Who in hell would mine under a river, anyway?

I mean, I realise that I just wrote, below, about agents and self-interest, but this was – to me – a lesson in recklessness; that’s even allowing for the fact that we’re talking about coal-mining.

Mines blamed for threat to water supply

Unrestricted underground coal mining south of Sydney is cracking riverbeds, draining swamps and putting the city’s water supply at risk, experts say.

In one of the most dramatic cases, longwall panels 500 metres beneath the Waratah Rivulet, to the west of Helensburgh, have cracked the sandstone bedrock, in some places 20 metres across, split rock ledges and tilted the riverbed. Water flows have disappeared down fractures along a 2 kilometre stretch of river, environmentalists say.

Within 20 years, 91 per cent of the Upper Nepean and Woronora catchments will have been undermined, the Sydney Catchment Authority has told a government inquiry. Dams in these areas are the sole source of water for the Illawarra, Camden, Campbelltown, and part of Wollondilly, and provide water to the Prospect water treatment plant.

It appears that this is filtering out via an inquiry into the effects of coal-mining beneath water catchments. The return to the government is AUD600m per year. The process:

Longwall mining removes a panel of coal by working a face of up to 300 metres wide and up to two kilometres long. The main problem is subsidence, most of which happens as soon as the mining begins.

Nor is this peculiar to NSW. Subsidence, the collapse of overlying rock layers into the void created by the mined-out coal (i.e. pretty bloody predictable) is inexorably going to follow longwall mining. All over.

Martin Krogh, in his submission to the inquiry (that link is to a .pdf), provided the following (by all appearances fairly accurate) summation:

“The short-term gains in increased efficiency of coal extraction (and profit from sales) may come at the expense of the long-term sustainability of Sydney’s metropolitan drinking water supply and environments,”

His submission is quite interesting, as are a bunch of others, findable by wandering aroung on Google. It still strikes me as idiotic to hollow-out out a mass of rock, with another mass above it and a river above that. Especially when we bloody need that river for drinking.

I look forward to the burgeoning market for the technological ‘fix’ to re-extract the fresh water from the bottom of a polluted coal shaft. Water-mining. You read it here first.

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