An attempt to drill a borehole beneath the Queenstown town centre for a new wastewater pipeline has been abandoned after the contractor struck "prehistoric" timber 20m underground.
Hadlee & Brunton began drilling the borehole for the 870m pipeline with a specialised rig at the resort’s recreation ground in September.
In a media statement on Friday, Queenstown Lakes District Council chief engineer Ulrich Glasner said the work, expected to take four weeks, was suspended last month after "unforeseen and unusual" ground conditions were encountered.
"While we spent considerable time and effort completing geotech investigations along the pipeline route to determine the suitability of horizontal directional drilling, we hit what is likely to be prehistoric timber 20m underground," Mr Glasner said.
Although the wood was being tested to determine its origins, after further technical assessment the council decided to complete the pipe installation using traditional, open-cut trenches.
When the Otago Daily Times asked the council last month why the work had stopped, council spokesman Jack Barlow said the drilling was expected to be completed, on budget, despite the contractor encountering the wood.
The council did not respond to a follow-up question early this month asking if the project had been completed.
The media statement said the new approach would involve 1.1km of pipe installed along a revised route taking in Camp St, Earl St, Marine Parade and across part of the Queenstown Gardens to Park St.
The work was expected to start in the middle of next month and continue until September.
Council property and infrastructure general manager Peter Hansby said the possibility the drilling might not be successful was identified as a risk during planning for the project, and a "plan B" was already designed and consented.
It would cause more disruption, including temporary road closures and loss of street car parks, but the project’s managers would be working with affected stakeholders about their concerns and considering mitigation efforts to maintain access, Mr Hansby said.
