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Friday, July 14, 2006

The environmental threat of Longwall Mining

"Longwall mining as a key threatening process"

Below my "opinion" piece here, I have re-published the text of a Fact Sheet prepared by the Dept of Environment and Conservation (NSW). 26 July 2005. Under the Copyright provisions cited by their website, my use of this document
, for non-commercial purposes, is legitimate. The DEC authorship is fully acknowledged, and the text of the document has not been altered in any way, by me.

It fully sets out the environmental damage inflicted by the process of Longwall Mining. There is an associated "Declaration" (see link at below) which is the formal document.
Alteration of habitat following subsidence due to longwall mining - key threatening process declaration
All very well and good.

What has happened since this declaration was published? Business as usual, in the mining industry, that's what.

The Dept of Environment and Conservation has done the right thing, but the decision makers in the Mines Department and whoever else decides these things are still going flat out to crack the bedrock in the Catchment - despite the formal declaration of this process as being an "Key Threatening Process" to Endangered Ecological Communities.
Hence my reference to the DEC as a "Toothless Tiger".

Don't get me wrong, I support what they have written. But have they really exercised their full powers under the Threatened Species Act to actually prevent damage being incurred?
Or have they just issued a "determination" - and left it at that?

These are just some of the powers available under that Act.

Interim Protection order
The Minister for the Environment may make an interim protection order for a period of up to two years over an area of land that has natural, scientific or cultural significance. The Minister may also make an interim protection order on land where the DEC Director-General intends to exercise functions relating to threatened species, critical habitat, or declared critical habitat under the NP&W or TSC Acts.

Stop Work Order
The Director-General of DEC may make a stop work order for a period of 40 days if an action is being, or is about to be carried out that would harm a threatened species, population or ecological community or it’s habitat. These orders can be renewed for 40-day periods as required.

I haven't heard of any such powers being used, to stop Longwall Mining by BHP Billiton or their subsidiaries. Have you?

Denis Wilson
The following it the text of the DEC Fact Sheet

Alteration of habitat following subsidence due to longwall mining as a key threatening process - fact sheet

'Alteration of habitat following subsidence due to longwall mining' has been listed by the NSW Scientific Committee as a key threatening process under the Threatened Species Conservation Act 1995.

What is longwall mining and how does it cause subsidence?

Longwall mining is an underground coal mining technique which involves removing a portion of an underground coal seam. Longwall mining can cause the land above the mined-out coal seam to destabilise and collapse – this is known as subsidence.

The extent of subsidence is influenced by various factors, including the width and depth of the longwall mine, topography, the type of overlying rock layers, the design of the mine and the location of the mine. These factors vary from site to site, so the amount of subsidence - and its subsequent impacts - also varies.

What is alteration of habitat?

The specific area or environment in which a plant or animal lives is called its habitat. A habitat provides all the basic requirements for survival. Alteration of habitat refers to a change in the structure or function of habitat, making it potentially unsuitable for the organism to live in. Subsidence due to longwall mining has been recognised as causing habitat alteration. Species and ecological communities that depend on aquatic and semi-aquatic habitats are particularly susceptible to the impacts of subsidence.

Subsidence due to longwall mining can cause deformation of ground surfaces as well as cracking of valley floors and creeklines. This can affect natural water flow regimes and water quality, depending on such factors as the width of the crack, riverbed steepness, the riverbed material and the presence of organic matter. Subsidence can also destabilise cliff faces.

In turn, these impacts can lead to the alteration of species habitats and changes to the ecological function of communities. Effects can be temporary or long-term. When water flows are altered, there can be permanent effects on the functioning of ecosystems in localised areas, which may be exacerbated in drought conditions.

Why list 'alteration of habitat following subsidence due to longwall mining' as a key threatening process?

The NSW Scientific Committee in its final determination concluded that alteration of habitat following subsidence due to longwall mining:

  • adversely affects two or more threatened species, populations or ecological communities, or
  • could cause species, populations or ecological communities that are not threatened to become threatened.

What species, populations and ecological communities are particularly affected?

Threatened species and ecological communities are known to occur in areas affected by subsidence due to longwall mining, and their habitats are likely to be altered by subsidence and mining-associated activities. Species include the following:

  • Blue Mountains water skink
  • giant dragonfly
  • broad-headed snake
  • Epacris hamiltonii
  • eastern pygmy possum
  • giant burrowing frog
  • stuttering frog
  • large-footed myotis.

Endangered ecological communities identified in the listing include the following:
  • Genowlan Point Allocasuarina nana heathland
  • O'Hares Creek shale forest
  • shale/sandstone transition forest
  • Newnes Plateau shrub swamp in the Sydney Basin Bioregion.

Subsidence associated with longwall mining can significantly affect the water balance of upland or hanging swamps. Even though subsidence may be detected within a few months of a mining operation, related changes in vegetation can occur over a longer time period.

Mining subsidence can also destabilise slopes and escarpments. Changes to cliff line topography can change the availability of roosting sites for bats and nest sites for cliff-nesting birds.

What are the implications of the listing?

The Department of Environment and Conservation is required to develop strategies for mitigating or managing the adverse effects of this threatening process on our native wildlife. The mining industry and wider community will be invited to contribute to the development of these strategies.

Strategies may include:

  • reviewing existing policies, regulatory and non-regulatory regimes
  • preparation of impact assessment guidelines.

A number of actions are currently underway to address the environmental impacts caused by subsidence. The actions include the development of subsidence management plans as required under the Mining Act 1992 (administered by the Department of Primary Industries). DEC is on the inter-agency committee that reviews these plans. The effectiveness of these actions will be taken into account when DEC is considering the need for a threat abatement plan.

What does the listing mean for the mining industry?

This listing does not change the current laws regulating longwall mining activities. However, the listing will lead to increased responsibility for - and consideration of - the biodiversity impacts of subsidence caused by longwall mining.

Longwall mining activities will continue to be regulated under the Mining Act 1992. The environmental regulation of the industry is shared with DEC, the Department of Lands, and the Department of Infrastructure, Planning and Natural Resources.

More information

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Last amended: 26 July 2005.

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