As Auckland merges to create a supercity, the Herald looks back at how Auckland has changed over the years. Click here to view the full series.

For a few years in the 1950s every second Aucklander was an engineer. Words like caissons, piers and spans were in their daily conversation.

They were watching a ribbon of steel being strung across the harbour, the realisation of a century's dream, a bridge that changed the city's shape and character and became an enduring icon.

There had been talk of a harbour bridge since at least 1860 when a structure on pontoons was proposed for the sake of North Shore farmers.

Nothing came of that suggestion, or any subsequent proposal for the next 86 years.

A 1930 Government commission decided a bridge would be "20 years before its time" and ferry services were adequate. The Great Depression and World War II were to pass before, in 1946, a royal commission decided the bridge's time had arrived.

By then a determined Auckland mayor, Sir John Allum, was leading the cause - but sceptics remained. In that year's election campaign Labour's candidate for North Shore, Martyn Finlay, called the bridge "a luxury" when people were in need of state housing.

The Labour Government had accepted the royal commission's report but progress was slow. Works Minister Bob Semple sought Auckland Harbour Board approval in 1947. Harbour bed base rock borings were completed in 1949 and British consulting engineers Freeman, Fox and Partners were engaged.

National came to power at the end of that year. Legislation in 1950 set up an Auckland Harbour Bridge Authority, to "construct, maintain, manage and control a bridge across the Waitemata Harbour from Point Erin to Stokes Point".

A crossing to Stokes Pt, Northcote, was preferred to the more populous Devonport or Stanley Pt so as not to interfere with shipping and for easier access to the north. But it would mean more reclamation for approach roads on both sides of the harbour.

St Marys Bay would be buried, as would Sulphur Beach at Northcote and the entire western shore of Shoal Bay.

The 1946 royal commission found the bridge could pay for itself from toll charges but raising loan finance did not prove straightforward. Local bodies needed the approval of the Government's Local Authority Loans Board and in 1952 the board turned the bridge authority's application down.

Prime Minister Syd Holland published a list of public works priorities that ranked houses, schools and an underground electric railway in Auckland ahead of the harbour bridge.

Sir John Allum, chairman of the bridge authority, spoke out against "croakers" and called on the people of Auckland to "stick together" against two Government departments that he did not name.

Over the next few months he strenuously lobbied Holland and Deputy Prime Minister Keith Holyoake. They agreed to let the authority go to the London market for £4,500,000 (about $10 million), considerably less that the almost £8 million it wanted.

The bridge plans had to be pared back, losing footpaths, a cycling lane and approach roads on the western side of both shores.

Then the British Government weighed in, refusing to give its consent to a loan from the London market. Chancellor of the Exchequer R. A. Butler cabled Holland that he could not agree to "money being raised for this project in New Zealand when I can certainly not agree to money being raised for a similar purpose in the United Kingdom".

Holland accepted that, Allum did not. "Auckland must have the bridge," he said. "It is unthinkable that two growing communities should be denied permanent access."

A crowd of 10,000 gathered at Windsor Reserve, Devonport in the evening of March 25, 1953, to demand that a loan be permitted.

At the 1953 mayoral election, Allum was defeated by J. H. Luxford who claimed the bridge would place untold costs on ratepayers for upgrading roads.

But Allum, still chairman of the bridge authority, got Government approval in December for a four-lane bridge that could be financed within the country.

In 1955, the bridge began to take shape on the harbour.

First, Aucklanders noticed a reclamation at Westhaven that was completed in September, then pontoons were anchored a little way out in the harbour where the first bridge pier would rise.

It would be built using "caissons", big steel boxes open at the top and bottom with two compartments. Concrete walls were built within the upper compartment, their weight pushing the caisson lower in the water while the rising walls remained above sea level.

When the weight of concrete caused the descending caisson to meet the harbour bed, its grounding had to be precise within a tolerance of 23cm. Twice a caisson had to be refloated for a second attempt.

Once in the correct position its metal edges went into the harbour floor and the water in its lower compartment was replaced with compressed air. Workers then went into the lower compartment to excavate mud until the caisson was down to bedrock.

Several times the work was held up by boulders in the sediment that had to be blasted. Once a caisson struck a layer of uneven strength and the pier tilted to an angle of 24 degrees. Fortunately nobody was working under it at the time, but it took a fortnight of work to right it.

When each caisson was on its base rock, its bottom chamber was filled with concrete. The piers may look slender above the water but they are massive below.

Those working down in the compressed air were liable to suffer the "bends" as divers do, if they returned to the surface too quickly. Aucklanders were asked to be patient with men who might appear inebriated - they might be building the harbour bridge.

One by one, the piers rose, each higher than the one before.

By December 1956, the piers were ready to receive the steel superstructure. It was prefabricated in six spans of different lengths, some of which were cantilevered from one pier to land on the next.

The longest spans are those forming the navigation arch and the span immediately to its south, which is over the deepest water.

The placement of that span involved a remarkable act of engineering, witnessed by many Aucklanders.

The long span was first built on top of a much shorter span at the city end of the bridge. Then, using pontoons on a rising tide, the whole structure was floated off the piers and taken to midstream. There the monster was moored until calm weather and a falling tide might permit the long span to be lowered into position.

The weather was not that calm on November 29, 1958, but the "pick-a-back" operation went ahead to avoid holding up the construction programme.

Retired engineer Ken Grant of Castor Bay, a student painting bridge trusses at the time, remembers "the control under the wind and tide was incredible".

Fifty five years later, he met the meteorological officer who was stationed at Mechanics Bay that day, and whose job it had been to forecast the weather and wind for the operation.

"He said the maximum wind they could handle was 15 knots. He forecast 25 and they still went ahead. The actual speed was 18 and all went well."

A bridge too small

The bridge opened for traffic at 3pm on May 30, 1959. The traffic it attracted exceeded all estimates from the first day.

By August 17, when Geoffrey Robbins stopped at the toll booth and received a silver tray from Lady Allum for making the millionth crossing, there was no doubt the bridge would pay for itself - there was only regret that short-sighted national financial controllers had not allowed Auckland to build a bigger one.

In its first year the bridge carried an average of 13,300 vehicles a day, compared to the 3800 daily average of vehicle ferries the year before.

In its second year the bridge averaged 15,200 vehicles a day. At that rate of increase the four lanes would reach capacity by 1969.

In 1964 the Bridge Authority announced an extra four lanes would be added, two on each side of the bridge. Freeman Fox had devised a method of supporting the additions on the existing piers.

The cost could be easily covered by existing tolls and this time there was no objection from Wellington to the raising of loan finance.

The additions took the form of 26 box-girders built in Japan and installed by two giant sea cranes that came from Japan for the purpose. Each could lift 250 tons to a height of more than 200 feet.

The "Nippon clip-ons" were installed just in time. The additional lanes opened to traffic on September 23, 1969, the year the original bridge would reach capacity.

Why not trains?

A suggestion that the bridge include an electric railway was reportedly put to the 1946 royal commission and advocated in Parliament by North Shore's National MP, Dean Eyre, in 1950 when the Bridge Authority was set up.

"I am not turning that suggestion down flat," said the authority's chairman Sir John Allum before talks with consulting engineers Freeman, Fox and Partners in April 1951.

"If the Railway Department want trains to go across the bridge we should ask the engineers what the extra cost will be," he said. "The department can then be prepared to pay accordingly."

Herald archives record nothing more of the idea.

Auckland's Harbour Bridge would be more than a crossing to the North Shore, it would be part of a new mode of roading, a motorway.

By the late 1940s the Great South Rd was frequently congested from the Harp of Erin to Papatoetoe, and the Great North Rd could not cope with the increasing traffic beyond Pt Chevalier.

Auckland regional planners drew up maps for a network of dedicated, multi-lane "motorways" that would enable traffic to flow unimpeded by crossroads or lights. They would pass over or under main roads and rail
crossings and sweep away old residential neighbourhoods in their path.

With their ramps for traffic to enter at speed and their cloverleaf
intersections, they were as wide as an urban block.

Auckland's first stretch of motorway was a four-lane strip between Penrose and Mt Wellington, built in 1953. Next to be built was the causeway from Pt Chevalier to Te Atatu as far as Lincoln Rd, finished in 1955, which shortened the journey to the airport, then at Whenuapai.

That same year the southern motorway was extended from Mt Wellington to Wiri and the approaches to the Harbour Bridge were built, from Fanshawe St in the city and northward to Northcote Rd.

None of those initial sections of motorway did much damage, though the bridge approaches involved reclamations of the shore on both sides of the harbour.

Bringing the motorways from Penrose and Pt Chevalier into the built-up city took more time. Houses had to be bought and buildings bowled.

The southern motorway advanced from Penrose to Ellerslie, cutting that borough in two, then to Green Lane. It reached Market Rd, Remuera, in 1965.

Newmarket was to be spared the fate of Newton and other older areas. A 48ft high viaduct would take the motorway over the borough.

Auckland Grammar School lost some of its playing fields but was compensated with land at Mt Eden Prison that could be spared because the Justice Department was building new premises at Paremoremo.

Governor Hobson's grave in the Symonds St cemetery looked to be in the path of a ramp but it avoided him by a few metres.

Many other colonial graves were not so fortunate. They have been memorialised on a wall.

Late in 1968 contracts were let for the first of the Karangahape Rd underpasses that were to become "spaghetti junction" and work resumed on the northwestern motorway from the city to Western Springs.

But the economy went into the doldrums in the midseventies and the motorway programme stalled. The beginnings of a Newton Gully ramp to
the west was for many years a bridge to nowhere.

It was not until 1978 that southern and northern motorways were joined for northbound traffic with a ramp under K Rd, and 1988 before the southern and northwestern motorways were joined.

Today traffic can pass through Auckland from any direction without meeting a stoplight, congestion permitting.