Wastewater pipe replacement project hampered by 4575-year-old timber

Stage one of the project has a budget of $2.389 million. Photo / Bevan Conley

An ancient problem is affecting contractors replacing a 113-year-old wastewater pipe on Nixon Street in Whanganui East.

Whanganui District Council senior stormwater engineer Kritzo Venter said the boring machine used for the project had been delayed several times because of underground timber.

“The timber originates, I believe, from the period that proceeds the Taupō eruption,” he said.

“It is only intermittently in the soil and the machine can’t get through these pieces. It comes to a grinding halt.”

The Chronicle first reported on the timber findings in July.

The wood, discovered at a depth of 8m and identified as tōtara, is around 4575 (plus or minus 21) years old.

In July, Parkinson and Holland contractor Paul Hall said his team had been drilling at a depth of around 8m when they hit a log.

“It drilled into it and it just matted the head,” Hall said.

“We took all the rods off, cleaned it up, poked it through again and got the same result.”

The wood discovered at a depth of 8m was identified as tōtara. Photo / Bevan Conley

Venter said a 7m shaft had to be sunk every time the machine needed cleaning.

“That’s a variation to the contract which means we have to pay the contractor to do that. We’ve consumed a lot more budget than what we anticipated.”

Stage one of the project - replacing the pipe from Anzac Parade to Moana St - has a budget of $2.389 million.

The current sewer was constructed in 1910 and extends for 911m from Anzac Parade to the five-road junction of Raine St, Wakefield St, Nixon St, Burton Avenue and Duncan St.

Venter said he would take a report to the council in December about reallocating funds and possibly asking for approval for unplanned expenditure “to get the job done”.

“We are into it and we can’t stop. We have to keep going.”

Archaeological finds, while expected, had also delayed the project and added to the cost, he said.

A pipi bed midden was discovered at the Anzac Parade end of Nixon St early in the project.

Mike Tweed is an assistant news director and multimedia journalist at the Whanganui Chronicle. Since starting in March 2020, he has dabbled in everything from sport to music. At present his focus is local government, primarily the Whanganui District Council.