Bridge It NZ

CATEGORY 1: Projects with a value of less than $1 million

Finely crafted bridges

Whangarei District Council needed to replace two 120-year-old footway bridges, one spanning 21 metres and the other 24 metres on the old Waimahanga/Boswell Track. Work involved a new pedestrian and cycle network connecting the seaside suburb of Onerahi to the CBD. The track follows a former railway route that is over 100 years old and the two old bridges had been well-used, as they formed part of a four kilometre walking track which has become a tourist attraction for the rich and diverse ecosystem of the mangrove forests in the area. Due to the age of the track, the bridges

CATEGORY nearing the end of their life span and the 1 HIGHLY COMMENDED CATEGORY 1 width (600mm) not meeting current requirements, the bridges needed to be repaired or replaced. Based on previous quotes, the council expected replacement bridges to cost in excess of $600,000. Bridge It NZ’s tender price was under $300k and, in December 2015, the company was awarded the contract on a design and construct basis and works included engineering design, contract management, quality control, environmental management, HSE management, earthworks, bridge construction, and the removal of two of the existing footway bridges.

A number of factors contributed to the complexity of this project including the fact the bridges were located in a remote marine environment. Bridge It NZ installed the new bridges separately to minimise their impact on the local surrounds. The contract period spanned six months and the bridges were completed in June 2016 to budget, plus an additional $32,000 agreed by the client to cover a design variation.

For this project a Contract Quality Plan to NZTA TQS1:1995 standard was submitted and approved by Opus, before construction started. Several hold points were identified throughout the construction of the bridges. Tiaki Engineering Consultants designed two glulam timber laminated beams spanning 21 metres and 24 metres, with an unusual I-section detail with top and bottom glulam flanges in order to reduce weight and create a slimmer and more appealing bridge profile. The glulam laminated beams and handrails for both bridges were made and assembled by Techlam NZ at its workshop in Levin. l