The Longwall Mining Process

Georges River Macarthur

General longwall mining

• longwall mining process - damage, cause and effects
• backstow - mining subsidence - backstow reduces surface damage, our politicians don't legislate for it
• Cataract river - Cataract river during the seventies
• Georges river dieing - Georges river greatly reduced water levels
• Iluka Creek - Iluka Swamp - Iluka Creek, Iluka Swamp, Georges River catchment
• Macarthurs rivers - Bargo, Georges, Cataract rivers - Broughton Pass Dam, Marhnes Hole, Appin
• Mine subsidence - mine subsidence in the Upper Nepean river catchment
• Georges River photographs - photographs of 7 km downstream of Freres Crossing
• Stokes Creek Wedderburn - Stokes Creek, Wedderburn, Georges River, Campbelltown
• Wedderburn - Wedderburns rivers, creeks and properties
• Wedderburn gorge - Wedderburn gorge, Georges River catchment, environmental damage
• Woolwash - The Woolwash junction with O'Hares creek Wedderburn - Minto
• Georges River catchment - Georges River, O'Hares Creek, Iluka Creek, Iluka Swamp, Maddens Creek, Dharawal State Recreation Area, Dharawal Nature Reserve, Campbelltown, Wedderburn.
• O'Hares - Wedderburn - Georges River, O'Hares Creek, Campbelltown, Wedderburn.
• Dharawal State Recreation Area - Georges River, O'Hares Creek, Darkes Forest.

• gr_punchbowl_kentlyn - Punchbowl Creek at the Basin Georges River NSW
• broken promises - longwall mining - deceit, denial and broken promises
• Cost clean coal - Clean coal, is it too costly to consider
• Longwall Mining - Global Climate Change, letter to Kevin Rudd, Prime minister Australia
• The hidden costs of clean coal - The environmental and human disaster of longwall mining - Multimedia from The Center for Public Integrity Washington DC. Video filmed in the mine and the effects above ground.
• BHP Billiton environmental damage - BHP Billiton, Fly river, Ok Tedi river, copper mines, Irian Jaya, Barrow Island, deforestation Indonesia, environmental damage, longwall mining
• BHP Billiton misinformation - BHP Billiton Illawarra Coal - Rio Tinto misinformation and the publics wrong impression of mining
• Politicians and approvals - These politicians approve longwall mining licences which pollutes our atmosphere, damages our rivers, water catchments and your homes
• Mine subsidence - longwall mining and its impact on water resources
• When longwall mining comes to your town - When longwall mining comes to your town, your home is in the hands of the mining company- from the US and applies here in Australia

Longwall Mining

Longwall mining is form of underground coal mining which uses a massive machine called a longwall. The longwall equipment consists of a number of hydraulic jacks, called chocks, roof supports or shields, which are placed in a long line up to 400m in length in order to support the roof.
An individual chock can extend to a maximum cutting height of up to 5m. The coal is cut by a rotating drum with bits called a shearer that moves along the length of the face in front of the chocks, disintegrating the coal.

The coal is then removed from the coal face by a moving chain or AFC (articulated face conveyor) (also called armoured face conveyor) to the main gate. Here it is loaded onto a conveyor belt and transported to the surface.

As the shearer removes the coal, the chocks move forward into the newly created cavity. As mining progresses and the entire longwall progresses through the seam, the cavity behind the longwall, known as the goaf, increases. This goaf collapses under the weight of the overlying strata.

Underground water table damage

Sometimes longwall mining is called destructive or environmentally unsafe because it causes the land above the mined-out panel to sink. This can damage underground water tables, structures at the surface, and can cause erosion of the soil. - wisegeek.com

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.

Deformation of ground surfaces - 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.

Permanent effects on the functions of ecosystems

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.

The Hidden Cost of Longwall Mining

In recent years, West Virginia has been the poster child for coal. In a state that has always been celebrated for its mountains, the  coal industry’s practice of mountain top removal is so overtly damaging that one or two pictures are all that is needed to persuade. Cutting away a mountain top of stone and clay to retrieve the narrow veins of coal beneath is such an obviously destructive practice that you don’t even have to know about the miles of streams that are destroyed in the process to be outraged.

Pennsylvania is not a poster child. Most mining damage is hidden away, out of sight. But it is damage nevertheless.

150 years of bad mining practices

Pennsylvania’s heritage over the past century and a half is one of bad mining practices. Scars rule the landscape in the eastern anthracite regions where miles of spoil stand barren and unreclaimed. Gob piles loom like barren mountains in southwestern Pennsylvania, reminders of the history of bituminous room and pillar mining. Thousands of miles of streams run acid because of bad surface and deep mining practices.

Throughout the state the coal industry now proclaims itself “Green and Clean,” but it is not. It claims that it no longer damages the landscape, that it doesn’t destroy streams, that it repairs any damage to houses to the satisfaction of the owners. Its claim is that longwall mining will cause subsidence so quickly and evenly that nothing is harmed.

Longwall Mining destructive in many ways

But the truth is that longwall mining is destructive in many ways. It cracks houses, sometimes irreparably. It damages roads and highways. It breaks gas and water lines. It dries springs and wetlands and destroys streams.

Consider Roy and Diane Brendels’ historic home in Greene County. After six years of torturous attempts to shore it up and stop the cracks, the mining company, Consol Energy, finally paid a settlement to the Brendels and tore down their 12-room stone and stucco Spanish Revival home which had been listed in the National Historic Register. The Brendels, worn out by litigation and unable to live in their beautiful old home, had to sign an agreement with Consol not to discuss the settlement in order to receive any recompense. Many believe that Mrs. Brendel’s death at 61 was hastened by the strain and grief she experienced during their ordeal.

Consider the dam at Duke Lake, in Ryerson Station State Park. This dam was cracked by by geologic stress from nearby longwall mining. However, Consol Energy claims that it is not to blame. The state of Pennsylvania is now suing Consol for $50 million.

Consider South Fork, a stream that the Fish Commission stocked with trout each spring. After it was undermined, it went dry and made a subsequent pond downstream.

Mining company denials

When damage is done, the mining company begins by denying the damage. Then it claims the damage is only temporary. Finally, it insists that it won’t pay for damage unless the home or farm owner agrees not to discuss the settlement. The industry knows that most damage is out of sight and therefore, out of mind. It knows that in another decade or two, it will have exhausted the available coal and will have left the area, taking its trainloads of wealth with it.

Longwall mining is the new mythology. Decades from now, it will be the old horror story. The industry will say, “We used to damage homes and streams, but we don’t do that any more; we have a new technology that is better than the old.”

Don’t believe it.

By Phil Coleman, Chair, Mining Committee, Allegheny Group - The Hidden Costs of Longwall Mining

Alteration of habitat following subsidence due to longwall mining - key threatening process listing

NSW Scientific Committee - final determination

17. Empirical methods have been developed from large data sets to predict conventional subsidence effects (ACARP 2001, 2002, 2003). In general, these models have proved more accurate when predicting the potential degree of subsidence in flat or gently undulating terrain than in steep topography (ACARP 2003). A major issue identified in the ACARP (2001, 2002) reports was the lack of knowledge about horizontal stresses in geological strata, particularly those associated with river valleys. These horizontal stresses appear to play a major role in the magnitude and extent of surface subsidence impacts. The cumulative impacts of multiple panels also appear to have been poorly monitored. The general trend in the mining industry in recent years toward increased panel widths (from 200 up to 300 m), which allows greater economies in the overall costs of extraction, means that future impacts will tend to be greater than those in the past (ACARP 2001, 2002).

18. In view of the above the Scientific Committee is of the opinion 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.

Dr Lesley Hughes
Chairperson
Scientific Committee
Exhibition period: 15/07/05 - 09/09/05