The bank under Bryce St that is at risk of collapsing on the rail corridor below. Photo: RNZ / Natalie Akoorie
An unstable city street is at risk of collapsing onto one of the country's busiest freight railway lines, but the road cannot be closed because it would cost at least $1 million.
The East Coast Main Trunk railway freights goods between Hamilton and the Port of Tauranga, with more than 20 trains a day using the track between the two cities.
It is then connected to Auckland by the North Island Main Trunk Line, and is known for being part of the Golden Triangle of Tauranga, Hamilton and Auckland.
KiwiRail called it the most important rail freight route in the country, but the rail corridor beneath Bryce Street in Hamilton is at risk because the road above is cracking due to drought.
Instead of closing the road, Hamilton City Council - together with NZTA Waka Kotahi - will spend $500,000 to stabilise it because closure would be too expensive, according to network operations manager Robyn Denton.
Denton said costs to complete a formal road closure were hard to quantify because the process could be challenged via the Environment Court.
She estimated it would be more than $1 million, based on the 2018 closure of part of Ruakura Rd in Hamilton.
The section of Bryce St at the centre of the problem runs between Tristram St and Seddon Road, and is next to Circus Park and near the Seddon Park cricket ground. Denton said closing the road would also restrict access to these places.
Since 2012 the road has been cracking for several reasons, including that it was thought to be built over an old dump site and because of reduced groundwater due to drought.
Bryce St by Circus Park is closed while work to stabilise the road is undertaken. Photo: RNZ / Natalie Akoorie
Denton said the problem was also caused by a concrete road under the existing road, built by American soldiers to drive their tanks on in the 1940s.
She said it was the concrete road that was built over organic material - believed to be an old dump.
The railway line was lowered in the early 1960s, but 12 years ago cracking and downward movement - known as settlement - was noticed on the surface of the road and pavement.
Since then, the trees and parking spaces on the southern side of the road have been removed, and the road was temporarily closed in 2018 and 2022.
Denton's four options presented to council in late May included closing the road altogether, digging out the concrete pad and building a new road, building a retaining wall, or changing the road layout and regrading the bank at risk of failing.
She recommended against closing the road, based on the legal process to close part of Ruakura Rd which council commercial and advisory executive director Chris Allen said was integral to developing the inland port at Ruakura.
The decision to stop the road was made by the council in November 2015, but with two objections unable to be resolved, it went to the Environment Court.
The court eventually confirmed the council's decision to stop the road, but only after a two-and-a-half year process which Denton said cost more than $1m.
Of the four options she presented, the council chose the cheapest, to regrade the bank and move the road and footpath to the north to reduce the impact on the slope's stability.
It was the preferred option by council staff, though Denton advised the work "may not entirely address the issue of residual settlement".
The works on the eastern section of Bryce St in Hamilton have temporarily closed the city street. Photo: RNZ / Natalie Akoorie
At the same time KiwiRail will pay to regrade the slope, but that work has been deferred to the 2024/25 financial year.
KiwiRail regional infrastructure manager Jake Barbarich said the East Coast Main Trunk [ECMT] track was a busy line with more than 20 freight trains a day travelling past Bryce St.
"It is the most important rail freight route in New Zealand, and carries almost half of the rail freight moved nationally."
He said some freight on the ECMT also travelled south from Hamilton.
"Given the freight volumes moved on the line, resilience is important. We had planned to carry out the slope stabilisation work at Bryce Street this financial year but the situation is more complicated than originally thought.
"Our geotechnical assessments found issues that may affect our proposed remediation approach and may require resource consents."
Barbarich said KiwiRail was working through this with the council and expected to carry out the stabilisation work in the next year.
The council and NZTA Waka Kotahi would each pay about $250,000 for the work with the hope of completing it before the end of June.