Plans are afoot to replace the old Mangere bridge across the Manukau Harbour from Onehunga before it turns 100 in 2015.

The Transport Agency yesterday said it would replace the bridge - which was closed to motor traffic in 1983 but is still used by hundreds of pedestrians, cyclists and anglers each day - with a "higher quality and safer connection".

It did not say what it would do about the existing structure, which is believed to be the oldest reinforced concert harbour crossing in New Zealand.

But Onehunga Enhancement Society chairman Jim Jackson hopes elements of it can be incorporated in its replacement or some nearby development.


He said his organisation was keen for the new bridge to include a lifting section, to allow for future inner-harbour development which may attract large vessels.

Not even small boats can fit under the old bridge at high tide, and it has warning signs about falling debris.

The Transport Agency says it will retain the existing clearance "as a minimum" and investigate providing a higher structure for all-tide access for boats.

Its predecessor, Transit NZ, intended demolishing the old bridge in association with its $230 million Manukau Harbour motorway crossing duplication project, which was completed in 2010, but it ran out of cash.

Transport Agency acting highways manager Steve Mutton said yesterday he hoped construction of a new bridge could start late next year or early in 2014, so it could open on the centenary of its predecessor.

Mr Jackson said a cost estimate of $12 million under the earlier plan was increased by $5 million to make the new bridge strong enough to withstand marine collisions.

He believe a lifting section would be included for no more $1 million - which he believed was reasonable considering the bridge should last another 100 years.

Given that more than 600 people used it on some days, he said it should be wider than six metres proposed by the Transport Agency. That is less than half the width of the old bridge, which was built for four lanes of traffic.

An agency spokesman said it was too early to give a precise cost estimate, and the community would be asked its views before designs were developed.

The Historic Places Trust would be on the project team.

* Public information sessions will be held from 10am to 2pm on August 11 and 12 at the Waterfront Road Reserve, Mangere Bridge.