Page 319 - Advances In Productive, Safe, and Responsible Coal Mining

Sustainable reclamation and water management practices 295

Demchak et al. [98] calculated a 2.2% decrease in acidity per year for 40 mines
between 1968 and 2000. Wood et al. [96] calculated a slightly higher 3.3% acidity
decrease per year in coal mine discharge chemistry over time in Scotland. Mack
et al. [103] found a 2% to 4% decrease per year in acidity from 40 underground mines
in West Virginia and modeled the decline with first-order decay rates.
Within the Coeur d’Alene District of Idaho at the Bunker Hill Superfund site,
groundwater samples were found to contain high concentrations of Zn, Pb, and Cd
[105]. The contamination originated from the leaching of old mine tailings deposited
on a sand-and-gravel aquifer. When settling ponds were constructed to catch the run-
off from the tailings, water from the ponds infiltrated into the aquifer and caused an
increase in metal concentration in the local groundwater system.
Gold (Au)-mining operations have used cyanide as a leaching agent to solubilize
Au from ores, which often contain arsenopyrite (As, Fe, and S) and pyrite. Unfortu-
nately, cyanide, in addition to being toxic on its own, is a powerful nonselective sol-
vent that solubilizes numerous substances that can be environmental contaminants.
These ore waste materials are often stored in tailing ponds and, depending on the local

geology and climate, the cyanide present in the tailings can exist as free cyanide (CN ,
HCN); inorganic compounds containing cyanide (NaCN, HgCN 2 ); metal-cyanide
complexes with Cu, Fe, Ni, and Zn; and/or the compound CNS. Because cyanide spe-
cies are mobile and persistent under certain conditions, a large potential for trace ele-
ment and cyanide migration into ground waters exists. For example, a tailings dam
failure resulted in cyanide contamination of groundwater at a gold-mining operation
in British Columbia, Canada [89].

14.5 Conclusion

Reclamation is a mining activity that is intended to produce land and water conditions
that meet human needs. Mined landscapes meet human needs when they support via-
ble economic enterprises and other forms of community development. Reclamation
practices have been described that will enable mined land to support agricultural pro-
duction (including food crops, hay land, pasture, and bioenergy crops), forest produc-
tion that can grow valued wood products, and developed land uses for building sites.
In order for mined landscapes to support human needs, it is also essential that rec-
lamation processes restore environmental quality. The relatively undisturbed ecosys-
tems that occupy many mine sites prior to mining produce environmental benefits that
are valued by human society. Reclamation practices have also been described that can
be applied to establish ecosystem structure, process, and function on postmining lands
that have some resemblance to premining conditions.
Today’s regulatory policies expect that coal mine operations will produce
reclaimed lands that will either support economically viable postmining land uses
while protecting environmental quality; and, for some uses, to establish ecosystem
structure and processes that resemble those present prior to mining. An ability to exe-
cute reclamation practices in a manner that satisfies regulatory and public expecta-
tions cost effectively is essential to any mining business.