- Thursday | 08/30/2012
There are four basic types of coal: Lignite, subbituminous, bituminous and anthracite.
- Lignite is the lowest rank of coal with the lowest energy content. Lignite is crumbly and has high moisture content. Lignite accounts for about 7% of U.S. coal production.
- Subbituminous coal has a higher heating value than lignite. Subbituminous coal typically contains 35-45% carbon, compared to 25-35% for lignite. About 44% of the coal produced in the United States is subbituminous.
- Bituminous coal contains 45-86% carbon and has two to three times the heating value of lignite. Bituminous coal was formed under high heat and pressure It is the most abundant rank of coal found in the United States, accounting for about half of U.S. coal production.
- Anthracite contains 86-97% carbon and has a heating value that is, on average, slightly higher than bituminous coal. It is very rare in the United States, accounting for less than 0.5% of the coal mined in the United States.
Coal is mined in 26 States. Wyoming mines the most coal, followed by West Virginia, Kentucky, Pennsylvania, and Texas. Coal is mainly found in three large regions, the Appalachian Coal Region, the Interior Coal Region, and Western Coal Region (includes the Powder River Basin).
More than one-third of the coal produced in the United States comes from the Appalachian Coal Region. West Virginia is the largest coal-producing State in the region, and the second largest coal-producing State in the United States. This region has large underground mines and small surface mines. Coal mined in the Appalachian coal region is primarily used for steam generation for electricity, metal production, and for export.
Coal is used to create almost half of all electricity generated in the United States. Power plants burn coal to make steam. The steam turns turbines (machines for generating rotary mechanical power) that generate electricity.
Coal continues to play an important role in supplying the energy needs of the United States and, more than any other domestic fuel resource, helps to assure this country’s energy independence by providing a reliable, domestic source for electricity generation and industrial consumption of energy. Coal is America’s most abundant fuel resource and it is provided to the market by a highly-trained and specialized workforce. Coal mining in the United States is also heavily regulated by mature environmental regulatory programs, including a specific federal statute directed specifically at coal mining.
West Virginia is the nation’s second largest coal producing state. Coal mining operations in West Virginia produced over 135 million tons of coal last year, down from a recent high of 165 million tons in 2008. West Virginia coal is used extensively by domestic utility companies to produce electricity. Metallurgical coal mined in West Virginia represents some of the highest quality coal found anywhere in the world, and both domestic and international steel companies rely on this coal to produce coke for use in the iron making process.
Coal extraction in West Virginia is accomplished generally by underground or surface mining. Both methods of coal extraction require the placement of fill structures, commonly referred to as “valley fills”, acknowledging the steeply-sloped terrain that exists in West Virginia, within CWA section 404 jurisdictional waters. Construction of these valley fills necessitates section 404 authorization from the Corps of Engineers (Corps).
Underground mining techniques, which account for the majority of West Virginia’s coal production, utilize machinery to drive tunnels under the surface of the land. These tunnels are situated in coal seams so as the machinery advances further underground, coal is removed. Using a combined system of vehicle haulage and conveyor belts, the coal extracted from the seam is transported to the surface. Underground mining is practical from engineering and safety standpoint for coal seams that are located more than 100 feet below the surface of the land. Underground mining in shallower coal reserves will often encounter mine roof integrity problems as the geology and overburden at such shallow depths is less consolidated and more susceptible to cracking and failure (roof falls) than the strata above deeper coal seams.
Underground mines are usually characterized by the way the coal seam is accessed from the surface and the underground extraction method used to mine the coal. The method for accessing a coal seam for underground extraction is largely dependent on its vertical position relative to the surface.
An individual underground mine may have more than one of these access methods, depending on the characteristics of the individual coal seam, the coal haulage system used at the mine, the ventilation, roof control and safety plans for the mine and the mine’s supply and employee transport considerations. Underground mining coal extraction methods can generally be divided into two categories: room and pillar mines and longwall mines. The type of extraction practiced is dictated by the characteristics of the coal seam and its related geology. Generally, longwall mining is restricted to seams with uniform geology and coal seam thickness while room and pillar mining is more adaptable to seams with varying thickness, uniformity and geologic settings.
Room and pillar mining is defined by the fact that portions of the coal seam being extracted are left in place to support the roof of the mine. Room and pillar mines are developed by using machinery to extract the coal seam in a grid like pattern through the development of a parallel series of extraction areas referred to as entries. The entries are connected together by extracting the coal perpendicular to the parallel entries in crosscuts. To support the coal extraction areas in the entries and crosscuts, roof support is installed by using machines to install long “bolts” into the roof of the mining area to consolidate and “tighten” the overlying rock strata. Referred to as “roof bolting”, this is the central point of a mine’s roof control plan that is developed by safety regulatory agencies and the operator to assure a maximum amount of safety by minimizing the possible occurrence of roof fractures and slips or roof falls.
Coal extracted from the entry and crosscut areas or “working faces” of the room and pillar mine is loaded onto special underground rubber tired haulage vehicles called shuttle cars. The shuttle cars move the coal from the working face to a centrally-located conveyor belt loading point where the coal is unloaded and transported to the surface for processing at the coal preparation plant. Some mines use shuttle cars to move the extracted coal to a loading point where it is transferred to narrow gauge railroad cars for movement to the surface. In slope and shaft mines there may also be a third transfer point where the coal from the working face is transferred again from the conveyor belt or rail car to an elevator-like haulage system where the coal is lifted vertically to the preparation plant. The initial development of a room and pillar mine, where entries and crosscuts are driven in the coal seam is referred to as primary extraction. Mines using primary extraction only can usually recover 40 to 60 percent of the coal in a given seam and reserve. Depending on the characteristics of the coal reserve, its overlying strata or roof and its underlying strata or floor, secondary production may be possible in room and pillar mines. In secondary production, some of the coal pillars that were established by the entries and crosscuts and were left in place for added roof control are removed. Extraction of the coal in the pillars, if possible at all, is governed by roof control and safety conditions as extraction of the pillars usually results in some level of roof collapse. Where it can be practiced secondary extraction is designed to remove the coal resource in the pillars in a calculated and designed fashion to allow for controlled roof collapse that will not endanger the safety of coal miners or compromise the overall geologic integrity of the entire mine. Where it is possible, secondary extraction can allow for recovery of 70 to 80 percent of the coal in a given coal seam.
The other major form of underground coal extraction is longwall mining. In longwall mines, equipment used in Room and Pillar mining is used to develop two or three parallel entries in a coal seam. The longwall mine entries or headings are usually separated by several hundred feet of solid coal. At a certain distance advancing into the coal seam (depending on mine-specific geology), the headings are connected by driving a crosscuts, or in longwall mines, cross headings to connect the entries to form a block of solid coal called a panel. Specialized equipment, known as longwall machines, that are usually custom-built for specific mines then begin extracting the coal along the face of the panel. These machines include a shear or plow device mounted on a track that moves back and forth across the panel cutting the coal with each pass of the machine, referred to as the cutting head. As the cutting head extracts the panel of coal, the longwall machine advances further into the coal seam extracting more of the seam as it advances through successive passes across the panel, allowing for recovery of up to 85 percent of a given coal seam and reserve. The cutting head is attached to a special type of armored conveyor that gathers the coal as it is cut by the head and moves it to a loading point where it is transferred to the main haulage system for movement to the surface and the coal preparation plant. Both the cutting head and the special conveyor are protected by a special form of hydraulic roof support devices known as shields. The shields support the roof immediately above the longwall machine and are designed to advance as the cutting head moves deeper into the coal reserve keeping the roof support parallel to coal face.
Surface coal mining techniques, which account for the majority of national coal production and roughly 42 percent of West Virginia’s coal production, involve the mechanical removal of overlying native earth and rock or “overburden” to reach underlying coal seams. Surface mining can be further categorized into three basic operational methods: contour mining, area mining and mountaintop removal mining. All three forms of surface mining are generally referred to as “mountaintop mining.”
“Mountaintop mining” is simply coal mining that occurs at or near the topmost portion of a mountain. There have been various emotional statements in the press about this form of mining that are neither based on fact nor supported by the truth.
Surface mining methods are essentially the same as highway construction.
Valley fills are areas where the rock and dirt from mining excavation is placed according to a plan designed by engineers and approved by government agencies. The fills usually occur in dry stream beds of what are known as ephemeral or intermittent streams – streams that flow only when it rains.
Contrary to what is portrayed in the press, the amount of actual stream loss from fills is minimal. In other words, where most valley fills are placed, there is no actual stream.
Far from the destructiveness portrayed in the mass media, mining operations have actually helped improve habitat for wildlife in Appalachia. Today, we are once again seeing elk and wild horses on former mountaintop mining sites.
Perhaps most important, mountaintop mining has also created numerous sites for new schools, hospitals, shopping centers, parks, golf courses, housing, airports, industry, agriculture and timber – providing southern West Virginia valuable sites for sustainable economic development.
Secondary extraction methods can also be employed with surface mining, usually through a process known as highwall mining. While surface mining includes a variety of methods, certain criteria used to determine the exact operation, layout and the extent and form of coal extraction are applicable to all forms of surface mining.
Included in the criteria that are transferable to all forms of surface mining are mining and reclamation considerations. Before any permit is issued under SMCRA or a state delegated program, the operator must submit a specific mining and reclamation plan for review and approval by the regulatory authority. The components of the mining and reclamation plan include a variety of issues such as initial mine development, final mine design, backfilling and regrading, achieving Approximate Original Contour or “AOC” (explained in greater detail in subsequent sections) and erosion and sediment control. Reclamation considerations, along with stripping ratios (explained in subsequent paragraph), are usually the dominant factors that dictate the form of surface mining that is used to extract a coal reserve.
In addition to permitting considerations, determining the extent to which a coal seam or block of coal seams is economically feasible for mining is an integral part of determining the method of surface mining used to extract the reserve. The typical method of assessing surface mining economics for a coal seam is a calculation of overburden (native rock and soil above a coal seam) moved per clean ton of coal produced, commonly referred to as “mining ratio”. The higher the mining ratio (or more overburden moved per clean coal ton), the higher the cost of producing coal. In situations where a given coal reserve includes more than one coal seam, the recoverable coal volume from the multiple seams is factored together to lower the overall mining ratio for the entire coal reserve. Because mining more than one seam lowers the mining ratio for a mining project and increases its economic potential, it allows for extraction of coal seams that would be uneconomic to recover by themselves.
The economic viability of a surface mining project, calculated through the mining ratio, is highly mine and coal reserve dependent. Site-specific factors such as overburden type and depth, excavation costs, coal value and overburden haulage distances and costs are all considered in the development of stripping ratios for a particular mine site and coal reserve.
The ability to construct valley fills is paramount to the economic and physical viability of a surface mining project. As explained in more detail in the following sections, all surface mining methods need valley fills for placement of excess overburden.
Without the ability to construct fills, surface mining becomes physically impossible in the steep terrain of Appalachia and West Virginia.
Contour Surface Mining
Contour mining is practiced in areas where it is uneconomical to remove all the overburden from a coal seam or series of coal seams. In contour mining, surface mining machinery follows the contours of a coal seam or seams around a ridge excavating the overburden and recovering the coal seam or seams as a “contour bench” around the mountain is created. Excavation proceeds inward towards the mountain to a pre-determined depth. Contour mining results in excavation areas or “contour cuts” that wrap around mountaintops or ridgelines parallel to the contour of a given mountain or ridge line. Contour cuts may be conducted on multiple seams on a ridge or mountain side, stepping upward in elevation much like a layer cake pattern. In multiple seam contour mining, the cuts for multiple seams extend deeper into the mountainside moving upwards towards the ridge top.
Mountaintop Removal Mining
Mountaintop removal mining (MTR) is a special form of area mining where complete coal seams are recovered between a given ridge or mountaintop down to a “basal coal seam” or lowest elevation of coal extraction. The mining sequence for MTR is basically the same as area mining, although the operational areas are generally larger and reclamation leaves a flat or gently rolling terrain versus the AOC restoration of area mining.
In the press and as used by anti-mining groups the term “mountaintop removal mining” is used more broadly than its SMCRA statutory definition to include all forms of surface mining in Appalachia and West Virginia. It is very important to note that for a mining site to be considered a MTR mining operation it MUST fit the narrow SMCRA definition of a surface mining operation that removes all of the coal seams in a given ridge and DOES NOT restore the mining area to AOC.
MTR mining operations do not restore AOC as do contour and area mines. Reclaimed MTR mines generally have lower slopes and elevation than the original topography. The ability to obtain a variance from AOC restoration (and change an area mine to a MTR mine) is dependent on the intended post-mining land use (PMLU) of the former mining area. The PMLUs that will qualify a site for a variance from AOC restoration are enumerated in SMCRA and the corresponding state programs (more detail on these PMLUs is provided in the section on mining regulation).
Generally, the approvable PMLUs for MTR mines are limited to commercial, industrial, residential or agricultural uses. In the steeply-sloped terrain of Appalachia and West Virginia, the potential for PMLU development has emerged as a solution to chronic economic problem in the region- the lack of land, outside of flooding zones with needed infrastructure that is suitable for development.
Sidebar: Constructing a Valley Fill
All forms of coal extraction, underground and surface, invariably rely on some form of fill construction to facilitate removal of the mineral resource. These fills, which are highly engineered and regulated, are usually constructed in small, ephemeral and intermittent stream courses.
The construction of fills is not unique to the mining industry in West Virginia or Appalachia. The steep, rugged terrain of the region has provided limited areas for development or construction of any kind. What little flat land that does exist in West Virginia is confined to the floodplains of rivers and creeks and is usually occupied by roads, railroads and highways. New construction or development, mining or otherwise, will require some form of stream impacts and fill construction.
As noted previously, all forms of mining in West Virginia require the construction of fills. In underground mining, fills are required to provide access to the coal seam for miners and the coal extraction machinery. Underground mines also require the construction of a flat area or “bench” for the construction of essential support structures such as bathhouses, ventilation devices (fans), raw coal storage areas and electrical installations. Additionally, coal extracted using underground mining techniques must be “cleaned” on the surface at a preparation plant. Coal seams in Appalachia typically contain non-coal materials that lay within, above or below the coal seam. This material is mined along with the coal in underground mining and is mechanically separated from the coal at the preparation plant. The leftover material is placed in an adjacent refuse fill or impoundment.
At surface mines, fills are required as a result of the “swell factor” that occurs when rock and soil is excavated to uncover coal seams. Most of the rock and soil that is excavated to allow removal of the coal is returned to the mined area as the first step of mine reclamation in a process known as backfilling. Backfilling also restores the pre-mining contours and appearance of the mined area to mirror the surrounding, undisturbed topography (surface mining is explained in more detail in subsequent sections). Fills are a necessary component of all forms of development in Appalachia and West Virginia and any actions that restrict these needed fill structures will restrain if not stop this same development. Prohibitions or restrictions on mining-related fill structures will cripple both the underground and surface coal mining industry in West Virginia and Appalachia.
Because West Virginia’s economy, both state and local, is so dependent on revenues and taxes from the coal industry, any decline in the industry will have a resulting negative impact on the state. If the construction of fills are restricted, coal mining will be restricted and the effects on the economy of West Virginia will be devastating. The severity of the economic impacts increase as fills are further restricted and coal production is further reduced as the ability to mine coal, surface or underground, is dependent on fills.
Recent mining engineering studies conducted as part of a programmatic Environmental Impact Statement on surface mining in Appalachia provide more detailed and exact evidence with respect to fill prohibitions:
Limiting valley fills to ephemeral streams resulted in significant or total loss of the coal resource for 9 of the 11 mine sites when compared to the original mine site plans. All of the coal resource was lost for 6 of the 11 mine sites.
A recent study in the central Appalachian coalfields indicated the draconian effects that prohibiting all mining [in intermittent and perennial streams] could have on our nation’s energy supply. Assuming that mining activities could not be conducted…this OSM [federal Office of Surface Mining] study has estimated that 92.5 percent of the available coal reserves in the Central Appalachian coal fields could not be mined.
In response to a 1999 judicial decision that would have limited fill construction (later overturned on appeal) the West Virginia Legislature commissioned a study of the economic and social consequences of limiting coal production:
The…analysis considers two scenarios that are both within the realm of reason. In the first of these two scenarios, surface mining is gradually reduced, as currently permitted mines are retired and no new surface permits are granted. Even under this restricted scenario, the economic effects on the counties that comprise the study region are likely to be devastating. Total regional employment is predicted to decline by 4.3 percent, while overall regional economic activity is predicted to decline by $620 million within the first year. The economic impacts observed under the extreme scenario, in which the Haden decision leads to the immediate curtailment of surface mining, are even more extreme. A sudden cessation in surface mining is predicted to cost the study region more than 10,500 jobs, $281 million in incomes, and $1.8 billion in total economic activity.