The+Hole+Story

=__The Hole Story__=

In December 2001 newspapers and television were full of stories about a house that had dropped in to a large hole in the ground in Waihi.

Children asleep in the house at the time escaped unharmed. The area was evacuated, and eventually several houses around the hole were removed. Nothing has been built on this land since the event.

How did this happen?

About a hundred years ago miners had tunnelled and dug large caves (called stopes) deep below the surface as they searched for and mined gold-bearing rock. When they finished mining the early miners did not fill in the holes. Over many years the roof of the big cave they dug fell in to the bottom of the cave. This meant that, as the roof fell bit by bit, the top of the cave got closer and closer to the surface. Eventually the roof got so close to the surface that the clay and soil above it could not hold the weight of the house, which then fell into the hole.

There were similar events in Waihi in 1999, and before that in 1961.

Can this happen today?

The simple answer is, no.

In modern mining the stopes are backfilled. This means that the large holes underground are filled up. For every truck of ore we bring to the surface we return a truckload of waste rock. If we do not have enough waste we bring in extra rock from a local quarry. Backfilling means that the ground above modern mines cannot fail as it did in 1961, 1999 and 2001.
 * [[image:newmontwaihigold/House In Hole.jpg width="702" height="672"]] ||
 * [[image:stope backfilling.jpg width="800" height="621"]] ||