Hapuawhenua Viaduct

Tongariro National Park, Ohakune; Horopito

  • Hapuawhenua Viaduct from the west.
    Copyright: NZ Historic Places Trust. Taken By: Karen Astwood. Date: 1/11/2008.
  • Hapuawhenua Viaduct.
    Copyright: Department of Conservation. Taken By: Glen Hazleton. Date: 1/12/2006.
  • Hapuawhenua Viaduct.
    Copyright: Department of Conservation. Taken By: Glen Hazleton. Date: 1/12/2006.

List Entry Information

List Entry Status Listed List Entry Type Historic Place Category 1 Public Access Able to Visit
List Number 7271 Date Entered 27th October 1995

Locationopen/close

Extent of List Entry

Extent includes part of the land described as Sec 8 SO 393634 (CT 519049), Wellington Land District, and the structure known as the Hapuawhenua Viaduct thereon, including its abutments, as shown in the extent map tabled at the Rarangi Korero Committee meeting on 29 September 2016.

City/District Council

Ruapehu District

Region

Horizons (Manawatu-Wanganui) Region

Legal description

Sec 8 SO 393634 (CT 519049), Wellington Land District.

Location description

The structure can be accessed from the Ohakune to Horopito Coach Road starting from its southern terminus on Marshalls Road, Ohakune.

Summaryopen/close

The Hapuawhenua Viaduct is situated in the North Island's Central Plateau just northwest of Ohakune. It was constructed as part of the North Island Main Trunk (NIMT) in 1908 and was a functioning part of that railway for the subsequent 80 years. The Hapuawhenua Viaduct is one of a pair of large curved steel truss railway viaducts, which is a unique occurrence within New Zealand.

The Hapuawhenua Viaduct was completed in 1908 and was one of a concentration of five viaducts that were built between Ohakune and Erua; a series that was necessary to navigate the difficult terrain which stood in the way of the completion of the NIMT. All of these structures were designed by the notable Public Works Department (PWD) engineer, Peter Seton Hay. Both the Hapuawhenua Viaduct and its close neighbour, the Taonui Viaduct, were constructed under the 'co-operative system' and the steelwork was manufactured at the PWD workshop at Mangaonoho, which was situated between Hunterville and Taihape and in operation from 1898. The workshop ran at full capacity in order to facilitate the construction of these viaducts which was a central reason why the other three viaducts in the crucial last section of the NIMT were contracted out to a private firm.

In 1906 the southern railhead had reached Ohakune which meant that the fabric for the viaduct travelled over the completed line for most of its journey, but a temporary line had to be built in order for it to then be transported to the Hapuawhenua site. There was also a service road built in 1906 which later became the road that coaches transported train passengers along between the railheads. The close proximity of the base of NIMT southern construction at Ohakune allowed the Resident Engineer, Frederick William Furkert (1876-1949), to monitor the progress of the co-operative system workers. Furkert kept a close eye on what was happening and made frequent visits to the Hapuawhenua site during construction as is evidenced by the fact that the various phases of the viaduct's construction were photographically documented by Furkert.

Unlike the other Hay designed viaducts on the NIMT, the Hapuawhenua and Taonui Viaducts are both rare examples of curved structures each being built with a 201m radius. Curved viaducts were first built for railways and came out of the railway boom of the mid-late 19th century. Despite the aesthetic appeal of curved viaducts, bridges are primarily meant to be functional structures and therefore curved examples are not common, as it was and still is more practical to build straight bridges because they are typically easier to construct and comparatively cost less to maintain over time. Within New Zealand there is only a small group of large curved bridges and viaducts, and the Hapuawhenua Viaduct is among the oldest, and longest at 284m, and its 45m height also ranks it among the tallest of this group.

By August 1907 the preparation of the Hapuawhenua site was completed, the labourer's camps were set up on the southern side of the gully, and excavations for the viaduct's pier footings were advanced. From then work progressed steadily, which meant that the abutments and 13 mass concrete flanking piers were completed by December 1907. While these were being constructed, work also began on the four central lattice steel piers. However, the curve of the Hapuawhenua Viaduct meant that these and the girders were constructed in a different sequence to contemporary straight NIMT viaducts.

The straight viaducts were generally built one pier at a time from edges inwards with the girders being placed as each couplet of piers was completed. However, the Hapuawhenua Viaduct's piers were built in a synchronised fashion, one tier at a time from the ground up using a series of guy lines attached to hoisting machines, called derricks, and then all the girders were raised into position last. Therefore, instead of construction being aided by being able to progressively walk further out onto the viaduct throughout construction, access to the pier heads at Hapuawhenua was via very tall ladders. This construction technique also meant that there was a heightened level of accuracy and precision needed in order to secure the components of each pier on the correct alignment and in manipulating the hoisting system. However, this finesse was combined with a certain amount of brute strength. For example, the pier head girders weighed about three and a half tons, and the truss girder approximately nine and half tons, and these were positioned using the manually operated derricks. Once the piers were capped with their steel plate pier heads, five 19.5m lattice trusses were positioned between them, and then the finishing touches were added to the structure so that it was finished in April 1908.

It was then a matter of laying track across the viaduct and finishing other structures and earthworks in the last section to facilitate the first through train trip from Wellington to Auckland, the 'Parliamentary Special,' in early August 1908. However, Premier Joseph Ward was able to experience the viaduct prior to participation in that historic event because he visited Ohakune in mid-June at which time he was taken on a train excursion over the structure. The Hapuawhenua Viaduct was then the second longest viaduct on the NIMT, but because the Mangaweka Viaduct was demolished in the early 1980s, it is now the longest NIMT construction-era viaduct.

It is a tribute to the skill of Hay as a designer, and the technical skill and capabilities of those manufacturing the components for the viaduct and the labourers who built it, that minimal alteration was needed during the 80 years it was in use. The most significant changes occurred as part of the NIMT wide strengthening programmes between 1925 and 1934, and again in 1971. The structures was also painted in 1964, and late in that decade telephone wire insulators were added to the western side of the viaduct.

As early as the mid-1960s there had been calls to bypass the Hapuawhenua and Taonui Viaducts for the good of the smooth and efficient operating on the NIMT. The main reason cited for this was that since the 1930s there had been a speed restriction of 20mph (32kph) on each of the structures due to their small radiuses, and a deviation would also reduce maintenance costs, as well as the risk of derailment. An added incentive for deviation was that the Hapuawhenua Viaduct required costly underpinning if it was to continue to be viable within the functioning railway. Therefore the Horopito Deviation, completed in 1987, was a practical and logical solution. Included in the bypass were two replacement viaducts for the NIMT construction-era Taonui and Hapuawhenua Viaducts. The Hapuawhenua's replacement in the functioning NIMT is close by, is also a curved viaduct, and has been described as 'an elegant and impressive study in reinforced concrete.'

When the deviation was opened for traffic in 1987 the Hapuawhenua Viaduct was rendered obsolete and its rails were removed. However, because it was still publically accessible a walkway was created down the centre of the deck using old sleepers and was flanked by a new wooden handrail. As part of the planning for the deviation possible uses for the NIMT construction-era structures were considered, and it was decided that they would be retained and placed under DoC management to eventually be incorporated into a walking track. The land immediately surrounding the viaducts had become part of the Tongariro National Park in 1916. Therefore, a like for like swap of land between DoC and the Railways Department was a logical arrangement when plans for the deviation were being devised. It was anticipated that the combination of these important structures and the natural features along the walking track would make it an appealing tourist attraction.

In early 2009 a conservation programme at the Hapuawhenua Viaduct was completed. In the period between its redundancy from the functioning railway and its reopening on 14 February 2009, the viaduct had been mostly unused aside from a brief stint as the platform for a bungy jumping operation in 1988. This very short lived AJ Hackett enterprise is reportedly the first commercial bungy jumping operation in New Zealand and the world. The installation of new decking and the conservation of the structure have meant that visitors using the Ohakune to Horopito Coach Road walking track can also walk over the Hapuawhenua Viaduct.

The Hapuawhenua Viaduct was an integral component in the push to finish the NIMT after 23 years of construction, and then the revolutionary effects that the railway created in regards to transport and New Zealand's economy. The longevity of the structure can be attributed to the technical skill of those involved in designing, manufacturing the fabric for, and constructing the viaduct. The extended length of the curved form of the viaduct creates an impressive impact and contributed to it being an aesthetic highlight of the NIMT, and subsequently the Tongariro National Park. This viaduct also gains historical significance because the railway's deviation away from the structure was a direct result of the electrification of the NIMT, which was a defining moment in New Zealand's rail history. The viaduct's subsequent retention and inclusion in the Tongariro National Park can be seen as evidence of the increased awareness of New Zealand's rail and engineering heritage.

Assessment criteriaopen/close

Historical Significance or Value

This historic place was registered under the Historic Places Act 1993. The following text is from the original Recommendation for Registration considered by the NZHPT Board at the time of registration.

The construction of the Hapuawhenua Viaduct was fundamental to the success of the central plateau route of the North Island Main Trunk Line.

This historic place was registered under the Historic Places Act 1993. The following text is from the original Recommendation for Registration considered by the NZHPT Board at the time of registration.

Aesthetic:

The 10 chain radius curve of the Hapuawhenua Viaduct distinguishes this viaduct as an impressive piece of construction because of the elegance with which the curve is handled in an otherwise massive engineering structure. The contrast with this curve with the bush and mountain site of the viaduct, emphasises the adaptability of an engineering structure to conform to the requirements of natural land forms.

Architectural:

This trestle viaduct is constructed of steel and is 284m (932 feet) in length with a 10 chain radius curve and 45.5m (149 feet) above the valley floor. It is one of the largest viaducts on the North Island Main Trunk Line and one of only two that were curved.

Technological:

The Hapuawhenua Viaduct is an excellent example of the form Engineer Peter Seton Hay standardised for such steel viaducts using steel braced trestle piers with pier heads having curved plate girders, and deck trusses for the main spans. At each end there are shorter plate girder spans supported on concrete piers. This design was technologically important at the time.

This historic place was registered under the Historic Places Act 1993. The following text is from the original Recommendation for Registration considered by the NZHPT Board at the time of registration.

Social:

The North Island Main Trunk Line was opened in February 1909 and the central section of the line is significant not only in transportation but more importantly in communication and the opening up of the North Island.

This historic place was registered under the Historic Places Act 1993. The following text is from the original Recommendation for Registration considered by the NZHPT Board at the time of registration.

The following comments are made in relation to the criteria identified under S.23(2) of the Historic Places Act 1993.

a) The extent to which the place reflects important or representative aspects of New Zealand history:

The Hapuawhenua Viaduct is physical evidence of the importance of New Zealand transport and communication history. In a broader sense it can be seen to be part of a political process that began with the public works policies of Vogel, and which were carried on by the Liberals under Seddon and Ward. In this case the process culminated in the historic completion of the difficult central section of the North Island Trunk Line in 1908-09.

The construction of the middle section of the North Island Main Trunk Line was fraught with difficulties and it was some years before the decision was made to use the central plateau route rather than one through Taranaki. On F.W. Furket's recommendation, it was decided to take the central route through very rough country which was heavily bushclad and without easy access. It involved the construction of two large steel viaducts, four substantial bridges, a tunnel, some very heavy cuttings in difficult ground and some equally large fillings, all in the space of 19km.

g) The technical accomplishment or value, or design of the place:

The Hapuawhenua Viaduct was designed in 1907, completed in 1908 and was the longest on the North Island Main Trunk Line with a length of 284 m. It is 45m high and has a curve radius of 210m having been designed by Peter Seton Hay, a brilliant engineer in the Public Works Department who later became Engineer-in-Chief.

This viaduct can be compared to the Makohine Viaduct at Ohingaiti (Category I). Several distinctions can be drawn between them, although the two structures are comparable in quality. While both are part of the middle section of the North Island Main Trunk Line, Makohine Viaduct was built and completed some nine to six years before the Hapuawhenua Viaduct. Thus it is an earlier example of the engineering expertise of the Public Works Department and the experience gained as a result of its design and construction would have been invaluable in the realisation of the Hapuawhenua Viaduct. At 72.5m, the Makohine Viaduct is considerably (27m or 60%) higher than the Hapuawhenua Viaduct.

The Makohine Viaduct still functions as part of the Main Trunk Line while the Hapuawhenua Viaduct has been modified to form part of a walkway. With the opening of the new deviation and viaduct in 1987, the tracks were removed from the original viaduct and replaced with a timber board walk. Hand rails were also added.

Conclusion:

Hapuawhenua Viaduct, Ohakune, is recommended for registration as a Category I as a place of special and outstanding historical and cultural heritage significance and value. The Viaduct is a magnificent piece of engineering designed by Peter Seton Hay and is evidence of the importance of New Zealand transport and communication history.

Linksopen/close

Construction Professionalsopen/close

Hay, Peter Seton

Peter Seton Hay (1852/1853? - 1907) was born in Glasgow, Scotland, probably in 1852 or 1853, the son of Janet (Jessie) Dalziel and her husband, James Johnston Hay, a journeyman engineer. When Peter was a child the family emigrated to New Zealand, arriving at Port Chalmers on the Storm Cloud in April 1860. Educated in Dunedin, he was the first graduate of the newly established University of Otago, obtaining a BA in 1877 and an MA with first-class honours in mathematics in 1878.

In June 1875 on the advice of a university teacher he had joined the Public Works Department as an engineering cadet. After completing his studies he was engaged in railway surveys and construction for the lines from Dunedin to Moeraki and Clinton. In the early 1880s he was employed on Central Otago railway surveys from Rough Ridge to Hawea, in the Cromwell district, and from Balclutha to the Catlins River. Hay's reputation as a brilliant young engineer was established in these Otago days. Stories were told of his prodigious mental calculations when he was working in the field without the usual aids such as logarithm tables. In 1884 Hay was transferred to the head office of the Public Works Department in Wellington. He began his steady progress through the ranks of the department, and two years later was promoted to resident engineer.

In 1896 he was promoted to superintending engineer, equivalent to assistant engineer-in-chief. By then the construction of the North Island main trunk rail link was the foremost Public Works Department project. Hay helped plan most of the important railway works of the central North Island section and was responsible for the primary design of the Makohine, Mangaweka, Hapuawhenua, Taonui, Manganui-a-te-ao and Makatote viaducts. By any standards the viaducts were great works of engineering. Much of the credit for their construction must be attributed to Peter Hay.

Hay succeeded W. H. Hales as engineer-in-chief of the Public Works Department in 1906, only to die in office on 19 March 1907. He suffered the effects of exposure while inspecting the main trunk railway works near Waiouru, and subsequently died from pleurisy at his home in Wadestown, Wellington. He was aged 54.

One of Hay's major achievements was his investigation and report on the proposed Southern Alps rail crossing by the Midland railway in 1903. The scheme recommended by the government's American advisory engineer, Virgil Gay Bogue, required a 3½-mile tunnel and a steep gradient incline track. Hay's scheme, which was ultimately adopted, avoided expensive grading and track work but required a tunnel over five miles long. This tunnel, at Otira, was completed in 1923, long after Hay's death. Equally important was Hay's contribution to the development of hydroelectric power generation in New Zealand.

Peter Seton Hay married Mary Clarke at Wairuna, Otago, on 22 April 1879 and they had four sons and one daughter. His wife and children survived him. Hay was the first New Zealand-trained engineer to rise to the rank of engineer-in-chief. He died at the height of his powers and before many of his projects had been completed. Although his life was relatively brief, his works endured.

Lowe, Peter. 'Hay, Peter Seton 1852/1853? - 1907'. Dictionary of New Zealand Biography, updated 16 December 2003 URL: http://www.dnzb.govt.nz/

Additional informationopen/close

Construction Dates

Other
1907 -
Site preparation and temporary line from Ohakune built

Other
1907 -
Excavations for footings is begun (August)

Other
1907 -
December 1907. Concrete piers complete. Construction of steel piers is begun

Other
1908 -
Piers are completed (January)

Original Construction
1908 -
Viaduct completed (April)

Other
1964 -
Viaduct painted

Modification
1970 - 1971
Viaduct strengthened

Other
1984 -
Horopito Deviation begun (June)

Other
1987 -
Horopito Deviation completed

Other
1988 -
Bungy jumping operates off of the viaduct

Other
2008 - 2009
Hapuawhenua Viaduct conservation project

Other
2009 -
Hapuawhenua Viaduct open to the public (14 February)

Completion Date

5th March 2009

Report Written By

Karen Astwood

Information Sources

Appendices to the Journals of the House of Representatives (AJHR)

Appendices to the Journals of the House of Representatives

1907, Vol. II

AJHR 1908, Vol. III

Alexander Turnbull Library

Alexander Turnbull Library, Wellington

MS-Papers-1073. Keller, P., 'Early Days on Railway Construction'

Archives New Zealand (Wgtn)

Archives New Zealand (Wellington)

AAZU W3619 2 22/9/64. Makatote Viaduct: New Zealand Railway NIMT 1964

Department of Conservation

Department of Conservation

D Veart, 'The Hapuawhenua and Taonui Railway Viaducts Conservation Plan, DoC Report, 2005

Evening Post

Evening Post

'Wellington to Auckland,' 10 August 1907

Otago Witness

Otago Witness

'The Main Trunk Line,' 11 December 1907

'Ohakune, the Halfway House,' Otago Witness, 13 May 1908

Progress

Progress

'Over the Main Trunk Line in a Ministerial 'Special',' 1 January 1908

'Hapuawhenua Viaduct, Progress, 1 August 1908

Thornton, 2001

Geoffrey Thornton, Bridging the Gap, Early Bridges in New Zealand 1830-1939, Auckland, 2001

Wanganui Herald

Wanganui Herald

'Ohakune Notes,' 22 April 1908

'The Premier in Ohakune,' 16 June 1908

Pierre, 1981

Pierre, W. 1981. North Island Main Trunk: An Illustrated History, Christchurch

Troyano, 2003

L F Troyano., Bridge Engineering: A Global Perspective, London, 2003

Other Information

A fully referenced upgrade report is available from the NZHPT Central region office

Please note that entry on the New Zealand Heritage List/Rarangi Korero identifies only the heritage values of the property concerned, and should not be construed as advice on the state of the property, or as a comment of its soundness or safety, including in regard to earthquake risk, safety in the event of fire, or insanitary conditions.