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Friday, 30 September 2016 10:24

Geotech Works Begin at Sumner Rd

A blessing and ceremonial planting officiated by local iwi Ngati Wheke marked the start this week of geotechnical risk mitigation works at Sumner Road in Christchurch.

Representatives from McConnell Dowell and partners Beca, Geovert and Doug Hood Mining were present to celebrate the official start to the project

Alongside Christchurch Mayor Lianne Dalziel and the NZ Transport Agency’s Southern Regional Director Jim Harland, McConnell Dowell Operations Manager Joe Edwards and Board Member Linda Constable planted some Kowhai, Ngaio and Griselinia shrubs at the top of the bluff to mark the occasion.

The team is excited to be starting on the challenging and complex project and proud to be helping deliver such an important project for the local community. Sumner Road from Evans Pass to Lyttelton has been closed since February 2011, when the earthquake damaged the road and made area too unstable to access. The project will mitigate geohazard risks to road users and return the roading corridor between the Sumner side of the causeway and Lyttelton to its pre-quake level of service.

“We have gathered experts in a number of fields including geotechnical analysis, rope access ground engineering, drilling, blasting, earthworks and roading to prepare Sumner Road for remediation works and reopening”, says Contractor’s Representative Marianne Rogers.

“Our focus is to inspect the terrain around Sumner Road and to stabilise the rock loosened by the earthquakes safely and efficiently, securing the cliffs so work to repair Sumner Road can begin.

Works will include scaling the upper reaches of the Crater Rims Bluffs, abseiling down the cliffs and removing any rock that isn’t stable or secure. Large rocks will need be removed using controlled blasting or bolted and meshed.

A 400m long, 15m wide catchbench will be excavated directly below the Crater Rim Bluffs and above the Sumner Road to catch and prevent rockfall from reaching the road. A rock bund several metres high and 50 metres long, will also be constructed in the gully to the west of the Crater Rim Bluffs to intercept rockfall. It will be covered with basalt cobbles to reflect the basalt stone walls in the area.

Structural repairs will be completed under the existing road so it can be used as a ‘haul road’ to transport excess rock from the excavation of the bench. This is a faster and more cost effective option than constructing a separate haul road and it also makes a start on the repair work required to return the road to two-lanes.

Work to make the area around Sumner Road stable enough so it can be repaired is a critical part of the rebuild effort and one of four projects within the Sumner-Lyttelton Corridor programme.

Once the geotechnical risk mitigation work is completed, the next stage of work will begin, investigating the extent of the damage to retaining walls along the road. The road will then be repaired and reinstated. At this stage, it’s expected that the road will reopen in 2018.