Manawatu Gorge Slip
The Manawatu Gorge Slip is the largest road slip in New Zealand history.
Manawatu Gorge section of SH3 is a vital link between the eastern and western regions of the lower North Island. On 18 August 2011 this link was severed by a large landslide, followed by other significant slips. The project to reinstate SH3 was huge.
As the head contractor, Higgins was responsible for project management and ultimate project completion including coordination with consultants and subcontractors; management of the slip works and communication with NZTA and other key stakeholders. To stabilise the slope, five massive benches were built from the top down, each longer than a rugby field. A track was built through bush at the top of the slope so equipment could be brought in.
During the slip clearing the machines pushed the material down to the crew that loaded out as much material as possible to minimise the effects of material reaching the gorge river itself. As the machines lowered the working bench, they could not climb back up, and couldn’t go down either - access was cut off for 80 days, until a track could be cut down to the road below. Vehicles had to be maintained and fuelled on the bench.
This slip damaged the road far more extensively than any of the previous slips in the Gorge. Once the slip was stabilised a massive multi rebuild phase commenced to:
• totally rebuild a three span bridge
• repair two further bridges
• construct an 85m-long retaining wall
• construct retaining netting the size of a rugby field
• build 200m of pavement and railings.
In May 2012 the benching was completed and the road was cleared. A total of 370,000 cubic metres of soil, rock and debris was removed from the site - that is enough material to overflow the Wellington Regional Stadium (Westpac Stadium). This combined with a vertical height of 155m made this the largest road landslide in New Zealand history. Stage two then began to fix the road bridgework damaged by the slip. A truely collaborative team environment delivered this technically complex task in four months - an operation that would normally take up to a couple of years to plan and build.
This project received the NZTA GEM (Going the Extra Mile) Award in 2012 for excellent customer service during an event or incident. In 2013 the project team also won the Roading New Zealand Excellence Award in the category medium sized road project as well as being highly commended in the NZ Contractors Federation Awards – category 3 Projects between $5m - $25m.