Transpower Tower Foundation Strengthening – Upper South Island Grid Upgrade
Construction Techniques Group Ltd

The grid upgrade project scored highly on all judging criteria, and the judges unanimously agreed it was a truly excellent example of engineering at its best.

The project involved upgrading transmission tower foundations over a 450-kilometre route in the upper South Island. Much of the line followed a remote and bleak path from Hanmer to St Arnaud, passing through Island Saddle which, at 1,370 metres (or 4,500 feet), is the highest road crossing in the country.

Integrity of the power grid is vital to New Zealand’s economy, and the project was clearly of significant national importance.
The judges were particularly impressed by the calibre of both the technical and logistical management over such an extended site.
Traditional approaches to providing greater uplift resistance to tower foundations involve mass concrete. Instead, the project team used four more focused techniques: grout enhancement of existing piles, self-drilling ground anchors, passive soil anchors and post-tensioned ground anchors. Some of these were not previously thought suitable for the site’s soil conditions, but close co-operation and interaction between the contractor and technical experts ensured a successful outcome. Moreover, the chosen solutions caused minimum disturbance to the existing foundations and
the environment.

The project team sucessfully faced the challenging problem of getting personnel, materials and equipment to remote sites efficiently, under severe time pressure and in an unforgiving environment.

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