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Impact of Ammonia on mine water quality as related to explosive uses for underground mining methods

by Michael de Luca, Masters of Science in Earth Sciences, Masters Project Report, University of Waterloo, 2000

Mine water quality of the Bell Creek, Dome and Holloway Joint Venture gold mines, located near the Timmins region in Northern Ontario was examined. Each mine employs a different mining method based on the grade, size and orientation of the orebody. These include shrinkage sloping, blasthole sloping and open sloping, each of which uses large volumes of explosives. The most common explosive used is ANFO, a mixture of 95% ammonium nitrate and 5% fuel oil, and is very soluble in water. The application of large amounts of ANFO in underground mining results in high ammonia and nitrogen concentrations in the mine water during production.

High concentrations of ammonia and nitrogen were not observed in the Bell Creek mine water. Since 1992 this has been on care and maintenance status, resulting in low concentrations since there has been no production at the site, and therefore no use of blasting agents.

Conversely, ammonia concentrations observed in the mine water at the Dome Mine and the Holloway Joint Venture mine are quite high, with the latter showing the highest values. Two reasons for this are the recycling of water within the mine and the improper handling of explosives during mining. Each of these mines recycles a fraction of the mine water within the underground mining areas. Dome Mine recycles 20% and Holloway Joint Venture recycles 70% of their mine water. The recycling of these waters has been shown as a contributing reason for the high ammonia concentrations found at these sites. Improper handling of blasting agents used for mining, is another contributing factor for high nitrogen levels found in the mine water of these mines. Improper handling of explosives is very common; 25kg per day of ANFO was reported lost at the Holloway Joint Venture mine in 1995. Poor handling of explosives is the main source of high ammonia and nitrogen levels at these mines. Combined with the recycling of water within the mine, improper explosive handling causes these very high concentrations in the mine water.

Proper care and attention when handling such large volumes of explosives can minimize these unnecessarily high levels of ammonia and nitrogen found in the mine water at underground mines.

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