Mountaintop removal mining
Mountaintop removal mining, also known as mountaintop mining, is a form of surface mining at the summit or summit ridge of a mountain. Coal seams are extracted from a mountain by removing the land, or overburden, above the seams. This process is considered to be safer compared to underground mining because the coal seams are accessed from above instead of underground. In the United States, this method of coal mining is conducted in the Appalachian Mountains in the eastern United States. Explosives are used to remove up to 400 vertical feet of mountain to expose underlying coal seams. Excess rock and soil is dumped into nearby valleys, in what are called "holler fills" or "valley fills".
Overview
Mountaintop removal mining, also known as mountaintop mining, is a form of surface mining that involves the topographical alteration and/or removal of a summit, hill, or ridge to access buried coal seams.The MTR process involves the removal of coal seams by first fully removing the overburden lying atop them, exposing the seams from above. This method differs from more traditional underground mining, where typically a narrow shaft is dug which allows miners to collect seams using various underground methods, while leaving the vast majority of the overburden undisturbed. The overburden from MTR is either placed back on the ridge, attempting to reflect the approximate original contour of the mountain, and/or is moved into neighboring valleys. When excess rock and soil containing mining byproducts are disposed into nearby valleys, the valleys are called "holler fills" or "valley fills".
MTR in the United States is most often associated with the extraction of coal in the Appalachian Mountains. Google Earth Engine and Landsat imagery report the extent of newly mined land from 1985 to 2015 to be 2,900 km2. Considering surface mining sites prior to 1985, the cumulative total of mined land was calculated to be 5,900 km2. Further studies calculated that 12 m2 of mined land produced one metric ton of coal. There are many MTR site locations ranging from Ohio to Virginia. It occurs most commonly in West Virginia and Eastern Kentucky, the top two coal-producing states in Appalachia. At current rates, MTR in the U.S. will mine over 1.4 million acres by 2010, an amount of land area that exceeds that of the state of Delaware. More than 500 mountains in the US have been destroyed by this process, resulting in the burial of of streams.
Mountaintop removal has been practiced since the 1960s. Increased demand for coal in the United States, sparked by the 1973 and 1979 oil crises, created incentives for a more economical form of coal mining than the traditional underground mining methods involving hundreds of workers, triggering the first widespread use of MTR. Its prevalence expanded further in the 1990s to retrieve relatively low-sulfur coal, a cleaner-burning form, which became desirable as a result of amendments to the U.S. Clean Air Act that tightened emission limits on high-sulfur coal processing.
Process
Mining
Land is deforested prior to mining operations and the resultant lumber is either sold or burned. According to the Surface Mining Control and Reclamation Act of 1977, the topsoil is supposed to be removed and set aside for later reclamation. However, coal companies are often granted waivers and instead reclaim the mountain with "topsoil substitute". The waivers are granted if adequate amounts of topsoil are not naturally present on the rocky ridge top. Once the area is cleared, miners use explosives to blast away the overburden, the rock and subsoil, to expose coal seams beneath. The overburden is then moved by various mechanical means to areas of the ridge previously mined. These areas are the most economical area of storage as they are located close to the active pit of exposed coal. If the ridge topography is too steep to adequately handle the amount of spoil produced then additional storage is used in a nearby valley or hollow, creating what is known as a valley fill or hollow fill. Any streams in a valley are buried by the overburden.A front-end loader or excavator then removes the coal, where it is transported to a processing plant. Once coal removal is completed, the mining operators back stack overburden from the next area to be mined into the now empty pit. After backstacking and grading of overburden has been completed, topsoil is layered over the overburden layer. Next, grass seed is spread in a mixture of seed, fertilizer, and mulch made from recycled newspaper. Depending on the surface land owner's wishes the land will then be further reclaimed by adding trees if the pre-approved post-mining land use is forest land or wildlife habitat. If the land owner has requested other post-mining land uses the land can be reclaimed to be used as pasture land, economic development or other uses specified in SMCRA.
Because coal usually exists in multiple geologically stratified seams, miners can often repeat the blasting process to mine over a dozen seams on a single mountain, increasing the mine depth each time. This can result in a vertical descent of hundreds of extra feet into the earth.
Reclamation
Surface Mining Control and Reclamation Act
Established in 1977, the Surface Mining Control and Reclamation Act set up a program "for the regulation of surface mining activities and the reclamation of coal-mined lands". Although U.S. mountaintop removal sites by law must be reclaimed after mining is complete, reclamation has traditionally focused on stabilizing rock formations and controlling for erosion, and not on the reforestation of the affected area. However, the Surface Mining Control and Reclamation Act of 1977 list "the restoration of land and water resources" as a priority.The act also introduced the Abandoned Mine Land Fund that provides financial assistance to reclaim mines abandoned before the act was implemented. However, subjective environmental quality assessments and the many forgotten or missed locations has led to disagreements on its effectiveness. The fund also promotes job creation and economic revitalization through reclamation projects. Workers are needed to dismantle dangerous mine locations and reclaimed areas become available for municipal development.
In 2022, OSMRE, along with states and tribes issued over 5,400 permits for reclamation sites and active mines. Totaling 2.7 million acres, the mines and supporting equipment are regulated through inspections, enforcements permits, and reclamation bonding requirements. Additionally in 2022, it was found that 91.3% of permitted sites had no off-site effects after 570 partial and 289 complete inspections were performed.
Appalachian Regional Reforestation Initiative (ARRI)
Historically, reforested mining sites have been characterized by seedling mortality, slow growth and poor production. Challenges associated with returning forests to their pre-mining state enabled grassland conversion to become standard. The Appalachian Regional Reforestation Initiative, established in 2004, works to promote the growth of hardwood trees on reclaimed mining sites. The ARRI operates utilizing the Forestry Reclamation Approach. In an effort to apply specific forest restoration practices, the FRA focuses on five main reclamation components: establish suitable soil deeper than four feet to enhance root growth, ensure non-compacted topsoil is present, plan vegetative ground cover to support tree growth include tree species that support local wildlife, as well as commercially desired products, ensure that proper planting techniques are utilized. This group also facilitates restoration efforts by educating and training members of the coal industry on their role in promoting and adopting effective management practices.Valley fill sites
Valley fill sites can be characterized by high sulfur concentrations from the weathering process of mountaintop sulfur-rich debris. Additionally, acid mine drainage increases the concentration of sulfate, iron, aluminum and manganese in surrounding streams. Some of the most common treatments include plugging mine openings, altering the landscape to divert incoming water from at-risk ecosystems, alkaline inputs, limestone channels and treatment ponds or wetlands.Biotic stream remediation index
Current remediation methods may vary, but expensive treatment costs persist. The cost efficiency of treatments can be increased through the use of models that are able to accurately predict ecosystem responses to various inputs; thus enabling restoration groups to determine the overall most effective treatment combination. Biotic indicators present within stream ecosystems impacted by valley fill activity and AMD are valuable assets to increase the cost efficiency of restoration efforts. Mayflies are abundant in streams in the Appalachian Mountain region. They are highly sensitive to water quality, as their immature forms require unpolluted water. VF and AMD are the leading causes of water chemistry and habitat alterations in this region, the driving factors limiting mayfly populations. Thus, they can be utilized as an effective indicator species to quantify restoration progress through modeling efforts focused on mountaintop mining driven changes in adjacent ecosystems. Effectively developed biotic response models can improve and refine restoration efforts by establishing target indicator species population goals and by enabling the monitoring and assessment of water chemistry and habitat changes impacting particular species.Economics
As of 2023, approximately 16% of U.S. generated electricity was coal-based, down from around one third in 2015. MTR accounted for less than 5% of U.S. coal production as of 2001. In some regions, however, the percentage is higher, for example, MTR provided 30% of the coal mined in West Virginia in 2006. As of 2023, only West Virginia was noted as producing coal through MTR. With a total of nearly 1,800 tons, that accounted for 0.5% of total coal production in the U.S.Historically in the U.S. the prevalent method of coal acquisition was underground mining which is very labor-intensive. In MTR, through the use of explosives and large machinery, more than two and a half times as much coal can be extracted per worker per hour than in traditional underground mines, thus greatly reducing the need for workers. In Kentucky, for example, the number of workers has declined over 60% from 1979 to 2006. The industry overall lost approximately 10,000 jobs from 1990 to 1997, as MTR and other more mechanized underground mining methods became more widely used. The coal industry asserts that surface mining techniques, such as mountaintop removal, are safer for miners than sending miners underground.
Proponents argue that in certain geologic areas, MTR and similar forms of surface mining allow the only access to thin seams of coal that traditional underground mining would not be able to mine. MTR is sometimes the most cost-effective method of extracting coal. However, in a comparison report on wind farms vs. surface mining on Coal River Mountain, WV, it was found that surface mining costs would outpace the income it would generate. Additionally, surface mining activity is limited. The study notes that those mines would only be active for 17 years, whilst wind farms have indefinite working potential. The authors proposed that wind farms would more greatly benefit Raleigh County, WV.
Several studies of the impact of restrictions to mountaintop removal were authored in 2000 through 2005. Studies by Mark L. Burton, Michael J. Hicks and Cal Kent identified significant state-level tax losses attributable to lower levels of mining. Mountaintop removal sites are normally restored after the mining operation is complete, but "reclaimed soils characteristically have higher bulk density, lower organic content, low water-infiltration rates, and low nutrient content".
Reclamation projects designed in conjunction with community needs can aid local economic development. Previously mined land can be reclaimed as sustainable agricultural land and solar farms. These efforts can help to diversify and stimulate the local economy by providing jobs and other economic opportunities.