The Onewa Road Interchange project on Auckland’s North Shore was part of Stage 2 of the Northern Busway, a dedicated 8.7km bus route from Constellation Drive to just before the Auckland Harbour Bridge, alongside a major upgrade of the existing Onewa Road interchange to improve safety and access on and off the Northern Motorway. This $33m project was funded by the New Zealand Transport Agency and North Shore City Council with construction works being undertaken by Fletcher Construction from early 2007 to November 2008.
The original Onewa Road Bridge was a two-lane structure with tight high speed turns not suited to modern traffic flows. The project involved completely removing this bridge and its approaches and replacing it with two new bridges dedicated to traffic entering and exiting the southbound lane of SH1. These bridges were built on sweeping curves to allow for safer, faster traffic flow and also included a bus lane for city bound commuters. A third bridge skirts the junction over the City of Cork beach to carry the busway unimpeded around the interchange to join the motorway south just before the Auckland Harbour Bridge.
The site was well-suited to the use of both Leica GPS1200 and TPS1200 Total Stations with the two new on and off ramps designed on superelevated arcs with non-perpendicular piers.
In order to calculate and model the complex three-dimensional shape of the piers, 12d software was used to great advantage from interrogation of design drawings to supplying setout coordinates for surveyors on site. Pre-cast T-Roff girders of up to 30 metres in length were craned into position between the piers after checks and setout of each girder centreline. The bridge deck itself was modelled in 12d and then set out using Road Runner software on a Leica TCRP1203. Constant as-built surveys were undertaken throughout the project to ensure construction tolerances were being adhered to as well as monthly monitoring surveys on areas of pre-loaded fill to keep an eye on the settlement of the four new embankments.
Apart from the need to cause minimum disturbance to traffic, the construction team had to take extra special care not to disturb the habitat of resident New Zealand dotterels. Works were programmed and halted around the nesting seasons of the birds in order to ensure the endangered species had every chance of breeding successfully.
For more information about the Leica GPS1200 GPS solution or the TPS1200 Total Stations please contact Global Survey 09 478 2032
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