A two-week survey of the Mt Pleasant area was undertaken by

Haast with the assistance of Arthur Dobson, the 19-year-old son of the Provincial Engineer, who was later to lend his name to Arthur’s Pass.

The two followed and pegged out each lava flow and dike along the proposed line of the tunnel, and Haast was able to draw cross-sections. On a recent summer evening I walked the Bridle Path musing upon Haast’s achievement, and indeed it was some achievement to complete the survey in two weeks. Although the geology is relatively simple it is easy to get confused by detail, and Haast would have had no previous body of literature to work from as a geologist would have today. Haast concluded that the hard rock encountered by the contractors was of limited extent, representing a thickening of lava flows where they flowed into hollows. Much of the sequence consisted of agglomerates and ashbeds — deposited as airborne volcanic material — which are relatively soft and would be easy to tunnel. He also noted that dikes — those more or less vertical sheets of lava which cut across the other rocks — did not form any significant obstable. He assessed that the tunnel could be completed at less cost and sooner than previously anticipated. Haast’s sections proved a remarkably accurate prediction of what was found in the tunnel, and soon afterwards he was appointed Canterbury Provincial Geologist. Moorhouse lost* no time in using Haast’s report; he went to Melbourne and engaged the services of Holmes and Richardson for £240,500. Thus the first sod of the first railway in New Zealand was turned by Moor-

house on July 17, 1861, and the “Lyttelton Times” reported it was “one of the very worst days of one of the worst July’s that it has been our lot to pass in

Canterbury.” Work commenced at both ends of the tunnel, and Haast kept a regular log of the strata exposed. He worked between midnight on Saturday and midnight on Sunday when tunnelling ceased. He found what would now be considered a fairly typical section through the crater rim of a composite volcano — one made up of alternations of lava flows and layers of pyroclastics or airborne volcanic material. In all, Haast recorded more than 100 lava flows, 39 beds of agglomerate, 19 beds of laterite clays and slope deposits, partly burned by overlying lava streams. These were intersected by 32 dikes. A number of caverns were encountered within the softer rocks, and Haast thought those resulted from the partial removal of the rock by water. Diagrams of these caverns, Haast’s original crosssections at a scale of 20 feet to 1 inch, and the rock collection are housed in Canterbury Museum. Both adits met near the centre of the one mile and three quar-ter-long tunnel on May 25, 1866, and the tunnel was opened for rail traffic on December 9, 1867. Haast’s work was good enough to last a century and was used in the construction of the nearby road tunnel opened in 1964. In his obituary notice Haast’s scientific deductions on the rocks from the surface of Mt Pleasant were referred to as “a triumph of reasoning from scientific observation. No achievement has had more lasting results on the fortune of the province.”

By

HOWARD KEENE