For hundreds, even thousands of years, human beings have mined for metals and stones, and with the advent of greater technology as well as greater needs, the demands for these resources continue to grow. While these resources benefit our lives in many ways, the effects of mining can be detrimental, and one such effect is the topic of this essay, acid mine drainage (A.M.D.). The causes of A.M.D. will be discussed, along with some of the physical and biological problems associated with it. Some prevention and remediation treatments will also be considered.

Acid mine drainage refers to water (leachate, drainage or seepage) that has come into contact with oxidised rocks or overburden that contains sulphide material (coal, zinc, copper, lead). (Keller, 2000; U.S.G.S.; U.S.E.P.A., 2002). A common sulphide is pyrite, or iron disulfide (FeS2), and throughout this essay it will be pyrite that will be the primary sulphide considered. Acid mine drainage is not a new phenomenon, early mining techniques utilized gravity to avoid water pooling, resulting in the water becoming polluted by acid, iron, sulphur and aluminium (U.S.E.P.A., 2002). It is most commonly associated with co

Acid mine drainage is particularly hazardous in mines that are now abandoned. A poignant example is that of the Tar Creek area of Oklahoma in the United States of America. During the late nineteenth century the area was mined for lead and zinc and mining continued until around 1960. The mines reached down to 100m below the water table and while mining occurred the subsurface groundwater was actively pumped out. However, after 1960 and the closure of the mines the ground water naturally rose and caused some of the mines to flood. The resulting water had a high concentration of sulphuric acid and the overflow polluted streams. The results were so great that in 1982 it was designated by the United States Environmental Protection Association as the worst hazardous waste site in the United States (Keller, 2000). This highlights the problem of abandoned mines and A.M.D.

Another approach is the management of water both during and after mining operations. Water flows can be altered so as to not come into contact with pyritic materials, over burdens can be placed "and rough graded to prevent ponding and subsequent infiltration" (O.S.M, 2002). Also water that accumulates can be removed and polluted water can be isolated and treated so as to not further contaminate more water.

As with most things prevention is the best cure, and techniques and protocols can be implemented to reduce the risk of A.M.D. Two approaches commonly in use for the last 20 years are controlled placement of the over burden, and water management (O.S.M, 2002). Controlled placement involves either excluding oxygen or water from the pyritic material. The exclusion of oxygen can be achieved through submergence. By completely submerging the pyritic material in deep (several tens of feet), stagnant water, oxygen is unable to diffuse easily through the water and the pyrites therefore can not oxidate. Submergence has many limiting factors and does not work with all mines. The positioning of the mine and the water table must be considered, as must the likelihood of the mine failing under pressure. Pyrites can also be kept inaccessible to water by isolation above the water table. This i

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Approximate Word count = 1455
Approximate Pages = 6 (250 words per page double spaced)