SH60 Repairs Accelerate Amidst Weather Concerns

New Approach Aims for Christmas Completion of Tākaka Hill Damage

Resilient infrastructure is the goal for the New Zealand Transport Agency (NZTA) as they tackle significant damage to State Highway 60 over Tākaka Hill. Following extensive rainfall, three critical sites require urgent attention, prompting an accelerated repair strategy.

Water: The Primary Adversary

Rob Service, the NZTA’s system manager for the Top of the South, identified water as the key culprit in road degradation. “Water, water, water… Water’s our archenemy,” he stated, highlighting the impact of recent weather events where Tasman district experienced half its annual rainfall in just two weeks, leaving the ground saturated.

The region has exited its state of emergency, shifting focus to recovery. NZTA faces three main repair sites on SH60 over Tākaka Hill: two underslips, one accompanied by an overslip, and a road slump caused by the movement of a historic landslide. “Three things wreck roads,” said Rob Service.

Innovative Solutions for Speedier Repairs

Normally, repairing an underslip, where ground erosion occurs beneath the road, can take up to a year, with significant time allocated for investigation and design. However, NZTA is adopting a streamlined approach for Tākaka Hill, leveraging past repair designs. “Let’s not reinvent the wheel every time we have one of these. Let’s take what we previously know, modify it, and deliver,” explained Service.

This strategy involves adapting existing underslip repair plans for the two newly damaged sites, rather than creating bespoke designs. This method proved successful for a previous underslip repair on the hill, which remained unaffected by the recent heavy rain. “We’re not starting from a blank sheet of paper, we’re using previous improvement designs that are on this hill… You’ve already got the basic recipe, you just might need to tweak it a little bit for each site. It’s not major engineering,” Service added.

Each underslip repair is estimated to cost at least $1 million. Further along SH60, at Drummonds Corner, a section of road has buckled due to the shifting of a historic landslide upon which the road was built. Repairing this site is projected to cost $2 million or more, including the removal of problematic trees and drainage work.

Long-Term Solutions for Landslide-Prone Areas

Considering the recurring instability at Drummonds Corner, NZTA is investigating the construction of a new road section to bypass the historic slip site entirely. This alternative route, estimated at $2-3 million, could offer a more cost-effective long-term solution by reducing future maintenance needs. “I think there’s a case worth investigating,” Service noted, envisioning a safer, smoother drive with better alignment. A decision will be made in the coming months after a financial analysis.

Anticipating Further Weather Impacts

Despite recent sunny periods, the ground remains saturated, and an orange rain warning for Tuesday has raised concerns for NZTA. Contractors are clearing drainage and culverts, and bunds have been installed around underslip sites to mitigate further damage. “It’s all we can do practically in the meantime to try and make it as safe,” said Service, acknowledging the possibility of additional slips. “The hill has been quite resilient, a lot more resilient than in previous years, so we’re hopeful that it’ll still hold up.”

In the wider region, ongoing disruption persists on SH6 at Spooners Saddle, Kohatu, Norris Gully, and Coal Creek, with some areas receiving temporary fixes until drier conditions allow for permanent repairs. The recent week-long closure of SH6/Rocks Road in Nelson has concluded, but crews are returning to prepare the cliff face for anticipated rain. Long-term solutions involving new retaining works are planned.

Much of SH63 in the Wairau Valley remains closed to non-essential traffic. NZTA’s immediate priorities on this route include addressing a washout at Andersons Bridge and flood scouring west of the Waihopai Bridge. The resilience of infrastructure against extreme weather remains a critical focus, as evidenced by the increased frequency of major storm events, with New Zealand experiencing an average of 15 extreme weather events per year that cause significant damage, costing millions in repairs Source: MPI 2022.