In 2017, a significant landslide occurred on Ngaio Gorge Road, causing a closure of a busy road into Wellington. The road is an important commuter route for those living in Wellington’s northern suburbs and a critical route if Ngauranga Gorge ever became blocked to traffic. As a temporary response, the Wellington City Council built shipping containers filled with concrete blocks to act as a temporary barrier, and in late 2020, work started to strengthen and stabilise the Ngaio Gorge slip to make this key transport route stronger and more resilient.
As part of the project, Moddex was engaged by the main contractor, Fulton Hogan to supply safety from falling pedestrian barriers to numerous retaining walls along the road. The retaining walls had an existing timber system, which to replace with the same system, would have been inefficient, costly and time consuming to install.
Moddex’s standardized design, with fast turn around times and adherence to loadings and New Zealand standards, proved to be an ideal alternative. Moddex supplied and installed their anti-climb mesh Bridge Barrier BR20M system. The galvanised steel finish offered increased durability, while the modular nature of the system facilitated quick on-site installation. Additionally, the ability to powdercoat the system green allowed for seamless integration into the surrounding environment.
Key Challenges Faced and How They Were Overcome
The project encountered significant challenges related to drilling and fixing the barrier into the retaining walls, due to irregular angles of the retaining walls, deviating from a standard flat and level surface.
This made the design, manufacture and installation of the barrier challenging, but with a meticulous approach, Moddex commenced with on-site measurements to obtain precise dimensions. Using these measurements, shop drawings were created that were subsequently submitted for approval by the client. Prior to manufacturing, Moddex cross-verified the shop drawings against the as-built dimensions on-site, ensuring a perfect fit on site.
The design and manufacture of Moddex’s BR20M system was executed within the parameters outlined in the PS1 documentation, aligning with the unique structure of the retaining walls. By offering an off-the-shelf design that met required standards, including the Bridge Manual Clause B6.4 loading requirements, Moddex ensured compliance and reliability throughout the project.