Task: A Breath of Fresh Air Coming up at the end of this section.

3.2 Developing an Underground Mine

		Developing an underground mine takes an average of 5 to 10 years and a capital investment of several hundred million dollars. It involves extensive construction and a lot of equipment. It is like building an underground plant.
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3.2.1 Shafts

The first step in developing an underground mine is boring or "sinking" shafts.

Shafts are vertical tunnels that are several metres wide (5 to 10 on average). They may be over 1,000 metres deep. Some mines have only one shaft. Others have two or more.

If two shafts are sunk, the first shaft is usually an exploration shaft.

Located at some distance from the deposit, it is used as a starting point to excavate horizontal exploration drifts at different depths.

		Planning the excavation of exploration drifts.
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The drifts are dug across the deposit to better define its characteristics and to determine the scope of the future operations. This step also establishes the distance between mine levels.

The underground exploration stage usually lasts two years.

Once the mine is in production, the exploration shaft is often used for ventilation, filtration, heating and to monitor the quality of the air in the drifts.

To facilitate this task, noxious gas detectors are installed throughout the mine. The ventilators may be fitted with measuring instruments that indicate their operating state.

The data collected is automatically transmitted to the surface to a computer that controls the ventilators in the parts of the mine that are occupied.

However, all operations are supervised by a technician or an engineer, for security is a must!

		Example of a ventilation control system.
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The second shaft is used for production. It is the main mine shaft. It is usually sunk after the exploration shaft as it is often located at the centre of the deposit.

During mine development, this shaft is used to take equipment and machinery underground. Once the mine is in production, it is used to carry staff and to remove extracted ore from the mine.