An atmospheric river in August dumped a metre of rain in the region and left a trail of destruction that severely interrupted critical transport links in and out of the region. On SH6 alone, four large washouts needed to be retained, and a section of road scoured by raging floodwaters needed to be realigned and new embankment built.
Elsewhere along the road, a 30-metre-high slip (12,000m3) needed to be removed to stabilise the hill. That involved new drainage measures.
Following the emergency response phase to clear and open the road to at least one lane, WSP was engaged to undertake designs, resource consents and property agreements. The project was managed from Nelson with WSP staff accepting the challenge from Nelson, Dunedin, Christchurch, Tauranga, Hamilton, Rotorua and Auckland offices.
The damage wrought on SH6 by August’s weather event was confronting and technically challenging. The extremely constrained nature of SH6 in these locations - perched on the side of very steep terrain - needed subtle but robust options.
The construction window was short to open the road before Christmas. Designs needed to be agile as the site conditions invariably changed from what was initially understood.
At times, the construction required twenty-four-hour operations. WSP staff were out there at all hours and in all weathers working alongside Fulton Hogan.
At the height of the initial response, WSP had up to thirty staff working around the clock to table the engineering designs. To-date, 5,500 design and follow-on engineering support hours of WSP work has gone into the project.
Now, after seven weeks of intensive construction, the two-lane road has been fully reinstated. The washout and slip sections that have been fixed have been designed with enhanced weather and drainage resilience.
This project illustrates what can be achieved in a relatively short space of time when client, contractors and engineers come together with focus, application and commitment. WSP is pleased to have played its part in reopening this main artery, just in time for the holiday season. The team has well and truly lived and breathed WSP’s guiding principles over the last few months.
