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| Punganui Bridge |
| Client: NZTA |
Location: Helensville, Auckland |
| Engineer: Opus International Consultants |
Main Contractor: Brian Perry Civil |
| Value: $6 million |
Completed: Due for Completion Dec 2010 |
Click image(s) to enlarge
The Punganui Bridge Project involves replacement of an existing 1950’s concrete bridge 7km North of Helensville on State Highway 16. The new concrete bridge will be built over 3 spans a full 2m higher elevation than the existing, on the same road alignment.
A unique feature is that the whole structure will be built with capacity to be raised by 600mm at some time in the future. The bridge is located in a low-lying geographical area, and raising it may be necessary to accommodate river level rises due to global warming.
Maintaining the same road alignment means the work is split into two Phases along the centreline of the road: one side of the bridge is built at a time while both directions of traffic use the other side.
In Phase 1 the southbound side of the new structure will be built and then temporarily opened to traffic, while Phase 2 involves construction of the northbound side.
The main challenges of the project are: the proximity of live traffic to the construction site; working at height; and the environmentally sensitive location of the project, spanning a river feeding the juvenile fish and shellfish beds in the Kaipara Harbour.
Work progress in May 2010
- Bridge Piers B and C have been a key focus this month. Pier C is now completed, and Pier B is formed and ready for final concrete pouring.
- Building the abutments at each end of the bridge has progressed well despite lots of rain making ground conditions very difficult. The settlement slab at Abutment A (at the Helensville end) has been completed. Abutment D on the other side is almost completed.
- The embankment work has progressed amongst the rain: the Helensville side is complete and the Kaukapakapa side has had drains installed and is ready for mass fill. The decision to go for more robust granular material to mitigate the weather risk is already paying dividends.
- We have planted lots of new vegetation on the Kaukapakapa embankment to stabilise the area before the expected further rainfall.
- The precast beams for Phase 1 have been constructed and will be relocated close to site so they are easy to shuttle in to the site at night. The beams have to be installed at night due to their close proximity to live traffic.
- The end of Phase 1 and opening of the southbound side of the new bridge to traffic is due at the start of July, so it’s going to be a busy month coming up with lots of beams to get in place!
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