A spoil tip (also called a boney pile, culm bank, gob pile, waste tip or bing)
The term "spoil" is also used to refer to material removed when digging a foundation, tunnel, or other large excavation. Such material may be ordinary soil and rocks (after separation of coal from waste), or may be heavily contaminated with chemical waste, determining how it may be disposed of. Clean spoil may be used for land reclamation.
Spoil is distinct from tailings, which is the processed material that remains after the valuable components have been extracted from ore.
Spoil banks can also refer to refuse heaps formed from removal of excess surface materials. For example, alongside livestock lots, spoil banks are formed of manure and other slurry periodically removed from the surface of the livestock lot areas.
The piles also create acid rock drainage, which pollutes streams and rivers. Environmental problems have included surface runoff of silt, and leaching of noxious chemical compounds from spoil banks exposed to weathering. These cause contamination of ground water, and other problems.George P. Hannah, Jr. "The Relation of Water to Strip Mine Operation."Lawrence E. Beyer and Russell J. Hutnik. "Chemical Properties of Toxic Strip-Mine Spoil Banks in Pennsylvania."
In the United States, current state and federal coal mining regulations require that the earth materials from excavations be removed in such a fashion that they can be replaced after the mining operations cease in a process called mine reclamation, with oversight of mining corporations. This requires adequate reserves of monetary bonds to guarantee a completion of the reclamation process when mining becomes unprofitable or stops. (See for example, the Surface Mining Control and Reclamation Act of 1977.)
Such fires can follow slow combustion of residual hydrocarbons. Their extinction can require complete encasement, which can prove impossible for technical and financial reasons. Sprinkling is generally ineffective and injecting water under pressure counter-productive, because it carries oxygen, bringing the risk of explosion.
The perceived weak environmental and public health effects of these fires leads generally to waiting for their natural extinction, which can take a number of decades.
The wider issue of stability had been known about prior to the Aberfan disaster; for example, it was discussed in a paper by Professor George Knox in 1927, but received little serious consideration by professional engineers and geologists — even to those directly concerned with mining. Also the Aberfan disaster was not the first landslide with casualties: for example, in 1955 two successive landslides killed 73 people in Sasebo, Nagasaki in Japan. 安部鉱業ボタ山崩壊事故(1955年)
In February 2013, a spoil tip landslip caused the temporary closure of the Scunthorpe to Doncaster railway line in England.
Landslides are rare in spoil tips after settling and vegetation growth act to stabilise the spoil. However, when heavy rain falls on spoil tips that are undergoing combustion, infiltrated water changes to steam; increasing pressure that may lead to a landslide. In Herstal, Belgium, a landslide on the Petite Bacnure spoil tip in April 1999 closed off a street for many years.
The oldest Coal refuse may still contain enough coal to begin spontaneous combustion. This results in a form of Glass transition of the shale, which then acquires sufficient mechanical strength to be of use in road construction. Some can therefore have a new life in being thus exploited; for example, the flattened pile of residue from the 11/19 site of Loos-en-Gohelle. Conversely, others are painstakingly preserved on account of their ecological wealth. With the passage of time, they become colonised with a variety of flora and fauna, sometimes foreign to the region. This diversity follows the mining exploitation. In South Wales some spoil tips are protected as Sites of Special Scientific Interest because they provide a unique habitat for 57 species of lichen, several of which are at risk due to their limited environment being developed and by vegetation development.
For example, because the miners threw their apple or pear cores into the wagons, the spoil tips became colonised with fruit trees. One can even observe the proliferation of buckler-leaved sorrel (French sorrel – Rumex scutatus), the seeds of which have been carried within the cracks in the pine timber used in the mines. Furthermore, on account of its dark colour, the south face of the spoil tip is significantly warmer than its surroundings, which contributes to the diverse ecology of the area. In this way, the spoil tip of Pinchonvalles, at Avion, hosts 522 different varieties of higher plants. Some sixty species of birds nest there.
Some are used to cultivate vines, as in the case of Spoil Tip No. 7 of the coal-mining region of Mariemont-Bascoup near Chapelle-lez-Herlaimont (province of Hainaut). It produces some 3,000 litres of wine each year from a vineyard on its slopes.
Some spoil tips are used for various sporting activities. The slopes of the spoil tips of 11/19 at Loos-en-Gohelle, or again, at Nœux-les-Mines, are used for winter sports, for example ski and luge. A piste was built on the flank of the heap. In Belgium, a long distance footpath along the spoil tips (GR-412, Sentier des terrils) was opened in 2005. It leads from Bernissart in western Hainaut to Blegny in the province of Liège.
In the United States, coal mining companies have not been allowed to leave behind abandoned piles since the Surface Mining Control and Reclamation Act was passed in 1977. The Virginia City Hybrid Energy Center uses coal gob as a fuel source for energy production.
In Heringen, Hesse, Germany, is the locally called "Monte Kali", made of spoil from potash mining and rising some 200 meters above the surrounding terrain. Facts & Figures about the Werra Monte Kali, Werra Kalibergbau Museum / The Werra Kali Mining Museum in Heringen (in German language). Retrieved on 19 February 2014. "La Muntanya de Sal" (The Salt Mountain), another potash mine spoil heap, lies in Cardona, Catalonia, at about 120 meters in height. "Cardona acull aquest dissabte una jornada científica sobre la mineria al període neolític" ("Cardona Hosts a Symposium on Mining in the Neolithic this Saturday"), Cardona Town Council website (in Catalan language). Retrieved 19 February 2014. Salt Mountain Culture Park, official Cardona Tourism website. Retrieved 19 February 2014. A larger and higher pile is that of "El runam del Cogulló" (The Spoil Heap of El Cogulló), also known as "El runam de la democràcia" (The Slag Heap of Democracy) or "Montsalat" (Salty Mountain), in Sallent, which has already grown higher than the small mountain it was named after (El Cogulló, 474 meters above sea level). "Prou Sal", 2007 (article in Catalan language). Retrieved 19 February 2014. "El runam del Cogulló" (The Cogulló Spoil Tip) in "La mineria de sal al Bages" (Salt Mining in the Bages). (study in Catalan language). Retrieved 19 February 2014.
Re-use
Examples
Literary references
The slagheap is moving again. I can hear it whispering to itself, and as it whispers, the walls of this brave little house are girding themselves to withstand the assault. For months, more than I ever thought it would have the courage to withstand, that great mound has borne down upon these walls, this roof. And for those months the great bully has been beaten, for in my father’s day men built well for they were craftsmen. Stout beams, honest blocks, good work, and love for the job, all that is in this house. But the slag heap moves, pressing on, down and down, over and all round this house which was my father’s and my mother’s and now is mine. Soon, perhaps in an hour, the house will be buried, and the slag heap will stretch from the top of the mountain right down to the river in the Valley. Poor river, how beautiful you were, how gay your song, how clear your green waters, how you enjoyed your play among the sleepy rocks (102).
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