Sinkholes at Narrabeen, Double Bay: What has caused them
There have been two sinkholes in two days in Sydney, with the latest crater appearing outside a school on the northern beaches. So, what’s causing them?
Manly
Don't miss out on the headlines from Manly. Followed categories will be added to My News.
- Anxious wait for beachfront residents as high tide hits
- Vote to be held on success of Northern Beaches Council
Two sinkholes have appeared in two days in Sydney this week following a bout of heavy rain.
On Wednesday morning a garbage truck became stuck in a two and a half metre wide sinkhole in Narrabeen, causing roads to two schools to be closed off to traffic.
The crater which was around 40cms deep, opened up on the corner of Namona St and Oak St, adjacent to Narrabeen Sports High and near Narrabeen North Public School, causing problems for parents at school drop-off.
It comes just 24 hours after a truck sent to fix a burst water main at Double Bay on Tuesday also fell into a sinkhole.
Sydney Water believes both sinkholes — which are very rare — were caused by burst water mains undermining the roads.
The Manly Daily understands that the two incidents, one after another. is just a “weird coincidence”, according to a source familiar with the situation.
It appears that in these two instances burst water pipes have eroded the stability of the roads and when a heavy vehicle has gone over the top it’s created or worsened a sinkhole.
While burst water pipes are not unusual, normally, the roads are closed off before this happens and repair crews are able to fix the leak and stabilise any structural damage before sinkholes can happen.
A Sydney Water spokesman said “periods of heavy rain like we’ve experienced are known to cause soil moisture leading to pipe and joint movement, resulting in water main breaks and leaks”.
In Wednesday’s incident the Mercedes-Benz garbage truck, owned by private company Remondis, was on a commercial pick up run to businesses and was on its way to the high school when the incident happened at around 6am.
It is understood that the truck’s right wheel burst as it hit the sinkhole early this morning when it was dark, with the two rear wheels eventually getting stuck.
A small crane was needed to help remove the truck from the hole.
In a statement from Sydney Water released at 1pm, it said the water main break had been fixed and water had been restored to a small number of impacted properties.
Road repairs have now begun.
The spokesman said Namona St will remain closed at the junction of Pittwater Rd and Oak St closed at the junction of Jacksons Rd during afternoon school pick-up and diversions are in place.
Around 15 school buses that drop children off in Namona St were diverted this morning.
Duty Officer Inspector Maree Kiem speaking early Wednesday morning said she understood the driver had been able to safely get out of the truck by himself.
“A burst water main has caused a sinkhole,” she said.
“A garbage truck accidentally got caught up in it.
“It is being towed from the scene.”
Resident Chris Borg, who lives on the corner of Oak St and the Namona St, was woken by the sound of the truck hitting the sinkhole.
“I heard two sharp bangs,” Mr Borg said.
“I thought the truck had hit the gutter going around the corner but when I came outside I saw the truck in the hole and there was water up to the gutter.”
Another resident said she spoke to the driver who told her he got quite a shock.
He hadn’t realised there was any damage to the road.