What Are the Effects of Mining Waste on Land?

Mining involves the removal of material from the earth, for the purpose of extracting ores, chemicals and sometimes gases and oils. Mining equipment consists of large excavating machines that remove sand, gravel, rock or other matrix material. Unfortunately, chemicals can be used in mining that have lasting damaging effects on the land and environment. The type of damage depends upon the mine and mineral extracted, but in most cases, mining leaves its negative mark in one way or another.

Land Dredging

• Land dredging results when a large hole or excavation has to be burrowed into the earth. A high pressure hose applies a forced jet of water into a hillside to expose layers of gold-bearing sand and clay. The material slurry then has to be pumped into a sluice box which filters and collects gold particles, but the tailings and waste water run off to fill up ditches and pits, sometimes forming man-made ponds and lakes. Some waste pools stagnate, becoming infested with scum and algae, while others serve as breeding grounds for malaria-carrying mosquitoes.

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River Dredging

• River dredging has to be performed from a boat or large barge equipped with heavy generator pumps. As the platform moves, bottom sediment that includes mud, sand and silt is suctioned up through hydraulic hoses. The thick slurry gets pumped over large felt mats, which trap the gold. The pumped waste water and tailings get deposited in another location of the river, which often disrupts the natural flow and current. Fish and plant life often die as a result of the obstructions and muddy condition of the water. Navigation becomes a hazard when river levels become shallow in unexpected areas.

Leaching and Floatation

• Sulfuric acid and water have to be used to leach copper from oxide ore during the mining process. Attempts are made to dilute and recycle the water, and it then gets stored in lined storage ponds. Sometimes, the containment structure of the pond develops cracks or holes, which leak sulfuric acid into the soil. The acid in the soil seeps into the ground water and travels to other locations, like farms, fresh water reservoirs and populated communities.

Cyanide

• The process of leaching gold with cyanide, although banned in many developed countries, continues as a crude method to extract gold in many mines. Tailing waste water that has cyanide in it escapes from containment ponds, enters the water table and ends up in streams, lakes and rivers. Animals that feed on vegetation and grasses can become ill and die from concentrated amounts of cyanide. Cyanide produces adverse effects on the human nervous system when exposed to the skin, inhaled or consumed.

Explosives

• Many mines have to be deepened and expanded by a means other than heavy digging and shoveling equipment. Very powerful explosives like ANFO, a combination of ammonium nitrate and fuel oil, blast out huge sections of rock from open pit mines. The waste product of the explosives leaves traces of harmful nitrates, which get picked up by rain and ice and transported to sensitive ecosystems.

Waste Containment Dams

• Mines often construct containment dams and ponds that hold metal-rich water and contaminated byproduct chemicals used in the mining process. Vents, pressure valves and pumps, as well as dirt and gravel containment walls, have failed in the past, leading to sudden and catastrophic releases of water. The floods that result from burst containment dams can erode hills and small mountains, obliterating anything in their path. Small cities and villages that occupy locations downstream from such dams can be flattened, resulting in property damage and loss of life.