Mining wastes and mine reclamation
Mining wastes refer to the byproducts generated during the extraction and processing of mineral resources, which can include solid waste, tailings, and gaseous emissions. These materials can significantly impact the environment, altering landscapes, polluting water sources, and harming local ecosystems and human health. The process can lead to acid mine drainage, where exposed minerals react with water and oxygen to form acidic runoff that damages aquatic life and water quality.
Mine reclamation is the practice of restoring land after mining activities have ceased, aiming to mitigate environmental damage and allow for alternative land uses, such as agriculture or recreation. Modern reclamation practices often integrate environmental planning from the outset, requiring operators to develop strategies to minimize negative impacts and ensure the safe handling of mining wastes. Effective reclamation not only stabilizes the land but can also involve efforts such as backfilling excavated areas, replanting vegetation, and treating contaminated water. As demand for mineral resources continues to grow, balancing extraction with responsible waste management and reclamation becomes increasingly important for sustainable development.
Mining wastes and mine reclamation
Mining and related operations generate waste materials that mar the landscape and pose a threat to human health and the environment. Reclamation and pollution-control efforts minimize the impact of mining on its surroundings and make the land fit for nonmining use.
Background
Humankind is dependent on resources extracted from the Earth. These resources cannot be obtained without impacting the environment. Mining involves not only the mine itself—either a large, open excavation or a small surface opening leading to extensive subsurface workings—but also access roads, utilities such as water and power, processing facilities, and other support buildings and equipment. These all take a toll on their surroundings, as do the solid, liquid, and gaseous wastes produced during mining, milling, and smelting. Unconstrained mining operations and wastes can alter and litter the landscape, pollute and groundwater, foul the air, harm plant and animal life, threaten human health and safety, and render land useless for subsequent purposes.
As the world’s human population grows and the overall standard of living continues to rise in both developed and undeveloped countries, the demand for mineral resources increases. Likewise, there are increasing and often conflicting demands upon the land where those resources are found. Wise management of and efforts after mining makes it possible to use land for timber, crops, grazing, recreation, or other nonmining purposes once mineral wealth has been extracted from it.
Mining Wastes and Their Impact
During mining operations, that does not contain economically significant concentrations of an must be removed. This waste material is known as spoil. In the case of surface mining, extensive areas are disrupted and laid bare as the vegetation, topsoil, and rock overlying the desired ore are stripped away. During ore processing, additional solid waste is generated in the form of tailings, the portions of washed or milled ores that are too poor to merit further processing. Surface-mined areas and piles of and generally cannot support vegetation without first undergoing treatment; as a result, they are vulnerable to and flooding. Silt from these unvegetated slopes finds its way into streams and other surface waters, where it impacts aquatic life. The barren waste materials remain unstable, increasing the likelihood of landslide. Substantial piles of spoil or tailings can also be a physical obstruction to continued mineral exploration in the area.
At mines where pyrite (iron sulfide) is associated with the ore body and water is present, can result. Exposed pyrite breaks down in the presence of oxygen to form iron sulfate and sulfur dioxide. The decay of pyrite is self-perpetuating; as the mineral breaks down and crumbles away, new surfaces are exposed to the air. Water, which is found in most mines in the form of direct precipitation, surface runoff, seeping groundwater, or atmospheric moisture, completes the reaction: Added to pyrite’s breakdown products, it creates sulfuric acid. As the acidified water flows, it dissolves and transports minerals from the surrounding rock, further degrading the quality of the water. This acid mine drainage affects streams, ponds, lakes, and the fish and other life they support. Neglected piles of spoil and tailings can also be a source of acid runoff.
Mining and related activities generate air pollution in the form of airborne dust and gaseous processing effluent. Drilling, excavating, blasting, and similar operations cause dust particles to become airborne. Fine metallic and mineral dusts can have particularly deleterious effects on mine workers and other persons inhaling them. produces gaseous effluents that, if not treated, are not only a nuisance, obscuring visibility and spreading noxious odors, but also a serious threat to animal and plant life. Gaseous smelter waste can contain such toxic metals as arsenic, lead, and mercury.
Inappropriate handling of mining wastes can change the contours of a landscape, leaving an area vulnerable to landslides and floods; can disrupt an ecosystem’s food chain, especially in the waste’s effects on land plants and aquatic organisms; can introduce toxic materials into the air and water; and can degrade the economy and overall quality of life in mined areas.
Reclamation and Pollution Control
Basic reclamation involves correcting undesirable conditions brought on by mining and related operations. Reclamation can proceed beyond this level to include the rehabilitation of restored land and water resources for agriculture, forestry, rangeland, recreation, industry, residences, or other productive use.
Modern mining efforts have incorporated reclamation into their preplanning and operational phases. Before mining commences, most industrialized countries require mine operators to prepare an environmental impact statement that addresses the potential impact of operations on surface water, groundwater, soil, local topography, plant and animal life, and other mineral reserves. Mine operators must plan in advance the reclamation and pollution-control measures that will minimize environmental damage.
In the case of surface coal mining, reclamation usually begins as soon as the resource has been removed. After the coal has been dug from a strip of land, from an adjacent strip is backfilled into the newly excavated strip and molded with heavy equipment to a shape resembling premining topography. is emplaced over the fill material and seeded, mulched, and irrigated. Topsoil and vegetation covers are also used to stabilize mounds of spoils and tailings at underground mining sites. An alternative method for handling these solid wastes is to mix them with the grout or used to fill inactive underground mines. Properly filling the mines keeps the overlying land from subsiding, thereby preventing any resulting disruption of local surface-water and systems and damage to overlying structures. In the case of underground coal mines, filling also seals them to prevent the outbreak of mine fires.
The best way to control acid mine drainage and runoff is to prevent their formation. If exposed pyrite, oxygen, or water is not present to sustain the chemical reaction, acid cannot form. To inhibit the reaction, water is diverted from mines, tailings, and spoil piles. Solid wastes are crushed and compacted to minimize and water infiltration. Inactive mines are sealed with grout or slurry to isolate pyrite from the other reactants; mixing the solid mining wastes with the fill material isolates them as well. Where the formation of acid drainage and runoff cannot be averted, the effluent is contained and treated. Treatment typically involves neutralizing the acid with lime or other alkaline materials and retaining the effluent in a treatment pond to allow impurities to settle out.
To suppress airborne dust, water sprays are typically employed. Gaseous emissions from smelters are filtered and otherwise treated before they are released to the atmosphere.
History
Before the twentieth century, mining’s focus was on short-term economic gain. Deposits of the greatest accessibility and grade were mined as cheaply as possible. Particularly in the United States, where land and resources appeared limitless, mining interests extracted the richest ores and exploited other natural resources as they saw fit, confident that they were putting the land to its highest and best economic use. Spoils and tailings were left to litter the landscape. Roads were cut indiscriminately through wilderness and across waterways. Surface waters were dammed or channeled into ditches, and drinking-water sources became tainted with heavy metals. Forests were denuded to provide wood for support operations or merely to clear the area for mineral exploration. Valleys grew clouded with toxic, acidic smelter smoke that killed vegetation and animals and eroded the health of human populations. As technology improved and made possible such techniques as hydraulic mining, dredging, strip mining, and open-pit mining, the potential for greater environmental damage arose.
In the late nineteenth and early twentieth centuries, mining companies experimented with reclamation and reworked spoils and tailings to extract low-grade ores. While driven by profit, these practices were more environmentally sound than what went before. Similarly, early regulations in the United States that controlled mining wastes and the use of water in mining defended downstream mining operations from conditions that would impede their efforts; they were not intended as environmental protection legislation, regardless of whatever positive effect they may have had on environmental quality.
In 1939, West Virginia enacted the first state legislation to control surface mining. Over the next few decades, other coal-producing states followed suit. Reclamation increased significantly after these laws were enacted; however, lack of funding and other factors influenced the states’ ability to enforce the laws. In the 1960s, a profusion of environmental laws that affected the mining industry, including the Appalachian Regional Development Act of 1965 (Public Law 89-4), under which the United States Bureau of Mines studied the effects of surface coal mining in the United States and made recommendations regarding a national program for reclamation and rehabilitation. This study led to the Surface Mining Control and Reclamation Act of 1977, or SMCRA (Public Law 95-87), which regulates surface coal-mining operations within the United States and provides for the reclamation of contaminated surface coal-mining sites. Federal clean air and clean water legislation regulates other environmental aspects of mining.
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"What Is Mine Reclamation? Benefits, Purpose, and Process." JOUAV, 30 Dec. 2024, www.jouav.com/blog/mine-reclamation.html. Accessed 23 Dec. 2024.