| 33 T T Hugh de Lacy Repairing the aftermath of major storm The most challenging of the seven sites, because it fronts the sea, was the Taieri Mouth Road where the remediation involved the use of interlocking hexagonal Ecoreef modules in place of rock buttressing. Dunedin City Council: Slips Repair project REGIONAL DEVELOPMENT Dunedin is still recovering from when the heavens opened on October 4 last year, with Christchurch-based Isaac Construction taking up seven separate slip remediations under the one contract with the Dunedin City Council. The $1.7m contract, 51% funded by Waka Kotahi, the New Zealand Transport Agency, is for a range of works to be completed by April 30 next year, including the use of Ecoreef modules in place of rock buttressing on the Taieri Mouth Road site. The October downpour was the wettest day in Dunedin’s history, prompting mass evacuations and the declaration of a state of emergency in Dunedin and in neighbouring Clutha District. The city was briefly cut off by road, and nine houses had to be red-stickered as uninhabitable. In late June this year the council issued a call for contractors to repair the damage on seven particular slips from among the raft of them that occurred, with Isaac Construction getting the nod. The most challenging of the seven sites, because it fronts the sea, was the Taieri Mouth Road where the remediation involved the use of interlocking hexagonal Ecoreef modules in place of rock buttressing. “The modules shape the structure to soften and absorb wave energy, rather than reflecting it, thereby preventing secondary erosion,” Dunedin City Council Capital Delivery Team Leader Kieran Trainor says. “Because they are a hexagonal block, they achieve a strong and efficient structure maximising in-fill and load distribution.” Kieran adds that the council was keenly aware of the need to adopt updated engineering solutions for road dropouts and slips, especially adjacent to coastal area, which is why the original solution of rock buttressing was discarded in favour of Ecoreef, which costs more but is more cost-effective because it lasts longer. “The Ecoreef modules will reinstate the two-way road and the road shoulder, and will support the adjacent dunes,” he says. This work is almost completed, and another job, the reinstatement of the slope on Castlewood Road, similarly damaged in last October’s downpour, has been completed. Almost finished too is the Emerson Street remediation, which involves installing a gabion basket wall 10m long and 4m high. Another slope remediation job is under way on Wickliff Terrace, due for completion in the second week of December. Reinforcing the slope on Highcliff Road that failed in the rains, and strengthening it with geo-grid tie-backs, will start in January. This section of the road made a name for itself in 2015 after a huge chunk of it dropped away, taking two cars with it, earning the name “the two-car slip”. February will see the beginning of the construction of another gabion basket wall, 14m long by 3m high, protecting Blueskin Road from further slipping. The final task will be on Harrington Point Road, involving a full closure for two months of the road to the albatross colony, a major tourist attraction, and a start on this has been postponed to April next year so as not to conflict with the tour ship season.
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