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Thursday, January 25, 2007

Long Wall Mining is a disaster for Rivers

The Waratah Rivulet
Amazingly, this is a river bed in the Sydney Catchment.

Dry and dead.

Surely not Sydney's catchment?

Yes it is.

The now dry riverbed of Waratah Rivulet, cracked,
uplifted and drained by longwall mining in 2006.
The Rivulet comprises nearly 30% of the Woronora Dam catchment.

This is what happens to river beds when mining is allowed to occur close to, or, in this case, underneath a river bed.

The issue is subsidence under the river. Mining has taken place deep underneath. But because of the mining companies use Long Wall Mining process, they take out a flat stratum of coal, entirely. Then, before they move on, they remove the chocks which temporarily supported the rock layers above where the coal was. The now empty cavern slumps down, and the rock layers above crack and subside.

In the picture, what you are seeing is caused by "upsidance", but it is a variant of normal subsidence. As the rock layers below collapsed, they sometimes slump unevenly. That can produce a twisting in the levels, and if there is not sufficient room for the rocks to drop evenly, the outer rocks drop down, and the bit in the middle has nowhere to go, and it pops up.

Most importantly. This is supposed to be a river.
Where is the water?

Well, guess? It has already fallen down other similar cracks in other rocks. And the water has disappeared down into an abandoned mine cavern below, perhaps 300 metres below.

It is a scandal. Mismanagement of a Catchment on this scale is totally unsupportable. It verges on the criminal. It certainly is negligent. This river can never be brought back to life.

The Total Environment Centre has produced a report called:
Impacts of Longwall coal mining on the environment in New South Wales.

It is a devastating indictment of the Sydney Catchment Authority, the mining companies, and the other NSW Government instrumentalities which approve this terrible damage.

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