46 | Southland District Council REGIONAL DEVELOPMENT Strengthening the rural transport network The work is being delivered through a design-and-build model that allows contractors to develop solutions suited to their own capabilities. T T Russell Fredric “We are getting 23 new bridges with a design life of 100 years and minimal maintenance required, so that’s good value for money.” Experienced in all types of steelwork, delivering precision and skill from residential steelwork to large-scale portals and frames www.jwengineering.co.nz • STRUCTURAL STEEL FABRICATION • PORTALS & FRAMES • CERTIFIED WELDING Delivering quality & reliability every step of the way We are your drilling & piling experts • Water Bores • Piling • Frankie piles • Coring • Sonic • Hollow Steam • Cpt and Spt testing 027 233 9465 or 03 2111 567 manager@southdrill.co.nz • Bored Piles • Driven Timber • Steel Piles Water bores from 150mm to 2000mm in diameter up to 600m deep. We are your one stop shop for all your water bore drilling needs, from consent to water test. All your Geotech needs: A large-scale bridge renewal programme across Southland is ensuring the region’s transport network remains reliable for decades to come. Across the Southland District Council network, the scale of the task is considerable; the council manages close to 1,100 bridges, many located on remote rural roads supporting farms, forestry operations and freight routes. Southland District Council senior project manager Phil Fahey says many of the bridges were built during the rapid expansion of farming following the Second World War, meaning large numbers are reaching the end of their design life at around the same time. This ageing infrastructure is one reason bridge renewals have accelerated in recent years, with funding support from the New Zealand Transport Agency playing a crucial role in enabling the programme to progress. “Seven or eight years ago we had about 90-odd bridges that had a posted weight restriction on them. Now we’re down to about 44, and that’s because we’ve been steadily replacing them,” Phil says. The council has replaced about 40 bridges during the past six to seven years as part of a wider effort to strengthen the district’s rural transport network, with the current programme representing the next stage of that work. For the 2025–26 financial year the council tendered a package to replace 23 bridges across the district, ranging in length from about seven metres to a multi-span structure approaching 26 metres. The work is being delivered through a design-and-build model that allows contractors to develop solutions suited to their own capabilities while still meeting strict engineering criteria. “The idea is that contractors can play to their strengths. Some have precast yards, others specialise in steel fabrication, so letting them design and build the bridge allows them to bring that expertise into the project.” Delivering bridge replacements across a large rural district presents its own logistical and engineering challenges. Each site has different geotechnical conditions, access constraints and river environments to work within. Modern replacements are built to significantly higher design standards than the structures they replace. All new bridges are designed for a 100-year life and built to full HN-HO-72 design loading under national bridge design specifications, allowing them to safely carry heavy freight vehicles. Even on relatively quiet rural roads, that capacity is essential. Milk tankers, logging trucks and other heavy vehicles are a regular feature of Southland’s rural roads, and weight restrictions on older bridges can force transport operators to take longer routes, adding extra cost. When bridges reach the point where replacement represents better long-term value than ongoing maintenance, NZTA typically funds about 50 percent of the cost. “It’s critical. Without that support we’d effectively only be replacing about half the bridges we’re doing at the moment.” The latest package of 23 bridge renewals carried a budget of $10.5 million, with tenders coming in slightly under budget. Packaging multiple bridges together with criteria that ensures a fair spread across contractors created efficiencies in design and construction while still allowing competitive tendering. “We got some good economy of scale and that was probably the biggest driver for us coming in under budget. We are getting 23 new bridges with a design life of 100 years and minimal maintenance required, so that’s good value for money.” The power of the written word. New Zealand Business News, delivered to you.
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