“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.