Problems with the pipe's condition were first raised to Wellington Water by workers on the Riverlink project, seen here in an artist's impression. Photo: Supplied/ RiverLink partners
A 60-year-old sewerage pipe that runs under State Highway Two would cause the motorway to slump if it collapses, Wellington Water has revealed.
RNZ reported last week that the pipe - which was laid in 1963 and carries all of Upper Hutt's sewage - is at risk in two separate areas.
A new statement from Wellington Water said due to corrosion, a 360-metre section of the pipe in Melling was at risk of collapse and could cause State Highway Two to slump.
Wellington Water wastewater chief advisor Steve Hutchinson told RNZ they were looking at contingency plans to "mitigate any impacts a collapse may have".
Infrastructure Minister and Hutt South MP Chris Bishop said it was very concerning.
"State Highway 2 is a critical thoroughfare for the Hutt Valley and indeed the wider region, [it] carries tens of thousands of cars per day and so obviously we need to figure out a plan."
Bishop said it reflected the state of water infrastructure in the area.
"I think it speaks to the level of under investment in pipes over the years in the Wellington region, which we are now grappling with as a region and as a government as well."
He said as a local MP he will be following up with the relevant agencies to make sure they came up with a plan for the pipe.
Hutchinson said Wellington Water were working with NZTA Waka Kotahi, Upper Hutt and Hutt City Council on what their next steps would be.
The water provider was first notified of the problem at the end of March by workers on the Riverlink project - a programme designed to improve flood protection along the Hutt River.
RNZ reported last month that the 12-kilometre pipe has been at risk from a slip at Taita Rock for years.
The pipe will be discussed at Hutt City Council's Audit and Risk Subcommittee which will be held at 2pm today.