- Project Name Waihou River High Voltage Power Crossing
- Client North Power / Powerco
- Date 2016
- Duration 4 weeks
- Location Waihou River, New Zealand
In January 2016 Universal Underground established on the West bank of the Waihou River to install a pipe deep under the river for a replacement strategic power cable. Two previous power cables over the years had been laid across the river bed but had aged and failed over time.
This was a lump sum contract and no ground investigation was included in the tender documents. UUL had to make some broad assumptions and the risk of possible encounter of underground timber and / or boulders was tagged.
All to often power projects lack any sort of ground investigation and they ring fence the project as a lump sum to control escalation. UUL negotiated a shared risk approach to unforeseen ground conditions.
In order to locate the drill head seven metres below the riverbed plus 6 metres below the water, standard location equipment could not be utilised. An SST transmitter was utilised. This special piece of equipment senses the earths magnetic field and obtains a bearing.
This information is fed back up through a wire running inside the drill string. The drill operator processes this information and applies the correct steering corrections. After the drill head exited the ground, it was removed and replaced with a reamer. The pipe was connected with a swivel and the drill string pulled the pipe back under the river taking a full day.