SH25/SH25A Thames-Coromandel

20 November 2023

Bridge update

The new SH25A bridge is another step closer to completion with the precast concrete side barriers now in place and further work to connect the bridge deck to solid ground at the abutments completed.

Last week the team lifted and placed 44 barriers along each side of the bridge deck. At the eastern abutment, the team poured the concrete for the expansion joint and knock off block - find out more about these structures below.

Soil nailing of the slip face above the bridge continues with night work as well to speed up progress.  Drainage installation under the bridge and at the western abutment is underway.

The team also completed the pavement layers for the new road at the eastern approach. These are the crushed rock layers that will be sealed with a layer of asphalt.

This week the team will set up the reinforcement and do the concrete  pours, which connect the barriers to the bridge deck and form and pour the expansion joint and knock off block at the western abutment. They will also start reinstatement of the road at the western approach.

Asphalt, road marking and barriers will be completed over the next few weeks ahead of the bridge opening.

The barriers from the side of the bridge

Road reconstruction the road at the western approach to the bridge

Technical terms explained

Both knock off blocks and expansion joints are design features that allow for movement in concrete bridges.

A knock off block is part of the earthquake resistance built into bridge design. It is a ‘sacrificial’ concrete structure built at the back wall of the abutment as a deliberate weak point.  If an earthquake causes the bridge deck to move, it can “knock off” the knock off block without damage to the abutment or bridge structure.

Expansion joints are included in concrete deck bridges to eliminate or relieve stress caused by several factors including thermal expansion and contraction.

SH25A – by the numbers

While there has been a huge focus on the new bridge, other teams have been working along SH25A itself.

This work will ensure the highway is in good condition, safe and more resilient ahead of its reopening by Wednesday December 20. Getting the repairs and maintenance work done now means we limit the impact and disruption our activities have on the road users once the road reopens.

By the time the road is reopened the following will have been done:
• 23 culverts replaced
• 11.5km of side drains with kerb and channel and riprap drains
• Seven bridges strengthened
• 6.6km of new seal
• New centre lines, edge lines and edge marker posts installed along the 28.2km highway.

High-tech tape used for SH25A bridges

Maintenance work on seven bridges along SH25A includes a new technique for strengthening bridges with a high-tech tape ‘glued’ to the underside of the bridge decks (shown above).

Alongside work to repair cracks in the concrete and repaint steel girders, the fibre reinforced polymer tape is being applied with high strength adhesive.

The tape is a comparatively new technology being used more widely as part of bridge repair and strengthening work across the country. 

Scaffolding is in place at each of the bridges so workers can carry out other maintenance work to the underside of each bridge.

Work underway at Ruamahunga

Preliminary work to stabilise the large slip site at Ruamahunga Bay involving helicopters began last week.

Helicopters were used to remove trees from the slope (pictured below) and bring equipment onto site, and a site compound was set up at the boat ramp car park.

Our teams will remove loose material and vegetation and insert rock anchors and mesh at three locations across the slip face.

During these works SH25 will be reduced to a single lane under stop/go traffic management, with 'stop/stop' when helicopters are operating.

Thank you for the ‘thank you’

We knew last week’s news that SH25A would reopen before Christmas would be warmly welcomed. What we didn’t expect was the flood of positive feedback we received from the community – both via our social media channels and directly to us.

Regional Manager Infrastructure Delivery, Jo Wilton says she and the team are delighted to see the response. 

“We really appreciate all those kind words.  Both our project team and contractors have been really buoyed by this feedback. They have worked hard hard to achieve this result, so it means a lot knowing the community has recognised those efforts.

More information

For more information on the SH25/SH25A Thames-Coromandel project, contact us at coromandel@nzta.govt.nz

Visit our website www.nzta.govt.nz/thames-coromandel