Mangere Bridge (bridge)

:"For the suburb of the same name at the south end of the bridge, see Mangere Bridge, New Zealand"

Mangere Bridge, officially also called the Manukau Harbour Crossing, is a motorway bridge over the Manukau Harbour in south-western Auckland, New Zealand, crossing between the suburb also known as Mangere Bridge (southern side) and the suburb of Onehunga (northern side). Completed in 1983, the current bridge carries a four-lane motorway with a cycle and pedestrian lane also suspended underneath the western side of the bridge.

In April 2008, work began on a duplication the bridge to cater for increased traffic (to be complete early 2011, and to serve up to 160,000 vehicles per day in 2021). The process was being delayed by disagreements over design and funding, as well as the scope of the bridge project and an associated interchange, which future is still not fully decided on as of May 2008.

Original bridges

The initial bridge in this location was built of timber and opened in January 1875. Rather narrow, it also soon began to be attacked by shipworms, and in 1910, more than 30 of the piles had been replaced, as well as the decking. [http://www.transit.govt.nz/projects/mhc/resources/pdf/Vol2-PartB-Tech-Rept-App-11.pdf Appendix 11 - Archaeological and Heritage Assessment] (Opus for Transit New Zealand, May 2006, Page 23-26. Accessed 2008-06-12.)]

In January 1914, a 246 m long replacement bridge was opened instead. Designed by R.F. Moore, the designer of Grafton Bridge, it was also built by the same company, the Ferro-Concrete Company of Australasia (in a time when almost all bridges in the country were being built by the Public Works Department). The ferro-concrete bridge with driven concrete piles was considered a substantial engineering achievement in its time. With a width of 11.6m, it allowed for a double tram track. The bridge however did not provide for enough clearance to let anything but small boats pass under it. In World War II, a anti-tank road block was erected on the bridge near the middle of the spans, with a small sentry shelter close by. The structure has since been removed, and it is unclear whether the bridge had also been mined.

The old bridge was closed in the 1970s to motor vehicles and is slowly deteriorating, especially after it sustained damage when a ship accidentally rammed it some years ago.Fact|date=June 2008 A second ship, the 300 ft container transport "Spirit of Resolution", also crashed into the old bridge on 8 October 2005 as it attempted to leave a nearby Port of Onehunga berth during winds estimated later on as being between 30-40 knots (with stronger gusts) and against a strong incoming tide. The collision occurred despite the ship's bow thrusters working at full power and a small harbour tug assisting. [ [http://www.maritimenz.govt.nz/publications/accidents/reports/Spirit%20of%20Resolution-053860.pdf Accident Report - Collision with Bridge, "Spirit of Resolution"] (from the Maritime New Zealand Investigation Report, October 2005. Accessed 2008-06-12.)]

As problems with the quality of the aging concrete and steel also make it unlikely that the bridge can be retained permanently, it was envisioned that the bridge would be dismantled and replaced by a newly designed footbridge. However, complaints about this course have for now (2006) stopped these plans while 'heritage options' are being considered as part of the general transport plans in the area." [http://www.nzherald.co.nz/section/1/story.cfm?c_id=1&objectid=10398552 Transit gives Mangere Bridge stay of execution] " - "The New Zealand Herald", Tuesday 29 August 2006] As of 2008, it is intended to retain the old bridge as a cycling / pedestrian link, and maintenance funds have been set aside for this continuing use.Fact|date=June 2008

Bridge duplication

Project history

Initial funding

On 17 May, 2006 Finance Minister Michael Cullen announced in the Budget that funds were being allocated to Land Transport New Zealand, to help the National Land Transport Programme accelerate certain projects. This includes funds for duplicating of the 1983 bridge to its the east. The Programme indicated that only $2.78 million funding was then approved for investigation of the project, though Transit New Zealand might apply for additional $1.5 million for further investigation of this project in the current financial year. The bridge was at that time expected to cost NZ$330 million."Second bridge project to go ahead: Transit" - "The New Zealand Herald", Thursday 22 March 2007, Page A11]

Wider area

As a wider part of the Manukau Harbour Crossing Project, the motorway is also to be widened between Walmsley Road in the south and Queenstown Road in the north from four lanes to six lanes. This widening will predominantly take place to the east of the existing motorway. The Onehunga interchange (known as the Gloucester Park Interchange) will be significantly reworked, to provide a more logical link with the motorway, and to ease congestion along Onehunga Harbour Drive. A standard diamond interchange was initially chosen by Transit, but after consultation with Auckland City Council this was then reworked into a quarter-diamond design, with the northbound onramp hooking underneath a proposed Neilson Road bridge.

As part of that investigation, Transit did consider whether it would have been worthwhile to toll new capacity to assist in funding its construction. This could have been in the form of tolling the new lanes along this route, which would ensure an untolled alternative is available (as legally required), while the tolled new lanes would be far less congested. In mid 2007, Transit indicated that it would not seek a decision on funding the bridge via road tolls before starting work on construction. Auckland Airport had accused Transit of threatening to defer the project if it could not gain backing from the public and local Councils. As the bridge is to be finished for the 2011 Rugby World Cup, further delays would possibly have resulted in the bridge not being completed in time.

Public transport link

In early 2007 Transit indicated that it would be "more than willing" to develop a bridge that could also accommodate a rail link, intended for a possible future Auckland City - Auckland Airport rail link (the closed Onehunga Branch, which has recently (2007) been approved for re-opening, currently terminates near the northern end of the bridge). A combination solution was debated which would see a rail link use the same bridge foundations. The change came after repeated lobbying by the Auckland Regional Council, which was of the opinion that a previous provision - restricted to allowing space for an additional, but separate bridge - was not sufficient. [" [http://subs.nzherald.co.nz/organisation/story.cfm?o_id=223&objectid=10423101 Transit opens door to cross-harbour rail link to airport] " - "The New Zealand Herald", Friday 09 February 2007]

In September 2007, ARTA proposed to pledge NZ$ 2.5 million for future-proofing works which are to ensure that a rail link can be included in the future. The design envisages the future railway line run on the new bridge piers for part of the distance underneath the motorway structure, thus saving some of the high costs associated with strengthening the bridge to be able to take a cantilevered bridge - estimated at around NZ$ 20 million in extra costs. ["$2.5 m offer to link airport to Britomart" - "New Zealand Herald", Friday 07 September 2007, Page A11] The bridge is already intended to accommodate bus shoulder lanes. ["SH20 Manukau Harbour Crossing" - "The New Zealand Herald", Saturday 30 June 2007, Page C6]

Interchange issues

In July 2007, Auckland City Council commissioners gave approval to widening the approach motorway for the bridge through Onehunga Bay, but opposed the new interchange design north of the bridge as favoured by Transit, which intended to construct it around 7 m high over Gloucester Park and the Hopua volcanic tuff ring. A favoured version would instead be built in a cut and cover tunnel.

The recommendation, which Transit could have ignored only at the risk of drawn-out legal fights at the Environment Court level (which would be likely to delay the project until after the 2011 Rugby World Cup), was based on the concerns of residents, who fear that the new interchange would increase and cement separation of their suburb from the Manukau Harbour." [http://www.nzherald.co.nz/location/story.cfm?l_id=117&objectid=10449237 Transit may have to drop motorway interchange] " - "The New Zealand Herald", Tuesday 03 July 2007] Partly due to this, Transit New Zealand decided in August 2007 to continue with building the new bridge without including new interchange for the time being. ["Bridge okay, interchange axed" - "The New Zealand Herald", Monday 13 August 2007, Page A4]

Construction

Construction of the new bridge officially began on 9 April 2008. The new bridge will provide four lanes and bus shoulder lanes (like the existing bridge). Existing pedestrian and cyclist links (on the old Mangere Bridge closed to motor vehicles) will be maintained and connected to a shared path along the Mangere Bridge waterfront reserve. Transit New Zealand also confirmed that provision will be made for a future rail link under both bridges to connect to Auckland Airport."Dawn breaks on new harbour crossing" - "Hiways and Byways", Transit New Zealand, Auckland Regional Office newsletter, May 2008]

ee also

*Auckland Harbour Bridge
*Upper Harbour Bridge

References

External links

* [http://www.transit.govt.nz/projects/mhc/ SH20 Manukau Harbour Crossing] (official Transit New Zealand project website)