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CSP Pacific’s Multiplate eliminates road and rail closures at Waipukurau Overpass project
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Principal: New Zealand Transport Agency (NZTA)
Engineers: Opus International Consultants Ltd, Napier
Main contractor: Infracon Ltd
Sub contractor: Morris and Bailey Ltd
Location: SH2 Waipukurau
Product: Steel Multiplate Arch
Partially completed overbridge at Waipukurau on SH 2, showing the old bridge in the distance.

A 90m long Multiplate arch, manufactured by CSP Pacific, has been installed on SH2, 2kms north of Waipukurau over a live rail line. The new overpass replaces a two-lane bridge built in 1937. The old bridge, built on a curve in the road, was a hazard for motorists and consequently had a poor safety record. The year-long project began in March and has also involved the realignment of SH2.

"In choosing the Multiplate culvert as opposed to rebuilding a new bridge it was possible for SH2 and the live rail line to remain open throughout construction," said Jeremy Mallender, Area Sales Manager Lower North Island for CSP Pacific.                  

"ONTRACK supplied a full time person to ensure that we were safe during construction and that there was no disruption to rail services," said Dominic Bailey, Contract Administrator, Morris and Bailey Ltd. "We tended to take our smoko breaks when the trains were due."

Opus International Consultants specified an epoxy paint system to be applied to the base channel and the bottom plates of the arch. This was to avoid corrosion at the base of the structure from build up of moisture and debris getting into the fixing channel. CSP Pacific and Morris and Bailey recommended the bottom section be coated with Oclyte Tuff Coat™, CSP Pacific's high performance, two component, high build polyurethane elastomeric coating which is specifically engineered to add corrosion abrasion and impact resistance to galvanised structures.

"We used Oclyte Tuff Coat™ on the bottom 150mm of the structure and the fixing channel," added Dominic. "This was then backfilled with a cementitious product to seal the steel even further. This is the first time a culvert has been installed with this specialist protection and it will considerably extend the design life of this structure."

Sections of the Multiplate were able to be preassembled and craned and bolted into place with the assembly process taking approximately two months, including completion of the necessary quality checks. Once the assembly of the structure was complete, backfilling began to create a temporary road over the new culvert allowing for the demolition of the old bridge.

"We will use approximately 90,000m³ of imported fill to complete this project," said Dave Cowlrick, Senior Engineer from Opus International Consultants, Napier. "The old bridge has been demolished but the backfilling is not at the right height yet as we complete all the retaining work. Once the retaining is finished we will then be able to back fill to the required height and surface the new road. It is quite amazing that there was not one closure to SH2 or the rail line while we built this new overpass. We are really happy with the way the project has progressed and the result."

"CSP Pacific, Jeremy, Joe and Sue in particular, have been excellent throughout this project," adds Dominic. "They have been supportive and helpful, they were great to work with."


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