Innovative X-blocs part of updated design
The Ngā Ūranga ki Pito-One section of Te Ara Tupua will make it safer and easier to walk and bike between Wellington and the Hutt, but that’s not all. It’ll also make the road and rail links more reliable and resilient thanks to new coastal defences along the edge of the shareed path.
In the past, the rail line has been washed out – disrupting transport for everyone.
When severe weather occurs, these new coastal defences need to be tough. Sloping armoured banks (known as ‘revetments’) made of very large rocks can provide this protection, but sourcing enough suitable rock to cover the 3.5km-long coastal edge turned out to be difficult.
Wellington’s rock is too fragmented, with our quarries providing mostly smaller pieces not large and heavy enough to withstand storm conditions on the coast. With other coastal and river protection projects nationwide absorbing supply of large rock from other regions, a new approach was needed.
A solution was found in the form of specialised concrete units called x-blocs. Forming an interlocking structure along the coast, the x-blocs can be placed more safely and quickly than rock, and a smaller volume is required. Where natural rock armour for the project must be brought to Wellington by truck or barge from quarries in Golden Bay or the central North Island, the x-blocs for Te Ara Tupua will be manufactured in Ōtaki, where they will support employment during the delivery of the project.
Innovative architectural and ecological features on the x-blocs have been developed especially for this project. Above water, a range of colours and shapes will provide visual variation and avoid a repetitive, artificial look. Below water, the blocks which include patterned and textured surfaces, will provide a foundation for seaweed, shellfish and other marine life to grow on.
Tonnes of rock and concrete is being sourced for the project with 6800 x-bloc units to be used, along 3 kilometres of the new coastal edge. A further 1 kilometre will be made up of quarried rock, while 600 metres will be vertical seawalls, also made using concrete. Later this year you’ll begin to see these structures taking place along the coast, particularly when travelling from the Hutt Valley to Wellington by train.
Along the coastal edge, features designed to provide habitat for penguins, birds and marine life will be incorporated including tidal pools and nest boxes.
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