The mining of ore in underground mines consists of several different processes, including blasting. Blasting has effects that may be noticeable by residents in areas adjacent to the mine area.
As production is continuous, blasting happens every night in all major production areas, so in both the eastern and western field in Malmberget. The ore bodies we mine are shown on the map.
The production areas must be evacuated before blasting can take place, and after the blasting, the mine has to be vented to clear blast gases for several hours before people can enter the area. For this reason, blasting takes place during the hours of 24.00-01.00.
There are various types of blasting processes. For tunnelling, what are known as preparation blasts are let off. These consist of relatively small charges and therefore seldom give rise to detectable vibrations. They can last for a few seconds and are perceived as a "rattling" sound (somewhat like popping popcorn).
During production, production blasts are left off, when the rock breaks into pieces and can be loaded for transport on within the production process. These blasts consist of slightly larger charges and can cause vibrations that are detectable in the vicinity. They consist of a short, powerful bang, but sometimes blasts in different places can be let off with a slight time delay, in which case there are a number of bangs.
When a new production area is to be taken into use, what are known as opening shots are left off. These are larger blasts drawn out over a longer period – they can last for up to 15 seconds. Like preparation blasts, they can also cause a "rattling" sound, but can also cause detectable vibrations, as they consist of larger charges.
Where we plan measures that we believe will result in an unusual impact on residents in the community, we announce this on our website and in the local news sheet "Kometen". Such events may involve an area being temporarily excluded from production or several opening shots being planned in an area, giving rise to more powerful vibrations.