A failed attempt to drill a borehole beneath Queenstown’s town centre, and instead install a new wastewater pipeline using traditional methods is expected to cost ratepayers up to $2.5million.
The Queenstown Lakes District Council has been forced into ‘‘plan B’’ after a horizontal drilling project encountered what is thought to be "prehistoric" wood about 20m underground.
It means contractors will be digging up town centre streets to complete the project from next May to September, resulting in street closures, loss of car parks and disruption to businesses along the 1.1km route.
Council programme director Gareth Noble said the anticipated additional cost of completing the project, including extra work to align it with a street upgrade, would be between $2million and $2.5million.
The pipeline now would be be laid in open-cut trenches, starting from the recreation ground car park, where a pumping station is under construction, along Camp St, Earl St, Marine Parade and across the Queenstown Gardens to Park St.
Contractor Hadlee & Brunton began drilling the borehole for the 870m pipeline with a specialised rig at the recreation ground in September.
The project was expected to take four weeks, but was suspended in October after the wood was encountered 20m below the Ballarat St and Camp St roundabout.
Council spokesman Jack Barlow said the results from testing were unavailable.
