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Before mining begins, mining companies must plan for the replacement of topsoil after the coal has been removed. Details involving the removal, storage, replacement, and protection of the topsoil from erosion are listed in the mine operation plan. Topsoil, which is removed in a separate layer from areas to be disturbed, is either immediately replaced, or stored on approved locations. Topsoil depth must be determined before mining to assure proper replacement for growing row crops and other vegetation. The replaced soil profile on areas designated as prime farmland must be at least 48 inches including topsoil and subsoil.
The coal operator places the blasted rocky material in the bottom of the pit once coal removal in the area is complete. Overburden can contain layers with pyrite, which when exposed to air and water, can produce acid. Mixing these layers and burying them with neutral materials in the pit, prevents acid production by blocking exposure to oxygen.
To assure that a suitable rooting material is available for cropland capability, the subsoil layers are placed on top of the graded rocky overburden during reclamation. Any toxic overburden identified in the pre-mining inventory must be treated or covered with an adequate layer of nontoxic, noncombustible material.
To prevent water pollution, all water affected by the mining operation must pass through approved sediment control structures before leaving the mine site, and must be in compliance with all applicable State and federal water quality laws, including water discharge permits issued by the Indiana Department of Environmental Management.
Coal companies maintain siltation structures on the site until permanent vegetation has been established, and water quality coming into the pond meets water quality limitations. Ponds not approved for retention after mining must be removed and reclaimed.
It is the responsibility of mining operators to monitor groundwater levels and quality throughout the mining and reclamation process. The operator will furnish an alternative water supply, in conformance with Indiana water law, where an existing water supply from groundwater used as a drinking water source is affected by contamination, depletion, or interruption due to surface mining activities.
The operation plan must detail where coal will be stockpiled, as well as what type of cleaning and processing are to occur. The waste produced from the coal cleaning process can be potentially acid-forming and detrimental to plant life. The material must be adequately treated or covered with an adequate layer of nontoxic, noncombustible earthen material, to neutralize and prevent production of acid water. Toxic materials must be placed in areas of the mine where contact with surface and groundwater is minimized.
Throughout the reclamation process, coal operators must meet detailed requirements. A mine reclamation plan will show how overburden will be graded, subsoil and topsoil replaced and re vegetated, post mining land uses established, and pre-existing streams restored. Coal operators give a timetable for the completion of each step in the reclamation process. They must also give an estimated cost of reclamation, including a statement as to how the operator plans to comply with the law.
Mining companies must plan to provide rough grading of mined overburden within 180 days of coal removal and have no more than four un graded spoil ridges behind the active pit, unless additional time is granted for a good reason such as adverse weather conditions. The replaced overburden must be shaped to the approximate original contour of the land so that it drains properly and pre-mining drainage patterns are re-established.
Materials from the initial pit or box cut must be graded to blend with un mined land. Final grading must be completed in a timely manner; usually in time for the next growing season. This includes any subsoil or topsoil replacement and installation of erosion control measures such as terraces, diversions, grass waterways, and drains. An attempt must be made to grade replaced soil in a manner which limits compaction. Most plans specify a crop of wheat or oats followed by a grass-legume mix for several years on reclaimed land to prevent soil erosion and to restore soil structure.
After this period, and before the company's reclamation responsibility ends, vegetation must be established which is consistent with the post-mining land use plan. Additionally, operators must establish row crop production on prime farmland areas. Field test plots are the most common method used to verify vegetative growth. A count of vegetation covering the ground is used on land uses other than row cropland. A five to ten-year vegetation liability period begins when all grading is completed and the land is planted to a crop capable of supporting the post-mining land use.
For prime farmland, full restoration of 100% of the original un mined land productivity is required. This may be accomplished using typical crops (eg. corn, soybeans, wheat) for three crop years before final release of reclamation responsibility.
Forest land use must show growth of 450 trees per acre for a three-year period. Permanent water impoundments may be constructed from the final pit of the mined area, or from a sediment pond, if the alternative land use proposal has been approved, or if water was present on the area prior to mining.
Today, underground mining accounts for almost a third, or more than 30% of the total coal mined in Indiana. At this time the prevalent underground mining technique employed in Indiana is the room and pillar mining method. The tunnels where the coal is removed are called "rooms". The coal blocks which are left behind to support the roof and the surface are called "pillars". A machine called a continuous mining machine rips the coal from the seam with a rotating head. Blasting is seldom used in underground extraction of coal in Indiana except for shaft development. Conveyors transport coal from the working face to the shaft or slope tunnel which transports it coal to the surface for processing and shipping.
Other methods of extraction exist which allow subsidence to occur in a controlled and predictable fashion. The most common planned subsidence mining technique used in the United States today is called long wall mining. Secondary mining for partial pillar recovery is sometimes used for higher extraction. The Division of Reclamation regulates the environmental affects of underground mining. Other state and federal agencies, such as the Indiana Bureau of Mines and U.S. Mine Safety and Health Administration are responsible for safety of mine workers.
Procedures for public notice, public participation and application review for underground permit applications are identical to those for surface mining applications. Environmental protection and reclamation requirements are also virtually identical, except that underground mining applications must also contain a subsidence control plan and special provisions for prior notice to surface owners, who will be affected by coal extraction.
Underground applicants must devise a detailed subsidence prevention or control plan based on detailed local geological analysis, engineered safety factor calculations and the sensitivity of surface features to be protected, such as buildings, impoundments, roads and utility transmission lines. Underground miners must provide information on the coal removal technique, percentage of coal extraction, pillar and room dimensions, geologic layers above and below the coal, mapping of proposed mined areas, groundwater systems as well as an extensive inventory of land features and structures located above the coal to be mined, such as homes, outbuildings, roads, churches, public buildings, impoundments, utility transmission lines and any other structures.
The DOR's subsidence specialist evaluates supplied information to obtain a determination that sufficient mine stability is designed for room and pillar mines; or, that planned subsidence mining, such as long wall mining or pillar removal mining, is designed to occur in a planned and predictable fashion which will be conducive to restoration of the land surface. In addition to plans to prevent or control subsidence, underground miners must provide back up plans for restoration of the surface land and features in the event that a subsidence results in damage in spite of extensive prevention provisions. The mitigation plan must demonstrate that the operator will restore the land and structures to a condition which will support the same uses which existed prior to subsidence. As an additional protection measure, the operators are required to carry a non-cancelable liability insurance policy which covers subsidence damages, should they occur.
Underground miners must alert surface owners of their intent to extract coal beneath their property by sending written notice directly to the surface owner at least 6 months prior to the beginning of mining beneath the property.
Anyone suspecting subsidence damage, should first contact the mining company with their claim. If a satisfactory conclusion is not reached, contact the Division. If the company is found liable, the regulations require that action be taken by the company to restore damaged areas. If structures are damaged by subsidence that results from active mining, the mining company will repair the structure.
Conventional homeowners insurance does not cover damage caused by mine subsidence. In 1986, the Indiana Legislature established the Indiana Mine Subsidence Insurance Fund to provide insurance to property owners in the 26 Indiana coal producing counties. Property owners in the following counties are eligible for this insurance: Clay, Crawford, Daviess, Dubois, Fountain, Gibson, Greene, Knox, Lawrence, Martin, Monroe, Montgomery, Orange, Owen, Parke, Perry, Pike, Posey, Putnam, Sullivan, Spencer, Vanderburgh, Vermillion, Vigo, Warren, and Warrick.
Maps of abandoned underground mine works are available through the Indiana Geological Survey in Bloomington (812-855-7636). These maps are beneficial in determining whether you live in or near an area where underground mining activity took place, although many historic mines were never surveyed and may not show on the maps. Purchasing mine subsidence insurance is mandatory before reporting suspected mine subsidence damage. Coverage is designed only for underground coal mines abandoned before August 3, 1977. You may add subsidence insurance to your property owners or homeowners policy when it is purchased or renewed. For more information about mine subsidence insurance, contact your insurance agent or the Indiana Subsidence Insurance Fund at the Indiana Department of Insurance: 1-800-332-IMSI.