Our most recent geotechnical project was for Trustpower, working with Riley Consultants – the aim of the works was to rock bolt and install a combination of passive and active retention systems using William’s Bar and the first Maccaferri Steelgrid HR 30 rock fall netting installation in New Zealand.

The finished installation provided rockfall protection to the transformers and switch gear which was situated below the rock face.


The work was under a strict time frame due to the periodic maintenance outage at the Cobb Valley Powerstation.


In total, just over 370m of 100mm diameter holes were drilled and grouted, with 30m of of sub-horizontal drainage, 500m2 of active and 90m2 of passive rockfall netting with all anchors tensioned to a minimum of 40kN.

When you drive through the iconic Otira Gorge you will be pleased to know that the possibility of being hit by rockfall will be greatly reduced as Abseil Access completed the installation of a 500kJ hybrid barrier, compromised of Maccaferri HEA panels and DT rockfall mesh.

This was the second installation in as many years by Abseil Access, with a smaller capacity barrier that was constructed in the winter of 2012.
The structure, 750m2, 30m long, 25m high with 2m high posts sits between the Rockfall Shelter and Reid Falls aqueduct.


In difficult winter conditions in an Alpine environment, the team drilled the foundation anchors with the Marini a-frame rig, on average 3m deep, 90mm diameter holes across the steep greywacke and mudstone bands. The panels of mesh were either craned up using a 28m hiab boom with fly-jib or hauled up with ingenious winching and pulley systems.