Work is continuing to fill in a four-metre deep sinkhole which opened up in a Norwich park - and it is likely to be a month before it is completed.
But engineers say they are confident that the gaping hole which opened up at the park in Frere Road, Heartsease, has not been caused by the collapse of an old chalk mine.
Sinkhole-on-Frere-Road-in-Norwich (1)
Worried members of the public called police about the hole on Tuesday, March 9.
The area around the cavity, which was three metres wide and four metres deep, was fenced off and council officials called to investigate.
Norwich City Council initially said it would take a week to fill in the hole.
They said engineers would need to install a concrete cap, then fill it in with gravel, sand and a topsoil.
But that work has yet to be completed, and engineers also wanted to confirm it was a case of the underlying chalk eroding away, rather than the collapse of one of the chalk mines which lie beneath the city's streets.
A city council spokeswoman said: "We’d made an initial estimate for the time it would take to treat the hole which appeared in the park, however we’re still a little while off.
"We wanted to be sure it wasn’t part of a wider issue – and we’re confident that it’s not, and caused by the underlying chalk having been washed away in a small patch – and that the hole wasn’t going to get bigger.
"Our engineer has also taken the decision to install additional concrete and allow more time for it all the settle and compact and the weather has not been on our side on this front.
"After the in-filling is complete in another week or so, we’ll leave the fencing up to make sure the topsoil is settled and the grass seed takes, so it could be up to a month before we completely re-open this small grass area.”
Norwich has a history of sinkholes occurring where chalk bedrock is near the surface, while collapsing medieval chalk mines have also caused holes to appear.
Most famously, the number 26 bus disappeared into a hole in Earlham Road in March 1988, when one such mine caved in.
The passengers managed to scramble off before the vehicle slipped further into the gaping gap which had opened up.
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