Auckland’s now infamous sinkhole on a busy road leading to the central city is part of a wider problem that will take months to fix at a cost of $2.5 million.

The 3m diameter and 1m deep sinkhole appeared on Monday when a 108-year-old stormwater pipe below College Hill cracked, leading groundwater to seep in during this year’s heavy rain, taking fill with it, and leading it to collapse.

A second sinkhole occurred on the same pipe a bit further down College Hill near the corner of Victoria Park during the January 27 floods. This sinkhole, on a busy intersection, was quickly filled in.

Andrew Chin, strategy manager at Auckland Council’s Healthy Waters division, said contractors are making a temporary fix on the sinkhole before work begins on July 31 to replace 290m of pipe down College Hill.

The sinkhole has been fenced off for work on a temporary fix. Photo / Michael Craig

“We are really sorry this has happened. We would have much preferred the project to happen in a much more planned and systematic way. Unfortunately, that hasn’t been the case and we are playing catch up now,” Chin said.

The old 450mm clay pipe will be replaced with a larger 700mm reinforced concrete pipe along College Hill between England St and the Victoria St West intersections. The new pipe will have more catchpits to collect more stormwater, and take about four months to install.

Chin said a contract had been let for the new pipe to be installed on August 7, but it just happened that heavy rain over the weekend tipped the pipe over the edge, and the sinkhole opened up.

The century-old pipe in Freemans Bay is one of many on the council’s renewals programme that is regularly surveyed for replacement, but in this case “we didn’t get there in time”, said Chin.

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He said the pipe was surveyed last summer and after it was damaged in the January 27 floods it was placed at the front of the queue, and the project was designed and tendered to be delivered this year.

The trickiest part of the project, said Chin, would be traffic management, adding that closing College Hill to do the work in one go would cause too much disruption.

Instead, the new pipe will be progressively installed in stages to minimise traffic disruption on College Hill, which is a busy route into the city from the inner western suburbs, and a route to the Northern Motorway.

The sinkhole at 3pm on Monday compared to just after 12pm Tuesday. Photo / RNZ

Chin said the council is working with Auckland Transport to keep both lanes open on College Hill, but this could depend on work by the contractors.

Since Monday, lanes have been closed on College Hill, and diversions put in place for traffic.

The owners of two cafes directly opposite the sinkhole on College Hill are worried about the impact of the temporary fix and the four-month schedule to install a new pipe.

Andrew Smith only opened the Kauri Creek Middle Eastern street food cafe four days ago, saying trade was reasonably busy on the first two days but there had been fewer customers since the sinkhole appeared on Monday and the site had been cordoned off

He wasn’t aware of the four-month plan to replace the pipe, but said “these things need to happen” and would remain “positive and philosophical”.

Himanshu Bhambani and his wife have run Cafe 28 on College Hill for seven years, and it’s the only income for the couple and their 20-month-old son.

He said they had struggled through Covid and business had slowly been improving, but the prospect of four months of construction disruption without any notice from the council was “very stressful”.

Cafe 28 owner Himanshu Bhambani says the impact of four months of construction will be very stressful. Photo / Michael Craig

Trade was down 75 per cent yesterday and fewer customers were in the cafe today, although contractors at the sinkhole site had bought takeaway coffees.

Bhambani said the council should pay businesses for loss of income.

The inner-city early suburb of Freemans Bay has a history of crumbling pipes.

A stormwater/wastewater separation project has blocked off Hepburn St on and off for several years.

A second stage to install a “gross pollutant trap” was meant to be installed between September and December last year with a final completion date of March this year. Work is continuing on the project and lower Hepburn St remains closed to traffic.

In 2013, the Herald reported safety concerns with relining an 80-year-old brick stormwater pipe in Runnell St, just off College Hill. At the time, the council refused to name the contractor and release a review of the project.

Bernard Orsman is an Auckland-based reporter who has been covering local government and transport since 1998. He joined the Herald in 1990 and worked in the parliamentary press gallery for six years.