Giant sinkhole linked to burst water main

Engineers working to repair a sinkhole which appeared in Godstone High Street in Surrey six months ago say the collapse started with a burst water main.

They have spent months trying to map the extent of a network of sand mines underneath the village but say they are not ready to blame the water leak for the appearance of the hole.

Work to repair the road won't be completed until December at the earliest due to the difficulty of detecting caverns under the ground, though a section of pavement has reopened in recent days.

Meanwhile Godstone remains severed by the closure of the road, and some businesses have suffered big drops in passing trade.

Lloyd Allen, infrastructure manager for Surrey County Council (SCC), who is overseeing the work on the sinkhole, confirmed a water main had burst creating a big crater in the road but added that "we don't know what caused the water main burst".

He said engineers responding to calls about the appearance of the hole immediately realised that the water was disappearing under ground.

Mr Allen said: "That's a huge volume of water to soak into the sand naturally.

"So that's why we started our investigations, talking to the people that lived in the area who know about the mines.

"It took some months using lots of different techniques to find them."

Boreholes, some of them more than 30m (98ft) deep, have been driven into the sandstone beneath the village in a search for tunnels, which he compared with playing the children's game Battleships.

"Sometimes you find one, sometimes you miss them," he said, adding that the work has been made more complicated by underground electrical cables and gas and water pipes.

"We have to make sure when we've finished this thing doesn't fall down again," he said. "Because this is a busy road, normally, with big lorries coming through."

Residents have been aware of the network of tunnels under Godstone for decades.

They were dug in the mid 1800s as the high quality sand in the area was excavated to supply glass-makers.

Unofficial mines were created by property owners digging underneath their gardens and creating the warren of tunnels which are now causing SCC's engineers such a headache.

The BBC has confirmed that one tunnel in the area is still accessible via a locked entrance, but has agreed not to give its location to avoid people trying to break in.

However, a local businessman said he had been into the tunnel in recent weeks, passing on a photo of a perfectly preserved space cut into the sandstone.

Mr Allen said he had never dealt with an engineering problem like it, since most landslips and sinkholes were created by naturally occurring geology.

It can now take 20 minutes to drive around the diversion required to get from one side of the hole to the other, around 100 yards apart.

Some residents have enjoyed the lack of passing traffic and don't want the road to reopen, but the drop in passing trade has resulted in cafes closing for some of the week.

The landlord of the Hare & Hounds pub, which has suffered a 40% drop in customers, says the sinkhole has "cut the village in half" by separating his pub from the M25 close by.

Mark Cullinan said when it first happened he thought "okay, this is going to hurt for a couple of weeks".

"And then they're telling you that there's caves under there," he added.

"If we're lucky, it'll be open by December. If we're not lucky, another three months after that."

This week excavators were slowly filling in the hole and the council insisted it was sticking to its timetable to finish the repairs by Christmas.