What work has already taken place?
In 2015, the NZ Transport Agency launched an investigation of the Wairau and Opawa bridges to improve travel on State Highway 1 north of Blenheim.
We considered strengthening, replacing or duplicating both bridges. The Wairau Bridge was found to be in serviceable condition, while the Opawa Bridge was identified for replacement.
In 2016, we asked for feedback from the community on the proposal. The feedback is available for review and has been factored into a revised the final proposal.
The developed design for the new bridge was finalised and Resource Management Act consents obtained in 2017. Downer New Zealand Ltd was appointed to carry out the construction of the new bridge and started work in September 2018.
Why is a new bridge needed?
Investigations of the Opawa Bridge confirmed that it is too narrow for some vehicles, particularly large freight vehicles. The bridge is vulnerable in an earthquake and susceptible to damage from heavy floods.
Our key objective is to keep people and goods moving along State Highway 1 between Blenheim and Picton. We want to make the region more resilient to natural disasters and support State Highway 1 as a strategic freight route between Picton and Christchurch.
The specific benefits of building a new bridge are increasing the number of freight and light vehicles travelling across it, greater certainty for journeys on the State Highway network, and greater structural resilience to natural hazards.
Were other options considered?
Yes, as part of our investigations, we developed a long list of all possible options to address the two problems. Thirteen separate options were investigated and assessed, including a do-nothing option, using a variety of criteria. You can read more about all of the options and the detailed analysis in the Consideration of options report [PDF, 7.6 MB].
What will the new bridge look like?
Community feedback about the preferred look of the new bridge over the Ōpaoa River indicated residents wanted it to be simple, cost effective, have the character of the existing bridge, and be functional and safe. The design has taken these factors into account while also meeting engineering requirements due to the partial curve in the route over the river. The character of the existing heritage bridge still dominates the landscape in the area while the new bridge meets the functional requirements.
You can find out more about the design that was selected and view a concept drawing here, and indicative drawings of the new bridge have been included in the Detailed Business Case [PDF, 18 MB].
How much will the new bridge cost?
The project has a budget of $21 million, which will cover the cost of bridge construction, professional services, landscaping and moving nearby telecommunications cables.
What will happen to the old bridge?
The existing bridge, a Heritage NZ Category 1 Historic place, will be kept for use by pedestrians and cyclists. We are working with Iwi, Marlborough District Council and Heritage New Zealand to introduce appropriate landscaping, lighting, and to ensure the history of the old bridge is recognised and acknowledged.
What does the construction process involve?
The work will begin by relocating and re-laying underground communication cables to allow foundation work for the new bridge. Steel casings for the seven piers will then be sunk up to 22 metres deep to gravel layers. Pier columns and headstocks will be constructed on top of the piles, and precast concrete beams will then be delivered and installed. While the piers are constructed, work on the bridge abutments will start by driving steel H piles 25m deep into the ground.
Once the headstocks and abutments are completed, 72 bridge concrete beams will be craned into place. These large 1.2m wide concrete beams, ranging from 21m to 26m long, will be trucked in from Christchurch. As the beams are being put into place, work will start on the construction of new retaining walls and pavement, before the connections from State Highway 1 to either end of the new bridge are built.
When construction is complete, a landscape plan will be carried out to beautify the area and create an attractive gateway to Blenheim that clearly marks the northern entrance to the town.
How is the environmental impact being minimised during construction?
We have put measures in place to minimise any disturbance to the river, in accordance with the project’s robust resource consent conditions. This meant no work was carried out in the flowing channel of the river during the spawning season (1 March to 30 April).
Other measures include reducing sediment run off from entering the Ōpaoa River or council stormwater systems by filtering the dirty water, and the installation of a temporary river crossing to reduce river disturbance.
When will it be completed?
The new bridge over the Ōpaoa River, and work on the old bridge to make it suitable for pedestrians and cyclists, is expected to be completed by mid-2020.
Why has the name changed from Opawa to Ōpaoa?
The Ōpaoa River was known as the Opawa River until 2014, when it was officially changed as part of a Treaty of Waitangi settlement(external link), to correct the spelling of the river’s name.
What are key elements of the landscaping plan?
The Transport Agency is working closely with mana whenua iwi to develop a landscaping plan. Mana whenua iwi – Rangitāne, Ngāti Rārua and Ngāti Toa – have met with NZ Transport Agency and Marlborough District Council (MDC) throughout 2019 to discuss gateway landscaping for the New Ōpaoa River Bridge.
The Marlborough District Council-commissioned Ōpaoa Gateway draft design incorporates an overarching theme of harakeke/flax. Flax and other indigenous native plants and trees are suggested to make up the extensive planting areas that cover both sides of the highway.
On the northern side of the bridge a proposed welcoming entrance statement wall, viewed from the highway, may include the Māori name for Blenheim – Wairau – and feature a weaving motif within the concrete wall structure. To continue the harakeke theme, a flax motif has been designed for use on the internal concrete barriers of the new bridge.
