Kopu Bridge is a rare surviving example of a swing span bridge in New Zealand, which marks the transition from river transport in the region to the domination of roads. Constructed in 1926-1928, the steel and reinforced concrete structure crosses the Waihou estuary near the town of Thames. It was erected soon after the Main Highways Board had been created by central government, taking over responsibilities for trunk roads from local authorities as a way of improving rural productivity. Both central and local government bodies funded the new structure, which connected Thames with the low-lying Hauraki Plains. The plains had been extensively drained and converted to dairy farming following an Act of Parliament in 1908. The bridge enabled road traffic to cross to and from Thames, while still allowing boats to transport butter exports and other goods from further upstream. The project to build the bridge was one of the largest undertaken at this time, with planning beginning in 1922. The structure was opened in May 1928 by the Prime Minister, Gordon Coates (1878-1943), who was leader of the farmer-orientated Reform Party and responsible for creating the Highways Board as a previous Minister of Public Works.
The bridge is an extensive 463 metre-long structure, which is mostly a single lane wide. It was designed by J. E. L. Cull, who had been the first design engineer employed by the Department of Public Works. The structure consists of 23 steel spans sitting on reinforced concrete piers. It has a central swinging span 42.7 m long, which turns on a central pier, providing boats with a clear width of 15.8 m between the fenders. The structure was technologically advanced, particularly in its use of deep piles to counteract a soft river bottom and strong tidal currents. A bridge master operated the electric swing mechanism, and was housed in a central cabin. Although a system of coloured lights was used to inform shipping about the opening of the swing span, early difficulties in boats adapting is evident from accidents in 1927 and 1928, when both the 'Tuhoe' and 'Taniwha' crashed into the bridge. As river transport declined, the bridge became more important for providing passage to the growing amount of long-distance road traffic between Auckland and the Coromandel peninsula. In the early 1990s it became the most heavily used single-lane road bridge in New Zealand, seeing 4,200 vehicles per day.
Kopu bridge is nationally significant as the only surviving road bridge of swing span type in the country. It makes a valuable contribution to the history of both motorised road transport and shipping, and is particularly significant for demonstrating early central government involvement in the development of highways. It marks the last stages in the history of major river transport on the Waihou, used by both Maori and Captain Cook. The bridge is important as a substantial technological achievement, occurring as New Zealand placed a greater emphasis on large-scale engineering projects in the 1920s. It demonstrates the political prestige placed in such works, being particularly linked with Gordon Coates and the development of the rural economy. The bridge was one of the most significant public projects carried out in the region, and is important for its connections with the expansion of farming and butter production. The bridge has had a long association with Thames and can be linked to the town's move away from its reliance on the mining industry. It is a distinctive part of the local landscape, and has educational value as a well-known and well-used historic structure on a major holiday route.
Registration covers the structure, its fixtures and finishes, including the bridge keeper's cabin and weatherboard structure adjoining the eastern end of the bridge. It also includes recent modifications.
Swing span including bridge keeper's cabin and swing mechanism.
- Concrete piers on piled foundations;
- Piers spanned by laterally braced plate girders surmounted by a reinforced concrete deck;
- Bridgeman's operating cabin, timber frame with long-run steel cladding;
- Shed (eastern end of bridge), timber frame with weatherboard cladding.
The Kopu Bridge was formally opened by Prime Minister J.G. Coates, on 11 May 1928. Negotiations between the Public Works Department and local authorities had commenced in 1911 although a bridge had been mooted prior to this date. The nearest bridge was 22 miles upstream near Paeroa although ferries crossed the river at various points. In 1922 the Hauraki Plains County, Thames County and Thames Borough Councils agreed that between them they would find £30,000 towards the cost of the £52,000 bridge, the balance to be provided by the Government.
The site chosen suited the trend of business and flow of traffic. The loading to which the structure was designed was the Public Works first class standard for traffic bridges. Navigation requirements for steamers such as the Taniwha of several hundred tons burden which plied the river called for a 50 foot wide opening.
Twelve test piles were driven abreast of the site in 1924. At a ceremony two years later the first pile of the bridge was driven by the Minister of Works, K.S. Williams. The construction of the central swing span and the fabrication of the steel girders was carried out at the Public Works Department depot at Tauranga. Girders ready for erection were transported by scow around the coast and lifted straight onto the piers by the scow's winches. Material required for substantial earthworks for the bridge approaches was provided by suction dredge from the river bed itself.
As a result of a gradual falling off of river traffic, the bridge keeper was not replaced when he retired in 1964. The swing span remained in use into the 1970s although is now no longer operated.
John Ernest Lelliot CULL (1879-1943) - Design Engineer, Public Works Department
Onslow Garth THORNTON (1890-1972) - Supervising Engineer, Construction
The total length of the bridge is 463 metres made up of twenty-three 18.2 metre plate girder spans, with a central swing span of 42.6 metres. The electrically operated swing span turns on a concrete pier 6 metres in diameter and provides boats navigating the river with a clear width of 15.8 metres between the fenders. The swing span has not operated for many years. The central operating cabin is a modest corrugated iron shelter with two nine-light windows and a shallow pitched roof.
The single-lane bridge is now regulated by traffic lights installed at its approaches in 1975. Eighteen of the bridge spans have a 3.6 metre wide roadway; five spans a 5.4 metre wide roadway. Handrails are Australian hardwood.
The bridge deck is supported on piers, each pier consisting of two groups of composite piles (a timber leader with spliced concrete pile). The heads of each group of piles are enclosed in a cylindrical casing, the whole then surmounted by a dwarf reinforced concrete pier. Each group of piers under the 3.6 metre wide roadway spans consists of three piles while those under the 5.4 metre wide roadway spans consist of four piles.
Prior to 1930 - Mattress of stone placed upon river bed around certain of the piers to provide resistance to movement of pile piers.
Date unknown - Weatherboard "shed" adjoining eastern end of bridge, southern side of road shoulder.
10th December 2001
Report Written By
Appendices to the Journals of the House of Representatives (AJHR)
Appendices to the Journals of the House of Representatives
1926 Vol. II - D1, p121
1927 Vol. II - D1, p132
1928 Vol. II - D1, pp139 & 143
Auckland Public Libraries
Auckland Public Libraries
Obituary Scrapbook, July 1971
- '42 years of service to Works Department', p75
- Obituary - Mr O.G. Thornton', p75
Auckland Weekly News
Auckland Weekly News
'Bridging the Waiho - Undertaking at Kopu', p25(4)) and Pictorial Supplement, 14.10.26
- 'The Hauraki Bridge - Spanning the Waihou', p23(2), 12.5.27
- 'Great Day at Thames - Hauraki Bridge Opened - Link with the Plains', p21(5), 17.5.28
Cyclopedia of New Zealand, 1903
Cyclopedia Company, Industrial, descriptive, historical, biographical facts, figures, illustrations, Wellington, N.Z, 1897-1908, Vol. 3, Canterbury Provincial District, Christchurch, 1903
C.A. Furniss, 'Waihou' - The River with a Past', Auckland Maritime Society: Voyage to Paeroa, 29-30 January 1972
New Zealand Herald
New Zealand Herald, 12 July 1932, p. 6; 28 September 1933, p. 6.
Obituary - Prof. J.E.L. Cull' p9(2) 24.4.43
New Zealand Historic Places Trust (NZHPT)
New Zealand Historic Places Trust
'Kopu Bridge, State Highway 25, Kopu', Buildings Classification Report, Wellington, 1990 (held by NZHPT, Auckland)
Plans: PWD 64802/5484 (29 sheets)
Geoffrey Thornton, Bridging the Gap, Early Bridges in New Zealand 1830-1939, Auckland, 2001
pp.14, 59 & 227
New Zealand Society of Civic Engineers Inc (NZSOCE)
The New Zealand Society of Civic Engineers Inc.
A.J. Baker, 'Waihou River Bridge, Kopu and Piled Foundations', The New Zealand Society of Civil Engineers Proceedings, Vol. XVII, 1930-1931
C Furniss, Servants of the North: Adventures on the Coastal Trade with the Northern Steam Ship Company, Wellington, 1977
O G Thornton, Who's Who in New Zealand, Wellington, 1941
This historic place was registered under the Historic Places Act 1980. This report includes the text from the original Building Classification Committee report considered by the NZHPT Board at the time of registration.
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.