HGM Construction was contracted to carry out anchoring work on two retaining walls as part of the Sumner Road Reopening Project following damage incurred in the 2010-2011 Canterbury Earthquakes. As an essential haulage route between Lyttelton and Christchurch, the retaining walls formed an essential part of the enabling work to allow the road to be strengthened and reinstated. The scope included drilling, anchor installation, grouting and testing of GRP anchors up to 12 m deep across the two retaining wall sites.

Project Challenges:

The key challenge for this project was access, with a steep drop off below the road down to the quarry. HGM worked with Hunter Civil to design a safe work system that allowed work to be carried out on scaffold without the requirement for rope access.

The remote-controlled excavator mounted drill rig setup was agreed to be the best option for under reaching the anchors from the road and allowing sufficient maneuverability to reach the required anchor locations and angles.  Controlling the rig via remote allowed the driller to be removed from the excavator for safety and to retain good visibility of the holes being drilled.

Another challenge for this project was working on a dynamic, large scale site with multiple Contractors working at the same time across various areas along the road including scaling and blasting taking place on the cliffs above the road. A high level of coordination and management had to take place to ensure the safety of everyone on site and there were times where drilling work had to be halted to ensure that rockfall risk from work on the cliff above could be suitably mitigated to allow our work to safely continue. Coordination was also required with the quarry below which was operational while this project was being completed.