KEY POINTS:
Aucklanders tend to scoff at the idea of Tauranga having traffic problems, but residents of the sunny Bay of Plenty city are anxiously awaiting the day their new harbour bridge is finished.
The project reached a milestone late last week with the pouring of concrete for the first beam of the bridge.
Work on the Harbour Link project began a year ago but until recently much of the effort has focused on roadworks for the bridge approaches.
The first beam provided a welcome sign that the construction schedule for the bridge and an accompanying viaduct was on track.
An on-site factory to cast the beams and body of the bridge is also finished, and those crossing the harbour can now see a construction jetty protruding across the water.
Every year, congestion between central Tauranga and Mt Maunganui worsens and traffic jams are a daily reality for commuters, increasing the longing for the scheduled completion of the project in autumn 2010.
It is hoped the new four-lane expressway will ease traffic flows between the two sides of the harbour and, in particular, improve access to and from Tauranga's busy port.
The Harbour Link involves building a duplicate bridge alongside the existing two-lane harbour bridge, and a viaduct to divert vehicles going to Auckland and Hamilton away from roads into Tauranga's CBD.
The viaduct will also pass over a railway line, and the harbour bridge will include a cycling and pedestrian lane separated from vehicle lanes by a concrete barrier.
Transit New Zealand says work on the project is progressing well and there is a good chance it will befinished before the scheduled date.
Project manager Kevin Reid is also hopeful it will come in under budget, having already managed to refund $30 million of Treasury money after the first phase of construction cost less than expected.
Fletcher Construction is building the bridge and viaduct, and Mr Reid said the company was using innovative methods.
Among those methods is an environmentally friendly way of piling using a material called bentonite.
Bentonite, a liquid clay, is pumped into the ground to stop the pile walls collapsing, and then forced to thesurface, in a funnel-like way, when the concrete for the actual pile is poured into the hole.
Because bentonite occurs naturally, it has no ill-effects on the environment if it leaches into the water, and can also be washed and reused.
Mr Reid said that piling method had never been used in New Zealand before, and Fletcher's was also re-using moulds from another bridge to cast the bridge deck.
The casting is being done on-site and sections of the deck will eventually be pushed into place to complete the structure.
The engineering team includes four people who worked on Tauranga's existing harbour bridge in the 1980s, and their knowledge is considered invaluable because of the engineering challenges presented by the area's poor ground quality.
Piles are having to be driven deep into the earth - up to 65m below the harbour floor and 30-40m down on land - because of the silty soil.
The Harbour Link project was initially going to be funded half by the Government and half by tolls, but is now being completed without tolls.
* Follow the bridge's progress on the Transit website, or visit the Harbour Link Public Information Centre.
TAURANGA'S HARBOUR LINK
* Bay of Plenty's largest roading project.
* Construction started a year ago and is scheduled for completion two years from now.
* Initial budget $255 million but now $215 million because of savings made in first phase of construction.
* During construction of the new bridge and flyover, 36,000 cu m of concrete will be poured - the equivalent of 6000 full concrete trucks.
* A total of 184 concrete beams up to 37m long and weighing up to 84 tonnes will act as supports.
* The viaduct structure is being built to withstand a one-in-1000-year earthquake and also uses 750km of "stress strand" metal cable for reinforcement of the beams.
* The project employs 120-150 engineers and construction workers at any one time.
* The existing harbour bridge, finished in 1988, has an ideal capacity of 29,000 vehicles a day but is currently used by 40,000, a quarter of which are heavy goods vehicles.
* Together, the existing bridge and the new bridge will have a capacity of 50,000 vehicles a day.
Source: Transit New Zealand
ROUNDABOUTS GET LIGHT RELIEF
Tauranga's traffic woes are also about to be eased by the country's first signalised roundabouts.
Traffic-light type signals will be introduced at the Maungatapu and Welcome Bay roundabouts later this year to try to reduce congestion.
The system will allow 3700 cars per hour through the roundabouts, which feed vehicles from southern suburbs into central Tauranga and east towards the Kaimai Ranges.
"It's a clever way of getting a lot more out of roundabouts," said Transit New Zealand project manager Kevin Reid, who managed signalised roundabouts in Britain and hopes the new system will be up and running by September.
He said the roundabout approaches would first be widened and more lanes added to allow a greater number of cars through at any given time.
Rather than giving way, drivers follow traffic light signals, which indicate green for shorter periods than normal lights - about 20 seconds at a time - to ensure vehicles enter the roundabout in an orderly way. Mr Reid said a similar signalised system was used temporarily on one Auckland roundabout, but this is the first time it will have been installed permanently.
The idea came from another Transit engineer who had seen it used on roundabouts with a very similar layout in East Kilbride, Scotland.
The Scottish city's South Lanarkshire Council and the Tauranga City Council have collaborated on the Maungatapu/Welcome Bay project.
The scheme is costing $4 million.
