The drilling team testing soil substructures for a possible future highway route from 15th Avenue to Hairini and the Welcome Bay underpass is undertaking their final tests - drilling from a scaffold over the harbour.
The over-the-mudflats drilling completes a series of 25 holes the team has drilled in the locality of the proposed Welcome Bay underpass and new causeway bridge in recent weeks.

The over the harbour drilling platform.

The tests are Geonor Shear Vane Tests. They drill a metre at a time before dropping a device into the hole to measure the torque as a cross-shaped vane is turned.
That happens every metre to a 25m depth to provide a profile of soil shear strengths.
Testing at each site takes 2-3 days. The testing is expected to be completed by July 2, and is costing about $200,000.