Work begins on Coromandel bridge

An artist's impression of the new Kopu Bridge as seen from the west bank. Photo / Supplied by Transit NZ

Relieved Coromandel Peninsula residents will join Prime Minister John Key today to celebrate the start of construction for a $47 million replacement of the rickety one-lane Kopu Bridge and its frustrating traffic queues.

Mr Key and Transport Minister Steven Joyce will break the ground for a two-lane steel bridge across the Waihou River south of Thames, which officials hope will be carrying motorists to and from the peninsula in free-flowing traffic by Easter, 2012.

That cannot be too soon for Thames car dealer Ian Richardson, who has driven to work across the 80-year-old structure for 18 years and campaigned for its replacement after reading on the former Transit NZ's website that it was at risk of collapsing in a moderate earthquake.

He believes the parlous state of the 465m bridge, which has timber and wire barriers and traffic lights to control vehicle crossings, deters some would-be visitors and expects its replacement will provide a needed economic boost to the Coromandel.

"There is not a one-way bridge into any other major area of New Zealand - it had to be done."

Transit's successor, the Transport Agency, acknowledges delays of up to three hours for holiday weekend traffic trying to cross the existing bridge.

The project, for which it will announce the construction contractors today, will include 2.5km of approach roads for the 580m replacement steel bridge, including a direct link to a new four-leg roundabout at an intersection with State Highway 26, the main route between Thames and Paeroa.

Although that will eliminate a cumbersome dog-leg through the Kopu industrial estate, the agency rejected as too costly an alternative proposal to build a new bridge 700m upstream of the existing structure, to hook up with State Highway 25A to Tairua and other eastern peninsula resorts.

A gap of just 28m will instead separate the new bridge from its predecessor, which opened in 1928 and will be preserved for its heritage value as a Category 1 historic site.

That is despite the old bridge's absence from a computerised simulation on the agency's website of easy traffic movements across the replacement structure.

The agency is still reviewing options for maintenance and use of the old bridge with the Thames-Coromandel and Hauraki district councils and the Historic Places Trust. One possibility could be to incorporate the structure, which has concrete piles but timber and wire edge barriers, into plans supported by Mr Key for cycleways through the Hauraki Plains and along disused railway lines between Thames, Waihi and Te Aroha.

However, the agency has designed a shared cycleway and footpath for the northern side of the new bridge, separated from traffic by a concrete barrier.

Whatever happens, a swing section of the existing low-lying structure will have to be maintained to allow large boats to sail up and down the Waihou River.

The bridge will 12.95m wide - more than three times its predecessor's width - and high enough at 6.5m above mean sea level to allow safe river passage beneath it.