Geotechnical investigations are set to begin along the preferred route of the Petone to Grenada Road of National Significance, with activity expected in several Lower Hutt and Wellington park areas.
NZ Transport Agency Waka Kotahi says work will start in Seton Nossiter Park, following ongoing investigations at Waihinahina Park and the Gilberd Bush Reserve.
Regional manager system design Kesh Keshaboina says contractors will prepare sites with vegetation clearing and trimming to allow specialist equipment to be installed.
“This is necessary to ensure the specialist equipment being used can be put in place properly,” Keshaboina says.
The agency says the investigations are temporary and steps are being taken to minimise environmental impact.
“Contractors will manage the sites in a way that leaves the roots of trees intact to allow regrowth, and replanting will be done if sites do not re-establish naturally,” Keshaboina says.
At Gilberd Bush and Seton Nossiter Park, 10 borehole sites and 20 window sampler sites are planned.
Boreholes involve drilling narrow holes of up to 100 metres deep to assess underground conditions. Drilling at each site can take between one and 14 days, depending on ground conditions.
Window sampling is a lower-impact method of taking soil samples, using small steel tubes driven up to 10 metres into the ground. Each test typically takes a few hours.
Keshaboina says the investigations are essential to the project’s design and planning.
“It is essential that we get an accurate picture of the local geology. For a project of this scale, the information is invaluable for its design and planning. It allows us to develop the most efficient and cost-effective approach.”
Helicopters will be used to deliver equipment to some sites, with the agency saying flights will avoid carrying loads over properties or members of the public.
A section of Lindsay’s Track will be closed from the beginning of March for around two weeks to allow the work to proceed safely.
“These are work sites and heavy equipment will be used. With helicopters operating as well, we want to ensure everyone is kept safe – both our contractors and the public,” Keshaboina says.
Investigations for the Petone to Grenada project began in November 2025 and will continue across various sites in the coming months, with work at each location expected to take between seven and 14 days. Core samples from boreholes will be used to inform the detailed design of the proposed route.
