Disasters: Environmental Mining Accidents
Disasters: Environmental Mining Accidents
Some of the most publicized environmental disasters are associated with the mining industry. These disasters are attributed to both natural and miningrelated causes. Acid drainage, for example, formed by rainwater or snowmelt in contact with mineral deposits can damage nearby ecosystems by polluting streams and destroying wildlife. The mining and processing of ores, however, may accentuate and accelerate the natural processes.
Long- and Short-term Impacts of Mining in the Environment
On a long-term basis, mining can increase the acidity of water in streams; cause increased sediment loads, some of which may be metal-laden, in drainage basins; initiate dust with windborne pathogens; and cause the release of toxic chemicals, some contained in exposed ore bodies and waste rock piles and some derived from ore-processing reactions. Contaminants containing such toxic chemicals as cyanide and lead may be transported far from a mining site by water or wind, polluting soils, groundwater, rivers, and the atmosphere. These toxic chemicals can be remobilized intermittently (e.g., by intense wind or rainstorms) and eventually distributed over vast regions. Some of this contamination, because of its scale or intensity, may not be amenable to remediation .
Mining may also have effects that can be short-term, depending on their severity, such as distortion to the surrounding topography or removal of vegetation. In many cases, these effects may be minimized or even prevented by means of a comprehensive mining plan that includes a reclamation and remediation stage. For example, in 1999 the Ruby Hill Mine, an open-pit gold mine located near Eureka, Nevada, received an "Excellence in Mine Reclamation Award," which is granted jointly by various state and federal mining and environmental bodies. Since its inception, the mine has exhibited outstanding innovation in its design, mitigation, and reclamation, all of which is the basis of the award. One of the techniques employed by the mine is concurrent reclamation practice. Since initial exploration, disturbed areas are continuously relegated to facilitate erosion control and provide improved esthetical value. In addition, one mitigation measure that was cited is the effort to offset potential impacts to local wildlife by constructing nesting structures for bats and hawks. As of 2002, the mine was still in operation.
The Summitville Mine in Colorado has become a case study of environmental damage as a result of mining. Gold was mined there from 1870 until 1992. In 1994 the U.S. Environmental Protection Agency (EPA) declared the area a Superfund site. Some of the following events affected the environment at the mine: Geologic characteristics at the mine site contributed to the generation of both natural and mining-related acid drainage; the height of the containing dike for cyanide leach solutions (used to chemically extract gold) was below the level required for snowstorms and spring runoff; broken pump lines and a French drain beneath the leach pad caused cyanide-contaminated solutions to be released into the local watershed ; several waste rock piles at the mine reacted with rain and snowmelt to form acidic waters that flowed into area streams; an underground tunnel released large volumes of contaminated waters; and mining deforested much of the land. Remediation of the site has included such projects as backfilling mine waste into existing open pits, which reduces polluted water percolating into the ground; plugging underground tunnels; and replanting. Remediation is ongoing with the goal of restoring the nearby Alamosa River to support aquatic life; the U.S. Public Health Service classified this site as "no apparent public health hazard."
Another case study is the Iron Mountain Mine in California, which the EPA declared a Superfund site in 1983. Mining for copper, gold, silver, and zinc began in 1879 and continued until 1963 using underground and open-pit methods. The site contains inactive mines and numerous waste piles from which harmful quantities of untreated acidic, metal-rich waters were discharged. Mining operations fractured the mountain, changing the hydrology and exposing the mineral deposit to oxygen and water, which resulted in intense acid mine drainage into nearby creeks and waterways. These caused numerous fish kills and posed a health risk to the area drinking water. Some current remediation projects include: capping areas of the mine and the diversion of nearby creeks, both of which serve to reduce surface water contamination; construction of a retention reservoir to control the area source acid mine drainage discharges; enlargement of a landfill to provide an additional thirty years of storage capacity for heavy metals sludges; and construction of a significant upgrade to facilities in mine tunnels to assure safe travel for workers and equipment to perform maintenance and routinely remove mine wastes from the tunnels and other projects.
see also Acid Rain; Heavy Metals; Mining; Superfund; Water Pollution.
"Hazardous Materials and Waste Management Division Summitville Mine." Colorado Department of Public Health and Environment, 2002. Available from http://cdphe.state.co.us.
Jorgenson, Pat. "World's Most Acidic Waters Are Found Near Redding, California." U.S. Geological Survey, 2000. Available from http://ca.water.usgs.gov.
"Public Health Assessment Summitville Mine Del Norte, Rio Grande County, Colorado." U.S. Department of Health and Human Services, 1997. Available from http://atsdr.cdc.gov.
Michael J. McKinley