A Swansea Heads couple returned home last night to find their three-storey home sliding into a large sinkhole which had opened up in their front yard.
The couple were approached by neighbours about 6pm who told them a sinkhole had appeared near their front deck about two hours earlier, sending tonnes of dirt and bricks into a workshop area below.
Police evacuated the house. The occupants were not hurt.
The sinkhole is believed to be as wide as 20 metres and as deep as 10 metres above a 20 metre vertical furnace shaft, police and the mine subsidence board said.
They said it was unknown how stable the structure was or whether the hole would develop overnight, causing further damage.
But mine subsidence board officers said they believed the house, built in the 1990s and one of the newest in the street, could be repaired and salvaged.
It was also unclear whether the hole appeared gradually or all at once, but police had not spoken to anyone who had seen or heard it developing.
Nearby residents were able to get a close look at the hole before police arrived, snapping photographs showing the cavity which nearly swallowed up a spare bedroom and an outdoor furniture set.
The picturesque section of Lambton Parade, which overlooks the ocean and entrance to the Swansea channel, was once home to the Swansea Pit.
The mine was abandoned in 1953 and dozens of expensive homes have since been built above.
Mine Subsidence Board officers believe the sinkhole appeared above an old furnace shaft.
Lake Macquarie police Inspector Sam Crisafulli said it was believed the subsidence was contained to the front corner of the home and the driveway of the home next door.
‘‘About 4pm today neighbours noticed the front corner of the house had started to collapse into a hole," Inspector Crisafulli said.
‘‘Police and other emergency services were called and it appears what has happened is that an old mine shaft, a furnace shaft has caused the collapse.
‘‘We’ve got the Mine Subsidence Board here and they have taken over the scene. They will be securing the location and doing some repairs tomorrow.
‘‘The area of the hole is about 15-20 metres wide and quiet deep. It’s confined, from what I’m told, just to the front corner of this house. You can see where the tape is that’s about the boundary of where the house has sunk and I’m told that it’s not going to go any further than that. These occupants are the only ones affected, no one else is at risk.’’
Inspector Crisafulli said Mine Subsidence Board contractors would today clear the debris and rubble before pouring concrete into the hole and propping the house up.
The sinkhole, and resulting emergency services and media contingent, saw more than 100 people out of their homes to have a look.
The occupants, who declined to comment, have been offered alternative accommodation after the home was deemed unstable.
Inspector Crisafulli said the owners would have received "quiet a shock" upon returning home.