The tomo is 4m wide. Photo: Supplied/NZTA
Waka Kotahi are "guardedly optimistic" a major route in and out of Tauranga will reopen on Tuesday.
Over the weekend, water from a leaking pipe carved out a 4m-deep cavity under a small pothole, closing a section of State Highway 29A and causing more than 11m of damage. State Highway 29A between Barkes Corner and Oropi Road Roundabout remains closed.
NZTA Waka Kotahi had warned that - combined with a lane closure on Totara Street for Tauranga City Council road rebuilding work - severe traffic congestion was likely on Monday morning. The agency suggested road users avoid travelling on Monday, work from home or use alternative transport if they can.
NZTA spokesperson Roger Brady said they were confident the road would re-open tomorrow after crews worked through the night to fill the hole.
"The great news is that we've actually made huge progress over the last 24 hours to repair the issue, and we've now reached the stage where we're starting backfill the road."
He said the hole was larger than first thought, and when measured last night was found to be four metres deep and four metres wide, and between 11 and 20 metres long.
"I'm guardedly optimistic that we may complete the work by dark tonight.
"If we could do it quicker we would, but it's a heck of a big job."
Congestion in Tauranga this morning, including through the detour route of Hewletts Road, has been better than expected, Brady said.
"Maximum delays around the centre have been around 20 minutes this morning. It's apparent people have actually made an effort to avoid travelling."
Brady advised people to complete any travel on Monday today before the school pick-up time, which was expected to be busy.
He said there should not be additional delays on Tuesday and the road should be open.
Tauranga Business Chamber chief executive Matt Cowley earlier told Morning Report the traffic was already bumper to bumper on a good day.
"A hole in the road is raising some eyebrows - how that can close down New Zealand's fifth-biggest city - but it happened on the wrong road.
"We've got a ring road state highway network, so closing down that and asking people to go via Hewletts Road - which is congested on a good day - is just going to grind the city to a halt."
The city's traffic woes were only going to get worse in coming years, and businesses would need to make continuity plans for staff who were unable to make it in, he said.
"We're already known as a bit of a cone city ... We've grown rapidly since Covid, [and we're] looking at doubling in size in the next 50 years, so we're just going to have to get used to the ... congestion."
Around the city were major employers in manufacturing and heavy industry that relied on workers to be on site, he said.
"A lot of people live in Papamoa and commute to Tauriko, a big industrial estate... I'm not sure what they're going to do."
NZTA pulled planned chipsealing of SH2 on Sunday and Monday nights to ease traffic pressure coming into the city, and was diverting resources to SH36 works.
Hewletts Road eastbound bus lane would open for all vehicles, going toward Maunganui Road.
Work on Totara Street was expected to be complete by 6am Wednesday.