Mine reclamation

DEFINITION: Process of returning disturbed land areas to stable and productive uses after minerals have been removed through mining

The reclamation of lands no longer used for mining is important to prevent various environmental problems, such as soil erosion, pollution of groundwater by acid drainage, and the physical dangers posed by abandoned shafts and tunnels.

Failure to reclaim mined land may result in substantial loss of biological productivity of the land surface, significant degradation of nearby water bodies, and hazards to human health and safety. Degradation of land and water is attributable to and of soils, acid mine drainage, and damage to aquifers. Hazards to human health and safety include open mine shafts, mine fires, subsidence of the ground above underground tunnels, clifflike surfaces known as highwalls, and landslides on steep slopes. Land areas disturbed by mining that have not been reclaimed are referred to as abandoned mine lands.

The amount of land to be reclaimed at any mine is determined by the amount of removed and the type of mining operation. Underground mines require little except near the tunnel entrance. Surface or strip mines disturb larger areas and volumes of soil and rock than do underground mines, and therefore they require more reclamation. In all forms of surface mining, rock and soil located above and between seams of the mineral are removed to expose the mineral for extraction.

Before soil and rock can be removed, all vegetation covering the land surface to be mined must be removed. Next, topsoil and subsoils are excavated and used in an adjacent area that is being reclaimed, or they are separated from other rock (rock that overlies deposits of minerals to be mined) and stockpiled for later use. The process of segregating and reusing fertile topsoils during mining is critical to the later success of reclamation efforts because a suitable growing medium is essential to the reestablishment of viable plant communities. Reclamation of abandoned mine lands where topsoil was not separated from other overburden is generally more difficult and expensive than reclamation at operating mines.

Reclamation Activities

Reclamation encompasses three activities: backfilling and grading, replacement of topsoil, and revegetation. Backfilling and grading occur after the mineral has been removed. Overburden is replaced in the mined area to reestablish a stable land surface that is consistent with the surrounding area and compatible with the intended postmining land use. Front-end loaders, heavy trucks, bulldozers, and graders are used to and grade the contours of highwalls, overburden piles, and depressions to approximate original slopes. The resulting surfaces must be stable—that is, not prone to landslides or erosion—and should blend in with the surrounding natural topography.

Mining operations sometimes unearth natural materials that are toxic or acid-forming. When exposed to the atmosphere, these materials may alter the acidity of surrounding soil or water bodies, destroying the organisms that live there. Such materials must be isolated from surface water and groundwater, soils, and vegetation so that they cannot contaminate the environment. This generally means placing them below the root zone of plants during backfilling and grading. During backfilling and grading, heavy equipment repeatedly crosses the work area, causing of the ground surface. Prior to redistribution of topsoil, it may be necessary to rip up this surface to relieve compaction. This helps prevent slippage of topsoil by creating a roughened surface and aids root penetration by vegetation, thus improving surface stability.

After backfilling and grading are completed, a layer of topsoil is spread over the graded overburden to a depth determined by the intended postmining land use and the amount of topsoil available, often 1.2 meters (4 feet) or more. Topsoil stockpiled for more than two or three years begins to lose nutrients, beneficial bacteria, and fungi that aid in plant establishment, so soil tests are used to determine what soil amendments may be needed. Where nutrients are lacking, they are replenished using fertilizers similar to those used on home lawns and gardens.

Revegetation must occur soon after placement of topsoil to control the effects of wind and water erosion. A fast-growing annual grass or cereal grain cover crop, as well as mulch, may be used to stabilize the soil until the first normal planting season. Shrubs and small trees may also be planted. The goal of revegetation is the establishment of a diverse, permanent vegetative cover of a seasonal variety native to the area, or of a variety that supports the intended postmining land use.

In the eastern United States, where water is plentiful, it may take five years to determine whether a mine reclamation project has been successful; in the semiarid western United States, determination may require ten years. Common uses of reclaimed mined land include cropland agriculture, commercial forestry, recreational areas such as parks, public works (such as airfields, roads, housing developments, and industrial sites), and fish and wildlife conservation.

Reclamation Laws

In the United States, reclamation of land disturbed during the mining of coal has been required since 1977 under national legislation known as the Surface Mining Control and Reclamation Act (SMCRA). Principal responsibility for enforcing this law rests with the U.S. Department of the Interior’s Office of Surface Mining Regulation and Enforcement and state regulatory authorities, with programs approved under the statute. A small fund is available for the reclamation of abandoned mine lands, financed by fees on each ton of coal produced by active mining operations.

The requirements of SMCRA apply only to coal mines operating since 1977. Lands disturbed by the mining of gold, silver, nickel, copper, bauxite, limestone, and other minerals and industrial materials are not subject to uniform national standards but may be subject to requirements for reclamation imposed by some states; such state regulations vary greatly, however. The knowledge and technology necessary for successful reclamation of land disturbed by mining are available for almost all ecological systems, except desert and alpine climate conditions that do not favor the rapid plant growth necessary to stabilize reclaimed soil.

Bibliography

Bierman, Paul, Richard Hazlett, and Dee D. Trent. Geology and the Environment. 8th ed. Cengage, 2023.

Hossner, Lloyd R., ed. Reclamation of Surface-Mined Lands. Boca Raton, FL: CRC Press, 1988.

Otto, James M. “Global Trends in Mine Reclamation and Closure Regulation.” In Mining, Society, and a Sustainable World, edited by J. P. Richards. New York: Springer, 2009.

"Laws & Regulations." Office of Surface Mining Reclamation and Enforcement, www.osmre.gov/laws-and-regulations. Accessed 19 July 2024.

Schor, Horst J., and Donald H. Gray. Landforming: An Environmental Approach to Hillside Development, Mine Reclamation, and Watershed Restoration. Hoboken, N.J.: John Wiley & Sons, 2007.