Contractors working on Whanganui wastewater line hit 4575-year-old tōtara logs

Whanganui District Council's Stuart Cawley, Bullocks Director & Operations Manager Glen Bullock and Parkinson & Holland contractor Paul Hall with some of the wood found on Nixon St. Photo / Bevan Conley

Workers replacing a 113-year-old wastewater system on Nixon St in Whanganui East have uncovered something much, much older.

Parkinson & Holland contractor Paul Hall said his team had been drilling at a depth of around eight metres when they hit a fairly large log - about 1800mm in diameter

“Our machine is designed to go through certain material but not timber,” he said.

“It drilled into it and it just matted the head.

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

Eventually, a hole was dug to seven and a half metres and a case was dropped into it so a contractor could be lowered down with a crane.

“We were just throwing it (wood) away, it was a pain to us,” Hall said.

It was then that Whanganui District Council three waters contracts manager Stuart Cawley decided to get a sample tested for its age.

Cawley said when he got the results back his jaw dropped.

The wood, identified as tōtara, was approximately 4575 (plus or minus 21) years old.

“It must be the oldest thing we’ve ever found in Whanganui that’s been dated,” he said.

“Most timber at this age turns to dust when you take it out. In this sample, they could clearly see the rings all the way through it.

“The next step is asking iwi if they’re interested in it. It could be part of their taonga.”

Whanganui District Council senior stormwater engineer Kritzo Venter said most of the land they normally dug had already been disturbed in the 18th or 19th centuries.

Earlier in the project, a pipi bed midden was discovered at the Anzac Parade end of Nixon St, he said.

A midden is a site where food remains such as shells and bones and charcoal from fires were thrown or buried.

Some of the wood discovered during the drilling work. Bevan Conley.

“We have an archaeologist on standby, supervising the excavations,” Venter said.

“Typically, they are only interested in certain depths. After that, they know it was before human occupation.

“When we first found the timber we thought it might have been from the time when that first main was put in.”

A report to the council from Heritage Preservation and Field Support Solutions senior conservator Susanne Rawson said they concluded “with high probability” that the outermost layer of sampled wood was formed during the 33rd century BCE (before the common era).

“There is a range of 265 years in which the sample could also date to, but overall, the dating has identified a range of 3364-3099 BCE,” it said.

“The area above the tunnelling where the timber was found is noted as having 1.5m to 2m of pumice from the Taupō eruption.”

The report said the Taupō eruption occurred about 1800 years ago (circa AD200) and resulted in a thick ash and pumice layer that affected the whole country.

Te Runanga O Tupoho representative John Maihi said he would suggest the wood be put on display in a place of prominence for “all the people to see”.

“It’s probably something we’ll never see again in our lifetimes,” he said.

“If you rub your hand over a tōtara that old, man, it would be electrifying.”

The existing sewer was constructed in 1910 and runs from Anzac Parade to the five-road junction at the Raine St, Wakefield St, Nixon St, Burton Avenue and Duncan St intersection - 911 metres.

Parkinson & Holland is using a Vermeer AXIS laser-guided boring system to complete stage one of the Nixon Street project. Photo / Bevan Conley

Due to its depth, condition, and location, micro-tunnelling has been used to replace it.

That requires a Vermeer AXIS laser-guided boring system - a pit-launched trenchless installation method that’s the only one of its kind in the country.

Rather than excavating the entire area, smaller pits are dug at intervals.

The drills are then lowered into them to begin drilling below the road surface. The system is guided by a camera and lasers.

Venter said it would have been a lot different when the original line was put in.

“We can’t find evidence on how exactly they did it and as engineers, we’ve always been really intrigued. They didn’t have diggers and tunnelling machines like we do now.

“There’s a wastewater line 7.5m deep though. It must have been pretty scary because the only thing we can come up with is they must have used timber shoring to sure up the sides of the trenches.

“Then, they would have sent people down there to lay the pipe. I’d imagine It would have all been hand dug.’

In 2021, archaeologist Annetta Sutton found early plough marks, the ruts of a former road and postholes from a protective palisade during excavations on Wilson Street.

Venter said finds like that slowed down progress on those kinds of projects.

“People might get annoyed but what they don’t know is all the stuff going on down there.

“We’re going at a snail’s pace to give the archaeologist a chance to record things.”

He said there were some really interesting archaeological stories from across the world in the engineering sector.

As a young engineer, he worked on various sites in the UK.

“It’s never boring. I remember talking to a digger driver who told me he once dug up part of a Roman chariot.”

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.