Christchurch City Council awarded McConnell Dowell the Sumner Road Re-opening Zone 3B Project in June 2016. These long-awaited geotechnical remediation works will enable the road between Lyttelton and Evans Pass (near Sumner) to be reopened for the first time since it was closed after the 2011 Canterbury earthquakes due to rockfall hazards. Sumner Road provides a vital link between Lyttelton Port and Christchurch and the Lyttelton and Sumner communities, and is a hugely popular recreational space with tourists and cyclists.
Our job is to reduce the rock fall risk to the road to the level of ARL-2, which means it is deemed an acceptable risk to transient road users (such those in as vehicles travelling along the road). The first phase of the works involves rockfall source treatment (scaling) to remove large loose rocks from the bluffs above the road and building rock fall protection barriers.
We have overseen and carried out scaling and ground support of the bluffs above Sumner Road, excavated a 400 m long, 18 m high, 15 m wide catch bench below the Crater Rim Bluffs to catch any falling rocks, and constructed a rockfall protection bund in the gully to the west of the Crater Rim Bluffs to capture rockfall in the gullies. The bund is several metres high and 50 m long, and covered with basalt cobbles to reflect the basalt stone walls in the area.
As this rock fall risk mitigation work is completed, the Council can start work to repair the road and the many retaining walls on the road. Council has awarded MCD some of this work starting at Windy Point and road corridor realignment and repairs to several retaining walls are underway. MCD continues to work with CCC to expedite these works and carry out as much work in parallel as possible to bring the road reopening forward as much as possible.
- 15 km of road corridor to be remediated
- 85,000m3 of material to be blasted and removed from catch bench
- 420 m of bluffs to be engineered/blasted
- 150 m maximum drop for rope access
Customer: Christchurch City Council
Contract Type: Design and Construct
Working 300 m ASL and within the Port Hill's rugged landscape presents a number of logistical constraints for accessing the working sites across the project area and transporting equipment. Further, the complex nature of the works requires specialist input across a number of disciplines including ground engineering, drilling, blasting, earthworks and roading, all of which need to be carefully coordinated to ensure the safety of personnel working across multiple faces along the roadway. The proximity of Lyttelton Port Company’s coal yard operations and infrastructure works requires strong stakeholder management to minimise disruption without impacting on the programme.
Safety has been a key driver informing our design and construction methodology and giving the client confidence that the high profile works, subject to public interest and scrutiny, would be delivered in a safe manner, as well as ensuring long term safety for future maintenance of the road (Safety in Design). McConnell Dowell, Doug Hood Mining and Geovert are using a combination of rope access scaling, low velocity blasting and earthmoving to remove unstable rock from the bluffs above Sumner Road. To reduce safety risks during scaling works, we developed an innovative rockfall decision matrix model to provide greater confidence around rockfall response decision making.
KEYS TO SUCCESS
McConnell Dowell gathered a team of experts to bid and deliver the project. We have built a collaborative, open culture which has enabled the development of a robust design and construction methodology and a sense of ownership in project outcomes. This open approach has also enabled the client to be involved closely in project delivery. The development of a strong relationship with the client has enabled further collaboration on design resulting in a change of temporary design elements into permanent design elements meaning savings for the client in costs and time. These works are integrated into the programme and will accelerate the reopening of the Sumner Road for the benefit of the community.