Māngere Bridge (bridges)

Natural causeway and initial bridge The location of the initial bridge was originally a naturally formed basalt rock causeway used by Tāmaki Māori, traversable by foot at low tide (except for a shallow tidal stream of a few metres in width). The causeway connected the two halves of the Ngāti Whātua Māngere-Onehunga kāinga complex in the early 19th Century. In 1847, the first ferry service between Onehunga and Māngere was established, where passengers would need to raise a flag on the Māngere shore to signal the ferry operator. In 1858, a large section of the rock walkway was destroyed with dynamite, to allow for more intensive shipping in the harbour. Civil engineer James Stewart was announced on 7 August 1866 as the winner of a competition for the bridge's design, however stalled due to the Ngāti Mahuta ownership of the land on the southern side of the proposed bridge location restricting what the company could create. In 1872, tenders for the development of the bridge were proposed. the narrow timber truss bridge featured 20 spans of 12.2 metres supported by jarrah timber piles from Australia, costing £14,997 to build. before being fully demolished. Old Māngere Bridge , circa 1980 A plan to replace the old wooden bridge was adopted by Māngere ratepayers in May 1911. Designed by R.F. Moore, the designer of Grafton Bridge and Queens Wharf, 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 17-span ferro-concrete bridge was constructed between 1912 and 1916, while construction of the ferro-concrete structure continued through 1914 and 1915. The ferro-concrete beams and piles of bridge were created using prefabricated concrete, a very unusual method of construction in New Zealand at the time. The bridge was officially opened on 31 May 1915 by Prime Minister William Massey, a resident of Māngere. By 1927, repair works on the concrete structure were needed due to degradation. Due to problems with the quality of the concrete and steel, plans for its removal were not finalised until 2012. Construction of a replacement structure, designed for walking, cycling and fishing, was scheduled for 2015, the centenary of the opening of the old bridge. Ngā Hau Māngere The New Zealand Transport agency dismantled the 1912 Māngere Bridge in 2018 due to safety issues. The new bridge, Ngā Hau Māngere, was built on the same abutments as the previous bridge, further from the port and allowing enough clearance for small boats to pass underneath. The bridge is eight metres wide and up to 12 metres wide in some bays to enable fishing activities. Ngā Hau Māngere opened on 27 August 2022. ==Motorway Bridge==

In 1963, a report by US consultancy firm De Leuw Cather and Co recommended that a motorway and rapid public transport system be developed for Auckland. This included the Southwestern Motorway, a link between the proposed Northwestern and Southern sections that would bypass the city centre, and would involve a large-scale motorway crossing of the Māngere Inlet adjacent to the Old Māngere Bridge. The first section of the Southwestern Motorway, the Onehunga Bypass, was completed in 1977, spanning Queenstown Road in Hillsborough and terminating at the Old Māngere Bridge. Two contracts were let for the construction of the motorway bridge: one to Gilberd Hadfield Pile Co Ltd to construct the foundations, signed on 25 January 1973, and a second for the construction of the bridge structure, awarded to the Wilkins & Davies Development Company Ltd and signed on 24 July 1974. The contract with Wilkins & Davies Development Company was suspended in July 1978, and a new contract with Fletcher Construction was awarded in November 1980 to finish construction. In September 2007, Auckland Regional Transport Authority proposed to pledge NZ$2.5 million for future-proofing works to ensure that a rail link would be included. The design envisaged 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. 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 favoured by Transit, which intended to construct it around 7 m high over Gloucester Park and the Hopua volcanic tuff ring. The council's preferred version was to build the interchange at ground level with part of the motorway in a cut and cover tunnel. Partly due to this, Transit New Zealand decided in August 2007 to continue with building the new bridge without including a new interchange for the time being. Design Transit New Zealand made provision for a future rail link under both bridges to connect to Auckland Airport, The bridge has 7 piers with a total of 14 columns, and consists of approximately 10,000 cubic metres of reinforced concrete (with the rebar weighing approximately 1,000 tons). Some of the piles were driven 50m deep, to avoid issues with the softer top layers in the Manukau Harbour. The bridge itself consists of single-pour concrete columns and form traveller-constructed balanced cantilever decks. Existing pedestrian and cyclist links on the old 1914 bridge closed to motor vehicles were retained and are connected to a shared path along the Mangere Bridge waterfront reserve via a new walking/cycling bridge over Onehunga Harbour Road – linking Onehunga to Mangere Bridge suburb and to the Waikaraka Cycleway. Ancillary works A number of works related to environmental mitigation, post-project landscaping or improvement of non-motorway transport links were associated with the project (and either paid for or undertaken by NZTA). These included a 3.5m wide replacement foot/cycle bridge over Beachcroft Road, a new 3.5m wide foot/cycle bridge over Onehunga Harbour Road at the Old Mangere Bridge, an upgraded underpass under the motorway connecting to Onehunga, as well as improved links to the walking and cycling paths along the harbour and motorway edges and improvement works on the Old Mangere Bridge causeway. After finishing work, NZTA reinstated their large construction staging site along the southern harbour front as an open space, "passive recreation" park with Pohutukawa. ==See also==