Environmental Consequences of Underground Mining #2

Terrestrial Vegetation Disturbances of natural, quasi-natural, or cultural landscapes inevitably result in changes in composition and structure of plant species, disrupt soil strata, and stimulate invasion by disturbed-site plant species that in turn can alter composition of local invertebrate and other associated species and habitat. Those disturbances may be associated with development of roads or use of off-road vehicles during exploration activities. Smelter and other mining facility emissions may also act to fumigate plant communities adjacent to mineral processing facilities through releases of toxic materials, such as sulfur dioxide (SO₂), which is often lethal to foliage and consequently to the plant itself. Increasing distance from the pollution source generally results in the plant community composition gradually returning to pre-disturbance conditions. However, long-term smelter emissions have historically adversely affected surrounding forest ecosystems, habitats, biodiversity, and soils.

Real World Examples include areas around Anaconda, Montana; Coeur D’Alene, Idaho; Salt Lake City, Utah; La Oroya, Peru; Haina, Dominican Republic; Tianying, China; and Norilsk, Russia, where much of the landscape surrounding mining/smelting facilities remains devoid of trees and other natural vegetation. Toxic metals from mining processes, as contaminants in the air, have the potential to affect terrestrial vegetation by settling onto soils or foliage and then being taken up by plants. Soils, vegetation, and wildlife habitat in areas affected by smelter emissions have been shown to contain elevated concentrations of metals, severely affecting vegetation abundance and species diversity. In addition, reclamation procedures that specify the use of non-native species may decrease the distribution of native species. Obviously, the injection of heavy metal particulates (including lead, copper, mercury, selenium, zinc, uranium, nickel, chromium, and others) and various noxious and hazardous gases (such as sulfur dioxide) into the atmosphere and such hazardous chemicals as cyanides and chlorobenzenes into surface and ground water systems has drastically and adversely affected the health and life spans of individuals, especially children, residing in areas around those mining facilities.

Terrestrial Wildlife: Mining activities may disrupt terrestrial wildlife, starting from exploration, operation of off-road vehicles, location of drillhead or mine pads, construction of permanent or semi-permanent long-distance haul roads or railroads, and combinations of mining-milling-smelting operations. Adverse effects include migration disruption of small mammals and changes in behavioral patterns for larger animals by destroying habitat, fragmenting territories, creating barriers to movement, and interfering with normal nesting/dening reproductive activities, potentially reducing the population of various affected species. Consumption of toxic plants and animals by terrestrial wildlife, waterfowl, and migratory birds may result in the accumulation of toxic materials through bioconcentration, potentially creating toxic levels of metals and other chemicals in those organisms and in prey species, including humans.

Water Quality issues result from acid drainage, construction of roads or railroads, metals (e.g., antimony, arsenic, lead, mercury, and selenium) and cyanide contamination, placer mining, pit lakes that concentrate metals and other contaminants, and surplus water drainage. Each of those issues can also generate long-term adverse effects on aquatic biota, aquatic habitat, and water chemistry, many of which are incredibly persistent. What should be a wake-up call but is often pointedly ignored by rosy-eyed mining advocates and their pet, bend-over politicians is that lead mines that were operational at the time of the Roman Empire are still producing acid drainage 2,000 years later. On August 5, 2015, EPA personnel and workers for an environmental restoration firm under federal contract to mitigate pollutants from the Gold King Mine, which had been closed for one hundred  years, accidentally caused a breach to a tailing pond, resulting in the catastrophic release of three million gallons of toxic lead, arsenic, cadmium, and other highly hazardous chemicals into the Animas River near Silverton, Colorado, and further downstream into the San Juan River, which is heavily used for drinking water and agriculture. As of mid-2016, the Gold King Mine continues to discharge acid mine drainage at a rate of about 600 gallons per minute. And that mine is one of at least 20,000 abandoned mines in Colorado alone, only a small fraction of which have been properly remediated.

Water Quantity issues include the following. Mine water discharges to streams from dewatering can adversely affect riparian vegetation, cause increased erosion, alter the stream regime with respect to natural hydro-period and therefore alter or destroy habitat. Groundwater withdrawal may adversely affect local water tables for many decades. For example, groundwater withdrawn from the Santa Cruz River Basin in southern Arizona for mineral processing at a nearby copper mine has lowered the water table by many meters and has altered the River’s flow characteristics. Runoff from hardened surfaces, especially roads and parking lots, produce more runoff to nearby streams than would be expected that may carry complex hydrocarbons, metals, and other pollutants from vehicles and sediment from roads or roadside areas. Impervious surfaces accelerate runoff during storms and reduce moisture percolating into the ground, potentially affecting stream hydrological functions, changing sediment transport characteristics, and altering habitat for fish and other aquatic organisms. Changes in regional hydrology (such as changes in hydrologic head) owing to mining activities have the potential to adversely affect wetlands, especially in the arid Southwest that are dependent on a continuous supply of water particularly at spring orifices, which often support threatened or endangered species. Even small changes in the hydrologic head may lower the local or regional water table several yards and may result in the drying up of springs and associated wetlands.

Other adverse consequences of mining activities that are not discussed in detail in this post include adverse effects on human health, tunnel collapse, surface subsidence, disruption of social networks and systems, land use changes, boom-and bust pressures on nearby communities in terms of sudden and often unanticipated demand for schools, public safety services, housing, transportation, social and medical services, recreation and entertainment, and rapid changes in local and regional real estate markets with mine start-up and closure, etc.