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Woolhouse Creek Bridge Replacement


Project: Woolhouse Creek Bridge Replacement

Client: NZTA

Engineer: Opus Consultants

Location: SH6, Ruatapu Ross Road

Description: Replace existing bridge with twin 2500 Multiplate CSP culverts, including cutoff walls, headwalls, conc and rock lining, guardrailing.

Value: (available on application)

Description: Replace existing bridge with twin 2500 Multiplate CSP culverts, including cutoff walls, headwalls, conc and rock lining, guardrailing.


This project is located on State Highway 6, approximately 20 km south of Hokitika on the Ruatapu Ross Road. This is a high rainfall area in which the existing bridges were too narrow and designed to cope with traffic volumes and loadings well below today's accepted norms.

Constructing the culverts on siteOpus consultants undertook the design and associated calculations, including flood events and water volumes. The nett outcome of their investigation and analysis of Woolhouse Creek site specifics was the proposal to replace the existing Woolhouse Creek bridge with twin, C.S.P. galvanised steel multi-plate pipe profile culverts. These culverts arrive on site completely knocked down as a set of plates slightly radius curved to conform to the ultimate pipe radius. The individual plates are then assembled adjacent to the site according to the recommended laying sequence of plate assembly. They are bolted together with M20 high stress galvanised bolts with the underside of the head and the bolt being shaped to fit very tight against the plate.

Placement of the first culvertDemolition of the old bridge and its abutment was required to fit the second culvert pipe alongside the first. These works were all undertaken to fit within a critical time frame and sequential programming of works to ensure minimum disruption to traffic flow on this busy State Highway. 

Constructing the cut-off wallsThe culverts required cut-off walls which entailed excavation into the creek bed followed by construction of a reinforced concrete cut-off wall embedded up to a metre into the creek bed. The culvert was lined with cobbled rock, obtained locally, on site, embedded into concrete, to provide an aesthetically pleasing and durable path for the waterway using locally sourced natural materials. 

Woolhouse Creek replacement bridgeThe highway was then reconstructed to the new, greater width above the new culverts and associated with this was the re-alignment and re-construction of a further kilometre of highway, which involved  major earthworks and realignment, with associated stormwater discharge works. The project was completed on time and within budget to a high standard and has proved to be an excellent asset contributing to the West Coast Highway network.

Download the Woolhouse Creek Case Study PDF print document.


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TruLine Civil is determined to incrementally improve the service we deliver our clients, and the quality and range of civil engineering services that we offer to owners and stakeholders who expect excellence.

Excellence in Infrastructure.

TruLine Civil.

Interested in our services? You can contact us +64 (21) 228-5090 and ask for Geoff Powell or e-mail me at 

Christchurch Address 

Greywacke Road extension,
New Zealand 

Credits: Photos and case study documentation by Shaun G. Waugh



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Woolhouse Creek Bridge Replacement

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