SH1 New Ōpaoa River Bridge

WSP provided design, conservation, and construction monitoring services for the new Ōpaoa River Bridge, combining safety, strength and celebration of mana whenua and the rich local history.

Location

Marlborough, New Zealand

Client

Waka Kotahi NZ Transport Agency

Project Value

$22.7m

Project Status

Start Date: September 2018 – October 2020. Construction Practical Completion, Now in three years defects liability period.

PROJECT DESCRIPTION

The Ōpaoa River Bridge has been both the northern gateway and boundary of Blenheim for over 100 years. The original structure, a concrete bowstring arch bridge, was built in 1914. It was an engineering achievement in its day but needed replacing to comfortably handle the ever-increasing demands of modern traffic. The new Ōpaoa River Bridge meets the current and future needs of the modern, growing Blenheim community.

Waka Kotahi approached WSP in 2016 to design and deliver this $22.7 million project. Our scope of services included:

developing the business case
detail design
regulatory authority applications and management
tender management
construction monitoring for the replacement bridge
heritage works on the historic bridge

The historic Opawa Bridge is a Heritage Category 1 concrete bowstring arch structure. The 160m-long bridge is part of New Zealand’s principal roading network, but a 2015 investigation found it was too narrow for large freight vehicles and vulnerable to earthquakes and flooding.

Waka Kotahi NZ Transport Agency, supported by WSP, began work to replace the bridge with a new structure that was safer, wider and more resilient. The new bridge would be a contemporary structure adjacent to the heritage bridge, which would be restored and repurposed for the local community. Construction was managed in a constrained zone to minimise impact on the nearby campground business, while still providing sufficient space to construct the structure safely.

Restrictions on fixings to the old bridge structure were instrumental in driving design decisions. Invasive drilling or permanent fixing to any part of the structure was not permitted due to concerns about long-term damage. As a result, the design team had to investigate opportunities for attaching lighting and electrical infrastructure that would not permanently fix to the old bridge structure, with some limited exceptions.

OUR SOLUTION

“More than just a bridge”
Recognising the importance of the wider site to the mana whenua of the Wairau region, Te Rūnanga a Rangitāne O Wairau, Ngāti Toa Rangatira, Ngāti Rārua, Heritage New Zealand Pouhere Taonga, and Marlborough District Council’s involvement was crucial to the urban design of these spaces. There was considerable collaboration throughout the lifecycle project, beginning at the preliminary design phase with ideas generated between the Waka Kotahi and engineers, and incorporating the artist, conservation architect, lighting designers, landscape architects, along with iwi and WSP in New Zealand.

The new Ōpaoa Bridge is 188m long, 10m wide, and curved on the southern three spans, with 700m of realigned approaches including retaining walls both sides of the southern approach, noise reduction walls, extensive landscaping and artwork.

The existing heritage bridge was repurposed into a walking and cycling facility, as well as a space to hold local community events. The bridge’s northern end has been transformed into a landscaped area complete with courtyard, cultural artwork, interpretative panels, and gateway signage. Tie-down points for stalls have been placed along the bridge deck, and weatherproof sockets were installed on the rear of the kerb line to provide power for food trucks or pop-up events.

From the start, we wanted the new structure to be sympathetic to the heritage bridge. The delicate shape and patterns on the new bridge reflect that approach, and the restored heritage bridge was designed
to serve the community well, long into the future.

Brent Morgan WSP Principal Project Director - Transport and Infrastructure, was project manager for the bridge.

Brent Morgan WSP Principal Project Director - Transport and Infrastructure, was project manager for the bridge.

WSP in New Zealand worked closely with Heritage New Zealand Pouhere Taonga and Marlborough District Council through the planning stages and developed a Conservation Management Plan early in the design phase to understand the history of the bridge and the best way to manage its long-term maintenance.

Accounting for natural capital

The Harakeke (Flax) motif was historically significant to the area and reflects the wetlands that were once abundant throughout the lower Wairau plains. Motifs representing local flora are sandblasted into the concrete safety barriers of the new bridge and complemented by actual plantings on the approaches to the bridge.

The interpretative panels are printed on aluminium sheets protected by special sealants and anti-graffiti coating and mounted on concrete walls in the courtyard. A pile from a previous timber bridge, recovered during excavations for the new bridge, is positioned beside the panels with an identification plaque.

Sophisticated lighting solutions

Due to the structure’s historic nature WSP used traditional simple lighting using contemporary LED lighting, including the occasional use of coloured lights used to celebrate prominent dates throughout the year.

In the landscaped area at the northern end of the bridge, in-ground luminaires with narrow beam optics highlight the 7m pou whenua. These are located at three points around the base to bring out its texture from all directions.

OUTCOME/CLIENT BENEFITS

WSP in New Zealand’s priority was incorporating the new bridge into the existing surrounding landscape so the two bridges would read as a compatible pair, as well as retain their own identities.

The approaches to the old and new bridges have incorporated complementary cultural aspects into their design, which together tell a story and represent the whole community. Schools have been involved throughout the process, with visits to witness the progress of the pou whenua, hear the stories incorporated in the pou whenua, and learn more about te ao Māori.

A pou whenua to stand at the northern end of the bridge was commissioned by mana whenua iwi and carved by a locally based artist. Master carver Reg Thompsett spent many months carving the pou, which represents the history and future of mana whenua in the area. The striking pou whenua Kei Puta te Wairau now stands at the entrance to Blenheim in a specially constructed paved courtyard. Alongside is a series of interpretation panels, designed by a local artist in consultation with mana whenua iwi. One interpretation panel summarises Māori settlement in Aotearoa New Zealand and the Marlborough area, exploring mana whenua connections. The second panel tells of the history of the heritage bridge from its construction 100 years before through to the present day.

Every step of the project - design, planning, construction and end-use – was developed with the intention that this structure will remain into the future for everyone to experience, enjoy and reflect on. We didn’t just build a bridge. We created a space designed for, and by, the community of Te Waiharakeke Blenheim.