Constructed in the mid 1800s, New Town Road Bridge is a historically significant part of Hobart’s infrastructure. Duratec is currently undertaking restoration works to this important piece of Tasmania’s history.
New Town is Hobart’s first suburb and its infrastructure includes New Town Road Bridge – a five-course, brick arch structure, built on sandstone abutments, which crosses the Maypole Rivulet adjacent to the Risdon Road intersection with New Town Road. Like much of the area’s infrastructure, New Town Bridge was by built by convicts between 1840 and 1841.
Over the years, the adjacent road has been widened and elevated to accommodate the increasing size of vehicles, as well as the volume of traffic. It was eventually covered over and is now completely embedded underneath the road surface, forming a tunnel within the rivulet system.
Last year, through a routine stormwater rivulet inspection, Hobart City Council identified a section of the bridge displaying degradation and sought local advice on the best way to remediate and strengthen the structure. Duratec was engaged to undertake ‘design-and-construct’ remediation works and the project is currently in the detail design phase.
So what’s the plan?
The scope of works for this project involves the following:
- Investigation of structure and design of a suitable lining to ensure bridge’s structural integrity and durability
- Implementation and maintenance of safe system of confined-space work within the tunnel
- Specialist grout injection with pozzolans to reinstate mortar loss
- Fabrication and installation of steel, including reinforcing bar and construction templates
- Temporary diversion of waterflow
- Installation of specified lining system
- Application of fairing coat
Challenges and solutions
Challenge
- Confined-space work with limited vertical manhole access; alternative horizontal access via 300-metre open-air rivulet and box culvert
Solutions
- Efficient set-up and pack-down to ensure no obstructions left outside work times and fast exit implemented for unanticipated inclement weather
- Detailed planning to establish weather monitoring, site-entry scheduling and ‘stop work system’
Challenge
- Several high-profile businesses, as well as associated vehicle and pedestrian movements, in vicinity
Solution
- Early and ongoing stakeholder engagement to ensure impacts are reduced or eliminated
- Development of traffic guidance methodology with key focus on safety and disruption minimisation
Challenge
- Works in a rivulet system that feeds into Derwent River
Solution
- Development and implementation of construction methodology that minimises environmental impacts
