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One of the most expensive stretches of the country’s new highway became more expensive, and was further delayed, due to buried pumice stone that went undetected despite tests conducted on land.
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The 2km stretch of the Bayfair to Baypark upgrade on SH2 south of Tauranga was already costing $ 70 million per kilometer, two to three times more than usual.
But three years after construction began in 2017, the New Zealand Waka Kotahi Transportation Agency (NZTA) realized that the soil is not stable enough for what it is building, after a layer of pumice stone during work.
That forced a major and ongoing redesign and related changes to the construction methodology and the rest of the Bay Link program.
NZTA said new equipment must be brought in, under a new contract, to begin building new flyover foundations, likely in November.
The Mayor of Tauranga, Tenby Powell, was surprised and frustrated.
He was not aware of the problem until RNZ told him on Wednesday.
“That is very frustrating for New Zealand’s fastest growing city.”
100 tests – no pumice stone
More than 100 ground tests were conducted before construction began, NZTA said.
But they couldn’t detect the pumice layer 40 feet underground, so preliminary work continued.
Tauranga is on the edge of the Taupō volcanic zone and the Bay of Plenty has a lot of pumice stone underground.
The fact that the earthworks failed to properly stabilize the soil only came to light after huge stone columns began to be installed 10 months ago.
That prompted further testing, including earlier this year at the Universities of Auckland and Canterbury, and the scrapping of the original design.
NZTA said a new design was being finalized.
He was still analyzing the cost and time impacts of the project.
NZTA did not respond to a question from RNZ about whether the additional costs would be borne by the taxpayer.
Even before the pumice problem forced redesign, project costs had risen from an initial estimate of $ 102 million to $ 146 million recently, and its completion was delayed from the end of this year to the end of 2022. .
Other complications are the consequences of Covid-19 and the addition of an underpass to the project.
The B2B project, as it is called, aims to reduce congestion on the final stretch to Tauranga in the Baypark, where the Eastern Link toll road stops, and traffic slows down.
The flyovers will carry traffic on State Highways 2 and 29 over highways and the rail line.
Tenby Powell.
Photo: Supplied
The highway is also intended to boost the local economy and motorist safety.
Powell said it was vital to complete the Eastern Corridor of the region.
“We have congestion on many of our routes in and out of the city, and we have a lot of work ahead of us in the next few years, so it is very frustrating to learn,” he said.
NZTA has not explained how the pumice stone was not detected at first.
“This type of test is not unusual,” he said.
“Projects often conduct ongoing testing of soil conditions as they progress through construction, and this process can sometimes identify previously unknown soil conditions.”
The new design, a combination of stone columns and piles in a lattice frame, was “necessary to limit settlement and ensure that the ground remains stable, securing the bridge.” [at Baypark] it is capable of withstanding seismic events. “
B2B is the NZTA’s latest troubled project.
It is dealing with blowouts on the billion dollar Transmission Gully Highway, costly cracks in the surface of the Kapiti and Waikato highways, and additional engineering reviews and roof panel tests on the Puhoi to Wellsford Highway.
The main B2B contractor, the main Australian CPB, declined to comment. CPB is also key in the Transmission Gully alliance and prime contractor on the conflict-affected Acute hospital project in Christchurch.
Powell said it had been good to work with NZTA, but that he had not treated the council as a partner by not informing him about B2B issues.
“I will pick up the phone and call the regional director and try to understand what exactly has happened and, in particular, why we are not on the same score in terms of communications.”
