By RNZ

Diversions, detours and lane shifts are expected to be in place for months on a busy central Auckland road as the city council deals with a growing sinkhole.

Heavy rains could cause more to open elsewhere, the council warns.

Part of College Hill Rd near the police headquarters started to cave in on Monday and today the collapse was big enough to swallow a car.

The hole would probably get bigger because of rain, Auckland Council Healthy Waters strategy head Andrew Chin told Morning Report.

“The system’s under a massive amount of stress, the ground is absolutely saturated so there’s a lot of ground movement, so where the infrastructure’s in a fragile state you’ll start to see these problems cropping up.”

The rain had opened the sinkhole because of a damaged stormwater pipe.

“It’s an old pipe, over 100 years old; an old clay pipe,” Chin said.

“[The sinkhole] probably will be getting bigger because of the rain. As the rain falls into the hole it washes the dirt into the pipe and it keeps flowing down the pipe and making the hole larger.”

Repairs to the stormwater pipe had been planned after the Auckland Anniversary deluges and had been weeks from starting, but had now been brought forward. The pipe would need to be replaced from England St to Victoria St West.

Auckland Council Healthy Waters strategy head Andrew Chin. Photo / RNZ

Chin has said it would take about four months to fix the pipe.

Businesses in the area were concerned about the loss of business while the road was disrupted.

Council staff would keep the area safe in the meantime, Chin said.

“It’s only going to get marginally worse ... the team’s gone out with a ground-penetrating radar and gone all the way up the road.

“We knew about the pipe - it was old and we’d surveyed it.

 “In the Anniversary Day floods the damage started to really accelerate, so we had a project not only to repair the pipe, but to do an upgrade, make a much larger pipe and improve the overall situation right down the road. ... It had been designed [and] the contract had been awarded and they were due to start in early August, so that’s all just been brought forward now.”

For now, Auckland Council recommended motorists use Franklin Road to avoid College Hill Road.

Eastbound lanes through the College Hill Rd to the central city were closed, with one westbound lane open for traffic heading toward Ponsonby. And a diversion was in place for drivers to access Gudgeon St and a detour through England, Ireland and Scotland Sts.

- RNZ