The Permitting Process

Once a promising orebody has been found, most countries demand a technical environmental study of the proposed development. These reviews are so detailed that they can take quite a few years to complete. In order to get a permit for mine construction, companies must provide details of their operating plans, as well as the results of engineering, environmental and socio-economic studies. A further step before permits are issued is often a series of public hearings that permit individuals to speak out their preocupations or support. Needless to say, obtaining permission to develop a new mine can be complex and consuming of time.

The permits spell out the terms under which an environmentally acceptable mine may be developed. As is common, a government agency which is responsible for environmental protection or mining development will inspect the study and allow or forbid the mining operation based on the study’s findings.

One concern is the simple physical stability of the mine workings – whether the pit walls will stay up or whether mine workings will cause nearby ground to subside. The other preocupation is that mining may permit contaminants to enter the atmosphere, surface waters, soils or the groundwater systems. Mines, mills, smelters, tailings ponds, effluent discharges and smokestacks must be designed to keep contaminants out of the environment that surrounds them.

Base metal ores are most of the time natural compounds of a useful metal with sulphur. In the presence of oxygen and water, the sulphide minerals react to form sulphates and sulphuric acid. These compounds are not highly concentrated, but contain enough acid and salts of heavy metals to be harmful to aquatic life in surface watercourses. Because coals also contain iron sulphide minerals, the same chemistry happens in coal mines.

Careful control of mine waters and surface runoff permits mines to prevent or minimize the effect of acid-generating waste rock and tailings. In difficult cases, the mine may channel its runoff water to treatment plants that make the acid waters neutral before they are released to surface watercourses.

Water also leaks into mines from the surface and through the groundwater system. This water is collected and pumped to surface, and needs to be disposed of. It can however be slightly acidic from its contact with the sulphide minerals in the mine or can carry heavy metals that it has dissolved from the mineral deposit. To mantain the mine from polluting its surroundings, this water may have to be treated to remove the contaminants before it is discharged to rivers or lakes.

There are quite a few ways of treating such waste waters. Lime or other alkaline compounds can be included to neutralize sulphuric acid, and the heavy metals can be extracted chemically. Most countries have limits on the concentration of contaminants waste waters can contain if they are to be released to surface watercourses. These waters are treated so that any contaminants are present in concentrations lower than the limits prescribed.

Mines also have to dispose of waste rock. It comes up every day of the life of a mine. Some can be used as backfill, but there is usually plenty left over when the mine is finally exhausted. Mines have to be designed with waste rock dumps that will not collapse or slide. The waste rock also may contain traces of mineralization, and the contact of rain or snow with metal sulphides can form acidic runoff that can poison watercourses which are nearby.

The best way to avoid acidic runoff from reaching watercourses is to prevent it from forming in the first place. This is done by diverting water away from the waste dumps and by capping the dumps with impermeable soils that prevent rain and snow from reaching the waste rock. If that solution isn't practical, then the runoff that forms can be collected and treated to lower concentrations of contaminants to a safe level before the water is discharged.

The allowing process and hearings can take from one to three years. Applicants very often amend their project plans to reflect local concerns or take advantage of cleaner technologies. The result is an economic development without lasting environmental disruption.